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Tissue Formation (tissue + formation)
Kinds of Tissue Formation Selected AbstractsInfluence of controlled immediate loading and implant design on peri-implant bone formationJOURNAL OF CLINICAL PERIODONTOLOGY, Issue 2 2007Katleen Vandamme Abstract Aim: Tissue formation at the implant interface is known to be sensitive to mechanical stimuli. The aim of the study was to compare the bone formation around immediately loaded versus unloaded implants in two different implant macro-designs. Material and Methods: A repeated sampling bone chamber with a central implant was installed in the tibia of 10 rabbits. Highly controlled loading experiments were designed for a cylindrical (CL) and screw-shaped (SL) implant, while the unloaded screw-shaped (SU) implant served as a control. An F -statistic model with ,=5% determined statistical significance. Results: A significantly higher bone area fraction was observed for SL compared with SU (p<0.0001). The mineralized bone fraction was the highest for SL and significantly different from SU (p<0.0001). The chance that osteoid- and bone-to-implant contact occurred was the highest for SL and significantly different from SU (p<0.0001), but not from CL. When bone-to-implant contact was observed, a loading (SL versus SU: p=0.0049) as well as an implant geometry effect (SL versus CL: p=0.01) was found, in favour of the SL condition. Conclusions: Well-controlled immediate implant loading accelerates tissue mineralization at the interface. Adequate bone stimulation via mechanical coupling may account for the larger bone response around the screw-type implant compared with the cylindrical implant. [source] Healing and prognosis of teeth with intra-alveolar fractures involving the cervical part of the rootDENTAL TRAUMATOLOGY, Issue 2 2002Miomir Cvek Abstract Healing and long-term prognosis of 94 cervical root fractures were evaluated. The teeth were divided into two groups according to type of fracture: transverse fractures limited to the cervical third of the root (51 incisors) and oblique fractures involving both the cervical and middle parts of the root (43 incisors). Neither the frequency nor the type of fracture healing differed significantly between the two groups. In the material as a whole, healing of the fracture with hard tissue formation was observed in 17 teeth (18%), and healing with interposition of periodontal ligament (PDL) and, in some cases, hard tissue between the fragments in 62 teeth (66%). Fifteen teeth (16%) showed no healing and a radiolucency adjacent to the fracture. Statistical analyses revealed that incomplete root formation and a positive sensibility test at the time of injury were significantly related to both healing and hard tissue repair. The same applied to concussion or subluxation compared with dislocation of coronal fragment, as well as optimal compared with suboptimal reposition of displaced coronal fragments. The type and duration of splinting (or no splinting) appeared to be of no significance for frequency or type of healing of cervical root fractures. During the observation time (mean = 75 months), 19 (44%) of the teeth with transverse fractures and 3 (8%) of those with oblique fractures were lost after healing. In conclusion, fractures in the cervical part of the root had a healing potential and the predictive parameters identified for fractures in other parts of the root seemed to be valid for the healing of cervical root fractures. Transverse fractures appeared to have a significantly poorer long-term prognosis compared to oblique fractures, apparently due to a marked post-treatment mobility, which often led to new luxation caused by even minor impacts. [source] Involvement of BMP-4/msx-1 and FGF pathways in neural induction in the Xenopus embryoDEVELOPMENT GROWTH & DIFFERENTIATION, Issue 4 2000Akihiko Ishimura The msx homeodomain protein is a downstream transcription factor of the bone morphogenetic protein (BMP)-4 signal and a key regulator for neural tissue differentiation. Xmsx-1 antagonizes the dorsal expression of noggin and cerberus, as revealed by in situ hybridization and reverse transcription,polymerase chain reaction assays. In animal cap explants, Xmsx-1 and BMP-4 inhibit the neural tissue differentiation induced by noggin or cerberus. A loss-of-function study using the Xmsx-1/VP-16 fusion construct indicated that neural tissue formation was directly induced by the injection of fusion ribonucleic acid, although the expression of neural cell adhesion molecule (N-CAM) in the cap was less than that in the cap injected with tBR or noggin. In contrast to the single cap assay, unexpectedly, both BMP-4 and Xmsx-1 failed to inhibit neurulation in the ectodermal explants to which the organizer mesoderm was attached. The results of cell-lineage tracing experiments indicated that the neural cells were differentiated from the animal pole tissue where the excess RNA of either BMP-4 or Xmsx-1 was injected, whereas notochord was differentiated from the organizer mesoderm. Neural tissue differentiated from BMP-4 -injected ectodermal cells strongly expressed posterior neural markers, such as hoxB9 and krox20, suggesting that the posterior neural cells differentiated regardless of the existence of the BMP signal. The introduction of a dominant-negative form of the fibroblast growth factor (FGF) receptor (XFD) into the ectodermal cells drastically reduced the expression of pan and posterior neural markers (N-CAM and hoxB-9) if co-injected with BMP-4 RNA, although XFD alone at the same dose did not shut down the expression of N-CAM in the combination explants. Therefore, it is proposed that an FGF-related molecule was involved in the direct induction of posterior neural tissue in the inducing signals from the organizer mesoderm in vivo. [source] bmp2b and bmp4 are dispensable for zebrafish tooth developmentDEVELOPMENTAL DYNAMICS, Issue 10 2010Sarah B. Wise Abstract Bone morphogenetic protein (Bmp) signaling has been shown to play important roles in tooth development at virtually all stages from initiation to hard tissue formation. The specific ligands involved in these processes have not been directly tested by loss-of-function experiments, however. We used morpholino antisense oligonucleotides and mutant analysis in the zebrafish to reduce or eliminate the function of bmp2b and bmp4, two ligands known to be expressed in zebrafish teeth and whose mammalian orthologs are thought to play important roles in tooth development. Surprisingly, we found that elimination of function of these two genes singly and in combination did not prevent the formation of mature, attached teeth. The mostly likely explanation for this result is functional redundancy