Development of a biodegradable load-bearing DBM carrier

可生物降解承重DBM载体的研制

• 批准号: 6957395
• 负责人: TIEN-MIN G CHU
• 金额: $ 7.38万
• 依托单位: INDIANA UNIV-PURDUE UNIV AT INDIANAPOLIS
• 依托单位国家: 美国
• 财政年份: 2005
• 资助国家: 美国
• 起止时间: 2005-09-01 至 2007-08-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6957395
• 关键词: biodegradable product; bioengineering /biomedical engineering; biomaterial development /preparation; biomaterial evaluation; biomechanics; biotechnology; bone density; bone disorder; bone regeneration; calcium phosphate; computed axial tomography; femur; laboratory rat; photon absorptiometry; polymethacrylate; tissue engineering; tissue support frame

Segmental defects in bones often are difficult to manage and require multiple-phase surgery to achieve adequate union and function. Current treatment options including autografts, allografts, and distraction osteogenesis have brought forth successes, yet are still with many limitations. In case of treatment failure, alternative treatment may involve serious consequences such as leg shortening or amputation. To overcome the limitations in these treatment options, we are exploring tissue engineering. Tissue engineering approach uses a biodegradable scaffold to carry biological factors and/or cells to facilitate tissue regeneration. This approach has been successful when scaffold is protected from load bearing. Bone regeneration in scaffolds subjected to loading has been challenging due to the relatively low mechanical properties in scaffolds. In this project, we propose to regenerate bone in large segmental bone defects using a load-bearing, biodegradable carrier carrying demineralized bone matrix (DBM). Unlike traditional porous scaffolds, the degradable carrier can be stabilized by intramedullary pin and participate in load-bearing function in the initial healing phase. After providing biomechanical stability and DBM delivery, the carrier will degrade at a later time. The hypotheses we have for this proposal are: 1. Load-bearing carrier combined with DBM shortens the time required for bone union to take place in rat femoral segmental defects. 2. Load-bearing carrier combined with DBM improves bone formation in rat femoral segmental defects. 3. Load-bearing carrier combined with DBM improves final mechanical properties of the rat femur after segmental defect regeneration. Forty-five Long-Evans rats will be used to test the hypotheses. Biodegradable carriers will be manufactured from poly(caprolacton) trimethacrylate/tricalcium phosphate composites. Low (0.05ml) and high (0.3 ml) dose of putty type DBM (DBX(r), Densply) will be incorporated into the carrier. The carrier will be implanted in a 5 mm segmental defect in rat femurs for 24 weeks. The time for unions to occur will be evaluated with x-ray at week 1, 3, 6, 15 and 24 weeks after implantation. The femurs will be retrieved after 24 weeks of implantation. Five femurs from each group will be evaluated with dual energy X-ray absorptiometry (DXA) for bone mineral content (BMC; g) and with peripheral computed tomography (pQCT) for the bone cross sectionaj area (CSA; mm2), volumetric bone density (vBMD; mg/cm3), and bone mineral content (BMC; mg/cm). The specimens will then be embedded in paraffin, decalcified, sectioned, and stained with McNeals Tetrachrome and Safarin-0 in alternating sections for bone and cartilage. The BMC, CSA, and vBMD of control versus low dose and control versus high dose groups will be compared. Ten femurs from each group will be tested with four-point-bending on a material testing machine for bending strength. The ultimate force (Fu; N), stiffness (S; N/mm) and energy to ultimate force (U; N.mm) will be compared between the control and the DBM treated groups.

骨中的节段性缺陷往往难以处理，需要多期手术才能达到充分的愈合和功能。目前的治疗方法包括自体移植、同种异体移植和牵张成骨，取得了成功，但仍有许多局限性。如果治疗失败，替代治疗可能会导致严重的后果，如腿部缩短或截肢。为了克服这些治疗方案的局限性，我们正在探索组织工程学。组织工程方法使用可生物降解的支架来携带生物因子和/或细胞，以促进组织再生。这种方法在脚手架不受承重的情况下获得了成功。由于支架的力学性能相对较低，在载荷作用下支架中骨的再生一直具有挑战性。在这个项目中，我们建议使用承载的、可生物降解的载体携带脱钙骨基质(DBM)来再生大段骨缺损区的骨。与传统的多孔支架不同，可降解的载体可以通过髓内钉稳定下来，并在愈合初期参与承载功能。在提供生物力学稳定性和DBM输送后，载体将在稍后的时间降解。我们对这一建议的假设是：1.承载载体联合DBM可缩短大鼠股骨节段性缺损发生骨愈合所需的时间。2.承载载体复合DBM可促进大鼠股骨节段性缺损区的骨形成。3.承载载体复合DBM可改善大鼠股骨节段性缺损再生后的最终力学性能。45只Long-Evans大鼠将被用来检验这些假设。生物可降解载体将由聚己内酯三甲基丙烯酸酯/磷酸三钙复合材料制造。低剂量(0.05毫升)和高剂量(0.3毫升)的PuTTY型DBM(DBX(R)，Densply)将被加入载体中。将该载体植入大鼠股骨5 mm节段性缺损处，为期24周。术后1周、3周、6周、15周、24周行X光检查，评估骨折愈合时间。股骨将在植入24周后被取回。用双能X线骨密度仪(DXA)测量骨矿含量(BMC；g)，并用外周计算机断层扫描(PQCT)测量骨横截面积(CsA；mm2)、体积骨密度(vBMD；mg/cm3)和骨矿含量(BMC；mg/cm)。然后将标本包埋在石蜡中，脱钙，切片，在交替的骨和软骨切片上用McNeals Tetrachrome和Safarin-0染色。比较对照组与低剂量组和对照组与高剂量组的BMC、CsA和vBMD。每组10根股骨将在材料试验机上进行四点弯曲测试，以测试弯曲强度。比较对照组和DBM组的极限力(FU；N)、刚度(S；N/mm)和能量与极限力之比(U；N.mm)。