Thrombin receptor and urokinase-type plasminogen activator are colocalized in vascular smooth muscle cells derived from human carotid atherosclerotic plaques

Since the u-PA/uPAR system and thrombin are main contributors to the process of proliferation and migration of vascular smooth muscle cells, which is essential in the pathogenesis and progression of atherosclerosis, we assessed the role of spatial expression of these two mediator systems on cells, derived from advanced human carotid artery plaques, We compared our results to human non-atherosclerotic tissue and as a positive control to tissue from mammary carcinoma. We have used a double immunolabeling approach, combining various anti-u-PA, anti-uPAR and anti-thrombin receptor antibodies, identifying smooth muscle cells, endothelial cells and inflammatory cells. In the carotid atherosclerotic plaques, u-PA and uPAR immunostaining was distributed focally, preferentially in the fibrous cap and in the inflammatory cell-rich region, Thrombin receptor staining was distributed similar to u-PA/uPAR staining. With double staining, combining anti-u-PA antibodies with anti-thrombin receptor antibodies, cellular colocalisation of both u-PA and thrombin receptor was demonstrated, which was restricted to vascular smooth muscle cells. Inflammatory cells, however, were mainly localised within the inflammatory cell-rich region and only stained positive for u-PA and uPAR, On the other hand in nonatherosclerotic lesions only weak immunoreactivity for both mediator systems was detectable. Our data demonstrate that u-PA/uPAR and thrombin receptor are cc-expressed on smooth muscle cells in human carotid artery atherosclerotic plaque tissue. Conclusion not based on data in this paper.