MO461: A Novel Chronic Kidney Disease to HFpEF Connection: Inflammatory Signaling, Micro-RNAs, and NF-KB

BACKGROUND AND AIMS

Chronic kidney disease (CKD) is an independent risk factor for heart failure with preserved ejection fraction (HFpEF), a progressive condition that affects ˃50% of patients in dialysis. We developed a swine model of CKD-HFpEF and showed that renal inflammatory signaling plays a key role in HFpEF pathophysiology via cardiac activation of nuclear factor-kappa B (NF-kB). However, the mechanisms of CKD-induced cardiac NF-κB activation remain unclear. We hypothesized that micro-RNA (miRNA)-mediated processes contribute to cardiac NF-kB activation in CKD-HFpEF.

METHOD

Using an in-silico approach (miRWalk3.0 and TargetScan 7.2), we identified all miRNAs capable of targeting the NFKB Inhibitor Alpha (NFKBIA) gene. We then identified those expressed in swine myocardium and measured their levels in normal and CKD pigs by qPCR. In a biomimetic heart culture system that mimics the cardiac CKD-HFpEF microenvironment, pig heart slices were exposed to plasma from normal or CKD pigs, and cardiac kinetics, NF-kB signaling, and miRNA expression levels were investigated in vitro.

RESULTS

We identified 5 miRNAs expressed in swine hearts capable of targeting NFKBIA, of which only miR-1271–3p showed higher expression in the myocardium of CKD-HFpEF pigs compared to normal pigs. miR-1271–3p upregulation was mirrored in pig heart slices exposed to plasma from CKD pigs, associated with blunted cardiac contraction/relaxation kinetics, downregulation of NFKBIA, and increased protein expression of NF-κB (Figure).

CONCLUSION

Our data support a novel pathophysiological mechanism for cardiac activation of NF-κB in CKD via post-transcriptional modulation of NFKBIA partly through miR-1271–3p. This miRNA might represent a novel therapeutic target to ameliorate the deleterious effects that renal inflammatory signaling in CKD imposes on the heart and may lead to HFpEF.

Microvascular remodeling and altered angiogenic signaling in human kidneys distal to occlusive atherosclerotic renal artery stenosis

BACKGROUND

Renal artery stenosis (RAS) is an important cause of chronic kidney disease and secondary hypertension. In animal models, renal ischemia leads to downregulation of growth-factor expression and loss of intrarenal microcirculation. However, little is known about the sequelae of large vessel occlusive disease on the microcirculation within human kidneys.

METHOD

This study included 5 patients who underwent nephrectomy due to renovascular occlusion, and 7 non-stenotic discarded donor kidneys (4 deceased donors). Micro-computed tomography was performed to assess microvascular spatial densities and tortuosity, an index of microvascular immaturity. Renal protein expression, gene expression, and histology were studied in-vitro using immunoblotting, polymerase-chain-reaction, and staining.

RESULTS

RAS demonstrated loss of medium-sized vessels (0.2-0.3mm) compared to donor kidneys (p = 0.037) and increased microvascular tortuosity. RAS kidneys had greater protein expression of angiopoietin-1, hypoxia-inducible factor (HIF)-1α, and thrombospondin (TSP)-1, but lower protein expression of vascular endothelial growth factor (VEGF) than donor kidneys. Renal fibrosis, loss of peritubular capillaries (PTC) and pericyte detachment were greater in RAS, yet they had more newly-formed PTC than donor kidneys. Therefore, our study quantified significant microvascular remodeling in the post-stenotic human kidney. RAS induced renal microvascular loss, vascular remodeling, and fibrosis. Despite downregulated VEGF, stenotic kidneys upregulated compensatory angiogenic pathways related to angiopoietin-1.

CONCLUSIONS

These observations underscore the nature of human RAS as a microvascular disease distal to main vessel stenosis, and support therapeutic strategies directly targeting the post-stenotic kidney microcirculation in patients with RAS.

Low-Energy Shockwave Treatment Promotes Endothelial Progenitor Cell Homing to the Stenotic Pig Kidney

Endothelial progenitor cells (EPCs) patrols the circulation and contributes to endothelial cell regeneration. Atherosclerotic renal artery stenosis (ARAS) induces microvascular loss in the stenotic kidney (STK). Low-energy shockwave therapy (SW) can induce angiogenesis and restore the STK microcirculation, but the underlying mechanism remains unclear. We tested the hypothesis that SW increases EPC homing to the swine STK, associated with capillary regeneration. Normal pigs and pigs after 3 wk of renal artery stenosis were treated with six sessions of low-energy SW (biweekly for three consecutive weeks) or left untreated. Four weeks after completion of treatment, we assessed EPC (CD34+/KDR+) numbers and levels of the homing-factor stromal cell-derived factor (SDF)-1 in the inferior vena cava and the STK vein and artery, as well as urinary levels of vascular endothelial growth factor (VEGF) and integrin-1β. Subsequently, we assessed STK morphology, capillary count, and expression of the proangiogenic growth factors angiopoietin-1, VEGF, and endothelial nitric oxide synthase ex vivo. A 3-wk low-energy SW regimen improved STK structure, capillary count, and function in ARAS+SW, and EPC numbers and gradients across the STK decreased. Plasma SDF-1 and renal expression of angiogenic factors were increased in ARAS+SW, and urinary levels of VEGF and integrin-1β tended to rise during the SW regimen. In conclusion, SW improves ischemic kidney capillary density, which is associated with, and may be at least in part mediated by, promoting EPCs mobilization and homing to the stenotic kidney.

