Dose-dependence of PTH-related peptide-1 on the osteogenic induction of MC3T3-E1 cells in vitro

Parathyroid hormone (PTH), an 84-amino acid peptide, is an endocrine hormone that is secreted by parathyroid glands. PTH performs important functions in calcium regulation and bone remodeling. The PTH (1-34) named teriparatide, a 34-amino acid peptide derived from the N-terminus of PTH, conserves most of the functions of PTH, specifically the osteogenic capability. However, teriparatide is only used by injection and exhibits short duration. In addition, this PTH could not thoroughly expose active sites. In this study, a novel PTH-related peptide (designated PTHrP-1) derived from the N-terminus of PTH was added into the complete medium at different concentrations of PTHrP-1 (0, 50, 100, and 200 ng/mL) to induce the MC3T3-E1 cells. PTHrP-1 was detected by high-performance liquid chromatography and matrix-assisted laser desorption/ionization-time-of-flight mass spectroscopy. Cell morphology, cell proliferation, alkaline phosphatase (ALP), and ALP activity, osteocalcin concentration, and collagen type I (Col-I), osteopontin (OPN), and osteocalcin (OCN) mRNA expression by RT-PCR and protein expression by western blotting were observed and detected. The purity of the PTHrP-1 was 95.14%, and the PTHrP-1 can induce MC3T3-E1 cells into osteoblasts, thus improving ALP activity and OCN concentration, and increasing Col-I, OPN, and OCN mRNA expression and protein expression in MC3T3-E1 cell cultures. The PTHrP-1 proved to be an ideal active peptide. In addition, the osteogenic ability of PTHrP-1 at 200 and 100 ng/mL concentrations was not significantly different but significantly higher than 50 and 0 ng/mL groups. Results indicate that PTHrP-1 is a kind of active peptides that exhibits good biocompatibility with MC3T3-E1 cells and could improve cell proliferation and osteogenic differentiation. Moreover, PTHrP-1, at the preferable concentration of 100 ng/mL, could effectively promote MC3T3-E1 cells into osteoblasts.