The role of cells expressing connective tissue growth factor CTGF and ErbB4 receptor during regeneration and/or skeletomuscular development

有报道在软骨细胞系HCS2/8的培养过程中，加入结缔组织生长因子（CTGF）可上调ErbB4受体的基因表达。提示ErbB4受体在软骨形成中可能与CTGF有一定的关系。因此，原位杂交与核糖核酸探针进行分析ErbB4和CTGF在小鼠发育过程中的基因表达模式。ErbB4基因在所有发育阶段的组织中均有表达，如体节、感觉神经节、周围神经、心肌、肺和骨骼形成中的软骨细胞等。比较成年大鼠股骨骨折后35d内再生过程中ErbB4、CTGF和X型胶原基因表达的变化，分析ErbB4和CTGF之间的关系。在股骨骨折后立即观察到血肿，并由来自骨髓的间充质干细胞形成骨痂。7天后，骨痂内充满了各期软骨细胞，并检测了骨痂内肥大软骨细胞CTGF基因的表达。CTGF和X型胶原的基因表达在35天后已经完成。而ErbB4和X型胶原基因的表达开始晚于CTGF基因的表达。即使再生完成，再生区周围的间充质细胞也能检测到ErbB4基因的表达。结果提示，CTGF和ErbB4基因表达均发生在肥大的软骨细胞上，CTGF和ErbB4在骨骼发育过程中可能存在一定的关系。ErbB2靶向突变体的软骨内成骨过程正常，但在钙化前沿未见凋亡细胞。

It was reported that the gene expression of ErbB4 receptor was up regulated by addition of connective tissue growth factor(CTGF) under the cultivation of a chondrocytic cell line HCS2/8. This suggests, that ErbB4 receptor may have certain relationship to CTGF in chondrogenesis. Therefore, in situ hybridization was performed with riboprobes to analyze the gene expression pattern of ErbB4 and CTGF during mouse development. The gene expressions of ErbB4 were detected some tissues through all developmental stages, like in somites, sensory ganglia, peripheral nerves, cardiac muscles, lungs and chondrocytes in skeletal formation etc. However, a dual phase gene expression patterns like that of CTGF was not identified. And then the gene expressions of ErbB4, CTGF and type X collagen were compared during regeneration from fractured bone through 35days in adult rat femurs to analyze the relationship between ErbB4 and CTGF. A hematoma was observed just after the femur was fractured and a callus was formed by mesenchymal stem cells derived from the bone marrow. After 7days, a callus was filled with every stages of chondrocytes and the gene expressions of CTGF were detected on hypertrophic chondrocytes in the callus. The gene expressions of CTGF and type X collagen have already finished after 35 days. Whereas, the gene expressions of ErbB4 and type X collagen began little late to the gene expression of CTGF on hypertrophic chondrocytes. Even the regeneration has finished, the gene expressions of ErbB4 could be detected on mesenchymal cells surrounded the regenerated area. These results indicate that the gene expressions of CTGF and ErbB4 take place on hypertrophic chondrocytes, therefore, CTGF may have certain relationship to ErbB4 in the skeletal development. In addition, the endochondral bone formation was took place normally in ErbB2 targeted mutants, however, there was no apoptotic figure in the calcification front of these mutants.