DataSheet1_Injectable hydrogel with immobilized BMP-2 mimetic peptide for local bone regeneration.pdf

Osteoporosis is a disease characterized by a decrease in bone mineral density, thereby increasing the risk of sustaining a fragility fracture. Most medical therapies are systemic and do not restore bone in areas of need, leading to undesirable side effects. Injectable hydrogels can locally deliver therapeutics with spatial precision, and this study reports the development of an injectable hydrogel containing a peptide mimic of bone morphogenetic protein-2 (BMP-2). To create injectable hydrogels, hyaluronic acid was modified with norbornene (HANor) or tetrazine (HATet) which upon mixing click into covalently crosslinked Nor-Tet hydrogels. By modifying HANor macromers with methacrylates (Me), thiolated BMP-2 mimetic peptides were immobilized to HANor via a Michael addition reaction, and coupling was confirmed with 1H NMR spectroscopy. BMP-2 peptides presented in soluble and immobilized form increased alkaline phosphatase (ALP) expression in MSCs cultured on 2D and encapsulated in 3D Nor-Tet hydrogels. Injection of bioactive Nor-Tet hydrogels into hollow intramedullary canals of Lewis rat femurs showed a local increase in trabecular bone density as determined by micro-CT imaging. The presented work shows that injectable hydrogels with immobilized BMP-2 peptides are a promising biomaterial for the local regeneration of bone tissue and for the potential local treatment of osteoporosis.

骨质疏松症（Osteoporosis）是一种以骨矿物质密度降低为特征的疾病，进而增加脆性骨折的发生风险。目前多数临床治疗手段为全身性给药，无法在骨缺损部位针对性恢复骨组织，易引发不良副作用。可注射水凝胶可实现空间精准的局部治疗性药物递送，本研究报道了一种负载骨形态发生蛋白-2（bone morphogenetic protein-2, BMP-2）肽模拟物的可注射水凝胶的开发过程。为制备可注射水凝胶，研究人员将透明质酸分别修饰为降冰片烯改性透明质酸（HANor）与四嗪改性透明质酸（HATet），二者混合后可通过点击化学反应形成共价交联的Nor-Tet水凝胶。通过将HANor大分子单体进一步修饰甲基丙烯酸酯（Me），可利用迈克尔加成反应将巯基化的BMP-2模拟肽固定于HANor上，且该偶联过程通过氢核磁共振（1H NMR）光谱得到了验证。无论是可溶性形式还是固定化形式的BMP-2肽，均可上调在二维培养及三维Nor-Tet水凝胶包埋的间充质干细胞（mesenchymal stem cells, MSCs）的碱性磷酸酶（alkaline phosphatase, ALP）表达水平。将具有生物活性的Nor-Tet水凝胶注射至Lewis大鼠股骨的髓内中空管腔后，通过显微计算机断层扫描（micro-CT）成像检测发现，局部骨小梁密度显著提升。本研究结果表明，负载固定化BMP-2肽的可注射水凝胶是一种极具应用前景的生物材料，可用于骨组织的局部再生以及骨质疏松症的潜在局部治疗。