The source of ACE during scar formation is from both bone marrow and skin tissue.

Angiotensin-converting enzyme (ACE) has been found in the pathogenesis of various fibrosis diseases, and ACE inhibitor (ACEI) may affect wound healing and cutaneous fibrosis. However, there is no scientific evidence as to where the ACE is produced during scar formation. Whether it is from the cutaneous tissue or the bone marrow, or both remains unknown. In this study, we investigated the source of ACE using bone marrow transplantation in genetically modified mice, analyzed the inflammatory milieu and some growth factors in the middle of the wound healing period (4 d after the wound was induced). After having deleted the ACE from bone marrow or skin tissue, the wound/scar width in the low-ACE groups were narrower than those in wild-type (WT) controls. Loosely arranged collagen deposition and reduced vessel density were also detected in ACE-deficient mice. Lower ACE levels during scar formation were also accompanied by lower levels of TGF-β1. In the middle of the wound healing period, ACE levels affected the inflammatory cells significantly. In the mice with a deficiency in ACE, the expression of TGF-β1 and TNF-α decreased, but not that of IL-4. Our findings indicate that both bone marrow and skin tissue release ACE during scar formation. Deleting either of them can affect the inflammatory cells and growth factors and reduce the expression of TGF-β1, resulting in a decreased level of scarring.-Fang, Q.-Q., Wang, X.-F., Zhao, W.-Y., Chen, C.-Y., Zhang, M.-X., Shi, B.-H., Zhang, L.-Y., Tan, W.-Q. The source of ACE during scar formation is from both bone marrow and skin tissue.