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

将重组人骨形态发生蛋白-2和I型腱胶原蛋白2微克（10mg）分别植入4周龄、10月龄和18月龄大鼠皮下组织。种植体于种植后1、2、3周取出。采用血红素-伊红染色、形态计量学分析、碱性磷酸酶活性和钙含量测定以及血管基底膜IV型胶原免疫组化染色，评价年龄对外植体异位骨形成的影响。2周和3周时，4周龄大鼠和10月龄大鼠均有骨形成，但10月龄大鼠骨形成量少于4周龄大鼠。在18月龄大鼠中，骨在3周龄时首次在植体的有限区域局部发现，骨的数量远少于4周龄大鼠。1周时，4周龄大鼠的外植体血管比10月龄和18月龄大鼠的血管多。在2周和3周时，4周大鼠的外植体中心区域的血管比10个月或18个月大鼠的相同区域的血管多。这些发现表明，老龄大鼠异位骨形成的速率和数量减少，并提示血管分布的差异与这种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.