with other Bmp ligands, which may differ between the zebrafish and the mouse. Developmental Dynamics 239:2534,2546, 2010. © 2010 Wiley-Liss, Inc. [source] Regionalized expression of ADAM13 during chicken embryonic developmentDEVELOPMENTAL DYNAMICS, Issue 3 2007Juntang Lin Abstract ADAMs are a family of membrane proteins possessing a disintegrin domain and a metalloprotease domain, which have functions in cell,cell adhesion, cell,matrix adhesion, and protein shedding, respectively. ADAMs are involved in morphogenesis and tissue formation during embryonic development. In the present study, chicken ADAM13 was cloned and identified, and its expression was investigated by semiquantitative reverse transcriptase-polymerase chain reaction and in situ hybridization during chicken embryonic development. Our results show that ADAM13 expression is temporally and spatially regulated in chicken embryos. At early developmental stages, ADAM13 is expressed in the head mesenchyme, which later develops into the craniofacial skeleton, in the branchial arches, and in the meninges surrounding the brain. Furthermore, ADAM13 mRNA was also detected in several tissues and organs, such as the somites and their derived muscles, the meninges surrounding the spinal cord, the dorsal aorta, the developing kidney, and several digestive organs. Developmental Dynamics 236:862,870, 2007. © 2007 Wiley-Liss, Inc. [source] Basolateral junctions are sufficient to suppress epithelial invasion during Drosophila oogenesisDEVELOPMENTAL DYNAMICS, Issue 2 2007Przemyslaw Szafranski Abstract Epithelial junctions play crucial roles during metazoan evolution and development by facilitating tissue formation, maintenance, and function. Little is known about the role of distinct types of junctions in controlling epithelial transformations leading to invasion of neighboring tissues. Discovering the key junction complexes that control these processes and how they function may also provide mechanistic insight into carcinoma cell invasion. Here, using the Drosophila ovary as a model, we show that four proteins of the basolateral junction (BLJ), Fasciclin-2, Neuroglian, Discs-large, and Lethal-giant-larvae, but not proteins of other epithelial junctions, directly suppress epithelial tumorigenesis and invasion. Remarkably, the expression pattern of Fasciclin-2 predicts which cells will invade. We compared the apicobasal polarity of BLJ tumor cells to border cells (BCs), an epithelium-derived cluster that normally migrates during mid-oogenesis. Both tumor cells and BCs differentiate a lateralized membrane pattern that is necessary but not sufficient for invasion. Independent of lateralization, derepression of motility pathways is also necessary, as indicated by a strong linear correlation between faster BC migration and an increased incidence of tumor invasion. However, without membrane lateralization, derepression of motility pathways is also not sufficient for invasion. Our results demonstrate that spatiotemporal patterns of basolateral junction activity directly suppress epithelial invasion by organizing the cooperative activity of distinct polarity and motility pathways. Developmental Dynamics 236:364,373, 2007. © 2006 Wiley-Liss, Inc. [source] Epigenetic dysregulation in cognitive disordersEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 1 2009Johannes Gräff Abstract Epigenetic mechanisms are not only essential for biological functions requiring stable molecular changes such as the establishment of cell identity and tissue formation, they also constitute dynamic intracellular processes for translating environmental stimuli into modifications in gene expression. Over the past decade it has become increasingly clear that both aspects of epigenetic mechanisms play a pivotal role in complex brain functions. Evidence from patients with neurodegenerative and neurodevelopmental disorders such as Alzheimer's disease and Rett syndrome indicated that epigenetic mechanisms and chromatin remodeling need to be tightly controlled for proper cognitive functions, and their dysregulation can have devastating consequences. However, because they are dynamic, epigenetic mechanisms are also potentially reversible and may provide powerful means for pharmacological intervention. This review outlines major cognitive disorders known to be associated with epigenetic dysregulation, and discusses the potential of ,epigenetic medicine' as a promising cure. [source] Micropatterned Polymer Surfaces and Cellular Response of Dictyostelium,ADVANCED ENGINEERING MATERIALS, Issue 5 2010Magdalena Eder Gecko inspired adhesives are surfaces with many microscale pillars that form Van der Waals forces with other surfaces. They differ from conventional tape in that adhesion is reversible and has the potential for switchability. These properties make gecko adhesives interesting for various biomedical applications. The two objectives of this project were to investigate the formation of biofilms on such surfaces and how the surfaces affect cell development. The developmental stages of the model organism Dictyostelium discoideum were observed by time lapse photography using light and environmental scanning electron microscopy. This study shows that micropatterned surfaces can be used as a biophysical tool to interfere with multicellular tissue formation in multiple ways. [source] Surgical treatment options for hidradenitis suppurativa and critical review of own experienceEXPERIMENTAL DERMATOLOGY, Issue 6 2006Wolfgang Christian Marsch HS (acne inversa) is a chronic, progressive, initially inflammatory, ultimately a fistulating and scarring disease affecting apocrine gland-bearing skin areas. Late phases afford a broad surgical removal of affected skin areas including subcutaneous fatty tissue, with secondary mesh grafting after a period of granulation tissue formation. Fifty-three patients have been treated surgically at our Dermatology Department. Long-term results are excellent concerning satisfaction of the patients and functional objectives. Local recurrences or development of new lesions in formerly unaffected areas were noticed only in some patients who did not stop smoking. Patient details were as follows: gender distribution: male (M) 20 (38%), female (F) 33 (62%), age: M 19,62 (average 40.7), F 15,56 (average 35.4), onset: M 16,57 (32.2), F 8,50 (25.5), duration: 3 months to 37 years (8.0), F 6 months to 37 years (9.9). Sites mainly affected: axillary and perigenital. Specific regions for men: perineum and rima ani, for women: inguinal, submammary and abdominal. Multiple anatomical regions involved: men 40%, women 91%. Familiarity 0.4%. Associated acne papulo-pustulosa or nodulo-cystica (=conglobata): 19%. Cigarette smokers: men 100%, women 