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.

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.

MO618: Influence of Butyrate and Acetate on Behavior and Metabolism of Human Glomerular Microvascular Endothelial Cells

BACKGROUND AND AIMS

The gut microbiota has emerged as an important modulator of cardiovascular and renal diseases, including diabetic nephropathy (DN), one of the most common complications caused by diabetes mellitus. Importantly, diabetic patients display a reduction in bacteria producing short chain fatty acids (SCFAs) when compared with healthy individuals. SCFAs are generally associated with beneficial effects on the vascular system, as they help to reduce both oxidative stress and pro-inflammatory stimuli [1].

Although SCFAs help to protect against DN, their mechanisms of action at cell level remain largely unknown. For this reason, we aimed to study the effect of two SCFAs, butyrate and acetate, on human glomerular microvascular endothelial cells (hgMVECs) that represent one of the main components of the glomerular filtration barrier. In case of DN, glomerular endothelium shows multiple signs of dysfunction, such as uncontrolled proliferation [2], mitochondrial fragmentation [3] and monolayer disruption [4].

METHOD

hgMVECs have been exposed to different concentrations of butyrate and acetate for 24 h and/or 48 h. After treatment with SCFAs, cells have been collected for qPCR, stained for mitochondrial mass or fixated for immunocytochemistry. For the latter, we have used antibodies for the proliferation marker ki-67 and cell-to-cell junction proteins. To measure the resistance of the endothelial monolayer, electric cell-substrate impedance sensing (ECIS) was used. This system lets a current go over and between cells and the tighter the monolayer, the higher the resistance. For this type of experiment, hgMVECs have been cultured on a specific plate that is located in the ECIS machine throughout the whole experiments (before and after treatment with SCFAs).

RESULTS

Butyrate decreases the number of ki-67 positive nuclei in a concentration-dependent manner, which implies lower cellular proliferation.

On the other hand, at the highest concentration tested (500 uM), butyrate increases mitochondrial mass and elongation, as opposite to acetate, which does not show any effect on mitochondrial mass.

These results are also supported by qPCR analysis, where it is possible to observe a decrease of genes involved in mitochondrial fragmentation upon butyrate exposure.

MOreover, butyrate increases the resistance of the endothelial monolayer, as we can see in the results of the ECIS experiments. After an initial decrease, butyrate induces a steady increase of the resistance of the monolayer, which does not happen with acetate.

We believe that the increase in resistance is due to a higher expression of genes and proteins involved in the formation of tight junctions. For instance, in cells treated with butyrate, gene expression of ve-cadherin, ZO-1, claudin 5 and occludin is upregulated and especially for ve-cadherin this is also observed by immunocytochemistry.

CONCLUSION

Our results show that in hgMVECs, on the one hand butyrate especially can increase monolayer resistance and influence mitochondrial morphology and possibly its metabolism, while on the other hand it decreases cellular proliferation. Therefore, at cellular level, butyrate can help against several hallmarks of endothelial dysfunction Of DN.

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.

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Proteomics revealed the differences between the renal fetal and mature extracellular matrix.

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EMILIN1 has a significant dominance in the fetal extracellular matrix.

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EMILIN1 depletion from the extracellular matrix reduces the adhesion strength and promotes migration of renal epithelial cells.