López-Guisa JM, Cai X, Collins SJ, Yamaguchi I, Okamura DM, Bugge TH, Isacke CM, Emson CL, Turner SM, Shankland SJ, Eddy AA. Mannose Receptor 2 Attenuates Renal Fibrosis. (2011) J Am Soc Nephrol :
Show Abstract · Added January 20, 2012Mannose receptor 2 (Mrc2) expresses an extracellular fibronectin type II domain that binds to and internalizes collagen, suggesting that it may play a role in modulating renal fibrosis. Here, we found that Mrc2 levels were very low in normal kidneys but subsets of interstitial myofibroblasts and macrophages upregulated Mrc2 after unilateral ureteral obstruction (UUO). Renal fibrosis and renal parenchymal damage were significantly worse in Mrc2-deficient mice. Similarly, Mrc2-deficient Col4α3(-/-) mice with hereditary nephritis had significantly higher levels of total kidney collagen, serum BUN, and urinary protein than Mrc2-sufficient Col4α3(-/-) mice. The more severe phenotype seemed to be the result of reduced collagen turnover, because procollagen III (α1) mRNA levels and fractional collagen synthesis in the wild-type and Mrc2-deficient kidneys were similar after UUO. Although Mrc2 associates with the urokinase receptor, differences in renal urokinase activity did not account for the increased fibrosis in the Mrc2-deficient mice. Treating wild-type mice with a cathepsin inhibitor, which blocks proteases implicated in Mrc2-mediated collagen degradation, worsened UUO-induced renal fibrosis. Cathepsin mRNA profiles were similar in Mrc2-positive fibroblasts and macrophages, and Mrc2 genotype did not alter relative cathepsin mRNA levels. Taken together, these data establish an important fibrosis-attenuating role for Mrc2-expressing renal interstitial cells and suggest the involvement of a lysosomal collagen turnover pathway. | Publication | 22095946 (PMID)
10.1681/ASN.2011030310 (DOI) |
Yamamoto S, Yancey PG, Zuo Y, Ma LJ, Kaseda R, Fogo AB, Ichikawa I, Linton MF, Fazio S, Kon V. Macrophage polarization by angiotensin II-type 1 receptor aggravates renal injury-acceleration of atherosclerosis. (2011) Arterioscler Thromb Vasc Biol 31: 2856-64
Show Abstract · Added January 20, 2012Angiotensin II is a major determinant of atherosclerosis. Although macrophages are the most abundant cells in atherosclerotic plaques and express angiotensin II type 1 receptor (AT1), the pathophysiologic role of macrophage AT1 in atherogenesis remains uncertain. We examined the contribution of macrophage AT1 to accelerated atherosclerosis in an angiotensin II-responsive setting induced by uninephrectomy (UNx). | Publication | 21979434 (PMID)
PMC3227118 (PMCID)
10.1161/ATVBAHA.111.237198 (DOI) |
Yang HC, Rossini M, Ma LJ, Zuo Y, Ma J, Fogo AB. Cells derived from young bone marrow alleviate renal aging. (2011) J Am Soc Nephrol 22: 2028-36
Show Abstract · Added January 20, 2012Bone marrow-derived stem cells may modulate renal injury, but the effects may depend on the age of the stem cells. Here we investigated whether bone marrow from young mice attenuates renal aging in old mice. We radiated female 12-mo-old 129SvJ mice and reconstituted them with bone marrow cells (BMC) from either 8-wk-old (young-to-old) or 12-mo-old (old-to-old) male mice. Transfer of young BMC resulted in markedly decreased deposition of collagen IV in the mesangium and less β-galactosidase staining, an indicator of cell senescence. These changes paralleled reduced expression of plasminogen activator inhibitor-1 (PAI-1), PDGF-B (PDGF-B), the transdifferentiation marker fibroblast-specific protein-1 (FSP-1), and senescence-associated p16 and p21. Tubulointerstitial and glomerular cells derived from the transplanted BMC did not show β-galactosidase activity, but after 6 mo, there were more FSP-1-expressing bone marrow-derived cells in old-to-old mice compared with young-to-old mice. Young-to-old mice also exhibited higher expression of the anti-aging gene Klotho and less phosphorylation of IGF-1 receptor β. Taken together, these data suggest that young bone marrow-derived cells can alleviate renal aging in old mice. Direct parenchymal reconstitution by stem cells, paracrine effects from adjacent cells, and circulating anti-aging molecules may mediate the aging of the kidney. | Publication | 21965376 (PMID)
PMC3231782 (PMCID)
10.1681/ASN.2010090982 (DOI) |
Eddy AA. The TGF-β route to renal fibrosis is not linear: the miR-21 viaduct. (2011) J Am Soc Nephrol 22: 1573-5
Added January 20, 2012 | Publication | 21836141 (PMID)
10.1681/ASN.2011070698 (DOI) |
