诊疗一体化的干细胞源性外泌体靶向递送新策略仿生性修复心肌损伤的实验研究

It is a new direction of inducing endogenous stem cells for repair of myocardial injury. Our previous studies have confirmed that genes transfection increase SDF-1α (stromal cell derived factor-1α, the strongest stem cell inducer) expression in infarct zone can promote endogenous stem cells homing and improve cardiac function. However, the transfection efficiency of SDF-1α gene in vivo is low and the therapeutic effect is not satisfactory. Recent studies have shown that exosomes are important functional biomaterials of endogenous stem cells and ideal therapeutic molecular carriers. So in this study we will use slow virus mediate SDF-1α gene transfect canine adipose-derived stem cells (ADSCs) in vitro to acquire abundant stem cells derived exosomes overexpressing SDF-1α. Then a novel targeted nanobubbles for myocardial infarction targeting imaging and drug delivery will be constructed as the carrier of exosomes. With the help of low intensity ultrasound exosomes will import the ischemic myocardium and then physiologically release. On the one hand, ADSCs derived exosomes can replace stem cells to inhibit apoptosis, promote angiogenesis and improve microcirculation. On the other hand, exosomes containing a lot of SDF-1α will induce stem cells homing and promote myocardial repair. So as to explore a cell-free therapy strategy for myocardial infarction.

通过内源性干细胞修复心肌损伤是目前心肌梗死治疗的新方向。项目组前期利用基因转染的方式使梗死区表达干细胞诱导剂SDF-1α，以促进内源性干细胞归巢，修复心肌，但是由于体内转染效率较低，疗效不理想。新近研究表明外泌体是内源性干细胞的重要功能物质，也是理想的治疗性分子载体。介于此，本研究另辟蹊径，用慢病毒介导SDF-1α基因体外转染犬自体脂肪来源干细胞(ADSCs)，大量获取SDF-1α高表达的干细胞源性外泌体，构建兼具心肌梗死靶向显像和药物递送功能的新型靶向纳米微泡作为外泌体的载体，在低强度超声作用下将外泌体反复多次导入梗死区并模拟生理性持续释放。一方面，ADSCs源性外泌体可替代干细胞发挥抗凋亡、促血管新生、改善微循环等功能；另一方面，外泌体富含SDF-1α，可诱导内源性干细胞靶向归巢，增强内源性修复效应。从而为心肌梗死治疗探索一条不同于干细胞移植的“无细胞治疗”新策略。

急性心肌梗死治疗的关键是尽早血运重建，对于错失血运重建时机的患者，目前临床上缺乏有效的治疗手段。干细胞源性外泌体具有与干细胞相似的心脏保护功能，能促进血管生成，减少细胞凋亡，且不会引起受体细胞的突变以及免疫排斥反应，有望成为心肌梗死治疗的新方法。然而，经静脉注射干细胞源性外泌体靶向性差、病灶区药物浓度低、治疗模式单一，疗效不佳。介于此，本研究构建了一种诊疗一体化的超声靶向外泌体递送系统：（1）采用慢病毒介导基质细胞衍生因子1(SDF-1α)基因在体外转染脂肪来源干细胞(ADSCs)，大量获取SDF-1α高表达的干细胞源性外泌体(ADSC-exoSDF-1α)；（2）构建靶向缺血心肌的纳泡TNBCD81-cRGD作为携带外泌体的载体，既可实现心肌梗死的超声靶向显像，又能在超声靶向微泡破坏作用下将ADSC-exoSDF-1α定向导入心肌梗死区；（3）导入梗死区的干细胞源性外泌体可实现仿生性修复心肌。一方面，ADSCs源性外泌体可替代干细胞发挥抗凋亡、促血管新生、改善心肌微环境等功能；另一方面，外泌体富含SDF-1α，可诱导内源性干细胞靶向归巢，增强内源性修复效应，从而明显提高了心肌梗死的疗效。这种诊疗一体化的干细胞外泌体递送系统为治疗心肌梗死提供了靶向、高效的新方法。