Deletion of the nuclear localization sequence and C-terminus of parathyroid hormone–related protein decreases osteogenesis and chondrogenesis but increases adipogenesis and myogenesis in murine bone marrow stromal cells

Abstract

The N-terminus of parathyroid hormone–related protein regulates bone marrow stromal cell differentiation. We hypothesized that the nuclear localization sequence and C-terminus are involved. MicroRNA and gene expression analyses were performed on bone marrow stromal cells from mice lacking the nuclear localization sequence and C-terminus ( PthrpΔ/Δ) and age-matched controls. Differentiation assays with microRNA, cytochemical/histologic/morphologic, protein, and gene expression analyses were performed. PthrpΔ/Δ bone marrow stromal cells are anti-osteochondrogenic, pro-adipogenic, and pro-myogenic, expressing more Klf4, Gsk-3β, Lif, Ct-1, and microRNA-434 but less β-catenin, Igf-1, Taz, Osm, and microRNA-22 ( p ⩽ 0.024). PthrpΔ/Δ osteoblasts had less mineralization, osteocalcin, Runx2, Osx, Igf-1, and leptin ( p ⩽ 0.029). PthrpΔ/Δ produced more adipocytes, Pparγ, and aP2, but less Lpl ( p ⩽ 0.042). PthrpΔ/Δ cartilage pellets were smaller with less Sox9 and Pth1r, but greater Col2a1 ( p ⩽ 0.024). PthrpΔ/Δ produced more myocytes, Des, and Myog ( p ⩽ 0.021). MicroRNA changes supported these findings. In conclusion, the nuclear localization sequence and C-terminus are pro-osteochondrogenic, anti-adipogenic, and anti-myogenic.