Expression of response gene to complement-32 in renal tissue of children with immunoglobulin A nephropathy

RGC-32 mediates proinflammatory and profibrotic pathways in immune-mediated kidney disease

Systemic lupus erythematosus is an autoimmune disease that results in immune-mediated damage to kidneys and other organs. We investigated the role of response gene to complement-32 (RGC-32), a proinflammatory and profibrotic mediator induced by TGFβ and C5b-9, in nephrotoxic nephritis (NTN), an experimental model that mimics human lupus nephritis. Proteinuria, loss of renal function and kidney histopathology were attenuated in RGC-32 KO NTN mice. RGC-32 KO NTN mice displayed downregulation of the CCL20/CCR6 and CXCL9/CXCR3 ligand/receptor pairs resulting in decreased renal recruitment of IL-17+ and IFNγ+ cells and subsequent decrease in the influx of innate immune cells. RGC-32 deficiency attenuated renal fibrosis as demonstrated by decreased deposition of collagen I, III and fibronectin. Thus, RGC-32 is a unique mediator shared by the Th17 and Th1 dependent proinflammatory and profibrotic pathways and a potential novel therapeutic target in the treatment of immune complex mediated glomerulonephritis such as lupus nephritis.

RGCC balances self-renewal and neuronal differentiation of neural stem cells in the developing mammalian neocortex

During neocortical development, neural stem cells (NSCs) divide symmetrically to self-renew at the early stage and then divide asymmetrically to generate post-mitotic neurons. The molecular mechanisms regulating the balance between NSC self-renewal and neurogenesis are not fully understood. Using mouse in utero electroporation (IUE) technique and in vitro human NSC differentiation models including cerebral organoids (hCOs), we show here that regulator of cell cycle (RGCC) modulates NSC self-renewal and neuronal differentiation by affecting cell cycle regulation and spindle orientation. RGCC deficiency hampers normal cell cycle process and dysregulates the mitotic spindle, thus driving more cells to divide asymmetrically. These modulations diminish the NSC population and cause NSC pre-differentiation that eventually leads to brain developmental malformation in hCOs. We further show that RGCC might regulate NSC spindle orientation by affecting the organization of centrosome and microtubules. Our results demonstrate that RGCC is essential to maintain the NSC pool during cortical development and suggest that RGCC defects could have etiological roles in human brain malformations.

Response gene to complement 32 regulates the G2/M phase checkpoint during renal tubular epithelial cell repair

Background

The aim of this study was to evaluate the influence of RGC-32 (response gene to complement 32) on cell cycle progression in renal tubular epithelial cell injury.

Methods

NRK-52E cells with overexpressed or silenced RGC-32 were constructed via transient transfection with RGC-32 expression plasmid and RGC-32 siRNA plasmid, and the cell cycle distribution was determined. The expression levels of fibrosis factors, including smooth muscle action (α-SMA), fibronectin (FN) and E-cadherin, were assessed in cells with silenced RGC-32.

Results

The cells were injured via TNF-α treatment, and the injury was detectable by the enhanced expression of neutrophil gelatinase-associated lipocalin (NGAL). RGC-32 expression also increased significantly. The number of cells at G2/M phase increased dramatically in RGC-32 silenced cells, indicating that RGC-32 silencing induced G2/M arrest. In addition, after treatment with TNF-α, the NRK-52E cells with silenced RGC-32 showed significantly increased expression of α-SMA and FN, but decreased expression of E-cadherin.

Conclusions

The results of this study suggest that RGC-32 probably has an important impact on the repair process of renal tubular epithelial cells in vitro by regulating the G2/M phase checkpoint, cell fibrosis and cell adhesion. However, the exact mechanism needs to be further elucidated.

The expression of response gene to complement 32 on renal ischemia reperfusion injury in rat

To investigate the expression of response gene to complement 32 (RGC32) in rat with acute kidney injury (AKI) and to explore the role of RGC32 in renal injury and repair induced by ischemia reperfusion. Rats were randomly divided into two groups, including sham operation group (n = 48) and acute ischemia reperfusion injury (IRI) group (n = 48). Rats were sacrificed following reperfusion 2 h, 6 h, 24 h, 48 h, 72 h, 1 week (w), 2 w, and 4 w. The distribution and expression of RGC32 in renal tissue were observed by means of immunohistochemistry. The mean density of the images detected by Image-Pro Plus 6 was designated as the representative RGC32 expression levels. Meanwhile, RGC32 mRNA expression was measured by qPCR. RGC32 mainly expressed in cytoplasm of proximal tubular epithelial cells. However, RGC32 did not express in renal interstitium and vessels. The expression levels of RGC32 measured by immunohistochemistry at different reperfusion time were 0.0168 ± 0.0029, 0.0156 ± 0.0021, 0.0065 ± 0.0013, 0.0075 ± 0.0013, 0.0096 ± 0.0014, 0.0132 ± 0.0016, 0.0169 ± 0.0014, 0.0179 ± 0.0022, respectively. Compared with the sham group, the level of RGC32 expression in IRI group was significant lower at 24 h, 48 h, 72 h after IRI (p < 0.05). The expression levels of RGC32 mRNA at different reperfusion time measured by qPCR were corroborated the immunohistochemistry finding. The in vitro experiments show the expression of α-SMA and extracellular matrix expression increased signification when the RGC32 was silenced. Our data showed that the RGC32 expression in AKI rat decreased significantly reduces with different reperfusion time and performs a time-dependent manner. RGC32 may play an important role in the pathogenesis of AKI following IRI and repair in rat.