Talley-Ronsholdt D J, Lajiness E, Nagodawithana K
Department of Basic Health Sciences, Marquette University School of Dentistry, Milwaukee, Wisconsin 53233, USA.
In Vitro Cell Dev Biol Anim. 1995 Apr;31(4):274-82. doi: 10.1007/BF02634001.
The latent form of transforming growth factor-beta (TGF-beta) is a component of the extracellular matrix of bone. The active form, when locally injected in vivo, stimulates both inflammation and ectopic bone formation. The present study was undertaken to determine if TGF-beta also stimulated mineralization by isolated rat calvarial osteoblasts cultured in collagen gels. Gels were used because they should mimic in vivo conditions better than classical monolayer culture. Compared to cells in monolayers, osteoblasts cultured in collagen gels exhibited slower growth, but higher alkaline phosphatase activity and mineral deposition. Cultured cells also synthesized the osteoblast-specific marker, osteocalcin. The increase in osteocalcin in cell layers was parallel to the increase in mineral deposition. In the presence of TGF-beta, neither cell growth nor alkaline phosphatase activity increased. Instead, a small decrease occurred in both parameters when compared to untreated cultures. Accumulation of collagen, the major component of the extracellular matrix where mineralization occurs, was similar in untreated and TGF-beta 1-treated cultures. However, 8 pM TGF-beta 1 dramatically suppressed mineral deposition in both types of cultures. Despite TGF-beta 1 stimulating a fourfold increase in lactic acid, the consequent increase in culture medium acidity did not account for the inhibitory effects of TGF-beta 1 on mineralization. These results demonstrate that collagen gel culture is an improved technique over conventional monolayer culture for demonstrating differentiated osteoblast function and sensitivity to TGF-beta 1. TGF-beta 1, at a concentration that has little effect on cell growth, alkaline phosphatase activity, or collagen accumulation, is a potent inhibitor of mineralization.(ABSTRACT TRUNCATED AT 250 WORDS)
转化生长因子-β（TGF-β）的潜伏形式是骨细胞外基质的一个组成部分。其活性形式在体内局部注射时，会刺激炎症和异位骨形成。本研究旨在确定TGF-β是否也能刺激在胶原凝胶中培养的离体大鼠颅骨成骨细胞矿化。使用凝胶是因为它们比传统的单层培养能更好地模拟体内条件。与单层培养的细胞相比，在胶原凝胶中培养的成骨细胞生长较慢，但碱性磷酸酶活性和矿物质沉积较高。培养的细胞还合成了成骨细胞特异性标志物骨钙素。细胞层中骨钙素的增加与矿物质沉积的增加平行。在TGF-β存在的情况下，细胞生长和碱性磷酸酶活性均未增加。相反，与未处理的培养物相比，这两个参数都略有下降。矿化发生的细胞外基质的主要成分胶原蛋白的积累，在未处理和TGF-β1处理的培养物中相似。然而，8 pM的TGF-β1显著抑制了两种培养物中的矿物质沉积。尽管TGF-β1使乳酸增加了四倍，但随之而来的培养基酸度增加并不能解释TGF-β1对矿化的抑制作用。这些结果表明，对于展示分化的成骨细胞功能和对TGF-β1的敏感性而言，胶原凝胶培养是一种优于传统单层培养的技术。TGF-β1在对细胞生长、碱性磷酸酶活性或胶原蛋白积累影响很小的浓度下，是一种有效的矿化抑制剂。（摘要截取自250字）
