Australian Institute for Bioengineering and Nanotechnology, University of Queensland, St Lucia, Queensland 4072, Australia.
Biomaterials. 2013 Dec;34(37):9430-40. doi: 10.1016/j.biomaterials.2013.08.072. Epub 2013 Sep 16.
Intervertebral disc (IVD) degeneration is one of the leading causes of lower back pain and a major health problem worldwide. Current surgical treatments include excision or immobilisation, with neither approach resulting in the repair of the degenerative disc. As such, a tissue engineering-based approach in which stem cells, coupled with an advanced delivery system, could overcome this deficiency and lead to a therapy that encourages functional fibrocartilage generation in the IVD. In this study, we have developed an injectable hydrogel system based on enzymatically-crosslinked polyethylene glycol and hyaluronic acid. We examined the effects of adding pentosan polysulphate (PPS), a synthetic glycosaminoglycan-like factor that has previously been shown (in vitro and in vivo) to this gel system in order to induce chondrogenesis in mesenchymal precursor cells (MPCs) when added as a soluble factor, even in the absence of additional growth factors such as TGF-β. We show that both the gelation rate and mechanical strength of the resulting hydrogels can be tuned in order to optimise the conditions required to produce gels with the desired combination of properties for an IVD scaffold. Human immunoselected STRO-1+ MPCs were then incorporated into the hydrogels. They were shown to retain good viability after both the initial formation of the gel and for longer-term culture periods in vitro. Furthermore, MPC/hydrogel composites formed cartilage-like tissue which was significantly enhanced by the incorporation of PPS into the hydrogels, particularly with respect to the deposition of type-II-collagen. Finally, using a wild-type rat subcutaneous implantation model, we examined the extent of any immune reaction and confirmed that this matrix is well tolerated by the host. Together these data provide evidence that such a system has significant potential as both a delivery vehicle for MPCs and as a matrix for fibrocartilage tissue engineering applications.
椎间盘（IVD）退变是导致下腰痛的主要原因之一，也是全球范围内的一个主要健康问题。目前的手术治疗包括切除或固定，这两种方法都不能修复退行性椎间盘。因此，基于组织工程的方法，将干细胞与先进的输送系统相结合，可以克服这一缺陷，并开发出一种治疗方法，促进 IVD 中功能性纤维软骨的生成。在这项研究中，我们开发了一种基于酶交联的聚乙二醇和透明质酸的可注射水凝胶系统。我们研究了添加戊聚糖多硫酸酯（PPS）的效果，PPS 是一种合成的糖胺聚糖样因子，先前已证明（体外和体内），当作为可溶性因子添加到该凝胶系统中时，即使在没有 TGF-β 等额外生长因子的情况下，也能诱导间充质前体细胞（MPC）向软骨分化。我们表明，所得水凝胶的凝胶化速率和机械强度都可以进行调整，以优化产生具有所需 IVD 支架特性组合的凝胶的条件。然后将人免疫选择的 STRO-1+ MPC 掺入水凝胶中。结果表明，在初始凝胶形成后以及体外长期培养期间，它们仍保持良好的活力。此外，MPC/水凝胶复合物形成了软骨样组织，通过将 PPS 掺入水凝胶中，特别是在 II 型胶原蛋白的沉积方面，显著增强了这种组织。最后，使用野生型大鼠皮下植入模型，我们检查了任何免疫反应的程度，并证实了这种基质被宿主很好地耐受。这些数据共同表明，该系统具有作为 MPC 输送载体和纤维软骨组织工程应用基质的巨大潜力。
