Fluorapatite-modified Scaffold on Dental Pulp Stem Cell Mineralization

In previous studies, fluorapatite (FA) crystal-coated surfaces have been shown to stimulate the differentiation and mineralization of human dental pulp stem cells (DPSCs) in two-dimensional cell culture. However, whether the FA surface can recapitulate these properties in three-dimensional culture is still unknown. This study examined the differences in behavior of human DPSCs cultured on electrospun polycaprolactone (PCL) NanoECM nanofibers with or without the FA crystals. Under near-physiologic conditions, the FA crystals were synthesized on the PCL nanofiber scaffolds. The FA crystals were evenly distributed on the scaffolds. DPSCs were cultured on the PCL+FA or the PCL scaffolds for up to 28 days. Scanning electron microscope images showed that DPSCs attached well to both scaffolds after the initial seeding. However, it appeared that more multicellular aggregates formed on the PCL+FA scaffolds. After 14 days, the cell proliferation on the PCL+FA was slower than that on the PCL-only scaffolds. Interestingly, even without any induction of mineralization, from day 7, the upregulation of several pro-osteogenic molecules (dmp1, dspp, runx2, ocn, spp1, col1a1) was detected in cells seeded on the PCL+FA scaffolds. A significant increase in alkaline phosphatase activity was also seen on FA-coated scaffolds compared with the PCL-only scaffolds at days 14 and 21. At the protein level, osteocalcin expression was induced only in the DPSCs on the PCL+FA surfaces at day 21 and then significantly enhanced at day 28. A similar pattern was observed in those specimens stained with Alizarin red and Von Kossa after 21 and 28 days. These data suggest that the incorporation of FA crystals within the three-dimensional PCL nanofiber scaffolds provided a favorable extracellular matrix microenvironment for the growth, differentiation, and mineralization of human DPSCs. This FA-modified PCL nanofiber scaffold shows promising potential for future bone, dental, and orthopedic regenerative applications.