Evidence for CD34/SMA positive cells in the left main coronary artery in atherogenesis

Regression of atherosclerosis is a key aspect of preventing further coronary artery disease and understanding which cell type forms smooth muscle cells in atherosclerotic fibrous caps will aid in reducing CAD. Atherogenesis is a complex interplay of cells migrating and proliferating into the vascular wall. CD34 positive hemapoetic stem cells are believed to not transform into vascular smooth muscle cells (SMC). The current study hypothesised that there would be no evidence for CD34+/α SMC actin+ cells in atherosclerotic coronary arteries. Aims: To identify CD34+/α actin positive cells in the fibrous cap and wall of atherosclerotic plaques in the coronary artery. Methods: Male New Zealand White rabbits were fed a diet containing 0.5% cholesterol and 1% methionine for 4 weeks, then 9 weeks of normal diet to induce regression. Immunohistochemistry was used to detect CD34+ haematopoietic progenitor cells and α SMC actin. Results: In the fibrous cap, the majority of cells were CD34−/α SMC actin+ spindle shaped cells. However very rare populations of CD34+/α SMC actin+ and CD34+/α SMC actin− cells were also present but these cells were not spindle shaped. Conclusion: Our study found that CD34+/α SMC actin− spindle shaped cells were absent from the fibrous cap. Moreover, the predominant cell population were the vascular smooth muscle cells (CD34−/α SMC actin+) but (CD34+/α SMC actin+) cells were also present. This model could be used to understand the role of each SMC population subtype to hasten atherosclerotic regression in the coronary artery.