HoxD3 expression and collagen synthesis in diabetic fibroblasts

Diabetic wound healing is characterized by deficiencies in both growth factor and collagen production. We have observed that expression of homeobox D3 (HoxD3), a collagen-inducing transcription factor, and expression of collagen are reduced in an established animal model of diabetic wound repair, the leptin-deficient diabetic (db/db) mouse. We sought to evaluate whether the diminished expression of collagen and HoxD3 would be maintained once fibroblasts were removed from the diabetic wound environment. Fibroblasts were isolated from both wild-type and diabetic animals and expression of HoxD3 and collagen assessed. We found that when removed from the diabetic wound environment, HoxD3 and type I collagen expression are increased in diabetic fibroblasts when compared to wild-type fibroblasts. The increase in type I collagen is not related to increased production or activation of transforming growth factor-beta1. However, when the diabetic fibroblasts are cultured in a 3D collagen matrix, expression of type I collagen and HoxD3 is markedly reduced and reflects the pattern of gene expression observed in the in vivo diabetic wound environment. Thus, although diabetic fibroblasts can regain the capacity to express high levels of collagen and HoxD3 once removed from the diabetic wound environment, culturing cells in the presence of a 3D collagen matrix is sufficient to revert these fibroblasts to their previous nonsynthetic state.