Sodium Butyrate as Key Regulator of Mitochondrial Function and Barrier Integrity of Human Glomerular Endothelial Cells.

The gut microbiota has emerged as an important modulator of cardiovascular and renal homeostasis. The composition of gut microbiota in patients suffering from chronic kidney disease (CKD) is altered, where a lower number of bacteria producing short chain fatty acids (SCFAs) is observed. It is known that SCFAs, such as butyrate and acetate, have protective effects against cardiovascular diseases and CKD but their mechanisms of action remain largely unexplored. In the present study, we investigated the effect of butyrate and acetate on glomerular endothelial cells. Human glomerular microvascular endothelial cells (hgMVECs) were cultured and exposed to butyrate and acetate and their effects on cellular proliferation, mitochondrial mass and metabolism, as well as monolayer integrity were studied. While acetate did not show any effects on hgMVECs, our results revealed that butyrate reduces the proliferation of hgMVECs, strengthens the endothelial barrier through increased expression of VE-cadherin and Claudin-5 and promotes mitochondrial biogenesis. Moreover, butyrate reduces the increase in oxygen consumption induced by lipopolysaccharides (LPS), revealing a protective effect of butyrate against the detrimental effects of LPS. Taken together, our data show that butyrate is a key player in endothelial integrity and metabolic homeostasis.

Extracellular matrix analysis of fibrosis: A step towards tissue engineering for urethral stricture disease.

The urogenital tract is a target for many congenital and acquired diseases, both benign and oncogenic. In males, the urethra that transports urine and semen can be obstructed by a fibrotic disease called urethral stricture disease (USD). In severe USD, the whole organ including the vascular embedding, the corpus spongiosum (CS), is affected. Recurrent or severe USD is treated by reconstructive surgery. Tissue engineering may improve the outcome of urethral reconstruction in patients with complicated USD. Currently in urethral reconstruction only the epithelial layer is replaced, no substitution for the CS is provided, while the CS is important for mechanical support and vascularization. To develop a tissue engineering strategy for the CS, it is necessary to know the protein composition of the CS. As the extracellular matrix (ECM) plays an important role in the formation of fibrosis, we analyzed the distribution and localization of ECM components in human healthy and fibrotic CS tissue using immunohistology. The morphology of components of the elastic network were affected in USD. After decellularization a clear enrichment of proteins belonging to the ECM was found. In the proteomic analysis collagens COL15A1 and COL4A2 as well as inter-alpha-trypsin inhibitor ITIH4 were upregulated in fibrotic samples. The glycoproteins Periostin (POSTN), Microfibrillar-associated protein 5 (MFAP5) and EMILIN2 are downregulated in fibrotic tissue. To our knowledge this is the first proteomic study of ECM proteins of the CS in healthy and in USD. With these results a regenerating approach for tissue engineered CS can be developed, including relevant ECM proteins that reduce fibrosis and promote healthy healing in urethral reconstructive surgery.

A proteome comparison between human fetal and mature renal extracellular matrix identifies EMILIN1 as a regulator of renal epithelial cell adhesion.

Cell-based approaches using tissue engineering and regenerative medicine to replace damaged renal tissue with 3D constructs is a promising emerging therapy for kidney disease. Besides living cells, a template provided by a scaffold based on biomaterials and bioactive factors is needed for successful kidney engineering. Nature's own template for a scaffolding system is the extracellular matrix (ECM). Research has focused on mapping the mature renal ECM; however, the developing fetal ECM matches more the active environment required in 3D renal constructs. Here, we characterized the differences between the human fetal and mature renal ECM using spectrometry-based proteomics of decellularized tissue. We identified 99 different renal ECM proteins of which the majority forms an overlapping core, but also includes proteins enriched in either the fetal or mature ECM. Relative protein quantification showed a significant dominance of EMILIN1 in the fetal ECM. We functionally tested the role of EMILIN1 in the ECM using a novel methodology that permits the reliable anchorage of native cell-secreted ECM to glass coverslips. Depletion of EMILIN1 from the ECM layer using siRNA mediated knock-down technologies does not affect renal epithelial cell growth, but does promote migration. Lack of EMILIN1 in the ECM layer reduces the adhesion strength of renal epithelial cells, shown by a decrease in focal adhesion points and associated stress fibers. We showed in this study the importance of a human renal fetal and mature ECM catalogue for identifying promising ECM components that have high implementation potential in scaffolds for 3D renal constructs.