Ultrastructural and ultraimmunohistochemical changes upon partial nephrectomy and uranyl intoxication in the rat kidney

Astragalus polysaccharide, a component of traditional Chinese medicine, inhibits muscle cell atrophy (cachexia) in an in vivo and in vitro rat model of chronic renal failure by activating the ubiquitin-proteasome pathway

The present study aimed to determine the effect of Astragalus polysaccharide (APS) in an in vivo and in vitro rat model of muscle atrophy (cachexia) caused by chronic renal failure (CRF), along with the potential corresponding roles of atroglin-1 and the ubiquitin-proteasome pathway. A rat model of CRF was established using subtotal bilateral nephrectomy. It was observed by reverse transcription-quantitative polymerase chain reaction and western blot analysis that APS and the specific inhibitor of nuclear factor (NF)-κB, pyrrolidine dithiocarbamate (PDTC), significantly reduced the expression of atrogin-1, ubiquitin and the NF-κB subunit p65 mRNA in rat skeletal muscle in vivo and in vitro, respectively (P<0.05). NF-κB and PDTC also markedly reduced the expression of atrogin-1, ubiquitin and p65 protein. In addition, cultured rat myoblasts pretreated with tumor necrosis factor (TNF)-α exhibited significantly reduced expression of atrogin-1, ubiquitin and p65 mRNA in vitro (P<0.05). Fluorescence microscopy was subsequently used to evaluate TNF-α-treated myoblasts administered with APS or PDTC, whereby no evidence of muscle cell atrophy was observed in cells treated with APS. These data suggest that APS may delay muscle cell atrophy associated with cachexia in CRF by targeting atrogin-1 and the ubiquitin-proteasome pathway.

Induction of epithelial-to-mesenchymal transition in proximal tubular epithelial cells on microfluidic devices

In proteinuric nephropathy, epithelial-to-mesenchymal transition (EMT) is an important mechanism that causes renal interstitial fibrosis. The precise role of EMT in the pathogenesis of fibrosis remains controversial, partly due to the absence of suitable in vitro or in vivo models. We developed two microfluidic and compartmental chips that reproduced the fluidic and three-dimensional microenvironment of proximal tubular epithelial cells in vivo. Using one microfluidic device, we stimulated epithelial cells with a flow of healthy human serum, heat-inactivated serum and complement C3a, which mimicked the flow of urine within the proximal tubule. We observed that epithelial cells exposed to serum proteins became apoptotic or developed a mesenchymal phenotype. Incubating cells with C3a induced similar features. However, cells exposed to heat-inactivated serum did not adopt the mesenchymal phenotype. Furthermore, we successfully recorded the cellular morphological changes and the process of transmigration into basement membrane extract during EMT in real-time using another three-dimensional microdevice. In conclusion, we have established a cell-culture system that mimics the native microenvironment of the proximal tubule to a certain extent. Our data indicates that EMT did occur in epithelial cells that were exposed to serum proteins, and C3a plays an essential role in this pathological process.