Abstract
Embryonic development of articular cartilage has not been well understood and the role of doublecortin (DCX) in determination of chondrocyte phenotype is unknown. Here, we use a DCX promoter-driven eGFP reporter mouse model to study the dynamic gene expression profiles in mouse embryonic handplates at E12.5 to E13.5 when the condensed mesenchymal cells differentiate into either endochondral chondrocytes or joint interzone cells. Illumina microarray analysis identified a variety of genes that were expressed differentially in the different regions of mouse handplate. The unique expression patterns of many genes were revealed. Cytl1 and 3110032G18RIK were highly expressed in the proximal region of E12.5 handplate and the carpal region of E13.5 handplate, whereas Olfr538, Kctd15, and Cited1 were highly expressed in the distal region of E12.5 and the metacarpal region of E13.5 handplates. There was an increasing gradient of Hrc expression in the proximal to distal direction in E13.5 handplate. Furthermore, when human DCX protein was expressed in human adipose stem cells, collagen II was decreased while aggrecan, matrilin 2, and GDF5 were increased during the 14-day pellet culture. These findings suggest that DCX may play a role in defining chondrocyte phenotype.
Highlights
Diseases of articular joints, such as osteoarthritis, cause pain and impaired mobility
This study focused on mouse handplates at E12.5 to E13.5, because differentiation of the condensed mesenchymal cells into chondrocytes occurs during this period
Our previous study showed that the proximal region of E12.5 handplate expresses high levels of DCX as shown by Enhanced green fluorescence protein (eGFP) signals, whereas the distal region is almost negative for eGFP signals except the faint signals in the digit rays [9]
Summary
Diseases of articular joints, such as osteoarthritis, cause pain and impaired mobility. The current tissue engineering of cartilage follows a paradigm of high-density cell culture such as pellet culture, micromass culture, or high-density culture in certain matrix scaffolds This paradigm essentially mimics embryonic development of skeletal anlage (i.e., endochondral cartilage), rather than articular cartilage. Embryonic development of articular cartilage has not been well understood This lack of complete understanding of articular chondrocyte phenotype establishment is a problem for the field of articular cartilage tissue engineering/regeneration. LacZ or enhanced green fluorescence protein (eGFP), we found that DCX is expressed in the mesenchymal cells in mouse embryonic limb buds, a population of mesenchymal cells maintain DCX expression when they differentiate into joint interzone cells and articular chondrocytes, whereas the other population of mesenchymal cells that differentiate into endochondral chondrocytes lose DCX expression [9]. The DCX-EGFP reporter mouse provides a unique tool to investigate the dynamic changes of chondrocyte phenotype in vivo or ex vivo
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