67%. Excised material from each operation was carefully examined histologically. The results endorse the concept of ,acne inversa' by recognizing a perifollicular accumulation of lymphocytes simultaneously at different infrainfundibula of terminal hair follicles. However, a follicular hyperkeratosis seems secondary to this, follicular perforation, and a combination of sinus, abscess and scar formation are most obviously tertiary events. Therefore, HS seems to be an inflammatory, probably an immunological disease with an initially strictly dermal target, even followed by an intradermal horizontal propagation. Laser flux imaging could visualize the subclinical peripheral extension of the basically dermal perifollicular inflammation. Biologics may have a beneficial effect on these early or perpetuating inflammatory events; however, thus far surgery remains the first-line therapy in late phases of the disease. [source] Porous Structures: In situ Porous Structures: A Unique Polymer Erosion Mechanism in Biodegradable Dipeptide-Based Polyphosphazene and Polyester Blends Producing Matrices for Regenerative Engineering (Adv. Funct.ADVANCED FUNCTIONAL MATERIALS, Issue 17 2010Mater. Abstract Synthetic biodegradable polymers serve as temporary substrates that accommodate cell infiltration and tissue in-growth in regenerative medicine. To allow tissue in-growth and nutrient transport, traditional three-dimensional (3D) scaffolds must be prefabricated with an interconnected porous structure. Here we demonstrated for the first time a unique polymer erosion process through which polymer matrices evolve from a solid coherent film to an assemblage of microspheres with an interconnected 3D porous structure. This polymer system was developed on the highly versatile platform of polyphosphazene-polyester blends. Co-substituting a polyphosphazene backbone with both hydrophilic glycylglycine dipeptide and hydrophobic 4-phenylphenoxy group generated a polymer with strong hydrogen bonding capacity. Rapid hydrolysis of the polyester component permitted the formation of 3D void space filled with self-assembled polyphosphazene spheres. Characterization of such self-assembled porous structures revealed macropores (10,100 ,m) between spheres as well as micro- and nanopores on the sphere surface. A similar degradation pattern was confirmed in vivo using a rat subcutaneous implantation model. 12 weeks of implantation resulted in an interconnected porous structure with 82,87% porosity. Cell infiltration and collagen tissue in-growth between microspheres observed by histology confirmed the formation of an in situ 3D interconnected porous structure. It was determined that the in situ porous structure resulted from unique hydrogen bonding in the blend promoting a three-stage degradation mechanism. The robust tissue in-growth of this dynamic pore forming scaffold attests to the utility of this system as a new strategy in regenerative medicine for developing solid matrices that balance degradation with tissue formation. [source] In situ Porous Structures: A Unique Polymer Erosion Mechanism in Biodegradable Dipeptide-Based Polyphosphazene and Polyester Blends Producing Matrices for Regenerative EngineeringADVANCED FUNCTIONAL MATERIALS, Issue 17 2010Meng Deng Abstract Synthetic biodegradable polymers serve as temporary substrates that accommodate cell infiltration and tissue in-growth in regenerative medicine. To allow tissue in-growth and nutrient transport, traditional three-dimensional (3D) scaffolds must be prefabricated with an interconnected porous structure. Here a unique polymer erosion process through which polymer matrices evolve from a solid coherent film to an assemblage of microspheres with an interconnected 3D porous structure is demonstrated for the first time. This polymer system is developed on the highly versatile platform of polyphosphazene-polyester blends. Co-substituting a polyphosphazene backbone with both hydrophilic glycylglycine dipeptide and hydrophobic 4-phenylphenoxy group generates a polymer with strong hydrogen bonding capacity. Rapid hydrolysis of the polyester component permits the formation of 3D void space filled with self-assembled polyphosphazene spheres. Characterization of such self-assembled porous structures reveals macropores (10,100 ,m) between spheres as well as micro- and nanopores on the sphere surface. A similar degradation pattern is confirmed In vivo using a rat subcutaneous implantation model. 12 weeks of implantation results in an interconnected porous structure with 82,87% porosity. Cell infiltration and collagen tissue in-growth between microspheres observed by histology confirms the formation of an in situ 3D interconnected porous structure. It is determined that the in situ porous structure results from unique hydrogen bonding in the blend promoting a three-stage degradation mechanism. The robust tissue in-growth of this dynamic pore forming scaffold attests to the utility of this system as a new strategy in regenerative medicine for developing solid matrices that balance degradation with tissue formation. [source] The Implications of Polymer Selection in Regenerative Medicine: A Comparison of Amorphous and Semi-Crystalline Polymer for Tissue RegenerationADVANCED FUNCTIONAL MATERIALS, Issue 9 2009Michelle D. Kofron Abstract Biodegradable polymeric scaffolds are being investigated as scaffolding materials for use in regenerative medicine. While the in vivo evaluation of various three-dimensional (3D), porous, biodegradable polymeric scaffolds has been reported, most studies are ,3 months in duration, which is typically prior to bulk polymer degradation, a critical event that may initiate an inflammatory response and inhibit tissue formation. Here, a 6,month in vitro degradation and corresponding in vivo studies that characterized scaffold changes during complete degradation of an amorphous, 3D poly(lactide- co -glycolide)(3D-PLAGA) scaffold and near-complete degradation of a semi-crystalline3D-PLAGA scaffold are reported. Using sintered microsphere matrix technology, constructs were fabricated in a tubular shape, with the longitudinal axis void and a median pore size that mimicked the architecture of native bone. Long-term quantitative measurements of molecular weight, mechanical properties, and porosity provided a basis for theorization of the scaffold degradation process. Following implantation in a critical size ulnar defect model, histological analysis and quantitative microCT indicated early solubilization of the semi-crystalline polymer created an acidic microenvironment that inhibited mineralized tissue formation. Thus, the use of amorphous over semi-crystalline PLAGA materials is advocated for applications in regenerative