Expression of Transforming Growth Factor-β1 by Pancreatic Stellate Cells and Its Implications for Matrix Secretion and Turnover in Chronic Pancreatitis

Abstract

Pancreatic stellate cells mediate fibrosis in chronic pancreatitis. Matrix metalloproteinases (MMPs) and tissue inhibitors of metalloproteinases (TIMPs)-1 and -2 are crucial modulators of fibrosis. Transforming growth factor-beta (TGF-beta) is a key regulator of extracellular matrix production and myofibroblast proliferation. We have examined MMP and TIMP synthesis by transformed cultured pancreatic stellate cells and their regulation by TGF-beta 1. By Northern analysis they expressed mRNAs for procollagen 1, TIMP-1, TIMP-2, and MMP-2. Expression of membrane type-1 MMP was confirmed by Western blotting. By immunohistochemistry these enzymes localized to fibrotic areas in human chronic pancreatitis. Active TGF-beta 1 constitutes 2 to 5% of total TGF-beta 1 secreted by pancreatic stellate cells; they express TGF-beta receptors I and II. Exogenous TGF-beta 1 (10 ng/ml) significantly increased procollagen-1 mRNA by 69% and collagen protein synthesis by 34%. Similarly TGF-beta 1 at 0.1, 1, and 10 ng/ml significantly reduced cellular proliferation rate by 37%, 44%, and 44%, respectively, whereas pan-TGF-beta-neutralizing antibody increased proliferation by 40%. TGF-beta1 (10 ng/ml) down-regulated MMP-9 by 54% and MMP-3 by 34% whereas TGF-beta 1-neutralizing antibody increased MMP-9 expression by 39%. Pancreatic stellate cells express both mediators of matrix remodeling and the regulatory cytokine TGF-beta 1 that, by autocrine inhibition of MMP-3 and MMP-9, may enhance fibrogenesis by reducing collagen degradation.

Immortalization of pancreatic stellate cells as an in vitro model of pancreatic fibrosis: deactivation is induced by matrigel and N-acetylcysteine

“…TGFb1 did not only induce the expression of ECM components Col I and FN, but also of the growth factors CTGF and TGFb1 itself, thus establishing an autocrine loop, which may result in the perpetuation of the fibrotic process. This autocrine stimulation of PSC was also demonstrated by Shek et al 47 pinpointing the central role PSC play in the development of pancreatic fibrosis. Taken together, the immortalized PSC retain the basic characteristics of activated PSC, as expression of marker protein and responsiveness to factors implicated in pancreatic fibrosis.…”

“…15,47,48 The same is true for HSC, where contrasting data describing the influence of TGFb1 on proliferation, ranging from growth inhibition to stimulation of proliferation, have been published, although the majority of publications report a TGFb1-induced growth inhibition in HSC. 44,[49][50][51] These differences may be attributed to different RT-PCR demonstrated that cultivation of immortalized PSC on Matrigel (M) for 7 days resulted in a marked decrease of Col I, TGFb1 and CTGF expression compared to cultivation on tissue culture (TC) plates, whereas aSMA expression was not altered significantly by this cultivation conditions, the housekeeping gene RPL13A served as control (a).…”

Plasma TGF-β1, MMP-1 and MMP-3 Levels in Chronic Pancreatitis

“…Studies have shown that TGF-b1 promotes fibrogenesis not only by increasing collagen production but also by inhibiting MMPs in the pathway of collagen degradation. It has been demonstrated by Shek et al [12] that activated PSCs also express activated TGF-b1, which up-regulates collagen-1 while down regulating the expression of MMP-3 and MMP-9 only and not on TIMP-1 expression. The pattern of expression of the mediators studied is similar to that described in parallel cell types of fibrosis of the liver and kidney and reinforces the hypothesis that there may be generic aspects to wound healing in organs [13].…”

“…Thus, the combination of low expression of collagenases and stromelysins results in the prevention of degradation of the fibrillar collagens deposited due to PSC activation. It is further strengthened by TGF-b1 influencing in decreasing the induction of MMP3 expression [12].…”

“…TGF-b1 has been shown to have a profibrotic role in a variety of organs including liver, skin, and kidneys [9][10][11][12]. Studies have shown that TGF-b1 promotes fibrogenesis not only by increasing collagen production but also by inhibiting MMPs in the pathway of collagen degradation.…”