Effect of p27 Deficiency and Rapamycin on Intimal Hyperplasia: In Vivo and In Vitro Studies Using a p27 Knockout Mouse Model

doi:doi:10.1038/labinvest.3780298

Lab Invest 2001, 81:895–903

Effect of p27 Deficiency and Rapamycin on Intimal Hyperplasia: In Vivo and In Vitro Studies Using a p27 Knockout Mouse Model

Mercè Roqué¹, Ernane D Reis³, Carlos Cordon-Cardo⁵, Mark B Taubman², John T Fallon^1,4, Valentin Fuster² and Juan J Badimon^1,2

¹Cardiovascular Biology Research Laboratories, Mount Sinai School of Medicine, New York City, New York
²Cardiovascular Institute, Mount Sinai School of Medicine, New York City, New York
³Department of Surgery, Mount Sinai School of Medicine, New York City, New York
⁴Department of Pathology, Mount Sinai School of Medicine, New York City, New York
⁵Department of Pathology, Memorial Sloan-Kettering Cancer Center, New York City, New York

Correspondence: Dr. Juan J. Badimon, Cardiovascular Biology Research Laboratory, Zena and Michael A. Wiener Cardiovascular Institute, The Mount Sinai School of Medicine, New York, NY 10029-6574. E-mail: Juan.Badimon@mssm.edu

Received 9 March 2001.

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Abstract

Rapamycin, an immunosuppressant and antiproliferative agent, reduces intimal hyperplasia after arterial injury in animal models and in a preliminary study in humans. Rapamycin treatment reportedly increases expression of p27, a cyclin-dependent kinase inhibitor. This mechanism was tested using a p27-deficient (p27 -/-) murine model. Aortic smooth muscle cells from wild-type (WT) and p27 -/- mice were isolated and cultured. Cell proliferation, assessed by cell count and ³H-thymidine incorporation, was inhibited significantly by rapamycin in WT and p27 -/- cells at concentrations of 1 ng/ml, 10 ng/ml, and 100 ng/ml (p < 0.05, versus control). The in vivo effect on intimal hyperplasia was studied in p27 -/- and WT mice after femoral artery transluminal injury. Rapamycin treatment was started 2 days before injury and maintained for 2 weeks (1 mg/kg per 48 hours, ip). No significant differences in intima-to-media ratio were found between WT (1.1 plusminus 0.1) and p27 -/- mice (1.0 0.1) 4 weeks after injury. Rapamycin significantly (p < 0.05) reduced intima-to-media ratios in both WT (0.7 0.1) and p27 -/- mice (0.5 0.1), compared with untreated mice. p27 deficiency did not alter the arterial wall proliferative response to injury. The inhibitory effect of rapamycin on intimal hyperplasia occurred via a p27-independent mechanism. The in vitro data showed that this effect was mediated through decreased proliferation and enhanced apoptosis.