Zeolite a increases proliferation, differentiation, and transforming growth factor β production in normal adult human osteoblast‐like cells in vitro

Silicon in trace amounts enhances bone formation, and the silicon‐containing compound zeolite A (ZA) increases eggshell thickness in hens. In the studies reported here, treatment of nearly homogeneous strains of normal human osteoblast‐like cells for 48 h with ZA at 0.1–100 μg/ml induced a dose‐dependent increase (r = 0.35, P < 0.001) in DNA synthesis (n = 31) to 162 ± 16% (mean ± SEM) of control and in the proportion of cells in mitosis (n = 4) from 9.1 ± 1.8 to 27.0 ± 4.5% (r = 0.69, P < 0.005). ZA treatment also increased alkaline phosphatase activity (P < 0.05) and osteocalcin release (P < 0.05) but did not significantly affect collagen production per individual cell. The mitogenic action of ZA was dependent on cell seeding density over the range of 1250–40,000 cells per cm², which is consistent with induction of an autocrine factors). TGF‐β is a potent mitogen for osteoblasts. ZA treatment increased the steady‐state mRNA levels of transforming growth factor β₁ (TGF‐β₁) and induced the release of the latent form of TGF‐β protein into the conditioned medium within 6 h. We conclude that ZA induces the proliferation and differentiation of cells of the osteoblast lineage.