Biomaterial Screening Identifies Enhanced Osteogenic and Angiogenic Potential of Mn-Doped Calcium Phosphate Coatings

Synthetic biomaterials such as calcium phosphate (CaP) ceramics are promising substitutes for autologous bone grafts, as they are easy to produce, cost-effective and closely resemble the mineral component of natural bone. However, their performance in bone repair and regeneration is often inferior to their biological counterparts, which highlights the need for further optimization and improvement. Incorporating inorganic additives has previously been shown as a promising approach to improve the performance of synthetic biomaterials, without compromising their synthetic character. Here, a library of carbonated apatite coatings with inorganic additives such as copper, magnesium, manganese, strontium, and zinc was established. Human mesenchymal stem cells (hMSCs) were seeded on these coatings. A CaP coating with high (1000 μM) manganese incorporation (CaMnP1000) stood out as material inducing a superior osteogenic response in hMSCs, based on a protein multiplex assay containing markers related to osteogenesis, angiogenesis and inflammation. Specifically, the levels of osteopontin, bone morphogenetic protein-2, matrix metalloproteinase-13 and tenascin-C were increased relative to the control group, as well as mRNA transcripts related to early and late osteogenic gene expression (RUNX2, BMP2, and OCN). Improved angiogenic properties were also observed in hMSCs on CaMnP1000, as indicated by increased levels of vascular endothelial growth factor-A and angiopoietin 1. The conditioned medium of hMSCs on CaMnP1000 was able to stimulate human umbilical vein endothelial cells to form an endothelial cell network. The cytokines measured in hMSCs on CaMnP1000, with increased interleukin-6, granulocyte-macrophage colony-stimulating factor and tumor necrosis factor-α expression, suggest an effect of the material on the inflammatory potential. This study highlights CaMnP1000 as a biomaterial with enhanced osteogenic, angiogenic and possibly inflammatory properties. Future research should focus on the underlying mechanisms and manganese-doped CaPs for therapeutic purposes in bone healing.