Renal Therapeutic Angiogenesis Using a Bioengineered Polymer-Stabilized Vascular Endothelial Growth Factor Construct

Abstract

Renovascular disease (RVD) induces renal microvascular (MV) rarefaction that drives progressive kidney injury. In previous studies, we showed that renal vascular endothelial growth factor (VEGF) therapy attenuated MV damage, but did not resolve renal injury at practical clinical doses. To increase the bioavailability of VEGF, we developed a biopolymer-stabilized elastin-like polypeptide (ELP)-VEGF fusion protein and determined its in vivo potential for therapeutic renal angiogenesis in RVD using an established swine model of chronic RVD. We measured single-kidney blood flow (RBF) and GFR and established the degree of renal damage after 6 weeks of RVD. Pigs then received a single stenotic kidney infusion of ELP-VEGF (100 mg/kg), a matching concentration of unconjugated VEGF (18.65 mg/kg), ELP alone (100 mg/kg), or placebo. Analysis of organ distribution showed high renal binding of ELP-VEGF 4 hours after stenotic kidney infusion. Therapeutic efficacy was determined 4 weeks after infusion. ELP-VEGF therapy improved renal protein expression attenuated in RVD, restoring expression levels of VEGF, VEGF receptor Flk-1, and downstream angiogenic mediators, including phosphorylated Akt and angiopoietin-1 and -2. This effect was accompanied by restored MV density, attenuated fibrogenic activity, and improvements in RBF and GFR greater than those observed with placebo, ELP alone, or unconjugated VEGF. In summary, we demonstrated the feasibility of a novel therapy to curtail renal injury. Recovery of the stenotic kidney in RVD after ELP-VEGF therapy may be driven by restoration of renal angiogenic signaling and attenuated fibrogenic activity, which ameliorates MV rarefaction and improves renal function. 27: 174127: -175227: , 201627: . doi: 10.1681 Renal vascular disease (RVD), usually caused by renal artery stenosis, can lead to CKD and ESRD. RVD increases cardiovascular morbidity and mortality, hospitalization, shortens life expectancy, and is increasing at a sustained pace in the United States. 1 Moreover, renal function does not improve or even deteriorates in almost half of the patients with RVD despite treatment. Recent clinical studies suggest that patients undergoing current therapeutic strategies, which include drugs and renal angioplasty, do not show differences in outcomes that could demonstrate distinct benefits of one treatment over the other when compared side by side. 2,3 Moreover, renal function does not improve or even deteriorates in almost half of patients with RVD despite treatment, highlighting a pressing need for novel therapeutic strategies for the growing population of patients suffering from RVD. J Am Soc NephrolUsing a clinically relevant swine model of chronic RVD that mimics several of the pathologic features

Therapeutic angiogenesis by vascular endothelial growth factor supplementation for treatment of renal disease

“…In collaboration with Dr. Chade, we tested the ELP-VEGF fusion protein’s ability to reverse vascular damage and improve renal function in the swine RVD model. We found that when administered intrarenally six weeks after induction of renal artery stenosis, ELP-VEGF was mostly retained in the injected kidney with some spillover into the contralateral kidney, and it significantly improved renal function and increased microvascular density in the stenotic kidney (47). Importantly, ELP-VEGF outperformed free VEGF in its ability to induce improved renal function, indicating that fusion to the stabilizing biopolymer is beneficial.…”

“…In a series of studies using a swine model of renal artery stenosis (41–43), Chade et al have implicated VEGF deficiency and resulting microvascular loss in the deterioration of renal function. Renal artery stenosis induced by placement of a local irritant coil lead to progressive deterioration of renal function over the course of several weeks that was accompanied by reduced renal VEGF expression (43).…”

A Maternally Sequestered, Biopolymer‐Stabilized Vascular Endothelial Growth Factor (VEGF) Chimera for Treatment of Preeclampsia

“…However, a potential limitation of this approach is that exogenously administered growth factors possesses a brief plasma half‐life and are prone to degradation 39. This limitation can be overcome by fusion of growth factors with a biopolymer synthetic protein based on human elastin 40, 41. Elastin‐like polypeptide (ELP) is composed of a repeating 5 amino acid motif that is thermally responsive,25, 41, 42 facilitating purification of ELP and ELP‐fusion proteins by thermal cycling 43.…”

Endothelial Dysfunction in Renal Interstitial Fibrosis

“…The renal endothelium lacks regenerative capacity early after IRI, unlike the tubule epithelium, potentially due to a low level of angiogenic signals and endothelial proliferation[2,12]. Approaches to preserve the renal endothelium such as infusion of VEGF in pigs after established renovascular disease, prevented microvascular rarefaction, attenuated fibrosis & normalized renal blood flow and kidney function compared to controls[13], suggesting that targeting therapeutic interventions to promote endothelial function may be an effective strategy to reduce fibrosis.…”

“…Blockade of prosurvival factors such as VEGFR2 or PDGFRβ has been shown to reduce pericyte proliferation and differentiation, microvascular rarefaction, inflammation and fibrosis[16]. The apparent discrepancy between these findings and that administration of VEGF protects against fibrosis [13] may be due to the complex signaling pathway including three VEGF receptors and the regulated expression of four distinct VEGF genes and multiple splice variants. Therefore, these studies cannot simply be explained by a binary ligand receptor interaction .…”