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Cellular Condensation (cellular + condensation)
Selected AbstractsAnalysis of N-cadherin function in limb mesenchymal chondrogenesis in vitro,DEVELOPMENTAL DYNAMICS, Issue 2 2002Anthony M. Delise Abstract During embryonic limb development, cartilage formation is presaged by a crucial mesenchymal cell condensation phase. N-Cadherin, a Ca2+ -dependent cell,cell adhesion molecule, is expressed in embryonic chick limb buds in a spatiotemporal pattern suggestive of its involvement during cellular condensation; functional blocking of N-cadherin homotypic binding, by using a neutralizing monoclonal antibody, results in perturbed chondrogenesis in vitro and in vivo. In high-density micromass cultures of embryonic limb mesenchymal cells, N-cadherin expression level is high during days 1 and 2, coincident with active cellular condensation, and decreases upon overt chondrogenic differentiation from day 3 on. In this study, we have used a transfection approach to evaluate the effects of gain- and loss-of-function expression of N-cadherin constructs on mesenchymal condensation and chondrogenesis in vitro. Chick limb mesenchymal cells were transfected by electroporation with recombinant expression plasmids encoding wild-type or two mutant extracellular/cytoplasmic deletion forms of N-cadherin. Expression of the transfected N-cadherin forms showed a transient profile, being high on days 1,2 of culture, and decreasing by day 3, fortuitously coincident with the temporal profile of endogenous N-cadherin gene expression. Examined by means of peanut agglutinin (PNA) staining for condensing precartilage mesenchymal cells, cultures overexpressing wild-type N-cadherin showed enhanced cellular condensation on culture days 2 and 3, whereas expression of the deletion mutant forms (extracellular/cytoplasmic) of N-cadherin resulted in a decrease in PNA staining, suggesting that a complete N-cadherin protein is required for normal cellular condensation to occur. Subsequent chondrogenesis was also affected. Cultures overexpressing the wild-type N-cadherin protein showed enhanced chondrogenesis, indicated by increased production of cartilage matrix (sulfated proteoglycans, collagen type II, and cartilage proteoglycan link protein), as well as increased cartilage nodule number and size of individual nodules, compared with control cultures and cultures transfected with either of the two mutant N-cadherin constructs. These results demonstrate that complete N-cadherin function, at the levels of both extracellular homotypic binding and cytoplasmic linkage to the cytoskeleton by means of the catenin complex, is required for chondrogenesis by mediating functional mesenchymal cell condensation. © 2002 Wiley-Liss, Inc. [source] Alterations in the temporal expression and function of cadherin-7 inhibit cell migration and condensation during chondrogenesis of chick limb mesenchymal cells in vitroJOURNAL OF CELLULAR PHYSIOLOGY, Issue 1 2009Dongkyun Kim Endochondral bone formation requires a complex interplay among immature mesenchymal progenitor cells to form the cartilaginous anlagen, which involves migration, aggregation and condensation. Even though condensation of chondrogenic progenitors is an essential step in this process, its mechanism(s) has not been well studied. Here, we show that cadherin-7 plays a central role in cellular condensation by modulating cell motility and migration. In this study, many mesenchymal cells failed to migrate, and precartilage condensation was inhibited, after knockdown of endogenous cadherin-7 levels. Exposure of mesenchymal cells to SB203580 (a specific inhibitor of p38MAPK), LiCl (an inhibitor of GSK-3,) or overexpression of ,-catenin resulted in inhibition of cadherin-7 levels and, subsequently, suppression of cell migration. Collectively, our results suggest that cadherin-7 controls cell migration in chick limb bud mesenchymal cells, and that p38MAPK and GSK signals are responsible for regulating cadherin-7-mediated cell migration. J. Cell. Physiol. 221: 161,170, 2009. © 2009 Wiley-Liss, Inc [source] Bone morphogenetic protein-2 modulation of chondrogenic differentiation in vitro involves gap junction-mediated intercellular communicationJOURNAL OF CELLULAR PHYSIOLOGY, Issue 2 2002Wei Zhang Undifferentiated mesenchymal cells in the limb bud integrate a complex array of local and systemic signals during the process of cell condensation and chondrogenic differentiation. To address the relationship between bone morphogenetic protein (BMP) signaling and gap junction-mediated intercellular communication, we examined the effects of BMP-2 and a gap junction blocker 18 alpha glycyrrhetinic acid (18,-GCA) on mesenchymal cell condensation and chondrogenic differentiation in an in vitro chondrogenic model. We find that connexin43 protein expression significantly correlates with early mesenchymal cellular condensation and chondrogenesis in high-density limb bud cell culture. The level of connexin43 mRNA is maximally upregulated 48 h after treatment with recombinant human BMP-2 with corresponding changes in protein expression. Inhibition of gap junction-mediated intercellular communication with 2.5 ,M 18,-GCA decreases chondrogenic differentiation by 50% at 96 h without effects on housekeeping genes. Exposure to 18,-GCA for only the first 24,48 h after plating does not affect condensation or later chondrogenic differentiation suggesting that gap junction-mediated intercellular communication is not critical for the initial phase of condensation but is important for the onset of differentiation. 18,-GCA can also block the chondrogenic effects of BMP-2 without effects on cell number or connexin43 expression. These observations demonstrate 18,-GCA-sensitive regulation of intercellular communication in limb mesenchymal cells undergoing chondrogenic differentiation and suggest that BMP-2 induced chondrogenic differentiation may be mediated in part through the modulation of connexin43 expression and gap junction-mediated intercellular communication. J. Cell. Physiol. 193: 233,243, 2002. © 2002 Wiley-Liss, Inc. [source] | ||||||||||