Growth hormone stimulates proliferation of normal human bone marrow stromal osteoblast precursor cells in vitro

In this study the effects of growth hormone (GH) in human marrow stromal osteoblast-like [hMS(OB)] cell cultures containing a population of osteoblast precursors, were tested. GH (dose range 0.1-500 ng/ml) stimulated hMS(OB) cell proliferation in a dose-dependent fashion as evidenced by increased 3H-thymidine incorporation into DNA and increased cell number. Maximal stimulation was 173 +/- 35% (P < 0.001, n = 12) and 145 +/- 6% (P < 0.0001, n = 10) of no-treatment controls for 3H-thymidine incorporation and cell number, respectively. GH did not exert major effects on differentiation markers in hMS(OB) cell cultures. 1,25-dihydroxy vitamin D3 (10(-9) M) alone increased cellular production of alkaline phosphatase (AP) and induced expression of osteocalcin. When GH was tested in combination with 1,25(OH)2D3, it tended to inhibit vitamin D-stimulated effects on differentiation markers but these effects were not statistically significant. Our results suggest that GH induces proliferation of less differentiated cells in the osteoblast lineage and this mechanism may in part mediate the in vivo effects of GH on bone formation.