Bioassay in the bone-inducing system using matrix including neovascularization related genes.

将2 μ g重组人骨形态发生蛋白-2和I型去端胶原（10 mg）植入4周龄、10月龄和18月龄大鼠皮下。植入后1、2、3周取出种植体。异位骨形成的大鼠年龄的影响进行了评价外植体使用苏木精-伊红染色，形态分析，碱性磷酸酶活性和钙含量测定，以及免疫组织化学染色的IV型胶原存在于血管的基底膜。在第2周和第3周，在4周龄和10月龄大鼠中观察到骨形成，但后者的骨形成量少于4周龄大鼠。在18个月大的大鼠中，3周时首次在外植体的有限区域发现局灶性骨骼，并且骨骼量远低于4周大的大鼠。在1周时，4周龄大鼠外植体中的血管比10月龄或18月龄大鼠中的血管多。在2周和3周时，在4周龄大鼠的外植体中心区域发现的血管多于10月龄或18月龄大鼠的相同区域。这些发现表明，在老年大鼠异位骨形成的速度和数量减少，并建议血管分布的差异与异位骨形成的减少有关。

Two microgram of recombinant human bone morphogenetic protein-2 and type I atellocollagen (10mg) was implanted in the subcutaneous tissues of 4-week, 10-month and 18-month-old rats. The implants were removed at 1, 2 and 3 weeks after implantation. The effects of rat age on ectopic bone formation were evaluated on the explants using haematoxylin-eosin staining, morphometric analysis, alkaline phosphatase activity and calcium content determination, as well as immunohistochemical staining of type IV collagen present in the basement membrane of blood vessels. At 2 and 3 weeks, bone was observed in 4-week and 10-month-old rats, but the amount of bone formed in the latter was less than in the 4-week-old rats. In 18-month-old rats, bone was first found focally in limited regions of the explants at 3 weeks and the amount of bone was much less than in 4-week-old rats. At 1 week, blood vessels in the explants of 4-week-old rats were observed more than in those, of 10-month or 18-month-old rats. At 2 and 3 weeks, blood vessels were found in the central regions of the explants in 4-week-old rats more than in the same regions in 10-month or 18-month-old rats. These findings indicate that the rate and quantity of ectopic bone formation are reduced in aged rats, and suggest that the difference in blood vessel distribution is related to this reduction in ectopic bone formation.