Expression of neuropeptide receptor mRNA during osteoblastic differentiation of mouse iPS cells

Various studies have shown a relationship between nerves and bones. Recent evidence suggests that both sensory and sympathetic nerves affect bone metabolism; however, little is known about how neuropeptides are involved in the differentiation of pluripotent stem cells into osteoblastic (OB) cells. To evaluate the putative effects of neuropeptides during the differentiation of mouse induced pluripotent stem (iPS) cells into calcified tissue-forming OB cells, we investigated the expression patterns of neuropeptide receptors at each differentiation stage. Mouse iPS cells were seeded onto feeder cells and then transferred to low-attachment culture dishes to form embryoid bodies (EBs). EBs were cultured for 4 weeks in osteoblastic differentiation medium. The expression of α1-adrenergic receptor (AR), α2-AR, β2-AR, neuropeptide Y1 receptor (NPY1-R), neuropeptide Y2 receptor (NPY2-R), calcitonin gene-related protein receptor (CGRP-R), and neurokinin 1-R (NK1-R) was assessed by reverse transcription-polymerase chain reaction (RT-PCR) and real-time PCR. Among these neuropeptide receptors, CGRP-R and β2-AR were expressed at all stages of cell differentiation, including the iPS cell stage, with peak expression occurring at the early osteoblastic differentiation stage. Another sensory nervous system receptor, NK1-R, was expressed mainly in the late osteoblastic differentiation stage. Furthermore, CGRP-R mRNA showed an additional small peak corresponding to EBs cultured for 3 days, suggesting that EBs may be affected by serum CGRP. These data suggest that the sensory nervous system receptor CGRP-R and the sympathetic nervous system receptor β2-AR may be involved in the differentiation of iPS cells into the osteoblastic lineage. It follows from these findings that CGRP and β2-AR may regulate cell differentiation in the iPS and EB stages, and that each neuropeptide has an optimal period of influence during the differentiation process.