Mammalian Target of Rapamycin (mTOR) Induces Proliferation and De-Differentiation Responses to Three Coordinate Pathophysiologic Stimuli (Mechanical Strain, Hypoxia, and Extracellular Matrix Remodeling) in Rat Bladder Smooth Muscle

Abstract

Maladaptive bladder muscle overgrowth and de-differentiation in human bladder obstructive conditions is instigated by coordinate responses to three stimuli: mechanical strain , tissue hypoxia , and extracellular matrix remodeling.1 ,2 Pathway analysis of genes induced by obstructive models of injury in bladder smooth muscle cells (BSMCs) identified a mammalian target of rapamycin (mTOR)-specific inhibitor as a potential pharmacological inhibitor. Strain-induced mTOR-specific S6K activation segregated differently from ERK1/2 activation in intact bladder ex vivo. Though rapamycin's antiproliferative effects in vascular smooth muscle cells are well known , its effects on BSMCs were previously unknown. Rapamycin significantly inhibited proliferation of BSMCs in response to mechanical strain , hypoxia , and denatured collagen. Rapamycin inhibited S6K at mTOR-sensitive phosphorylation sites in response to strain and hypoxia. Rapamycin also supported smooth muscle actin expression in response to strain or hypoxia-induced de-differentiation. Importantly , strain plus hypoxia synergistically augmented mTOR-dependent S6K activation , Mmp7 expression and proliferation. Forced expression of wild-type and constitutively active S6K resulted in loss of smooth muscle actin expression. Decreased smooth muscle actin , increased Mmp7 levels and mTOR pathway activation during in vivo partial bladder obstruction paralleled our in vitro studies. These results point to a coordinate role for mTOR in BSMCs responses to the three stimuli and a potential new therapeutic target for myopathic bladder disease.

Blocking IL-17A Promotes the Resolution of Pulmonary Inflammation and Fibrosis Via TGF-β1–Dependent and –Independent Mechanisms

“…Rapamycin, a classical autophagy agonist (30), was used to determine the role of IL-17A in the regulation of collagen production. Activation of autophagy by rapamycin reduced the IL-17A-induced increase in the secretion of collagen by MLE-12 cells (Fig.…”

Dedifferentiated fat cells: an alternative source of adult multipotent cells from the adipose tissues

“…Despite the malignant outcome, in the free-fat transfer in plastic and reconstructive surgery, some mature adipocytes also dedifferentiate into fibroblast-like cells under the ischemic conditions [21]. Hypoxia is also considered to be the main factor involved in not only the formation of DFAT cells in ceiling cultures, but also the dedifferentiation process of chondrocytes [40] and smooth muscle cells [41]. However, no evidence has been given that autologous or allogeneic implantation of DAFT cells into the human or animal bodies will lead to tumor or other diseases.…”

Optical assessment of tissue anisotropy in <italic>ex vivo</italic> distended rat bladders

“…7,27 A simple anatomical representation of the bladder and a photo of the ex vivo harvested bladder are shown in Fig. 1.…”

“…Three bladders (referred to as 1, 2, and 3 in the text) were distended at three different reservoir heights of 15, 30, and 45 cm, corresponding to pressures of 1.0, 2.2, and 3.3 kPa; this range of pressures in within the relevant physiologic range. 7 With this method, we could image bladder 1 distended at 1.0 kPa, bladder 2 at 2.2 kPa and bladder 3 at 3.3 kPa. This was done instead of distending a single bladder to three different pressures, to avoid any possible hysteresis effects.…”

“…4 Bladder wall is composed of extracellular matrix (including collagen and elastin) and smooth muscle. 7 During outlet obstructive diseases, the bladder wall experiences smooth muscle overgrowth (hypertrophy and hyperplasia) or changes in smooth muscle cell orientation, an increase in total wall thickness, and excessive extracellular matrix deposition and remodelling. 1,3 In many cases, over the long-term these alterations become irreversible, decrease patient quality of life, and increase risk of kidney failure and urinary tract infections.…”