Immunoelectron microscopic localization of Collagen type XV during human mesenchymal stem cells mineralization

Purpose/Aim of the study. We previously identified collagen type XV (ColXV) as a novel component of bone extracellular matrix (ECM). The present study aimed to investigate ColXV localization along with mineral deposition in osteodifferentiated human mesenchymal stem cells (hMSCs). Material and Methods. hMSCs cultured in osteogenic medium were analyzed at day 14 and 28 for mineral matrix deposition by alizarin red S staining, ultrastructure organization, and ColXV expression by immunogold electron microscopy. Results. Our data showed an intimate association of ColXV with fibrillar fibers in defined regions which were definitely localized far from calcified deposits. Conclusions. We demonstrated the efficacy of ultrastructural analysis combined with immunocytochemistry to establish a temporal and spatial localization of ColXV, and to validate previous evidence regarding the negative effects of calcium deposits on ColXV expression.