Medium conditioned by human mesenchymal stromal cells reverses low serum and hypoxia-induced inhibition of wound closure.

Chronic wounds, such as pressure ulcers, are a common complication of impaired peripheral circulation, such as in advanced diabetes. Factors secreted by mesenchymal stromal cells (MSCs) have been shown to enhance wound healing in vitro and in vivo. However, there is little understanding of the impact of the chronic wound environment, namely the limited supply of nutrients and oxygen, on the ability of wound cells to respond to MSCs. In this study, we first established the effects of hypoxia (1% O2) and low serum (1% serum) concentration on the proliferation and migration of keratinocytes. We found that hypoxia and low serum significantly slowed down these processes. Next, we found that supplementation with human MSC-concentrated conditioned media (hMSC-CM) enhanced both cell migration and proliferation in the presence of hypoxia and low serum. Furthermore, low serum and hypoxia decreased cell spreading and F-actin expression, which was reversed in the presence of hMSC-CM. Several wound healing mediators were identified in hMSC-CM, including IL-5, IL-6, IL-8, IL-9, IP-10, MCP-1, FGF-2, and VEGF. This study suggests that the concentrated secretome of human MSCs can reverse the inhibitory effect of hypoxia and low serum on keratinocyte proliferation and migration. This phenomenon may contribute to the beneficial effects of hMSC-CM on wound healing in vivo.