BACKGROUND The treatment of osteochondral defects (OCDs) constitutes a major problem for orthopaedic surgeons. The altered mechanics and the cell types, with associated soluble factors derived from the exposed subchondral bone, are likely responsible for the mechanically and structurally inferior articular cartilage subsequently obtained as a repair tissue. There is therefore an unmet clinical need for bioresponsive biomaterials that allow cell delivery, reduce cell infiltration from the bone marrow, and support chondrogenesis in the presence of joint mechanical loading. PURPOSE To develop a cell-laden injectable biomaterial, with bioadhesive properties, low cell invasion, and good mechanoresilience, in which simulated joint loading could induce tissue maturation through the production and activation of transforming growth factor beta 1 (TGF-β1). STUDY DESIGN Controlled laboratory study. METHODS Human bone marrow-derived mesenchymal stromal/stem cells were encapsulated in tyramine-modified hyaluronic acid (HA-Tyr) hydrogels, with crosslinking initiated by the addition of horseradish peroxidase (HRP) and various concentrations of hydrogen peroxide (H2O2; 0.3-2 mM). Cytocompatibility and biomechanical and adhesive properties were analyzed by live/dead staining, rheology, and push-out test, respectively. For multiaxial loading, cell-laden hydrogels were subjected to 10% compression superimposed onto a 0.5-N preload and shear loading (±25°) at 1 Hz for 1 hour per day and 5 times a week for 4 weeks. TGF-β1 production and activation were measured by enzyme-linked immunosorbent assay (ELISA). RESULTS The viscoelastic properties of the cell-laden HA-Tyr hydrogels, as crosslinked with different ratios of HRP and H2O2, were demonstrated for a range of cell densities and HRP/H2O2 concentrations. In the absence of serum supplementation, cell invasion into HA-Tyr hydrogels was minimal to absent. The bonding strength of HA-Tyr to articular cartilage compared favorably with clinically used fibrin gel. CONCLUSION HA-Tyr hydrogels can be mechanically conditioned to induce activation of endogenous TGF-b1 produced by the embedded cells. HA-Tyr hydrogels function as cell carriers supporting biomechanically induced production and activation of TGF-β1 and as bioadhesive materials with low cell invasion, suggesting that they hold promise as a novel biomaterial for OCD repair strategies. CLINICAL RELEVANCE Leveraging physiological joint mechanics to support chondrogenic graft maturation in an optimized mechanosensitive hydrogel in the absence of exogenous growth factors is of highest interest for OCD repair.

中文翻译：

---

关节关节模拟机械负荷激活高度细胞化的生物粘附水凝胶中的内源性TGF-β，以修复软骨。

背景技术骨软骨缺损（OCD）的治疗构成了整形外科医生的主要问题。力学和细胞类型的改变以及相关的可溶性因子来自暴露的软骨下骨，可能是随后作为修复组织获得的机械和结构性下软骨的原因。因此，对于生物响应性生物材料存在未满足的临床需求，该生物响应性生物材料允许细胞递送，减少细胞从骨髓的浸润并在存在关节机械负荷的情况下支持软骨形成。目的开发一种具有生物粘附特性，低细胞侵袭性和良好机械弹性的充满细胞的可注射生物材料，其中模拟关节负荷可通过产生和激活转化生长因子β1（TGF-β1）诱导组织成熟。研究设计受控的实验室研究。方法将人骨髓源间充质干/干细胞封装在酪胺修饰的透明质酸（HA-Tyr）水凝胶中，并通过添加辣根过氧化物酶（HRP）和不同浓度的过氧化氢（H2O2; 0.3-2）进行交联毫米）。通过活/死染色，流变学和推出试验分别分析了细胞相容性，生物力学和粘附特性。对于多轴加载，将载有细胞的水凝胶进行10％压缩，然后叠加在0.5-N的预加载和1 Hz的剪切负载（±25°）上，每天1小时，每周5次，共4周。通过酶联免疫吸附测定（ELISA）测量TGF-β1的产生和活化。结果载有细胞的HA-Tyr水凝胶的粘弹性为 在不同的细胞密度和HRP / H2O2浓度范围内，均以不同比例的HRP和H2O2交联。在没有补充血清的情况下，几乎没有细胞侵入到HA-Tyr水凝胶中。与临床使用的纤维蛋白凝胶相比，HA-Tyr与关节软骨的结合强度优越。结论HA-Tyr水凝胶可以进行机械调节，以诱导由包埋细胞产生的内源性TGF-bl的活化。HA-Tyr水凝胶可作为细胞载体，支持生物力学诱导的TGF-β1的产生和活化，并具有低细胞入侵的生物粘附性材料，这表明它们有望作为OCD修复策略的新型生物材料。