Virtual ligand-based screening reveals purmorphamine analogs with the capacity to induce the osteogenic differentiation of human mesenchymal stem cells.

Human mesenchymal stem cells (hMSCs) have extensive proliferative capacity, are able to self-renew and have the potential to differentiate into cells of the connective tissue lineages. These properties make them a putative cell type for tissue engineering applications, as well as a possible in vivo target for the pharmaceutical modulation of the differentiation processes. The aim of this study was to find one or more small-molecule substances that would enhance the osteogenic differentiation of hMSCs in vitro. The strategy used here was ligand-based virtual screening for substances similar to the previously suggested osteoinductive purmorphamine followed by an in vitro screening of the selected analogs in hMSCs isolated from bone marrow. We investigated the osteoinductive capacity of several purmorphamine analogs by determining the protein and gene expression of markers for osteogenic differentiation as well as the extracellular matrix (ECM) mineralization of these cells. Treatment with two candidate substances or purmorphamine resulted in increased levels of alkaline phosphatase (ALP) activity compared to the control. Other purmorphamine analogs demonstrated higher calcium deposition in the ECM after 5 weeks of osteogenic differentiation, compared to both purmorphamine and the control condition. The resulting substances, which had positive effects on the osteogenic differentiation, are promising as possible modes of treatment for bone-related diseases or defects that target and enhance the osteogenic differentiation of MSCs, in vitro or in vivo. Furthermore, the concept of combining the virtual ligand-based screening method with in vitro screening, using human adult stem cells as a possible strategy for drug discovery, is demonstrated.