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

临界尺寸骨缺损（CSBD）是需要治疗干预以诱导骨形成的非愈合性骨损伤。这些损伤是由于创伤、肿瘤切除、发育异常和感染而发生的。骨愈合受损，包括延迟愈合或骨不连，在加拿大占150，000至200，000例住院治疗， 每年18 B美元的医疗保健系统负担。目前的金标准是将患者髂嵴的自体骨移植到缺损处。需要进行第二次手术干预会增加术后并发症和伤口感染的风险，并需要更长的住院时间。一种可以使用微创手术进行管理的可注射治疗方式将减少感染的风险、住院时间和手术费用。我们成功地证明了我们实验室开发的可注射壳聚糖海绵具有生物相容性，并且在60天内完全生物降解。向壳聚糖海绵中添加酶提供了磷酸根离子的恒定释放，这显著增加了前成骨细胞MC3T3细胞中的生物矿化。此外，可以实现成骨因子在海绵中的高包封效率及其在30天内的受控释放。MC3T3和脂肪源性干细胞（ASC）的包封表明支架对于细胞存活、增殖和分化的适用性。 和差异化。在此，我们建议研究海绵作为递送系统和作为ASCs封装、酶和成骨因子的3D支架，并最终作为CSBD体内生物矿化的组织构建。为了将这一有前途的技术平台转化为临床，必须在CSBD的相关动物模型中验证海绵。我们与参与该提案的行业和商业化专家合作，在CHRP提案中取得成功，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.