The role and potential mechanism of p75NTR in mineralization via in vivo p75NTR knockout mice and in vitro ectomesenchymal stem cells

OBJECTIVE: The aim of this study is to investigate the role and potential mechanism of p75NTR in mineralization in vivo using p75NTR‐knockout mice and in vitro using ectomesenchymal stem cells (EMSCs). MATERIALS AND METHODS: Femur bone mass and daily incisor mineralization speed were assessed in an in vivo p75NTR‐knockout mouse model. The molecular signatures alkaline phosphatase (ALP), collagen type 1 (Col1), melanoma‐associated antigen (Mage)‐D1, bone sialoprotein (BSP), osteocalcin (OCN), osteopontin (OPN), distal‐less homeobox 1 (Dlx1) and Msh homeobox 1 (Msx1) were examined in vitro in EMSCs isolated from p75NTR(+/+) and p75NTR(ExIII−/−) mice. RESULTS: p75NTR‐knockout mice were smaller in body size than heterozygous and wild‐type mice. Micro‐computed tomography and structural quantification showed that the osteogenic ability of p75NTR(ExIII)‐knockout mice was significantly decreased compared with that of wild‐type mice (P < .05). Weaker ALP and alizarin red staining and reduced expression of ALP, Col1, Runx2, BSP, OCN and OPN were also observed in p75NTR(ExIII−/−) EMSCs. Moreover, the distance between calcein fluorescence bands in p75NTR(ExIII)‐knockout mice was significantly smaller than that in wild type and heterozygous mice (P < .05), indicating the lower daily mineralization speed of incisors in p75NTR(ExIII)‐knockout mice. Further investigation revealed a positive correlation between p75NTR and Mage‐D1, Dlx1, and Msx1. CONCLUSION: p75NTR not only promotes osteogenic differentiation and tissue mineralization, but also shows a possible relationship with the circadian rhythm of dental hard tissue formation.