Mesenchymal stem cell therapy inhibited inflammatory and profibrotic pathways induced by partial bladder outlet obstruction and prevented high-pressure urine storage

Abstract

Partial bladder outlet obstruction (pBOO) is characterized by an initial inflammatory response that progresses to smooth muscle hypertrophyand fibrosis. Current treatment modalities carry high risk of morbidity. Mesenchymal stem cells (MSCs) are undifferentiated adult cells with reparative, immunomodulatory, and anti-inflammatory capacities. The ability of MSCs to inhibit inflammatory and profibrotic pathways in bladder cells has been recently reported. This study aimed to investigate the therapeutic effects of MSCs on pBOO-induced inflammatory, profibrotic signaling pathways and end-organ physiology. Twenty Sprague Dawley rats were randomly assigned to 5 groups: unobstructed controls, pBOO for 2 and 4 weeks, pBOO+MSCs for 2 and 4 weeks. Partial bladder outlet obstruction was surgically induced followed by intravenous injection of MSCs. Endpoint urodynamics was performed, and bladder tissueharvested for analysis. Reverse transcription real time polymerase chain reaction (RT-PCR) and immunohistochemistry were performed to study gene and protein expression of major inflammatory and profibrotic markers. Partial bladder outlet obstruction resulted in an upregulation of transforming growth factor beta (TGFβ1), mothers against decapentaplegic homolog 2/3 (SMAD2/3), hypoxia inducible factor 1 alpha (HIF1α), hypoxia inducible factor 3 alpha (HIF3α), vascular endothelial growth factor (VEGF), tumor necrosis factor (TNFα), mechanistic target of rapamycin (mTOR), p70 ribosomal S6 protein kinase (p70 S6K), collagen 1 (COL1), and collagen 3 (COL3) expression in a time-dependent manner. This was coupled with a downregulation of interleukin (IL)-10 expression. Increase of bladder fibrosis was directly related to the duration of pBOO and associated with high urine storage pressure. Injected MSCs were identified in the bladder 4 weeks after therapy. The immunomodulatory effect of MSCs(defined by reduced TNFα and increased IL-10 and VEGF) was most predominant 2 weeks after therapy. Significant downregulation of profibrotic genes occurred 4 weeks after therapy. End filling pressure, hypertrophy, and fibrosis were significantly reduced after MSCtherapy (P<0.05). Mesenchymal stem cell therapy led to a profound systematic improvement of the obstructed bladder. This included an initial anti-inflammatory response and a subsequent antifibrotic reaction. Essentially, both phases were associated with a reduction of urine storage pressure. The intravenously injected MSCs were tracked in the bladder. However, their presence in non-target organs such as the lungs, spleen, and liver was not tracked. Partial bladder outlet obstruction induced significant upregulation of hypoxic, inflammatory, and profibrotic markers. Mesenchymal stem cell therapy potently inhibited these pathways and improved bladder function.