medicine. [source] Nanostructured Biomaterials for Regeneration,ADVANCED FUNCTIONAL MATERIALS, Issue 22 2008Guobao Wei Abstract Biomaterials play a pivotal role in regenerative medicine, which aims to regenerate and replace lost/dysfunctional tissues or organs. Biomaterials (scaffolds) serve as temporary 3D substrates to guide neo tissue formation and organization. It is often beneficial for a scaffolding material to mimic the characteristics of extracellular matrix (ECM) at the nanometer scale and to induce certain natural developmental or/and wound healing processes for tissue regeneration applications. This article reviews the fabrication and modification technologies for nanofibrous, nanocomposite, and nanostructured drug-delivering scaffolds. ECM-mimicking nanostructured biomaterials have been shown to actively regulate cellular responses including attachment, proliferation, differentiation, and matrix deposition. Nanoscaled drug delivery systems can be successfully incorporated into a porous 3D scaffold to enhance the tissue regeneration capacity. In conclusion, nanostructured biomateials are a very exciting and rapidly expanding research area, and are providing new enabling technologies for regenerative medicine. [source] Frequency distribution of a Cys430Ser polymorphism in peroxisome proliferator-activated receptor-gamma coactivator-1 (PPARGC1) gene sequence in Chinese and Western pig breedsJOURNAL OF ANIMAL BREEDING AND GENETICS, Issue 1 2005T. Kunej Summary Identification of major genes, that genetically impact fat tissue formation is important for successful selection of lean animals with good meat quality. Because of its central role in fat cell differentiation and muscle fibre type determination, PPARGC1 is a potential candidate gene affecting fattening traits and pig meat quality. In this study, a T/A substitution at position 1378 (GenBank accession no. AY346131) in the porcine PPARGC1 gene causing a Cys430Ser amino acid substitution at position 430 was genotyped on a total of 239 animals, including 101 from seven Chinese and 138 from six Western pig breeds. Bayesian analysis revealed that the mean frequency of allele T (Cys) was 92.64 ± 4.82% in Chinese pigs, and 45.99 ± 4.13% in Western pigs. The 95% interval of the posterior mean frequency of allele T was 0.82,1.00 in Chinese pigs and 0.38,0.54 in Western pigs, indicating these two groups of pigs diverged at this locus during genetic evolution of the breed. Because marked differences in fat and lean tissue deposition exist between Western and Chinese pig breeds, this Cys430Ser exchange in the PPARGC1 gene deserves further evaluation to determine its phenotypic effect on fattening and carcass traits in commercial pig populations. [source] A forward genetic screen for genes regulating mineralized tooth and bone formation in zebrafish (Danio rerio)JOURNAL OF APPLIED ICHTHYOLOGY, Issue 2 2010P. C. Yelick Summary Our laboratory studies craniofacial skeletal and tooth regeneration. One approach we are using is to exploit the zebrafish model via a large-scale, forward genetic, chemical N-ethyl-nitroso-urea (ENU) mutagenesis screen to identify genes regulating mineralized craniofacial, axial and dental development. The fact that zebrafish continuously regenerate their teeth makes them an extremely useful model to study tooth regeneration. Our goal is to identify and characterize molecular genetic signaling pathways regulating these processes, which can be manipulated via targeted gene delivery strategies. Through these efforts, we hope to eventually define methods for effective, clinically relevant bone and tooth replacement therapies in humans. Here, we describe our studies using the zebrafish model, which are proving to be useful for the identification and characterization of genes regulating mineralized tissue formation, regeneration, and homeostasis. Although preliminary at the present time, we anticipate the elucidation of novel signaling pathways regulating bone and tooth regeneration, which will eventually facilitate the repair of human skeletal and dental dysplasias. [source] Modulation of peritendinous adhesion formation by alginate solution in a rabbit flexor tendon modelJOURNAL OF BIOMEDICAL MATERIALS RESEARCH, Issue 1 2007Jiro Namba Abstract To examine the antiadhesive effect of an alginate solution following tendon surgery, unilateral subtotal laceration of the flexor digitorum communis tendon was created in one hind limb while the other side was left intact in 32 Japanese white rabbits. The lesion was coated with alginate solution in 16 animals and not coated in the other 16. Degree of adhesion formation was assessed histologically and biomechanically by measuring the flexion angle of the first toe when the flexor digitorum tendon was pulled with a specified force at 4 weeks postoperatively. When compared with the control group, the alginate-treated group demonstrated significantly greater toe flexion, with less scar tissue formation at the repair site. Histologically, complete tendon healing with longitudinal remodeling of collagen fibers was observed in the alginate-treated group, while a random pattern of fibers was observed in the control group. Reduction in adhesion formation using alginate solution represents a novel strategy for the management of tendon injury and repair in the clinical setting. © 2006 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2007 [source] Shock Wave Application Enhances Pertussis Toxin Protein-Sensitive Bone Formation of Segmental Femoral Defect in Rats,JOURNAL OF BONE AND MINERAL RESEARCH, Issue 12 2003Yeung-Jen Chen Abstract Extracorporeal shock waves (ESWs) elicit a dose-dependent effect on the healing of segmental femoral defects in rats. After ESW treatment, the segmental defect underwent progressive mesenchymal aggregation, endochondral ossification, and hard callus formation. Along with the intensive bone formation, there was a persistent increase in TGF-,1 and BMP-2 expression. Pretreatment with pertussis toxin reduced ESW-promoted callus formation and gap healing, which presumably suggests that Gi proteins mediate osteogenic signaling. Introduction: Extracorporeal shock waves (ESWs) have previously been used to promote bone repair. In our previous report, we found that ESWs promoted osteogenic differentiation of mesenchymal cells through membrane perturbation and activation of Ras protein. In this report, we show that ESWs elicit a dose-dependent effect on the healing of segmental defects and that Gi proteins play an important role in mediating ESW stimulation. Materials and Methods: Rats with segmental femoral defects were subjected to ESW treatment at different energy flux densities (EFD) and impulses. Bone mass (mineral density and calcium