Platelet-Derived Growth Factors Stimulate Proliferation and Extracellular Matrix Synthesis of Pancreatic Stellate Cells: Implications in Pathogenesis of Pancreas Fibrosis

Abstract

SUMMARY:At present, the cell-cell interactions and molecular mechanisms of pancreas fibrogenesis are largely unknown. The purpose of this study was to investigate paracrine stimulatory loops between platelets and pancreatic stellate cells (PSC). Human PSC were obtained by outgrowth from fibrotic human pancreas. Native platelet lysate (nPL) and transiently acidified platelet lysate (aPL) were added to cultured PSC (passage 4 to 7) in the absence of serum. The synthesis of collagen types I and III and c-fibronectin (cFN) was demonstrated on protein (immunofluorescence and quantitative immunoassay) and mRNA (Northern blot) level. Using sections of human pancreas with acute pancreatitis, platelet aggregates in capillaries were demonstrated by transmission electron microscopy. nPL, and to an even greater extent aPL, significantly increased the synthesis of collagen types I and III and of c-FN (120 l/ml aPL increased collagen type I concentration in PSC supernatants by 1.99 Ϯ 0.17 times and c-FN of 2.49 Ϯ 0.28 times, mean Ϯ SD, n ϭ 3). nPL and aPL also significantly stimulated cell proliferation (increased bromodeoxyuridine (BrdU) incorporation by 6.4 Ϯ 0.78 times and 10 Ϯ 0.29 times, respectively). By preincubating aPL with transforming growth factor ␤ (TGF␤)-and platelet-derived growth factor (PDGF)-neutralizing antibodies and the TGF␤-latency associated peptide, respectively, TGF␤1 was identified as the main mediator stimulating matrix synthesis and PDGF as the responsible mitogen. Our data demonstrate that platelets contain fibrogenic mediators that stimulate proliferation (PDGF) and matrix synthesis (TGF␤1) of cultured PSC. We suggest that platelets and PSC cooperate in the development of pancreas fibrosis. (Lab Invest 2000, 80:47-55).

Bone marrow-derived pancreatic stellate cells in rats

“…The generation of α-SMA stress fibers defines the formation of the myofibroblastic phenotype associated with functional cell activation [3,16]. The correlation between leukocyte infiltration and PSC activation in the DBTC-induced model of acute pancreatitis was in agreement with numerous reports showing PSC stimulation by inflammatory reactions [20,21]. The restoration process requires the deletion of cells that infiltrated and/or proliferated within the time of acute injury.…”

Inhibition of transforming growth factor β decreases pancreatic fibrosis and protects the pancreas against chronic injury in mice

“…26,27,29,30 Moreover, previous studies strongly support the existence of autocrine and paracrine stimulatory loops of ECM protein synthesis in PSCs via TGF-b. [36][37][38] Thus, inhibition of TGF-b action may block these loops and thereby inhibit PSC activation and ECM protein deposition in the pancreas. However, the inhibitory effect of AdTb-ExR on pancreatic fibrosis was less impressive than that Mice were injected once intraperitoneally with either AdLacZ or AdTb-ExR, or with saline, and then treated with cerulein for 3 weeks.…”

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

“…15,17 After TGFb1 treatment, RNA isolation and RT-PCR or Western blot analysis was performed as described above.…”

“…11,15,16 Platelet-derived growth factor (PDGF) seems to be the most potent mitogen, whereas transforming growth factor b 1 (TGFb1) predominantly induces matrix synthesis. 15,17 Different methods for isolation of these cells have been published, using either dispersed acini, enzymatic tissue digestion and density centrifugation, or outgrowth of PSC from pancreatic tissue. 18,8,9,19 These methods need fairly large amounts of tissue to obtain a sufficient number of cells.…”