Injectable Hydrogels to Deliver Gene Therapy for Myocardial Infarct

心肌梗死（MI）后，局部组织重塑导致心脏功能慢性恶化， 这是美国人死亡的主要原因。几项临床前研究表明，局部递送生长因子或 生长因子编码基因可以显著改善心脏功能。不幸的是， 跳动心脏的治疗仍然是一个巨大的挑战，阻碍了新药的临床转化 治疗学理想的MI药物递送系统将是导管可注射的，将防止从药物递送系统中挤出。 收缩心肌，并将提供有效治疗剂量的持续递送。不幸的是， 大多数导管可注射的生物材料是从收缩的心脏组织中快速挤出的弱水凝胶。 为了克服这一临床挑战，我们提出了通过动态交联的可注射凝胶的设计。 共价化学（DCC）键是强而可逆的。因此，这些DCC水凝胶联合收割机结合了临床上 可注射和具有保持在打浆中所需的机械完整性的所需性质 心具体来说，我们的凝胶是通过化学修饰的透明质酸之间的DCC腙键形成的。 酸和重组弹性蛋白样蛋白。所得到的凝胶是酶可生物降解的， 在FDA研究中确定未来的潜力。在目的1中，制备了具有不同粘弹性机械性质的20种凝胶的家族。 将合成和表征性能，以便于导管注射和保留在收缩中， 心我们将通过改变透明质酸的分子量和产率来调节凝胶的粘度 通过改变DCC交联竞争剂的浓度， 可注射性的定量。在目标2中，我们同时评估了以下假设： 再生有效载荷可以通过组合混合具有不同切割的药物系链来实现 动力学具体来说，我们的有效载荷是编码基质细胞衍生因子-1 α（SDF-1α）的小环基因， 已知可诱导血管生成并改善MI后的心脏功能。这个有效载荷被拴在注射器上 通过与肽核酸（PNA）-肽的DNA杂交凝胶。在目标3中，使用来自目标1的凝胶制剂， 最佳的体内保留特性和来自Aim 2的具有持续基因释放的药物系链设计将是 与注射性心肌梗死疗法结合将在临床前大鼠MI模型中评价功能性能 使用携带SDF-1α和萤火虫荧光素酶报告基因的小环基因。诱导MI后 通过结扎左前降支（LAD）动脉，将动物随机分配至假手术组或对照组， 或治疗组。给药动物将仅接受60 μL生理盐水、水凝胶心肌内注射 仅限盐水中的未束缚基因、凝胶中的未束缚基因或凝胶中的束缚基因。生物发光成像 (days 0、1、4、7、21、42、60和90）将用于监测基因表达。MI后的功能恢复将是 使用超声心动图（第7、21天）和血液动力学测量（第90天）进行评估。最后，心 分析外植体的坏死、炎症、血管生成和组织再生的证据（第90天）。

Following myocardial infarction (MI), local tissue remodeling leads to chronically worsening heart function that is a major cause of death in the US. Several preclinical studies have shown that local delivery of growth factors or growth factor-encoding genes can significantly improve cardiac function. Unfortunately, effective delivery of therapeutics to the beating heart remains a formidable challenge, impeding clinical translation of novel drug therapeutics. The ideal MI drug-delivery system would be catheter injectable, would prevent extrusion out of the contractile myocardium, and would provide sustained delivery of an effective therapeutic dosage. Unfortunately, most catheter-injectable biomaterials are weak hydrogels that are rapidly extruded out of contractile heart tissue. To overcome this clinical challenge, we propose the design of injectable gels that are crosslinked by dynamic covalent chemistry (DCC) bonds that are strong yet reversible. Thus, these DCC hydrogels combine the clinically desired properties of being injectable and having the mechanical integrity required for retention in the beating heart. Specifically, our gels are formed through DCC hydrazone bonds between a chemically modified hyaluronic acid and a recombinant, elastin-like protein. The resulting gel is enzymatically biodegradable and fully chemically defined for future potential in FDA studies. In Aim 1, a family of 20 gels with distinct viscoelastic mechanical properties will be synthesized and characterized for ease of catheter injection and retention in the contracting heart. We will modulate the viscosity of the gels by altering the molecular weight of hyaluronic acid and the yield stress of the gel by varying the concentration of a DCC crosslink competitor and perform in vitro and in vivo quantifications of injectability. In parallel in Aim 2, we evaluate the hypothesis that sustained release of a regenerative payload can be achieved through combinatorial mixing of drug tethers with distinct cleavage kinetics. Specifically, our payload is minicircle genes encoding stromal cell-derived factor-1α (SDF-1α), which is known to induce angiogenesis and improved heart function following MI. This payload is tethered to the injectable gel via DNA hybridization with peptide nucleic acid (PNA)-peptides. In Aim 3, the gel formulation from Aim 1 with optimal in vivo retention properties and the drug tether design from Aim 2 with sustained gene release will be combined into an injectable MI therapy. Functional performance will be evaluated in a preclinical rat MI model using minicircle genes carrying both SDF-1α and a firefly luciferase reporter gene. Following induction of MI through ligation of the left anterior descending (LAD) artery, animals will be randomly assigned into either sham or treatment groups. Treatment animals will receive a 60-μL intramyocardial injection of saline only, hydrogel only, untethered genes in saline, untethered genes in gel, or tethered genes in gel. Bioluminescence imaging (days 0, 1, 4, 7, 21, 42, 60, and 90) will be used to monitor gene expression. Functional recovery after MI will be assessed using echocardiography (days 7, 21) and hemodynamic measurements (day 90). Finally, heart explants will be analyzed for evidence of necrosis, inflammation, angiogenesis, and tissue regeneration (day 90).