IL-7, SDF-1, and integrin α4/VCAM-1 ligation mediate the B generation from PTH-stimulated cocultures. (A, left-hand panel) Intracellular staining of IL-7 in osteoblasts cultivated in vitro. (A, right-hand panel) PTH treatment enhances the production of IL-7 and SDF-1 from osteoblast cultures. (B) Il-7 and SDF secretion, and B-cell differentiation are favored by PTH-driven osteogenesis and inhibited by induction of adipogenesis. CD45.2+ osteoblasts cultured in β-glycerol phosphate, ascorbate, and dexamethasone were digested and replated in either the same medium, or induced to adipocyte differentiation by the addition of 10−7 M dexamethasone and 10 μg/mL human insulin for 10 days. CD45.1+ LSK cells were added to each monolayer culture, and IL-7, SDF-1 secretion, and B220 cell production from the LSK cells measured on day 10 (mean ± SD; n = 3). (C) Inclusion of neutralizing antibody against IL-7, SDF-1, TSLP, or M-CSF in the coculture modulates the production of B220+ cells (means ± SD, n = 3). (D) Neutralizing antibody against integrin α4 or VCAM-1 inhibits the production of B220+ cells from coculture (means ± SD, n = 3).
