Therapy to slow the relentless expansion of interstitial extracellular matrix that leads to renal functional decline in patients with CKD is currently lacking. Because chronic kidney injury increases tissue oxidative stress, we evaluated the antifibrotic efficacy of cysteamine bitartrate, an antioxidant therapy for patients with nephropathic cystinosis, in a mouse model of unilateral ureteral obstruction. Fresh cysteamine (600 mg/kg) was added to drinking water daily beginning on the day of surgery, and outcomes were assessed on days 7, 14, and 21 after surgery. Plasma cysteamine levels showed diurnal variation, with peak levels similar to those observed in patients with cystinosis. In cysteamine-treated mice, fibrosis severity decreased significantly at 14 and 21 days after unilateral ureteral obstruction, and renal oxidized protein levels decreased at each time point, suggesting reduced oxidative stress. Consistent with these results, treatment of cultured macrophages with cysteamine reduced cellular generation of reactive oxygen species. Furthermore, treatment with cysteamine reduced a-smooth muscle actin-positive interstitial myofibroblast proliferation and mRNA levels of extracellular matrix proteins in mice and attenuated myofibroblast differentiation and proliferation in vitro, but did not augment TGF-b signaling. In a study of renal ischemia reperfusion, cysteamine therapy initiated 10 days after injury and continued for 14 days decreased renal fibrosis by 40%. Taken together, these data suggest previously unrecognized antifibrotic actions of cysteamine via TGF-b-independent mechanisms that include oxidative stress reduction and attenuation of the myofibroblast response to kidney injury and support further investigation into the potential benefit of cysteamine therapy in the treatment of CKD.

Background: We investigated the roles of p120 catenin, Cdc42, Rac1, and RhoA GTPases in regulating migration of presomitic mesoderm cells in zebrafish embryos. p120 catenin has dual roles: It binds the intracellular and juxtamembrane region of cadherins to stabilize cadherin-mediated adhesion with the aid of RhoA GTPase, and it activates Cdc42 GTPase and Rac1 GTPase in the cytosol to initiate cell motility. Results: During gastrulation of zebrafish embryos, knockdown of the synthesis of zygotic p120 catenind1 mRNAs with a splice-site morpholino caused lateral widening and anterior-posterior shortening of the presomitic mesoderm and somites and a shortened anterior-posterior axis. These phenotypes indicate a cell-migration effect. Co-injection of low amounts of wild-type Cdc42 or wild-type Rac1 or dominant-negative RhoA mRNAs, but not constitutively-active Cdc42 mRNA, rescued these p120 catenin d1-depleted embryos. Conclusions: These downstream small GTPases require appropriate spatiotemporal stimulation or cycling of GTP to guide mesodermal cell migration. A delicate balance of Rho GTPases and p120 catenin underlies normal development. Developmental Dynamics 241:1545-1561, 2012. V C 2012 Wiley Periodicals Inc.Key words: p120 Catenin (CTNND1); ARVCF; Delta-catenin (CTNND2b); Cdc42 GTPase; Rac1 GTPase, RhoA GTPase; gastrulation; presomitic mesoderm; somites; zebrafish Key findings p120 catetin is required for extension of the dorsal axis and normal migration of the presomitic mesoderm. Cdc42 and Rac1 GTPases are downstream of p120 catenin d1 signaling and require exchange of GTP for GDP. Local stimulation of the exchange of GTP for GDP in Cdc42 and Rac GTPases mediates directional migration of the presomitic mesoderm. A balance of the amount of p120 catenin d1 and localized activation or turnover of Cdc42, Rac1, and Rho GTPase are required for normal zebrafish cell migration. Accepted 31 July 2012 Developmental DynamicsABBREVIATIONS Ab antibody ARVCF armadillo repeat gene deleted in velo-cardio-facial syndrome CA constitutively active Chr chromosome C(t) relative amount of RT-PCR product hpf hours post-fertilization DN dominant negative d1 splice-MO antisense morpholino oligonucleotide to the 12 th splice site of zebrafish p120 catenin d1 p120 catenin d1 (CTNND1) also called p120 catenin, Xenopus p120 catenin is a CTNND1 p120 catenin d2b (CTNND2b) also called Delta-catenin Rok1 Rho kinase1 RT reverse transcriptase minus-RT controls without reverse transcriptase qRT-PCR quantitative real-time PCR WT wild-type Xp120 catenin mRNA Xenopus p120 catenin d1 mRNA.Additional Supporting Information may be found in the online version of this article.

The removal of apoptotic cells is an innate function of tissue macrophages; however, its role in disease progression is unclear. The present study was designed to investigate the role of macrophage CD36, a recognized receptor of apoptotic cells and oxidized lipids, in two models of kidney injury: unilateral ureteral obstruction (UUO) and ischemia reperfusion. To differentiate the macrophage CD36-specific effects in vivo, we generated CD36 chimeric mice by bone marrow transplantation and evaluated the two models. Fibrosis severity was substantially decreased after UUO with a corresponding decrease in matrix synthesis in macrophage CD36-deficient mice. Despite a reduction in fibrosis severity, a 56% increase in apoptotic cells was found without an increase in apoptotic effectors. In addition, a substantial reduction was observed in tumor necrosis factor-α and transforming growth factor-β1 mRNA levels and intracellular bioactive oxidized lipid levels in CD36-deficient macrophages. To validate the functional role of macrophage CD36, we performed unilateral ischemia reperfusion, followed by contralateral nephrectomy. Similarly, we found that the severity of fibrosis was reduced by 55% with a corresponding improvement in kidney function by 88% in macrophage CD36-deficient mice. Taken together, these data suggest that macrophage CD36 is a critical regulator of oxidative fibrogenic signaling and that CD36-mediated phagocytosis of apoptotic cells may serve as an important pathway in the progression of fibrosis.

Solid organ fibrosis is a major burden on global health and medical care costs. Muroid rodents of the genus Acomys (African Spiny mice) are terrestrial mammals that evolved remarkable abilities to regenerate severe skin wounds without scar formation. However, whether scar-free wound repair in Acomys extends beyond skin to vital internal organs is not known. Here, we used two aggressive kidney injury models known to produce severe renal fibrosis and show that despite equivalent acute kidney injury, there was rapid restoration of nephron structure and function without fibrosis in Acomys compared to extensive fibrosis leading to renal failure in Mus musculus. These results suggest Acomys species have evolved genomic adaptations for wound healing that activate regenerative repair pathways not only in skin, but also in vital internal organs. Our findings have important implications for discovering a long-sought evolutionary solution to internal organ injury and regeneration.

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