Control of proliferation in human mesenchymal stem cells by Secreted Frizzled Related Protein 1

Abstract

Human mesenchymal stem cell (hMSC) is adult stem cell that is useful tool for a various disease. However, it has limitations that lost proliferation and differentiation ability in long-term in vitro culture and occurred senescence. This study would like to confirm the relationship between Wnt signaling and proliferation of hMSCs. When checked mRNA expression of various genes that were related to Wnt signaling, most of genes were decreased gradually as follow passages, except Wnt11. Especially, gene expression of sFRP1, an antagonist of Wnt signaling, was also decreased. To confirm whether sFRP1 affects proliferation of hMSC, MSC/sFRP1 and MSC/shsFRP1 were made and then cell proliferation was measured. Growth kinetics result showed that sFRP1 could affect hMSCs’ proliferation and this could be dependent on concentration.

Meanwhile, Wnt signaling can be divided into canonical and non-canonical pathway depending on beta-catenin involvement in the pathway. RORα is down-stream gene of non-canonical Wnt pathway and it could be translocated into nucleus to interact with β-catenin, resulting in suppression of cell proliferation. This study confirmed that RORα expression and nuclear translocation were increased in late passage of hMSCs. Also, MSC/shRORα

showed promoted growth kinetics, indicating that RORα

could be a negative regulator of hMSCs’ proliferation. To figure out whether sFRP1 inhibits nuclear translocation of RORα to suppress non-canonical Wnt signaling, 10ng/ml sFRP1 was treated to hMSCs and localization of RORα was observed. ICC data showed that nuclear translocation of RORα was inhibited in rhsFRP1 treated hMSCs, suggesting that sFRP1 promotes hMSCs’ proliferation by suppressing non-canonical Wnt signaling