content), osteogenic activities (bone alkaline phosphatase activity and osteocalcin content), and immunohistochemistry were assessed. Results: An optimal ESW energy (500 impulses at 0.16 mJ/mm2 EFD) stimulated complete bone healing without complications. ESW-augmented healing was characterized by significant increases (p < 0.01) in callus size, bone mineral density, and bone tissue formation. With exposure to ESW, alkaline phosphatase activity and osteocalcin production in calluses were found to be significantly enhanced (p < 0.05). After ESW treatment, the histological changes we noted included progressive mesenchymal aggregation, endochondral ossification, and hard callus formation. Intensive bone formation was associated with a persistent increase in transforming growth factor-beta 1 (TGF-,1) and bone morphogenetic protein-2 (BMP-2) expression, suggesting both growth factors were active in ESW-promoted bone formation. We also found that pertussis toxin, an inhibitor of membrane-bound Gi proteins, significantly reduced (p < 0.01) ESW promotion of callus formation and fracture healing. Conclusion: ESW treatments enhanced bone formation and the healing of segmental femoral defects in rats. It also seems likely that TGF-,1 and BMP-2 are important osteogenic factors for ESW promotion of fracture healing, presumably through Gi protein-mediated osteogenic signaling. [source] Evaluation of blood vessel ingrowth in fibrin gel subject to type and concentration of growth factorsJOURNAL OF CELLULAR AND MOLECULAR MEDICINE, Issue 9a 2009A. Arkudas Abstract Our aim was to quantitatively assess the angiogenetic effects of VEGF and bFGF immobilized in a fibrin-based drug delivery system in a suitable subcutaneous rat model. After evaluation of a suitable implantation technique (6 rats), four teflon isolation chambers containing fibrin gel matrices were implanted subcutaneously in an upside-down fashion on the back of 30 Lewis rats. The matrices consisted of 500 ,l fibrin gel with two different fibrinogen concentrations (10 mg/ml or 40 mg/ml fibrinogen) and 2 I.U./ml thrombin and contained VEGF and bFGF in five different concentrations (0 to 250 ng/ml each). At 3, 7 and 14 days after implantation, matrices were explanted and subjected to histological and morphometrical analysis. At 1 week, the volume of the fibrin clots was significantly smaller in the 100 and 250 ng/ml VEGF and bFGF groups in comparison to lower concentrated growth factors. At 1 and 2 weeks, the use of growth factors in low concentrations (25 ng/ml VEGF and bFGF) significantly increased the amount of fibrovascular tissue, average fraction of blood vessels and number of blood vessels at the matrix,host interface in comparison to growth factor-free controls. Higher concentrations were neither associated with further increase of tissue formation nor with increased sprouting of blood vessels in this model. This study demonstrates that fibrin gel-immobilized angioinductive growth factors efficiently stimulate generation of fibrovascular tissue and sprouting of blood vessels in a newly developed subcutaneous upside-down isolation chamber model with an optimum between 25 and 100 ng/ml. [source] Classically and alternatively activated macrophages contribute to tissue remodelling after myocardial infarctionJOURNAL OF CELLULAR AND MOLECULAR MEDICINE, Issue 9b 2009C. Troidl Abstract An important goal in cardiology is to minimize myocardial necrosis and to support a discrete but resilient scar formation after myocardial infarction (MI). Macrophages are a type of cells that influence cardiac remodelling during MI. Therefore, the goal of the present study was to investigate their transcriptional profile and to identify the type of activation during scar tissue formation. Ligature of the left anterior descending coronary artery was performed in mice. Macrophages were isolated from infarcted tissue using magnetic cell sorting after 5 days. The total RNA of macrophages was subjected to microarray analysis and compared with RNA from MI and LV-control. mRNA abundance of relevant targets was validated by quantitative real-time PCR 2, 5 and 10 days after MI (qRT-PCR). Immunohistochemistry was performed to localize activation type-specific proteins. The genome scan revealed 68 targets predominantly expressed by macrophages after MI. Among these targets, an increased mRNA abundance of genes, involved in both the classically (tumour necrosis factor ,, interleukin 6, interleukin 1,) and the alternatively (arginase 1 and 2, mannose receptor C type 1, chitinase 3-like 3) activated phenotype of macrophages, was found 5 days after MI. This observation was confirmed by qRT-PCR. Using immunohistochemistry, we confirmed that tumour necrosis factor ,, representing the classical activation, is strongly transcribed early after ligature (2 days). It was decreased after 5 and 10 days. Five days after MI, we found a fundamental change towards alternative activation of macrophages with up-regulation of arginase 1. Our results demonstrate that macrophages are differentially activated during different phases of scar tissue formation after MI. During the early inflammatory phase, macrophages are predominantly classically activated, whereas their phenotype changes during the important transition from inflammation to scar tissue formation into an alternatively activated type. [source] Embryonic undifferentiated cells show scattering activity on a surface coated with immobilized E-cadherinJOURNAL OF CELLULAR BIOCHEMISTRY, Issue 1 2008Masato Nagaoka Abstract Rearrangement of cell,cell adhesion is a critical event in embryonic development and tissue formation. We investigated the regulatory function of E-cadherin, a key adhesion protein, in the developmental process by using E-cadherin/IgG Fc fusion protein as an adhesion matrix in cell culture. F9 embryonal carcinoma cells usually form colonies when cultured on gelatin or fibronectin matrices. However, F9 cells cultured on the E-cadherin/IgG Fc fusion protein matrix formed a scattered distribution, with a different cytoskeletal organization and E-cadherin-rich protrusions that were regulated by Rac1 activity. The same scattering activity was observed in P19 embryonal carcinoma cells. In contrast, three types of differentiated cells, NMuMG mammary gland cells, MDCK kidney epithelial cells, and mouse primary isolated hepatocytes, did not show the scattering activity observed in F9 and P19 cells. These results suggest that migratory behavior on an E-cadherin-immobilized surface is only observed in embryonic cells, and that the regulatory mechanisms underlying E-cadherin-mediated cell adhesion vary with the state of differentiation. J. Cell. Biochem. 