An Injectable Phosphate Releasing Bone Tissue Construct Encapsulating Adipose-Derived Stem Cells and Diphosphate Cleaving Enzymes to Promote Biomineralization in Critical Size Bone Defects

临界大小的骨缺损(CSBD)是一种不可愈合的骨损伤，需要通过治疗干预来诱导骨形成。这些损伤是由于创伤、肿瘤切除、发育异常和感染造成的。骨愈合受损，包括延迟愈合或骨不连，在加拿大占15万至20万次住院治疗，产生12至 每年给医疗保健系统带来180亿美元的负担。目前的黄金标准是将患者的自体髂骨移植到缺损处。需要进行第二次手术干预会增加手术后并发症和伤口感染的风险，并需要更长的住院时间。一种可注射的治疗方式，可以使用微创手术进行管理，将减少感染的风险，住院时间和手术费用。本实验室研制的可注射壳聚糖海绵具有良好的生物相容性，可在60天内完全降解。在壳聚糖海绵中添加酶可以持续释放磷酸盐离子，从而显著增加成骨前细胞MC3T3的生物矿化。此外，成骨因子在海绵中的包封率很高，并可在30天内得到控制释放。MC3T3和脂肪来源干细胞(ASCs)的包裹表明该支架适合细胞的存活、增殖 和差异化。在这里，我们建议研究海绵作为一种输送系统和作为ASCs包裹、酶和成骨因子的3D支架，最终作为CSBD体内生物矿化的组织构建。为了将这一有前景的技术平台转化为临床，迫切需要验证海绵在CSBD相关动物模型中的有效性。我们与参与这项提议的行业和商业化专家合作，在这项CHRP提议中取得成功，将提供这一机会。

Critical size bone defects (CSBD) are non-healing bone injuries that require a therapeutic intervention to induce bone formation. These injuries occur due to trauma, removal of tumors, developmental anomalies, and infections. Impaired bone healing, including delayed union or non-union, accounts for 150,000 to 200,000 hospitalizations in Canada generating a $12 to $18 B/y burden on the health care system. The current golden standard is to graft autologous bone from the patients iliac crest onto the defect. The need to create a second surgical intervention increases the risk of post-surgical complications and wound infections, and requires longer hospitalization. An injectable therapeutic modality that can be administered using minimally invasive surgery will reduce risk of infection, time of hospitalization and\ surgical costs. We successfully demonstrated, that injectable chitosan sponges developed in\ our laboratory, are biocompatible, and completely biodegrade within 60 days. The addition of enzymes to the chitosan sponges provided a constant release of phosphate ions, which significantly increased biomineralization in pre-osteoblast MC3T3 cells. Further, a high encapsulation efficiency of osteogenic factors in the sponge and its controlled release over a period of 30 days could be achieved. The encapsulation of both MC3T3 and Adipose-Derived Stem Cells (ASCs) indicated the suitability of the scaffold for cells survivability, proliferation and differentiation. Herein, we propose to investigate the sponge as a delivery system and as a 3D-scaffold for ASCs encapsulation, enzymes and osteogenic factors, and ultimately as a tissue construct for in vivo biomineralization in CSBD. To translate this promising technology platform to clinics, it is imperative to validate the sponge in relevant animal model of CSBD. This opportunity will be offered by our success in this CHRP proposal in partnership with industry and commercialization specialists involved in this proposal.