The influence of bone morphogenetic protein-binding endothelial regulator on osteogenic differentiation of human mesenchymal stem cells

INTRODUCTION. More than 80,000 bone transplants / -translocations performed annually in Germany alone illustrate the relevant demand for bone tissue. In contrast, alloplastic substitute material was only used about 23,000 times. These numbers show that up to this date, the transplantation of autologous bone often remains the only option, despite its limited availability and the associated donor site morbidity. To improve the treatment of significant bone defects, new tissue engineering approaches are attempting to mimic the osteoinductive properties of grafts. BMPER is such a promising growth factor, and its knock-out phenotype is shown by impaired skeletal development. It is also a key regulator of angiogenesis and endothelial function. Interestingly, various publications have shown both its agonistic and antagonistic effects on BMP signaling. AIM. Therefore, we wanted to investigate whether recombinant human BMPER can potentiate the osteogenic effect of BMPs or even promote osteogenesis itself. METHODS. First, the BMPER regulation in human bone marrow stem cells with osteogenic monolayer differentiation was studied using qPCR, Western Blot, and ELISA. In a second step, the osteogenic differentiation medium was supplemented with rhBMPER. The monolayer differentiation of hMSCs was carried out with ten donors over seven days and three over 21 days. Sample times were continuously taken and analyzed for gene expression of osteogenic markers and BMP receptors using qPCR. On day 21, Alizarin Red staining and a Western blot were also carried out. In the last step, we tested 45 possible combinations of rhBMPER with either BMP-2 or BMP-6 for the gene expression of differentiation markers. RESULTS. During 21 days of naïve osteogenic differentiation (without rhBMPER), the upregulation of BMPER gene expression was observed. Short-term treatment (seven days) with rhBMPER induced BMP-receptor changes and stimulated the RUNX2/SOX9 ratio as well as PPARG. The second-lowest dose of 10 ng was the most effective, confirming the ...