103: 296,310, 2008. © 2007 Wiley-Liss, Inc. [source] Biological mediators and periodontal regeneration: a review of enamel matrix proteins at the cellular and molecular levelsJOURNAL OF CLINICAL PERIODONTOLOGY, Issue 2008Dieter D. Bosshardt Abstract Background: Despite a large body of clinical and histological data demonstrating beneficial effects of enamel matrix proteins (EMPs) for regenerative periodontal therapy, it is less clear how the available biological data can explain the mechanisms underlying the supportive effects of EMPs. Objective: To analyse all available biological data of EMPs at the cellular and molecular levels that are relevant in the context of periodontal wound healing and tissue formation. Methods: A stringent systematic approach was applied using the key words "enamel matrix proteins" OR "enamel matrix derivative" OR "emdogain" OR "amelogenin". The literature search was performed separately for epithelial cells, gingival fibroblasts, periodontal ligament cells, cementoblasts, osteogenic/chondrogenic/bone marrow cells, wound healing, and bacteria. Results: A total of 103 papers met the inclusion criteria. EMPs affect many different cell types. Overall, the available data show that EMPs have effects on: (1) cell attachment, spreading, and chemotaxis; (2) cell proliferation and survival; (3) expression of transcription factors; (4) expression of growth factors, cytokines, extracellular matrix constituents, and other macromolecules; and (5) expression of molecules involved in the regulation of bone remodelling. Conclusion: All together, the data analysis provides strong evidence for EMPs to support wound healing and new periodontal tissue formation. [source] Bone formation at rhBMP-2-coated titanium implants in the rat ectopic modelJOURNAL OF CLINICAL PERIODONTOLOGY, Issue 5 2007Jan Hall Abstract Background: The objective of this study was to evaluate local bone formation at titanium porous oxide (TPO) implant surfaces adsorbed with recombinant human bone morphogenetic protein-2 (rhBMP-2). Methods: In vitro studies were used to estimate the kinetics of I125 -labeled rhBMP-2 released from TPO surfaces with narrow (N) or open (O) pores. Machined/turned titanium (MT) surfaces served as control. The rat ectopic model was used to assess local bone formation. Briefly, TPO-N, TPO-O, and MT disc implants adsorbed with 5, 10, or 20 ,g rhBMP-2, respectively, were implanted subcutaneously into the ventral thoracic region in 5-week-old male Long Evans rats. The animals were euthanized at day 14 postsurgery when implants with surrounding tissues were removed, radiographed, and gross observations recorded. The specimens were processed for histologic evaluation using conventional cut-and-grind techniques. TPO implants without rhBMP-2 included in a preliminary evaluation revealed no evidence of bone formation, tissue encapsulation, or vascularity, thus such controls were not further used. Results: TPO and MT implant surfaces adsorbed with 5 ,g rhBMP-2 retained 2.3,5.4% rhBMP-2 following immersion and rinse in buffer, and 1.1,2.2% rhBMP-2 following repeated immersions and rinses over 27 days. TPO implants retained the most rhBMP-2 and MT implants retained the least. Explants revealed increased hard tissue formation, tissue encapsulation, and vascularity at TPO compared with MT implants. Radiographic observations were consistent with the explant observations. The histologic analysis showed greater amounts of bone formation, osteoblastic cells, osteoid, marrow, tissue encapsulation, vascularity, and bone voids for implants adsorbed with 10 and 20 ,g rhBMP-2, and for TPO implants at the 5- ,g rhBMP-2 dose. The histometric analysis revealed significantly greater bone formation at TPO-O than at MT implants at the 5- ,g rhBMP-2 dose. All surfaces showed significant bone formation at the 10- and 20- ,g dose. Conclusions: rhBMP-2 adsorbed onto TPO implant surfaces executes an osteoinductive effect including bone contacting the implant surface. This effect is surface- and dose-dependent; the TPO-O surface yielding the most bone at the low discriminating rhBMP-2 dose. [source] Improved bioengineered cartilage tissue formation following cyclic compression is dependent on upregulation of MT1-MMPJOURNAL OF ORTHOPAEDIC RESEARCH, Issue 7 2010J. N. Amrith De Croos Abstract The generation of bioengineered cartilage tissue suitable for transplantation is a potential therapy to treat damaged cartilage. We have shown previously that the physical and biomechanical properties of bioengineered cartilage can be improved by the application of 30,min of cyclic compression by a mechanism involving sequential upregulation of gene and protein levels of membrane type-1 matrix metalloproteinase (MT1-MMP) and MMP-13. In the current study, we demonstrated that MT1-MMP is critical to this response, as blocking the upregulation of MT1-MMP prevented the improvement in tissue formation. MT1-MMP seems to act by inducing tissue remodeling as evidenced by the presence of aggrecan degradation products by Western blot analysis and increased release of matrix molecules into the media. Release of these molecules was diminished when MT1-MMP upregulation was prevented. This matrix degradation was likely due to MT1-MMP, as under conditions where MMP-13 expression is maintained (stimulation in the presence of MT1-MMP siRNA) the release of these matrix molecules into the media was still prevented. It also appears that MT1-MMP does not regulate MMP-13 gene expression, as MT1-MMP-siRNA pretreatment had no effect on MMP-13 expression following mechanical stimulation. Further analysis of the anabolic genes and proteins involved in mechanically stimulated cartilage will lead to better understanding of the mechanism(s) underlying tissue formation yielding improved bioengineered cartilage. © 2010 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 28:921,927, 2010 [source] Formation of cartilage repair tissue in articular cartilage defects pretreated with microfracture and covered with cell-free polymer-based implants,JOURNAL OF ORTHOPAEDIC RESEARCH, Issue 10 2009Christoph Erggelet Abstract The aim of our study was to evaluate the mid-term outcome of a cell-free polymer-based cartilage repair approach in a sheep cartilage defect model in comparison to microfracture treatment. Cell-free, freeze-dried implants (chondrotissue®) made of a poly-glycolic acid (PGA) scaffold and hyaluronan were immersed in autologous serum and used for covering microfractured full-thickness articular cartilage defects of the sheep (n,=,4). Defects treated with microfracture only served as controls (n,=,4). Six months after implantation, cartilage implants and controls were analyzed by immunohistochemical staining of type II collagen, histological staining of proteoglycans, and