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发挥着不可或缺的作用。然而，创面愈合过程中血管外和血管内纤维细胞的分布范围尚不清楚。本研究旨在探讨循环纤维细胞和浸润性纤维细胞之间的分布关系及其与血管形成水平的关系。对49例人皮肤组织标本进行CD34或白细胞特异性蛋白-1(LSP-1)和I型胶原原双重染色后，发现血管外和血管内的纤维细胞数量明显不同，循环纤维细胞明显少于浸润性纤维细胞。随着愈合的推进，浸润性纤维细胞的表达发生改变，但循环纤维细胞的表达没有变化，这表明纤维细胞的细胞特性在血管外和血管内区域之间存在差异。三重染色显示胶原原I+/CD34+循环纤维细胞特异性分布于小动脉/小静脉，CXCL12在血管内皮细胞的表达明显增强。基于CXCL12阳性小动脉内胶原原I+/CD34+循环纤维细胞在小动脉/小静脉中的相对特异性分布，CXCL12阳性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，微动脉/小静脉内纤维细胞和内皮细胞的协调细胞反应是循环纤维细胞进入组织损伤部位所必需的。

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.