• Ralf Köhler, Heike Wulff, Ines Eichler, Marlene Kneifel, Daniel Neumann, Andrea Knorr, Ivica Grgic, Doris Kämpfe, Han Si, Judith Wibawa, Robert Real, Klaus Borner, Susanne Brakemeier, Hans-Dieter Orzechowski, Hans-Peter Reusch, Martin Paul, K George Chandy, and Joachim Hoyer.
• Department of Nephrology, Benjamin Franklin Medical Center, Berlin, Germany. koe@zedat.fu-berlin.de
• Circulation. 2003 Sep 2; 108 (9): 1119-25.

BackgroundAngioplasty stimulates proliferation and migration of vascular smooth muscle cells (VSMC), leading to neointimal thickening and vascular restenosis. In a rat model of balloon catheter injury (BCI), we investigated whether alterations in expression of Ca2+-activated K+ channels (KCa) contribute to intimal hyperplasia and vascular restenosis.Methods And ResultsFunction and expression of KCa in mature medial and neointimal VSMC were characterized in situ by combined single-cell RT-PCR and patch-clamp analysis. Mature medial VSMC exclusively expressed large-conductance KCa (BKCa) channels. Two weeks after BCI, expression of BKCa was significantly reduced in neointimal VSMC, whereas expression of intermediate-conductance KCa (IKCa1) channels was upregulated. In the aortic VSMC cell line, A7r5 epidermal growth factor (EGF) induced IKCa1 upregulation and EGF-stimulated proliferation was suppressed by the selective IKCa1 blocker TRAM-34. Daily in vivo administration of TRAM-34 to rats significantly reduced intimal hyperplasia by approximately 40% at 1, 2, and 6 weeks after BCI. Two weeks of treatment with the related compound clotrimazole was equally effective. Reduction of intimal hyperplasia was accompanied by decreased neointimal cell content, with no change in the rate of apoptosis or collagen content.ConclusionsThe switch toward IKCa1 expression may promote excessive neointimal VSMC proliferation. Blockade of IKCa1 could therefore represent a new therapeutic strategy to prevent restenosis after angioplasty.

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