histological scoring. Histological analysis showed the formation of a cartilaginous repair tissue rich in proteoglycans. Histological scoring documented significant improvement of repair tissue formation when the defects were covered with the cell-free implant, compared to controls treated with microfracture. Immunohistochemistry showed that the cell-free implant induced cartilaginous repair tissue and type II collagen. Controls treated with microfracture showed marginal formation of a mixed-type repair tissue consisting of cartilaginous tissue and fibro-cartilage. Covering of microfractured defects with the cell-free polymer-based cartilage implant is suggested to be a promising treatment option for cartilage defects and improves the regeneration of articular cartilage. © 2009 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 27:1353,1360, 2009 [source] The effect of oxygen tension on the in vitro assay of human osteoblastic connective tissue progenitor cellsJOURNAL OF ORTHOPAEDIC RESEARCH, Issue 10 2008Sandra M. Villarruel Abstract Connective tissue progenitors (CTPs) are defined as the heterogeneous set of stem and progenitor cells that reside in native tissues and are capable of proliferation and differentiation into one or more connective tissue phenotypes. CTPs play important roles in tissue formation, repair, and remodeling. Therefore, in vitro assays of CTP prevalence and biological potential have important scientific and clinical relevance. This study evaluated oxygen tension as an important variable in optimizing in vitro conditions for quantitative assays of human CTPs. Bone marrow aspirates were collected from 20 human subjects and cultured using established medium conditions at ambient oxygen tensions of 1, 5, 10, and 20%. Colony-forming efficiency (CFE), proliferation, and colony density were assessed. CFE and proliferation were greatest at 5% O2. Traditional conditions using atmospheric oxygen tension (20% O2) reduced CFE by as much as 32%. CFE and proliferation at 1% O2 were less than 5% O2 but comparable to that seen at 20% O2, suggesting that CTPs are relatively resilient under hypoxic conditions, a fact that may be relevant to their function in wound repair and their potential use in tissue engineering applications involving transplantation into settings of moderate to severe hypoxia. These data demonstrate that optimization of quantitative assays for CTPs will require control of oxygen tension. © 2008 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 26:1390,1397, 2008 [source] Interleukin-1 modulates periprosthetic tissue formation in an intramedullary model of particle-induced inflammationJOURNAL OF ORTHOPAEDIC RESEARCH, Issue 3 2005Noah J. Epstein Abstract Interleukin-1 (IL-1) is a proinflammatory cytokine that has been implicated in wear-debris associated total joint replacement failure. We hypothesized that the absence of the IL-1 type-1 receptor would mitigate the inflammatory response to titanium particles and decrease periprosthetic inflammatory tissue in a murine intramedullary rod model. Methods: An intramedullary rod with and without commercially pure titanium particles was placed in the femora of 24 wild type mice (WT) and 24 mice lacking a functional type-1 receptor to IL-1. Femora were analyzed histologically and by ELISA of organ culture explant supernatants. Results: The presence of titanium particles in WT mice stimulated increased expression of interleukin-6 (IL-6) and macrophage chemoattractant protein-1 (MCP-1) relative to rod only controls. In contrast, IL-6 and MCP-1 expression were diminished in IL-lrl-KO mice exposed to titanium particles. Additionally, the formation of a periprosthetic fibro-inflammatory membrane in IL-lrl-KO mice was blunted at 2 weeks when compared to that in wild-type mice. Inflammatory changes and the quality of periprosthetic bone of IL-lrl-KO mice was similar to WT mice in response to titanium particles. Conclusions: These results implicate IL-1 as an important modulator in the local inflammatory response to intramedullary titanium particles. MCP-1 appears to be significantly modulated in IL-lrl-KO mice in response to titanium particles. This may be responsible, in part, for the diminished periprosthetic membrane observed in IL-lrl-KO mice at 2 weeks. Expansion of this murine model of intramedullary particle-induced inflammation to other gene targets may contribute to a more mechanistic understanding of wear-debris associated prosthesis failure. © 2004 Orthopaedic Research Society. Published by Elsevier Ltd. All rights reserved. [source] Creep dominates tensile fatigue damage of the cement,bone interfaceJOURNAL OF ORTHOPAEDIC RESEARCH, Issue 3 2004Do-Gyoon Kim Abstract Fatigue damage from activities of daily living has been considered to be a major cause of aseptic loosening in cemented total hip arthroplasty. The cement,bone interface is one region where loosening could occur, but to date the fatigue response of the interface has not been examined. Cement,bone specimens were prepared from fresh frozen human cadaver tissue using simulated in vivo conditions. Tensile fatigue tests to failure were performed in an environmental chamber. Loss of specimen stiffness (stiffness damage) and permanent displacement after unloading (creep damage) were found in all specimens. At failure, creep damage accounted for the majority (79.9 ± 10.6%) of the total strain damage accumulation at failure (apparent strain, , = 0.0114 ± 0.00488). A power law relationship between strain-damage rate and time-to-failure showed that the strain-damage rate was an excellent predictor of the fatigue life of the cement,bone interface. The S,N response of the interface was obtained as a function of the applied stress ratio and the initial apparent strain. The total motion between cement and bone (72.2 ± 29.8 ,m) prior to incipient failure due to both stiffness and creep fatigue damage may be sufficient to result in fibrous tissue formation and contribute to eventual clinical loosening. © 2004 Orthopaedic Research Society. Published by Elsevier Ltd. All rights reserved. [source] Acceleration of cartilage repair by genetically modified chondrocytes over expressing bone morphogenetic protein-7JOURNAL OF ORTHOPAEDIC RESEARCH, Issue 4 2003Chisa Hidaka Background: Cartilage has a limited capacity to heal. Although chondrocyte transplantation is a useful therapeutic strategy, the repair process can be lengthy. Previously we have shown that over expression of bone morphogenetic protein-7 (BMP-7) in chondrocytes by adenovirus-mediated gene transfer leads to increased matrix synthesis and cartilage-like tissue formation in vitro. In this context we hypothesized that implantation of genetically modified chondrocytes expressing