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Vascular smooth muscle cell apoptosis induced by "supercooling" and rewarming
Wai-ki Yiu1, Stephen W K Cheng, Bauer E Sumpio
1Department of Vascular Surgery, Yale University School of Medicine, 333 Cedar Street, New Haven, Connecticut 06520-8062, USA, and Department of Vascular Surgery, Queen Mary Hospital, Hong Kong.
Purpose:
The underlying mechanisms for the reduction in restenosis caused by cryoplasty for peripheral atherosclerotic lesions are not well understood. Because vascular smooth muscle cells (SMCs) are known to play a critical role in restenosis and neointimal hyperplasia, the aim of this study was to determine SMC survival under conditions of "supercooling" and/or rewarming.
Materials And Methods:
Bovine aortic SMCs were supercooled to -10 degrees C for 0, 60, or 120 seconds with a custom-designed conduction cooling stage and then rewarmed to 37 degrees C in an incubator for 0, 12, or 24 hours. A terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling assay was used to measure the degree of apoptosis. Activation of Akt (ie, protein kinase B), a key signal protein involved in cell survival, was assessed by Western blot analysis.
Results:
An increase in apoptotic SMCs was observed with increasing supercooling and rewarming time. Akt was significantly activated at only the most severe condition (120 seconds of supercooling and 24 hours of rewarming), which showed a 2.03-fold increase compared with the group without rewarming.
Conclusions:
The data suggest that SMC apoptosis occurs with supercooling and rewarming. Protective cell survival mechanisms were activated only late in the rewarming phase. This may partially explain the long-term patency observed with cryoplasty of atherosclerotic peripheral lesions.
Insights
Cryoplasty supercooling and rewarming induce vascular smooth muscle cell apoptosis. Cell survival mechanisms activate late in rewarming, potentially explaining cryoplasty
Area of Science:
- Cardiovascular Biology
- Cellular Physiology
- Medical Device Mechanisms
Background:
- Restenosis after peripheral artery interventions is a significant clinical challenge.
- Vascular smooth muscle cells (SMCs) are key mediators of neointimal hyperplasia and restenosis.
- The precise mechanisms by which cryoplasty reduces restenosis remain incompletely understood.
Purpose of the Study:
- To investigate the impact of supercooling and rewarming on vascular smooth muscle cell (SMC) survival.
- To elucidate the role of apoptosis and cell survival signaling pathways in response to cryoplasty conditions.
Main Methods:
- Bovine aortic SMCs were subjected to controlled supercooling (-10°C) and subsequent rewarming (37°C) for varying durations.
- Apoptosis was quantified using the terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL) assay.
- Activation of Akt (protein kinase B), a critical cell survival regulator, was assessed via Western blot analysis.
Main Results:
- Increased SMC apoptosis correlated directly with prolonged supercooling and rewarming times.
- Akt activation was significantly elevated (2.03-fold increase) only under the most extreme conditions (120 seconds supercooling, 24 hours rewarming).
Conclusions:
- Supercooling and rewarming induce SMC apoptosis, a potential contributor to cryoplasty's therapeutic effect.
- Cellular protective mechanisms, including Akt activation, appear to be engaged late in the rewarming phase.
- These findings offer insights into the long-term patency observed following cryoplasty for atherosclerotic peripheral lesions.
