Induction of DNA Synthesis by a Single Transient Mechanical Stimulus of Human Vascular Smooth Muscle Cells

Abstract

Background Although mechanical vascular injury leads to smooth muscle cell proliferation that contributes to restenosis after balloon angioplasty, the role of the single transient mechanical stimulation of smooth muscle cells in this process is unknown. Methods and Results To test the hypothesis that a single transient mechanical stimulus can increase DNA synthesis, human vascular smooth muscle cells cultured in a three-dimensional collagen gel system were subjected to transient compression. Transient compression (5-minute duration) of smooth muscle cell–collagen gel cultures in defined serum-free conditions led to delayed increases in [ 3 H]thymidine incorporation. At 12 to 24 hours after compression, there was a 3.3±0.5-fold ( P <.001 versus control) and 3.0±0.6-fold ( P <.002 versus control) increase for 60% and 80% strain, respectively; at 24 to 36 hours after compression, there was a 1.8±0.5-fold ( P <.05 versus control) and 4.3±0.8-fold ( P <.001 versus control) increase. Also, serum-free media conditioned by transiently compressed gel cultures induced DNA synthesis in control, unstimulated smooth muscle cell cultures, suggesting the release of growth factors by transient compression. Although neutralizing antibodies against platelet-derived growth factor did not affect the mechanical induction of DNA synthesis, a neutralizing monoclonal antibody against fibroblast growth factor–2 (FGF-2) decreased this induction by 89% and completely blocked the increase in DNA synthesis caused by media conditioned by transiently compressed gels. Media conditioned by transient compression contained elevated levels of FGF-2 (17±5 versus 2±2 pg/mL for control, P <.005) with no increase in lactate dehydrogenase activity, suggesting release of FGF-2 with sublethal cellular injury. Conclusions A single transient mechanical stimulus increases DNA synthesis in human vascular smooth muscle cells, in part by autocrine or paracrine FGF-2 release.