Immunophenotypical analyses of myofibroblasts in rat excisional wound healing: possible transdifferentiation of blood vessel pericytes and perifollicular dermal sheath cells into myofibroblasts.

Cutaneous fibrosis after wound is evoked by myofibroblasts capable of producing collagen; the derivation and features remain to be investigated. Immunophenotypical characteristics of myofibroblasts were analysed in excisional rat wound healing, of which samples were obtained on post-wounding (PW) days 1 to 26. Myofibroblasts were characterized for expressions of intermediate cytoskeletons such as vimentin, desmin, and α-smooth muscle actin (α-SMA). To pursue the progenitor, immunolabeling analyses were performed using stromal-/bone marrow-stem cell markers (Thy-1 and A3). Myofibroblasts reacting to vimentin and α-SMA were first seen on PW day 5, then peaked on PW day 9 in granulation tissues, and gradually decreased in remodeling tissues; these immunopositive cells reacted simultaneously to Thy-1. Desmin-reacting cells were limited to newly-formed blood vessels in wound bed. The single/double immunolabelings revealed that pericytes (identified by positive reaction to PDGFR-β and negative reaction to endothelial markers) in newly-developing blood vessels reacted to vimentin, α-SMA, Thy-1 and A3, and occasionally to desmin, and that perifollicular dermal sheath cells in the wound periphery showed increased expressions for vimentin, Thy-1 and A3. There is considerable immunophenotypical similarity between myofibroblasts (expressing vimentin, α-SMA and Thy-1), pericytes (reacting to vimentin, α-SMA, Thy-1 and A3) in newly-developing blood vessels, and perifollicular dermal sheath cells (reacting to vimentin, Thy-1 and A3). Collectively, myofibroblasts in rat cutaneous fibrosis are characterized by vimentin, α-SMA and Thy-1 expressions, and the cells might be generated from the pericytes or perifollicular dermal sheath cells in the lineage of stroma-/bone marrow-stem cells.