Stem Cells and Tissue Repair Group, Institute of Medical Biology, A*STAR, Biopolis, Singapore 138648, Singapore.
Bone. 2012 Apr;50(4):954-64. doi: 10.1016/j.bone.2011.12.013. Epub 2011 Dec 28.
Lowering the efficacious dose of bone morphogenetic protein-2 (BMP-2) for the repair of critical-sized bone defects is highly desirable, as supra-physiological amounts of BMP-2 have an increased risk of side effects and a greater economic burden for the healthcare system. To address this need, we explored the use of heparan sulfate (HS), a structural analog of heparin, to enhance BMP-2 activity. We demonstrate that HS isolated from a bone marrow stromal cell line (HS-5) and heparin each enhances BMP-2-induced osteogenesis in C2C12 myoblasts through increased ALP activity and osteocalcin mRNA expression. Commercially available HS variants from porcine kidney and bovine lung do not generate effects as great as HS5. Heparin and HS5 influence BMP-2 activity by (i) prolonging BMP-2 half-life, (ii) reducing interactions between BMP-2 with its antagonist noggin, and (iii) modulating BMP2 distribution on the cell surface. Importantly, long-term supplementation of HS5 but not heparin greatly enhances BMP-2-induced bone formation in vitro and in vivo. These results show that bone marrow-derived HS effectively supports bone formation, and suggest its applicability in bone repair by selectively facilitating the delivery and bioavailability of BMP-2.
降低骨形态发生蛋白-2（BMP-2）的有效剂量对于修复临界尺寸的骨缺损非常重要，因为超生理剂量的 BMP-2 会增加副作用的风险，并给医疗保健系统带来更大的经济负担。为了满足这一需求，我们探索了使用硫酸乙酰肝素（HS），即肝素的结构类似物，来增强 BMP-2 的活性。我们证明，从骨髓基质细胞系（HS-5）中分离出的 HS 和肝素都能通过增加碱性磷酸酶（ALP）活性和骨钙素 mRNA 表达来增强 C2C12 成肌细胞中 BMP-2 诱导的成骨作用。来自猪肾和牛肺的商业 HS 变体没有像 HS5 那样产生巨大的效果。肝素和 HS5 通过以下方式影响 BMP-2 活性：（i）延长 BMP-2 的半衰期，（ii）减少 BMP-2 与其拮抗剂 noggin 之间的相互作用，以及（iii）调节 BMP2 在细胞表面的分布。重要的是，HS5 的长期补充而不是肝素的补充，极大地增强了 BMP-2 诱导的体外和体内骨形成。这些结果表明，骨髓来源的 HS 能有效地支持骨形成，并表明其通过选择性地促进 BMP-2 的递送和生物利用度，在骨修复中的适用性。
