Jennewine Brenton, Fox Jonathan, Ramamurthi Anand
Department of Biomedical Engineering, The Cleveland Clinic, 9500 Euclid Avenue, ND 20, Cleveland, OH 44195, USA; Department of Biomedical Engineering, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, OH 44106, USA.
Department of Biomedical Engineering, The Cleveland Clinic, 9500 Euclid Avenue, ND 20, Cleveland, OH 44195, USA; Department of Chemical and Biomedical Engineering, Cleveland State University, 2121 Euclid Avenue, Cleveland, OH 44115, USA.
Acta Biomater. 2017 Apr 1;52:60-73. doi: 10.1016/j.actbio.2017.01.032. Epub 2017 Jan 10.
Abdominal Aortic Aneurysms (AAA) involve slow dilation and weakening of the aortic wall due to breakdown of structural matrix components, such as elastic fibers by chronically overexpressed matrix metalloproteinases (MMPs), primarily, MMPs-2 and -9. Auto-regenerative repair of disrupted elastic fibers by smooth muscle cells (SMCs) at the AAA site is intrinsically poor and together with chronic proteolysis prevents restoration of elastin homeostasis, necessary to enable AAA growth arrest or regression to a healthy state. Oral doxycycline (DOX) therapy can inhibit MMPs to slow AAA growth, but has systemwide side-effects and inhibits new elastin deposition within AAA tissue, diminishing prospects for restoring elastin homeostasis preventing the arrest/regression of AAA growth. We have thus developed cationic amphiphile (DMAB)-modified submicron particles (SMPs) that uniquely exhibit pro-elastogenic and anti-proteolytic properties, separate from similar effects of the encapsulated drug. These SMPs can enable sustained, low dose DOX delivery within AAA tissue to augment elastin regenerative repair. To provide greater specificity of SMP targeting, we have conjugated the DOX-SMP surface with an antibody against cathepsin K, a lysosomal protease that is highly overexpressed within AAA tissue. We have determined conditions for efficient cathepsin K Ab conjugation onto the SMPs, improved SMP binding to aneurysmal SMCs in culture and to injured vessel walls ex vivo, conjugation did not affect DOX release from the SMPs, and improved pro-elastogenic and anti-proteolytic effects due to the SMPs likely due to their increased proximity to cells via binding. Our study results suggest that cathepsin K Ab conjugation is a useful targeting modality for our pro-regenerative SMPs. Future studies will investigate SMP retention and biodistribution following targeting to induced AAAs in rat models through intravenous or catheter-based aortal infusion and thereafter their efficacy for regenerative elastic matrix repair in the AAA wall.
Proactive screening of high risk elderly patients now enables early detection of Abdominal Aortic Aneurysms (AAAs). Current management of small, growing AAAs is limited to passive, imaging based growth monitoring. There are also no established drug-based therapeutic alternatives to surgery for AAAs, which is unsuitable for many elderly patients, and none which can achieve restore disrupted and lost elastic matrix in the AAA wall, which is essential to achieve growth arrest or regression. We seek to test the feasibility of a regenerative therapy based on localized, one time delivery of drug-releasing Sub-Micron-sized drug delivery polymer Particles (SMPs) that are also uniquely chemically functionalized on their surface to also provide them pro-elastin-regenerative & anti-matrix degradative properties, and also conjugated with antibodies targeting cathepsin K, an elastolytic enzyme that is highly overexpressed in AAA tissues; the latter serves as a modality to enable targeted binding of the SMPs to the AAA wall following intravenous infusion, or intraoartal, catheter-based delivery. Such SMPs can potentially stimulate structural repair in the AAA wall following one time infusion to delay or prevent AAA growth to rupture. The therapy can provide a non-surgical treatment option for high risk AAA patients.
腹主动脉瘤（AAA）是由于结构基质成分（如弹性纤维）被长期过度表达的基质金属蛋白酶（MMPs），主要是MMP - 2和 - 9破坏，导致主动脉壁缓慢扩张和弱化。AAA部位平滑肌细胞（SMC）对受损弹性纤维的自我再生修复本质上较差，加上慢性蛋白水解作用，阻止了弹性蛋白稳态的恢复，而弹性蛋白稳态的恢复是使AAA生长停滞或恢复到健康状态所必需的。口服强力霉素（DOX）治疗可抑制MMPs以减缓AAA生长，但具有全身性副作用，且抑制AAA组织内新弹性蛋白的沉积，减少了恢复弹性蛋白稳态以阻止AAA生长停滞/消退的前景。因此，我们开发了阳离子两亲物（DMAB）修饰的亚微米颗粒（SMPs），其独特地表现出促弹性生成和抗蛋白水解特性，与封装药物的类似作用不同。这些SMPs能够在AAA组织内实现持续、低剂量的DOX递送，以增强弹性蛋白的再生修复。为了提供更高的SMP靶向特异性，我们将DOX - SMP表面与抗组织蛋白酶K抗体偶联，组织蛋白酶K是一种溶酶体蛋白酶，在AAA组织中高度过表达。我们确定了将组织蛋白酶K抗体有效偶联到SMPs上的条件，改善了SMPs在培养物中与动脉瘤SMC以及离体损伤血管壁的结合，偶联不影响DOX从SMPs的释放，并且由于SMPs通过结合增加了与细胞的接近度，可能改善了其促弹性生成和抗蛋白水解作用。我们的研究结果表明，组织蛋白酶K抗体偶联是我们的促再生SMPs的一种有用的靶向方式。未来的研究将通过静脉内或基于导管的主动脉输注，研究靶向大鼠模型中诱导的AAA后SMPs的保留和生物分布，以及它们对AAA壁中再生弹性基质修复的功效。
对高危老年患者进行主动筛查现在能够早期发现腹主动脉瘤（AAAs）。目前对小型、生长性AAAs的管理仅限于基于成像的被动生长监测。对于AAAs，也没有既定的非手术药物治疗替代方案，手术不适用于许多老年患者，并且没有一种方法能够恢复AAA壁中破坏和丢失的弹性基质，而这对于实现生长停滞或消退至关重要。我们试图测试一种再生疗法的可行性，该疗法基于局部一次性递送释放药物的亚微米级药物递送聚合物颗粒（SMPs），这些颗粒在其表面还经过独特的化学功能化，以赋予它们促弹性蛋白再生和抗基质降解特性，并且还与靶向组织蛋白酶K的抗体偶联，组织蛋白酶K是一种在AAA组织中高度过表达的弹性溶解酶；后者作为一种方式，使SMPs在静脉内输注或基于导管的动脉内递送后能够靶向结合到AAA壁上。这种SMPs在一次性输注后可能刺激AAA壁的结构修复，以延迟或防止AAA生长至破裂。该疗法可以为高危AAA患者提供一种非手术治疗选择。
