LRG1 Promotes Diabetic Kidney Disease Progression by Enhancing TGF-β–Induced Angiogenesis

Abstract

Background Glomerular endothelial dysfunction and neoangiogenesis have long been implicated in the pathogenesis of diabetic kidney disease (DKD). However, the specific molecular pathways contributing to these processes in the early stages of DKD are not well understood. Our recent transcriptomic profiling of glomerular endothelial cells identified a number of proangiogenic genes that were upregulated in diabetic mice, including leucine-rich a-2-glycoprotein 1 (LRG1). LRG1 was previously shown to promote neovascularization in mouse models of ocular disease by potentiating endothelial TGF-b/activin receptorlike kinase 1 (ALK1) signaling. However, LRG1's role in the kidney, particularly in the setting of DKD, has been unclear.Methods We analyzed expression of LRG1 mRNA in glomeruli of diabetic kidneys and assessed its localization by RNA in situ hybridization. We examined the effects of genetic ablation of Lrg1 on DKD progression in unilaterally nephrectomized, streptozotocin-induced diabetic mice at 12 and 20 weeks after diabetes induction. We also assessed whether plasma LRG1 was associated with renal outcome in patients with type 2 diabetes.Results LRG1 localized predominantly to glomerular endothelial cells, and its expression was elevated in the diabetic kidneys. LRG1 ablation markedly attenuated diabetes-induced glomerular angiogenesis, podocyte loss, and the development of diabetic glomerulopathy. These improvements were associated with reduced ALK1-Smad1/5/8 activation in glomeruli of diabetic mice. Moreover, increased plasma LRG1 was associated with worse renal outcome in patients with type 2 diabetes.Conclusions These findings identify LRG1 as a potential novel pathogenic mediator of diabetic glomerular neoangiogenesis and a risk factor in DKD progression.Diabetic kidney disease (DKD) is a frequent complication of diabetes mellitus (DM) and the most common cause of ESRD in the United States. 1 Intensive glycemic control, BP control, and blockade of the renin-angiotensin-aldosterone system are the gold standard for current treatment of patients with DKD. 2-4 However, these established regimens provide only partial therapeutic effects, 5 indicating that pathogenic mechanisms driving DKD progression may not be targeted by current treatments. In addition, several recent clinical trials in DKD treatments were unsuccessful, 5-8 highlighting an unmet need for better understanding of mechanisms mediating the early stages of DKD for the design of novel preventive therapeutic strategies.Lrg1 expression that colocalize with CD31 outside the tubules. Scale bars, 20 mm. (D) Semiquantitative scoring of Lrg1 mRNA colocalized with Pecam mRNA (n=3 mice per group, 20 gloms scored per mouse). (E) In situ hybridization of LRG1 mRNA (red) combined with CD31 immunofluorescence (green) on human kidney sections with nuclear counterstain. Glomeruli are outlined with dotted lines on upper panels, and magnified view of the box is shown in lower panels. Scale bar, 50 mm. (F) Semiquantitative scoring of LRG1 mRNA colocalized with CD31...

LRG1 May Accelerate the Progression of ccRCC via the TGF-β Pathway

“…A previous study showed that LRG1 promoted angiogenesis by modulating endothelial TGF-β signaling [5]. We also found that LRG1 promoted diabetic kidney disease progression by enhancing TGF-β-induced angiogenesis [6]. TCGA analysis showed that TGF-β expression was upregulated in ccRCC patients ( Figure 5(a)).…”

“…LRG1 has a close relationship with TGF-β. Our previous work demonstrated that LRG1 significantly accelerated diabetic kidney injury and TGF-β/ALK1-induced angiogenesis in an experimental model of early diabetic kidney disease [6]. Consistently, LRG1 promotes angiogenesis by modulating endothelial TGF-β signaling in retinal vascular [5] and NSCLC [22].…”

“…LRG1 has been indicated to promote neovascularization in mouse models of ocular disease by potentiating endothelial TGF-β/activin receptor-like kinase 1 (ALK1) signaling [5]. Our previous study showed that LRG1 promoted diabetic kidney disease (DKD) progression by enhancing TGF-βinduced angiogenesis [6]. In this study, we found that LRG1 was closely related to ccRCC.…”

C‐X‐C motif chemokine receptor 4 aggravates renal fibrosis through activating JAK/STAT/GSK3β/β‐catenin pathway

“…However, it was largely preserved by treatment with AMD3100 (Figure F, J, and K). To further confirm the role of CXCR4 in tubular cell injury, we examined the mRNA expression of neutrophil gelatinase–associated lipocalin (NGAL) and transforming growth factor‐β1 (TGF‐β1), two markers of tubular cell injury by quantitative real‐time PCR. As shown in Figure L and M, administration of AMD3100 significantly blocked UUO‐induced up‐regulation of NGAL and TGF‐β1.…”

Single-Cell RNA Profiling of Glomerular Cells Shows Dynamic Changes in Experimental Diabetic Kidney Disease

“…We recently observed that leucine-rich a-2-glycoprotein 1 (Lrg1) was upregulated in GECs in the same diabetic mouse model using bulk RNA-seq, 4 and we further demonstrated that it plays an important role in early diabetic endothelial injury (Hong et al, this issue). 31 Interestingly, its expression in single cells showed that the observed increase in bulk endothelial cells may be in large part due to a greater number of individual endothelial cells expressing Lrg1 in the diabetic conditions ( Figure 6). Because variability in gene expression detected in single-cells may also be due to background (technical) noise, further studies are required to confirm the variability of Lrg1 expression in individual cells as a contributor to its increased expression in the diabetic kidneys.…”