Proceedings of The Physiological Society

University of Edinburgh (2011) Proc Physiol Soc 25, PC33

Poster Communications

Resident phenotypically modulated myocytes in human arteries under normal physiological conditions

M. I. Harhun1, C. L. Huggins1, K. Ratnasingham2, D. Raje2, R. F. Moss3, K. Szewczyk3, I. A. Greenwood1, T. K. Khong1, A. Wan2, M. Reddy2, G. Vasilikostas2

1. Division of Biomedical Sciences, St George's, University of London, London, United Kingdom. 2. Department of Surgery, St. George

It is generally accepted that contractile vascular smooth muscle cells (VSMCs) are not terminally differentiated and may change their phenotype in response to environmental cues such as injury or disease. On the other hand, vascular interstitial cells (VICs), which were recently described in various blood vessels of rodents under normal physiological conditions, display some features of the phenotypically modulated VSMC. The objective of this study was to identify and characterise VICs in human arteries. The samples of healthy adipose tissue containing small fragments of human gastro-omental arteries were obtained during abdominal surgery and blood vessels were dissected and used in experiments. VICs were identified in the wall of resistance-sized gastro-omental arteries following enzymatic cell dispersal using transmission and scanning electron microscopy. Freshly dispersed VICs showed the ability to form new and elongate existing filopodia and actively change body shape, while contractile VSMCs did not display significant changes of their body during the same period of observation. RT-PCR analysis performed on separately collected contractile VSMCs and VICs (~200 cell of each type) showed that both cell types expressed the gene for smooth muscle myosin heavy chain (SM-MHC), thus confirming that VICs represent phenotypically modulated or de-differentiated VSMCs. Immunocytochemical staining showed that both VSMCs and VICs had similar fluorescence for SM-MHC and αSM-actin, VICs, however, had significantly lower fluorescence for smoothelin, myosin light chain kinase, and SM22α. It was also found that VICs do not have a cytoskeleton as rigid as in contractile VSMCs. In addition VICs displayed the presence of sparse individual stress fibers enriched in f-actin and aSM-actin. In VSMCs these two proteins were more densely packed so it was impossible to identify individual strands at the same resolution of the confocal microscope. Our results indicate that VICs from human arteries display multiple features of the putative phenotypically modulated VSMCs. VICs therefore represent resident phenotypically modulated VSMCs that are constitutively present in human arteries under normal physiological conditions.

Where applicable, experiments conform with Society ethical requirements