Polyphenol, an Extract of Green Tea, Increases Culture Recovery Rates of Isolated Islets from Nonhuman Primate Pancreata and Marginal Grade Human Pancreata

Abstract

Investigations indicate that an extract of green tea, polyphenol, can significantly increase the culture survival rate of rat islets without deteriorating their functionality. In this study, we examined the effect of adding polyphenol to islets isolated from human pancreata and nonhuman primate pancreata. Islets were isolated from human pancreata that did not meet criteria for clinical transplantation (n = 6) and from nonhuman primate pancreata (n = 5). The islets were cultured in CMRL-1066 + 10% FCS with the addition of 0, 30, 60, 125, 250, or 500 µg/ml of polyphenol. After 24 or 48 h of culture, islet yield, viability, purity, morphology, and stimulation index was assessed. RT-PCR and Western blot analysis were also performed to assess the expression levels of the apoptotic related genes, Bcl-2 and BAX. After 24 h of culture, islet yields were significantly higher in cultures supplemented with 30-250 µg/ml of polyphenol than in cultures without polyphenol. After 48 h of culture, significant differences in islet numbers were observed with polyphenol concentrations of 125 µg/ml ( p < 0.01) and 250 µg/ml ( p < 0.01). However, no significant differences were noted in islet viability, purity, morphology, and stimulation index at each time point with or without polyphenol. RT-PCR and Western blot analysis of the islets indicated that Bcl-2 levels increased by 2.5-fold and BAX levels decreased by twofold in cultures supplemented with polyphenol. This resulted in BAX/Bcl-2 ratios that were lower in polyphenol-supplemented cultures than with control cultures. Polyphenol increases culture recovery rates by precluding islet apoptosis.

Green-tea polyphenol (-)-epigallocatechin-3-gallate provides resistance to apoptosis in isolated islets

“…The first purpose of the present study, therefore, was to assess whether the addition of EGCG to the islet‐culture medium could reduce any loss of normal islet function caused by damaging events such as apoptosis in normal (conventional) culture conditions. In agreement with previous reports,, this study indicated that EGCG prevented apoptosis and necrotic cell lysis in isolated islets following 48 h in vitro culture. In accord with our result, it has been shown that the exogenous expression of the Bcl‐2 gene or the addition of a caspase inhibitor or leptin — which regulate expression of the Bcl‐2 gene — to culture media, inhibits apoptosis in isolated islets in vitro .…”

Risk factors for islet loss during culture prior to transplantation

“…For example, Zhang et al. [4] reported that only 18% islet mass was recovered after 48‐h culture. Bottino et al.…”

Preincubation with green tea polyphenol extract is beneficial for attenuating sperm injury caused by freezing‐thawing in swine

“…Many biological functions of PFs have been studied, including anti-inflammatory , antimutagenic (Shiraki et al 1994) and anti-carcinogenic (Huang et al 1992;Yang & Wang 1993) effects. (Hyon 2004;Zhang et al 2004;Ikeguchi et al 2005;Han et al 2005a,b;Hyon et al 2006). Green tea PFs promote the preservation of tissues, such as blood vessels, cornea, nerve, islet cells, articular cartilage and myocardium, at room temperature.…”