Mesenchymal stem cells protect renal tubular cells via TSG-6 regulating macrophage function and phenotype switching

Tumor necrosis factor (TNF)-α-induced gene/protein (TSG)-6 regulates the immunomodulatory properties of mesenchymal stem cells (MSCs), but its ability to protect the ischemic kidney is unknown. In a swine model of renal artery stenosis (RAS) and metabolic syndrome (MetS), we assessed the contribution of TSG-6 produced by MSCs to their immunomodulatory properties. Pigs were studied after 16 wk of diet-induced MetS and unilateral RAS and were either untreated or treated 4 wk earlier with intrarenal autologous adipose tissue-derived MSCs (n = 6 each). Lean, MetS, and RAS sham animals served as controls. We studied renal function in vivo (using computed tomography) and kidney histopathology and macrophage phenotype ex vivo. In vitro, TSG-6 levels were also measured in conditioned media of human MSCs incubated with TNF-α and levels of the tubular injury marker lactate dehydrogenase in conditioned media after coculturing macrophages with injured human kidney 2 (HK-2) cells with or without TSG-6. The effects of TSG-6 on macrophage phenotype (M1/M2), adhesion, and migration were also determined. MetS + RAS showed increased M1 macrophages and renal vein TNF-α levels. After MSC delivery, renal vein TSG-6 increased and TNF-α decreased, the M1-to-M2 ratio decreased, renal function improved, and fibrosis was alleviated. In vitro, TNF-α increased TSG-6 secretion by human MSCs. TSG-6 decreased lactate dehydrogenase release from injured HK-2 cells, increased expression of macrophage M2 markers, and reduced M1 macrophage adhesion and migration. Therefore, TSG-6 released from MSCs may decrease renal tubular cell injury, which is associated with regulating macrophage function and phenotype. These observations suggest that TSG-6 is endowed with renoprotective properties.NEW & NOTEWORTHY Tumor necrosis factor-α-induced gene/protein (TSG)-6 regulates the immunomodulatory properties of MSCs, but its ability to protect the ischemic kidney is unknown. In pigs with renal artery stenosis, we show that MSC delivery increased renal vein TSG-6, decreased kidney inflammatory macrophages, and improved renal function. In vitro, TSG-6 decreased inflammatory macrophages and tubular cell injury. Therefore, TSG-6 released from MSCs may decrease renal tubular cell injury, which is associated with regulating macrophage function and phenotype.

Mesenchymal Stem/Stromal Cells and their Extracellular Vesicle Progeny Decrease Injury in Poststenotic Swine Kidney Through Different Mechanisms

Novel therapies are needed to address the increasing prevalence of chronic kidney disease. Mesenchymal stem/stromal cells (MSCs) and MSC-derived extracellular vesicles (EVs) augment tissue repair. We tested the hypothesis that EVs are as effective as MSCs in protecting the stenotic kidney, but target different injury pathways. Pigs were studied after 16 weeks of renal injury achieved by diet-induced metabolic syndrome (MetS) and renal artery stenosis (RAS). Pigs were untreated or treated 4 weeks earlier with intrarenal delivery of autologous adipose tissue-derived MSCs (10⁷) or their EVs (10¹¹). Lean pigs and sham RAS served as controls (n = 6 each). Stenotic-kidney function was studied in vivo using computed tomography and magnetic resonance imaging. Histopathology and expression of necroptosis markers [receptor-interacting protein kinase (RIPK)-1 and RIPK-3], inflammatory, and growth factors (angiopoietin-1 and vascular endothelial growth factor) were studied ex vivo. Stenotic-kidney glomerular filtration rate and blood flow in MetS + RAS were both lower than Lean and increased in both MetS + RAS + MSC and MetS + RAS + EV. Both MSCs and EV improved renal function and decreased renal hypoxia, fibrosis, and apoptosis. MSCs were slightly more effective in preserving microvascular (0.02-0.2 mm diameters) density and prominently attenuated renal inflammation. However, EV more significantly upregulated growth factor expression and decreased necroptosis. In conclusion, adipose tissue-derived MSCs and their EV both improve stenotic kidney function and decrease tissue injury in MetS + RAS by slightly different mechanisms. MSCs more effectively preserved the microcirculation, while EV bestowed better preservation of renal cellular integrity. These findings encourage further exploration of this novel approach to attenuate renal injury.