BMP-7 would accelerate the formation of hyaline-like repair tissue in an equine model of cartilage defect repair. Methods: Chondrocytes treated with adenovirus vector encoding BMP-7 (AdBMP-7) or as control, an adenovirus vector encoding an irrelevant gene (Escherichia coli cytosine deaminase, AdCD) were implanted into extensive (15 mm diameter) articular cartilage defects in the patellofemoral joints of 10 horses. Biopsies were performed to evaluate early healing at 4 weeks. At the terminal time point of 8 months, repairs were assessed for morphology, MRI appearance, compressive strength, biochemical composition and persistence of implanted cells. Results: Four weeks after surgery AdBMP-7-treated repairs showed an increased level of BMP-7 expression and accelerated healing, with markedly more hyaline-like morphology than control. Quantitative real-time polymerase chain reaction (PCR) analysis of the repair tissue 8 months after surgery showed that few implanted cells persisted. By this time, the controls had healed similarly to the AdBMP-7-treated defects, and no difference was detected in the morphologic, biochemical or biomechanical properties of the repair tissues from the two treatment groups. Conclusions: Implantation of genetically modified chondrocytes expressing BMP-7 accelerates the appearance of hyaline-like repair tissue in experimental cartilage defects. Clinical relevance: Rehabilitation after cell-based cartilage repair can be prolonged, leading to decreased patient productivity and quality of life. This study shows the feasibility of using genetically modified chondrocytes to accelerate cartilage healing. © 2003 Orthopaedic Research Society. Published by Elsevier Science Ltd. All rights reserved. [source] The initial phase of fracture healing is specifically sensitive to mechanical conditionsJOURNAL OF ORTHOPAEDIC RESEARCH, Issue 4 2003Petra Klein Abstract Interfragmentary movements affect the quality and quantity of callus formation. The mounting plane of monolateral external fixators may give direction to those movements. Therefore, the aim of this study was to determine the influence of the fixator mounting plane on the process of fracture healing. Identically configured fixators were mounted either medially or anteromedially on the tibiae of sheep. Interfragmentary movements and ground reaction forces were evaluated in vivo during a nine week period. Histomorphological and biomechanical parameters described the bone healing processes. Changing only the mounting plane led to a modification of interfragmentary movements in the initial healing phase. The difference in interfragmentary movements between the groups was only significant during the first post-operative period. However, these initial differences in mechanical conditions influenced callus tissue formation significantly. The group with the anteromedially mounted fixator, initially showing significantly more interfragmentary movements, ended up with a significantly smaller callus diameter and a significantly higher callus stiffness as a result of advanced fracture healing. This demonstrates that the initial phase of healing is sensitive to mechanical conditions and influences the course of healing. Therefore, initial mechanical stability of an osteosynthesis should be considered an important factor in clinical fracture treatment. © 2003 Orthopaedic Research Society. Published by Elsevier Science Ltd. All rights reserved. [source] Induction of a neoarthrosis by precisely controlled motion in an experimental mid-femoral defectJOURNAL OF ORTHOPAEDIC RESEARCH, Issue 3 2002Dennis M. Cullinane Bone regeneration during fracture healing has been demonstrated repeatedly, yet the regeneration of articular cartilage and joints has not yet been achieved. It has been recognized however that the mechanical environment during fracture healing can be correlated to the contributions of either the endochondral or intramembranous processes of bone formation, and to resultant tissue architecture. Using this information, the goal of this study was to test the hypothesis that induced motion can directly regulate osteogenic and chondrogenic tissue formation in a rat mid-femoral bone defect and thereby influence the anatomical result. Sixteen male Sprague Dawley rats (400 ± 20 g) underwent production of a mid-diaphyseal, non-critical sized 3.0 mm segmental femoral defect with rigid external fixation using a custom designed four pin fixator. One group of eight animals represented the controls and underwent surgery and constant rigid fixation. In the treatment group the custom external fixator was used to introduce daily interfragmentary bending strain in the eight treatment animals (12°s angular excursion), with a hypothetical symmetrical bending load centered within the gap. The eight animals in the treatment group received motion at 1.0 Hz, for 10 min a day, with a 3 days on, one day off loading protocol for the first two weeks, and 2 days on, one day off for the remaining three weeks. Data collection included histological and immunohistological identification of tissue types, and mean collagen fiber angles and angular conformity between individual fibers in superficial, intermediate, and deep zones within the cartilage. These parameters were compared between the treatment group, rat knee articular cartilage, and the control group as a structural outcome assessment. After 35 days the control animals demonstrated varying degrees of osseous union of the defect with some animals showing partial union. In every individual within the mechanical treatment group the defect completely failed to unite. Bony arcades developed in the experimental group, capping the termini of the bone segments on both sides of the defect in four out of six animals completing the study. These new structures were typically covered with cartilage, as identified by specific histological staining for Type II collagen and proteoglycans. The distribution of collagen within analogous superficial, intermediate, and deep zones of the newly formed cartilage tissue demonstrated preferred fiber angles consistent with those seen in articular cartilage. Although not resulting in complete joint development, these neoarthroses show that the induced motion selectively controlled the formation of cartilage and bone during fracture repair, and that it can be specifically directed. They further demonstrate that the spatial organization of molecular components within the newly formed tissue, at both microanatomical and gross levels, are influenced by their local mechanical environment, confirming previous theoretical models. © 2002 Orthopaedic Research Society. Published by Elsevier Science Ltd. All rights reserved. [source] | |||||||||||||||||||