The Contribution of CD26-Negative Fibroblasts to Endometrial Scarring.

The human endometrium is unique in that it has a high potential for regeneration after menstruation without scarring. Although growth factors are thought to be responsible for scar formation, it has recently been shown for foetal skin that CD26-negative fibroblasts are essential. Thus, we investigated whether CD26 might be involved in scar formation. Primary human endometrial stromal cells (HPESCs) were stimulated with interleukin-1 alpha (IL1α) to induce CD26 protein expression, and secretion of the scar-associated proteins collagen 1 alpha 1 (COL1A1) and TGF-β3 was measured using ELISAs. The contribution of CD26 to wound closure was analysed using a wound healing assay. The CD26 inhibitor diprotin A (DPA) was used to attenuate CD26 activity. Immunohistochemistry of human uterine samples showed negligible stromal staining of CD26, but CD26 was abundant in the endometrial glands. Treatment of CD26-negative HPESCs with IL1α induced CD26 protein expression, strongly stimulated wound healing in vitro, and increased secretion of COL1A1, but decreased TGF-β3 secretion. DPA effectively attenuated all IL1α-induced effects. We suggest that the stromal non-expression of the scar-associated protein CD26 might contribute to non-scarring during endometrial wound healing.