Role of elevated plasma transforming growth factor-beta1 levels in wound healing

Transforming growth factor (TGF)-beta1 plays a central role in wound healing. Wounds treated with neutralizing antibody to TGF-beta1 have a lower inflammatory response, reduced early extracellular matrix deposition, and reduced later cutaneous scarring, indicating the importance of local tissue TGF-beta1. By contrast, increasing the local, tissue levels of TGF-beta1 increases the early extracellular matrix deposition but does not alter scar formation. Increased levels of plasma TGF-beta1 correlate with increased fibrogenesis in the lung, kidneys, and liver. The aim of the present study was to investigate the role of elevated systemic levels of TGF-beta1 on wound healing. We used transgenic mice that express high levels of active TGF-beta1 and have elevated plasma levels of TGF-beta1 and wild-type mice of the same strain as controls. Incisional wounds and subcutaneously implanted polyvinyl alcohol (PVA) sponges were analyzed. Surprisingly, cutaneous wounds in transgenic, TGF-beta1-overexpressing mice healed with reduced scarring accompanied by an increase in the immunostaining for TGF-beta3 and TGF-beta-receptor RII and a decrease in immunostaining for TGF-beta1 compared with wounds in control mice. By contrast, the PVA sponges showed the opposite response, with PVA sponges from transgenic mice demonstrating an enhanced rate of cellular influx and matrix deposition into the sponges accompanied by an increase in the immunostaining for all three TGF-beta isoforms and their receptors compared with PVA sponges from control mice. Together, the data demonstrate that increased circulating levels of TGF-beta1 do not always result in increased expression or activity in selected target tissues such as the skin. The two wound models, subcutaneously implanted PVA sponges and cutaneous incisional wounds, differ significantly in terms of host response patterns. Finally, the data reinforce our previous observations that the relative ratios of the three TGF-beta isoforms is critical for control of scarring.