Critical overexpression of thrombospondin 1 in chronic leg ischaemia.

The aim of this study was to identify gene expression governing the balance of angiogenic and angiostatic factors in human ischaemic leg tissues. In situ hybridization was used to screen for the expression of angiogenesis-related genes in tissues from 13 amputated limbs from patients suffering from critical leg ischaemia. The authors tested for mRNA of hypoxia-inducible transcription factors 1 alpha and 2 alpha, vascular endothelial growth factor, and its receptors VEGFR-1 and -2, the angiopoietin receptor Tie2, and the anti-angiogenic molecule thrombospondin 1. The expression levels of the genes in proximal, healthy muscles were compared with those in the distal, ischaemic counterparts. Surprisingly, only thrombospondin 1 was overexpressed in the ischaemic part of the leg of all patients studied. Thrombospondin 1 mRNA was assayed by real-time RT-PCR and the gene was overexpressed 20-fold. The presence of its encoded protein was confirmed by western blotting. The overproduction of this anti-angiogenic molecule was associated with a decrease in capillary density in the affected muscles. Thrombospondin 1 is thus a marker of chronic ischaemia and may affect angiogenesis in ischaemic tissues. Copyright (c) 2005 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd