Recent studies show that bone marrow (BM)-derived cells migrating into a dermal
wound promote healing by producing
collagen type I. However, their contribution to the repair process has not been fully verified yet. It is also unclear whether BM-derived cells participate in dermal fibrogenesis. We have addressed these issues using transgenic mice that harbor tissue-specific enhancer/promoter sequences of α2(I)
collagen gene linked to either
enhanced green fluorescent protein (COL/EGFP) or the
luciferase (COL/LUC) reporter gene. Following dermal excision or subcutaneous
bleomycin administration, a large number of EGFP-positive
collagen-producing cells appeared in the dermis of COL/EGFP reporter mice. When wild-type mice were transplanted with BM cells from transgenic COL/EGFP animals and subjected to dermal excision, no EGFP-positive BM-derived
collagen-producing cells were detected throughout the repair process.
Luciferase assays of dermal tissues from COL/LUC recipient mice also excluded
collagen production by BM-derived cells during dermal excision healing. In contrast, a limited but significant number of CD45-positive
collagen-producing cells migrated from BM following
bleomycin injection. These results indicate that resident cells in the skin are the major source of de novo
collagen deposition in both physiological and pathological conditions, whereas BM-derived cells participate, in part, in
collagen production during dermal fibrogenesis.