Matsusaka T, Sandgren E, Shintani A, Kon V, Pastan I, Fogo AB, Ichikawa I. Podocyte injury damages other podocytes. (2011) J Am Soc Nephrol 22: 1275-85
Show Abstract · Added January 20, 2012Loss of podocytes promotes glomerulosclerosis, but whether this results from a continued primary insult or a secondary mechanism triggered by the initial loss of podocytes is unknown. We generated chimeric mice in which only a subpopulation of podocytes expressed hCD25, which is the receptor for the immunotoxin LMB2. In addition, genetic labeling of hCD25-negative cells with human placental alkaline phosphatase allowed the study of these two distinct podocyte populations. Administration of LMB2 did not cause podocyte injury in hCD25-negative control mice. In contrast, LMB2 severely damaged or sloughed off the subpopulation of hCD25-positive podocytes within the chimeric glomeruli. Moreover, hCD25-negative podocytes, which were immune to the initial toxin injury, developed injury as early as 4 d after LMB2 injection, evidenced by foot process effacement, upregulation of desmin, and downregulation of nephrin, podocin, and podocalyxin. Furthermore, the magnitude of secondary injury correlated with the magnitude of primary injury, supporting the concept of an amplified cascade of podocyte injury. In conclusion, podocyte damage can propagate injury by triggering secondary damage of "remnant" intact podocytes, even when the primary insult is short-lived. This transmission of podocyte injury may form a vicious cycle leading to accelerated podocyte deterioration and glomerulosclerosis. | Publication | 21719786 (PMID)
PMC3137575 (PMCID)
10.1681/ASN.2010090963 (DOI) |
Eddy AA, López-Guisa JM, Okamura DM, Yamaguchi I. Investigating mechanisms of chronic kidney disease in mouse models. (2011) Pediatr Nephrol :
Show Abstract · Added January 20, 2012Animal models of chronic kidney disease (CKD) are important experimental tools that are used to investigate novel mechanistic pathways and to validate potential new therapeutic interventions prior to pre-clinical testing in humans. Over the past several years, mouse CKD models have been extensively used for these purposes. Despite significant limitations, the model of unilateral ureteral obstruction (UUO) has essentially become the high-throughput in vivo model, as it recapitulates the fundamental pathogenetic mechanisms that typify all forms of CKD in a relatively short time span. In addition, several alternative mouse models are available that can be used to validate new mechanistic paradigms and/or novel therapies. Here, we review several models-both genetic and experimentally induced-that provide investigators with an opportunity to include renal functional study end-points together with quantitative measures of fibrosis severity, something that is not possible with the UUO model. | Publication | 21695449 (PMID)
PMC3199379 (PMCID)
10.1007/s00467-011-1938-2 (DOI) |
Fogo AB. The targeted podocyte. (2011) J Clin Invest 121: 2142-5
Show Abstract · Added January 20, 2012The podocyte plays a key role both in maintenance of the glomerular filtration barrier and in glomerular structural integrity. Podocyte injury and loss contribute to proteinuria and progressive sclerosis. Inhibitors of mammalian target of rapamycin (mTOR) have variably decreased or caused proteinuria and sclerosis in human disease and experimental settings. In this issue of the JCI, two interesting studies of podocyte-specific manipulation of the mTOR system shed light on the complexity of this pathway in the podocyte. | Publication | 21606599 (PMID)
PMC3104780 (PMCID)
10.1172/JCI57935 (DOI) |
Zuo Y, Yang HC, Potthoff SA, Najafian B, Kon V, Ma LJ, Fogo AB. Protective effects of PPAR{gamma} agonist in acute nephrotic syndrome. (2011) Nephrol Dial Transplant :
Show Abstract · Added January 20, 2012Background Peroxisome proliferator-activated receptor gamma (PPARγ) agonists have beneficial effects on renal structure and function in models of diabetes and chronic kidney diseases. However, the increased incidence of weight gain and edema potentially limits their usefulness. We studied an acute minimal-change disease-like nephrotic syndrome model to assess effects of PPARγ agonist on acute podocyte injury and effects on fluid homeostasis. Methods Acute podocyte injury and nephrotic syndrome were induced by puromycin aminonucleoside (PAN) injection in rats. Results PPARγ agonist, given at the time or after, but not before PAN, reduced proteinuria, restored synaptopodin, decreased desmin and trended to improve foot process effacement. There was no significant difference