Fibrocyte behavior relative to blood vessels under skin wound healing

纤维细胞是骨髓来源的间充质祖细胞，在组织损伤后的修复过程中起着不可或缺的作用。然而，在伤口愈合过程中，纤维细胞在血管外和血管内的范围仍然不清楚。本研究旨在探讨循环和浸润纤维细胞与血管形成水平之间的分布关系。用CD34或白细胞特异性蛋白-1 （LSP-1）加前胶原I双染色49例人皮肤组织样本后发现，血管外区和血管内区纤维细胞数量明显不同，循环纤维细胞明显少于浸润纤维细胞。随着愈合的进展，浸润性纤维细胞的表达发生了变化，而循环纤维细胞的表达则没有变化，这表明纤维细胞的细胞特性在血管外和血管内区域有所不同。三层染色显示前胶原+/CD34+循环纤维细胞在小动脉/小静脉的特异性分布，内皮细胞中CXCL12的表达明显升高。基于前胶原I+/CD34+循环纤维细胞在小动脉/小静脉内的相对特异性分布，cxcl12阳性的小动脉可能提供了促进cxcr4介导的纤维细胞趋化的微环境。这些发现表明，小动脉/小静脉中纤维细胞和内皮细胞的协调细胞反应对于循环纤维细胞运输到组织损伤部位至关重要。

Fibrocytes are bone marrow-derived mesenchymal progenitor cellsand play an integral role for the repair process following tissue injury. However, the extent of fibrocytes in extra- and intra-vascular regions during wound healing process remains obscure. The present study was undertaken to investigate the distributional relationship between circulating and infiltrated fibrocytes in relation to the level of vessel formation. After double-staining of 49 human skin tissues samples with CD34 or leukocyte-specific protein-1 (LSP-1) plus pro-collagen I, a considerable difference in the numbers of fibrocytes was evident between extra- and intra-vascular regions, with obviously fewer circulating, than infiltrated fibrocytes. The expression of infiltrated, but not of circulating fibrocytes, changed as healing advanced, suggesting that the cellular properties of fibrocytes differed between extra- and intra-vascular regions. Triple staining demonstrated the specific distribution of pro-collagenI+/CD34+ circulating fibrocytes in arterioles/venules, with the obviously increased expression of CXCL12 in the endothelial cells. Based on the relatively specific distribution of pro-collagen I+/CD34+ circulating fibrocytes within arterioles/venules, CXCL12-positive arterioles might provide a microenvironment that promotes CXCR4-mediated fibrocyte chemotaxis. These findings suggest that the coordinated cellular response by fibrocytes and endothelial cells in arterioles/venules is essential for trafficking of circulating fibrocytes into sites of tissue injury.