Electrical stimulation of adipose‐derived mesenchymal stem cells and endothelial cells co‐cultured in a conductive scaffold for potential orthopaedic applications

Electrical stimulation (ES) has emerged as a useful tool to regulate cell behaviour, but the effect of ES on mesenchymal stem cell (MSC)/vasculogenic cell co‐culture has not been investigated. Herein, human adipose‐derived MSCs (AD‐MSCs) and umbilical vein endothelial cells (HUVECs) were co‐cultured in an electrically conductive polypyrrole/chitosan scaffold. Compared with AD‐MSC monoculture, calcium deposition in the co‐culture without and with ES (200 μA for 4 h/day) was 139% and 346% higher, respectively, after 7 days. As the application of ES to AD‐MSC monoculture only increased calcium deposition by 56% compared with that without ES after 7 days, these results indicate that ES and co‐culture with HUVECs have synergistic effects on AD‐MSCs' osteogenic differentiation. ES application also significantly enhanced CD31 expression of HUVECs. In HUVEC monoculture, application of ES increased CD31 expression by 224%, whereas the corresponding increase in AD‐MSC/HUVEC co‐culture with ES application was 62%. The gene expression results indicate that ES enhanced the cellular functions in AD‐MSC and HUVEC monoculture via autocrine bone morphogenetic protein‐2 (BMP‐2) and vascular endothelial growth factor (VEGF), respectively. In co‐culture, crosstalk between AD‐MSCs and HUVECs due to paracrine BMP‐2 and VEGF enhanced the cellular functions compared with the respective monoculture. With application of ES to the AD‐MSC/HUVEC co‐culture, autocrine signalling was enhanced, resulting in further promotion of cellular functions. These findings illustrate that co‐culturing AD‐MSC/HUVEC in a conductive scaffold with ES offers potential benefits for bone defect therapy.