in glomerular filtration, effective circulating volume, blood pressure or fractional sodium excretion. PAN-injured podocytes had decreased PPARγ, less nephrin and α-actinin-4, more apoptosis and reduced phosphorylated Akt. In PAN-injured cultured podocytes, PPARγ agonist also reversed abnormalities only when given simultaneously or after injury. Conclusions These results show that PPARγ agonist has protective effects on podocytes in acute nephrotic syndrome without deleterious effects on fluid homeostasis. PPARγ agonist-induced decrease in proteinuria in acute nephrotic syndrome is dependent at least partially on regulation of peroxisome proliferator-response element-sensitive gene expression such as α-actinin-4 and nephrin and the restoration of podocyte structure. | Publication | 21565943 (PMID)
10.1093/ndt/gfr240 (DOI) |
Ma LJ, Corsa BA, Zhou J, Yang H, Li H, Tang YW, Babaev VR, Major AS, Linton MF, Fazio S, Hunley TE, Kon V, Fogo AB. Angiotensin type 1 receptor modulates macrophage polarization and renal injury in obesity. (2011) Am J Physiol Renal Physiol 300: F1203-13
Show Abstract · Added January 20, 2012The mechanisms for increased risk of chronic kidney disease (CKD) in obesity remain unclear. The renin-angiotensin system is implicated in the pathogenesis of both adiposity and CKD. We investigated whether the angiotensin type 1 (AT(1)) receptor, composed of dominant AT(1a) and less expressed AT(1b) in wild-type (WT) mice, modulates development and progression of kidney injury in a high-fat diet (HFD)-induced obesity model. WT mice had increased body weight, body fat, and insulin levels and decreased adiponectin levels after 24 wk of a high-fat diet. Identically fed AT(1a) knockout (AT1aKO) mice gained weight similarly to WT mice, but had lower body fat and higher plasma cholesterol. Both obese AT1aKO and obese WT mice had increased visceral fat and kidney macrophage infiltration, with more proinflammatory M1 macrophage markers as well as increased mesangial expansion and tubular vacuolization, compared with lean mice. These abnormalities were heightened in the obese AT1aKO mice, with downregulated M2 macrophage markers and increased macrophage AT(1b) receptor. Treatment with an AT(1) receptor blocker, which affects both AT(1a) and AT(1b), abolished renal macrophage infiltration with inhibition of renal M1 and upregulation of M2 macrophage markers in obese WT mice. Our data suggest obesity accelerates kidney injury, linked to augmented inflammation in adipose and kidney tissues and a proinflammatory shift in macrophage and M1/M2 balance. | Publication | 21367915 (PMID)
PMC3094053 (PMCID)
10.1152/ajprenal.00468.2010 (DOI) |
López-Guisa JM, Rassa AC, Cai X, Collins SJ, Eddy AA. Vitronectin accumulates in the interstitium but minimally impacts fibrogenesis in experimental chronic kidney disease. (2011) Am J Physiol Renal Physiol 300: F1244-54
Show Abstract · Added January 20, 2012Vitronectin (Vtn) is a glycoprotein found in normal serum and pathological extracellular matrix. Given its known interactions with plasminogen activator inhibitor-1 (PAI-1) and Vtn cellular receptors, especially αvβ3 integrin and the urokinase receptor (uPAR), this study was designed to investigate its role in renal fibrogenesis in the mouse model of unilateral ureteral obstruction (UUO). Kidney Vtn mRNA levels were increased ×1.8-5.1 and Vtn protein levels ×1.9-3 on days 7, 14, and 21 after UUO compared with sham kidney levels. Groups of age-matched C57BL/6 wild-type (Vtn+/+) and Vtn-/- mice (n = 10-11/group) were killed 7, 14, or 21 days after UUO. Absence of Vtn resulted in the following significant differences, but only on day 14: fewer αSMA+ interstitial myofibroblasts (×0.53), lower procollagen III mRNA levels (×0.41), lower PAI-1 protein (×0.23), higher uPA activity (×1.1), and lower αv protein (×0.32). The number of CD68+ macrophages did not differ between the genotypes. Despite these transient differences on day 14, the absence of Vtn had no effect on fibrosis severity based on both picrosirius red-positive interstitial area and total kidney collagen measured by the hydroxyproline assay. These findings suggest that despite significant interstitial Vtn deposition in the UUO model of chronic kidney disease, its fibrogenic role is either nonessential or redundant. These data are remarkable given Vtn's strong affinity for the potent fibrogenic molecule PAI-1. | Publication | 21270094 (PMID)
PMC3094052 (PMCID)
10.1152/ajprenal.00701.2010 (DOI) |
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