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Matrix Vesicles (matrix + vesicle)

Distribution by Scientific Domains
Medical Sciences80%

Selected Abstracts

Functional Differences Between Growth Plate Apoptotic Bodies and Matrix Vesicles,

JOURNAL OF BONE AND MINERAL RESEARCH, Issue 10 2003
Thorsten Kirsch
Abstract Mineralization often occurs in areas of apoptotic changes. Our findings indicate that physiological mineralization is mediated by matrix vesicles. These matrix vesicles use mechanisms to induce mineralization that are different from the mechanisms used by apoptotic bodies released from apoptotic cells. Therefore, different therapeutic approaches must be chosen to inhibit pathological mineralization depending on the mechanism of mineralization (matrix vesicles versus apoptotic bodies). Introduction: Physiological mineralization in growth plate cartilage is restricted to regions of terminally differentiated and apoptotic chondrocytes. Pathological mineralization of tissues also often occurs in areas of apoptosis. We addressed the question of whether apoptotic changes control mineralization events or whether both events are regulated independently. Methods: To induce mineralization, we treated growth plate chondrocytes with retinoic acid (RA); apoptosis in these cells was induced by treatment with staurosporine, anti-Fas, or TNF,. The degrees of mineralization and apoptosis were determined, and the structure and function of matrix vesicles and apoptotic bodies were compared. Results: Release of matrix vesicles and mineralization in vivo in the growth plate occurs earlier than do apoptotic changes. To determine the functional relationship between apoptotic bodies and matrix vesicles, growth plate chondrocytes were treated with RA to induce matrix vesicle release and with staurosporine to induce release of apoptotic bodies. After 3 days, approximately 90% of staurosporine-treated chondrocytes were apoptotic, whereas only 2,4 % of RA-treated cells showed apoptotic changes. RA- and staurosporine-treated chondrocyte cultures were mineralized after 3 days. Matrix vesicles isolated from RA-treated cultures and apoptotic bodies isolated from staurosporine-treated cultures were associated with calcium and phosphate. However, matrix vesicles were bigger than apoptotic bodies. Furthermore, matrix vesicles but not apoptotic bodies contained alkaline phosphatase and Ca2+ channel-forming annexins II, V, and VI. Consequently, matrix vesicles but not apoptotic bodies were able to take up Ca2+ and form the first mineral phase inside their lumen. Mineralization of RA-treated cultures was inhibited by antibodies specific for annexin V but not mineralization of staurosporine-treated cultures. Conclusion: Physiological mineralization of growth plate chondrocytes is initiated by specialized matrix vesicles and requires alkaline phosphatase and annexins. In contrast, mineral formation mediated by apoptotic bodies occurs by a default mechanism and does not require alkaline phosphatase and annexins. [source]

Study of the Structure of Canine Mesenchymal Stem Cell Osteogenic Culture

ANATOMIA, HISTOLOGIA, EMBRYOLOGIA, Issue 5 2010
M. B. Eslaminejad
With 6 figures and 1 table Summary This study was designed to investigate the morphological features of osteogenic cultures that were established from canine marrow derived-mesenchymal stem cells (MSCs). Tripotent canine MSCs were plated in osteogenic conditions for 3 weeks, at the end of which the cultures were observed by light and transmission electron microscopy. Alkaline phosphatase (ALP) activity of the culture was determined during the differentiation period. To assess whether endochondral or intramembranous ossification was involved in MSC bone differentiation, the cultures were explored for cartilage-related gene expression. Multiple nodule-like cell aggregates appeared to form in the osteogenic cultures. These nodules were covered by a periosteum-like layer and osteocyte-like cells of varying morphology were located in lacuna-like cavities within the nodule mass. Furthermore, the bone nodules possessed an abundant matrix in which clearly striated collagen I fibres were arranged in perpendicular bundles. Matrix vesicles involving in matrix mineralization were evident in the nodules. This was in accordance with increased ALP activity in the culture. No expression of cartilage-related genes was observed, which suggested that osteogenesis might occur by intramembranous ossification. In conclusion, canine MSCs could be an appropriate model for studying in vitro bone development. [source]

