Einfluss von Wachstumsfaktoren auf die Differenzierung von porcinen Linsenepithelzellen

Zusammenfassung

Hintergrund: Neben der gesteigerten Zellproliferation stellt die Entdifferenzierung von Linsenepithelzellen zu myofibroblastenartigen Zellen einen wesentlichen Mechanismus bei der Nachstarentwicklung dar. Diese Entdifferenzierung geht einher mit Expression von α-smooth muscle actin (α-SMA). In dieser Studie wurde der Einfluss der Wachstumsfaktoren bFGF, TGF-β2, EGF und IGF-1 auf die Expression von α-SMA bei porcinen Linsenepithelzellen untersucht. Material und Methoden: Porcine Linsenepithelzellen wurden über einen Zeitraum von sieben Tagen in serumfreiem Medium ohne bzw. mit 1 - 50 ng/ml bFGF, TGF-β2, EGF oder IGF-1 kultiviert. Die α-SMA-Expression wurde immunzytochemisch mit einem monoklonalen Antikörper detektiert und der Anteil an α-SMA-positiven Zellen im Vergleich zur Gesamtzellzahl ausgewertet. Die statistische Auswertung erfolgte mit dem Student-t-Test für ungepaarte Stichproben. Ergebnisse: Der Anteil an α-SMA-positiven Zellen lag bei den Zellen, die über sieben Tage in serumfreiem Medium kultiviert worden waren, bei 36 ± 11,9 % (Mittelwert ± Standardabweichung). BFGF reduzierte diesen Anteil dosisabhängig auf 11,2 ± 7,3 % bei einer Konzentration von 50 ng/ml (p < 0,0001). EGF reduzierte den Anteil auf 25,1 ± 15,7 % (p = 0,05) bei einer Konzentration von 50 ng/ml. IGF-1 (10 ng/ml) verminderte den Anteil an entdifferenzierten Zellen auf 16,8 ± 5,8 %, was jedoch nicht signifikant war (p = 0,0787). TGF-β (50 ng/ml) erhöhte den Anteil an α-SMA-positiven Zellen geringfügig auf 44,2 ± 13,8 %. Nach einer Kulturperiode von sieben Tagen war dieser Anstieg jedoch nicht signifikant (p = 0,1202). Schlussfolgerungen: BFGF und EGF reduzierten die α-SMA-Expression von Linsenepithelzellen statistisch signifikant im Gegensatz zu TGF-β und IGF-1, die keinen signifikanten Einfluss hatten. Diese Ergebnisse können so interpretiert werden, dass bei der Nachstarentwicklung bFGF und EGF nicht primär über den Mechanismus der Zellentdifferenzierung wirken.

Abstract

Background: Besides cell proliferation, transdifferentiation of lens epithelial cells (LECs) to myofibroblasts is one of the mechanisms of secondary cataract formation. This process is characterized by increased expression of α-smooth muscle actin (α-SMA). This study investigated the influence of bFGF, TGF-β2, EGF and IGF-1 on the expression of α-SMA in porcine LECs. Materials and methods: Porcine LECs were cultured for 7 days in serum-free medium without or with 1 to 50 ng/ml bFGF, TGF-β2, EGF or IGF-I. Alpha-SMA was detected immunocytochemically with a mouse monoclonal antibody, and the relative numbers of α-SMA-positive cells were calculated. Statistical analysis was performed using Student’s unpaired t-test. Results: The ratio of α-SMA-positive cells cultured for 7 days in serum-free medium was 36 ± 11.9 % (mean ± SD). BFGF significantly reduced this ratio in a dose-dependent manner to 11.2 ± 7.3 % at a concentration of 50 ng/ml (p < 0.0001). EGF reduced the ratio significantly to 25.1 ± 15.7 % (p = 0.05) when 50 ng/ml were applied. IGF-1 (10 ng/ml) reduced the relative numbers of transdifferentiated cells to 16.8 ± 5.8 %, but the reduction was not statistically significant (p = 0.0787). TGF-β2 (50 ng/ml) slightly increased the relative number of α-SMA-positive cells to 44.2 ± 13.8 %. However, this increase was not significant (p = 0.1202) during a culture period of 7 days. Conclusions: BFGF and EGF significantly reduced the expression of α-SMA by LECs while TGF-β and IGF-1 had no statistically significant effect. These results suggest that bFGF and EGF do not primarily induce secondary cataract formation by the mechanism of cell transdifferentiation.

Schlüsselwörter

BFGF - Differenzierung - EGF - IGF-1 - Linsenepithelzellen - Nachstar - α-SMA-Expression - TGF-β

Key words

BFGF - differentiation - EGF - IGF-1 - lens epithelial cells - secondary cataract - α-SMA expression - TGF-β

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