Ultrastructural preservation of rat embryonic dental tissues after rapid fixation and dehydration under microwave irradiation

EUROPEAN JOURNAL OF ORAL SCIENCES, Issue 1 2000
Luciana F. Massa
Adequate preservation of the cells and matrix of mineralising tissues remains difficult, as organic components and initial mineral deposits may be lost during conventional processing for electron microscopy. In this study, we have reduced significantly the processing time using microwave irradiation. Rat molar tooth germs were fixed in 4% glutaraldehyde+4% formaldehyde with 0.1 M sodium cacodylate in a laboratory microwave oven for two periods of 20 s with a maximal temperature of 37°C. After conventional washing and post-fixation, specimens were dehydrated in graded ethanols under microwave irradiation for a total of 7 min 20 s. For comparison, some specimens were processed by conventional methods. After embedding, ultrathin sections were examined by electron microscopy. In differentiating ameloblasts and odontoblasts, plasma membranes, mitochondria, rough endoplasmic reticulum, the Golgi complex, together with all other cytoplasmic organelles exhibited excellent preservation. Microtubules, microfilaments and coated vesicles were particularly evident. Crystal-like mineral deposits were conspicuously present in relation to dentine matrix vesicles and collagen fibrils as well as in enamel matrix. The matrix of forming enamel had a globular electron-lucent appearance. It is concluded that this is a rapid method which provides a preserved or even improved morphology. [source]

Functional Differences Between Growth Plate Apoptotic Bodies and Matrix Vesicles,

JOURNAL OF BONE AND MINERAL RESEARCH, Issue 10 2003
Thorsten Kirsch
Abstract Mineralization often occurs in areas of apoptotic changes. Our findings indicate that physiological mineralization is mediated by matrix vesicles. These matrix vesicles use mechanisms to induce mineralization that are different from the mechanisms used by apoptotic bodies released from apoptotic cells. Therefore, different therapeutic approaches must be chosen to inhibit pathological mineralization depending on the mechanism of mineralization (matrix vesicles versus apoptotic bodies). Introduction: Physiological mineralization in growth plate cartilage is restricted to regions of terminally differentiated and apoptotic chondrocytes. Pathological mineralization of tissues also often occurs in areas of apoptosis. We addressed the question of whether apoptotic changes control mineralization events or whether both events are regulated independently. Methods: To induce mineralization, we treated growth plate chondrocytes with retinoic acid (RA); apoptosis in these cells was induced by treatment with staurosporine, anti-Fas, or TNF,. The degrees of mineralization and apoptosis were determined, and the structure and function of matrix vesicles and apoptotic bodies were compared. Results: Release of matrix vesicles and mineralization in vivo in the growth plate occurs earlier than do apoptotic changes. To determine the functional relationship between apoptotic bodies and matrix vesicles, growth plate chondrocytes were treated with RA to induce matrix vesicle release and with staurosporine to induce release of apoptotic bodies. After 3 days, approximately 90% of staurosporine-treated chondrocytes were apoptotic, whereas only 2,4 % of RA-treated cells showed apoptotic changes. RA- and staurosporine-treated chondrocyte cultures were mineralized after 3 days. Matrix vesicles isolated from RA-treated cultures and apoptotic bodies isolated from staurosporine-treated cultures were associated with calcium and phosphate. However, matrix vesicles were bigger than apoptotic bodies. Furthermore, matrix vesicles but not apoptotic bodies contained alkaline phosphatase and Ca2+ channel-forming annexins II, V, and VI. Consequently, matrix vesicles but not apoptotic bodies were able to take up Ca2+ and form the first mineral phase inside their lumen. Mineralization of RA-treated cultures was inhibited by antibodies specific for annexin V but not mineralization of staurosporine-treated cultures. Conclusion: Physiological mineralization of growth plate chondrocytes is initiated by specialized matrix vesicles and requires alkaline phosphatase and annexins. In contrast, mineral formation mediated by apoptotic bodies occurs by a default mechanism and does not require alkaline phosphatase and annexins. [source]