The use of fluorescent nuclear dyes and laser scanning confocal microscopy to study the cellular aspects of arterial remodelling in human subjects with critical limb ischaemia

Resistance arteries isolated from patients with critical limb ischaemia (CLI), a hypotensive/hypoperfusion state of the lower leg, have been shown to undergo morphological changes opposite to those observed in hypertension, that is, decreased wall thickness, reduced cross-sectional area and a decreased wall : lumen ratio. The aim of this present study was to use laser scanning confocal microscopy (LSCM) to study intact resistance arteries isolated from patients with CLI, specifically to identify the cellular aspects of the morphological changes identified in ischaemic subcutaneous and skeletal muscle resistance vessels. Using LSCM, a significant reduction in adventitial and medial thickness, cross-sectional area and wall : lumen ratio was confirmed in resistance arteries from both distal ischaemic subcutaneous and skeletal muscle vascular beds when compared with corresponding arteries from the proximal non-ischaemic sites. The cellular composition of the adventitial, medial and intimal layers of these distal ischaemic arteries was significantly different compared with proximal non-ischaemic arteries. These differences in the distal arteries were characterised by hypoplasia in the adventitial and medial layers of the arterial wall and hypertrophy in the intimal layer. The differences observed in both distal ischaemic vascular beds (subcutaneous and skeletal muscle) were similar

Increased α1- and α2- adrenoceptor-mediated contractile responses of human skeletal muscle resistance arteries in chronic limb ischaemia

Objective: Recently, we have shown augmented contractile responses of skeletal muscle resistance arteries to noradrenaline in patients with critical limb ischemia. We investigated whether this increased sensitivity in skeletal muscle resistance arteries is due to either α1- or α2-adrenoceptor-mediated responses or both. Methods: Skeletal muscle resistance arteries were isolated from the proximal (non-ischemic) and distal (ischemic) parts of limbs amputated for critical limb ischemia and mounted on a small vessel wire myograph. Cumulative concentration response curves of the vessel segments to noradrenaline, phenylephrine and brimonidine were obtained in the presence or the absence of the selective antagonists, prazosin and RS79948. Results: Noradrenaline and phenylephrine produced almost equal maximal contractile responses. Brimonidine responses were smaller and were almost abolished by 0.1 μM RS 79948 while those of phenylephrine and noradrenaline were not affected. Prazosin reduced the maximum responses to brimonidine, shifted the concentration response curves of noradrenaline and phenylephrine rightwards giving pKB values of 9.86 and 9.33, respectively. Maximum responses produced by all three agonists in distal vessels were significantly higher than those obtained in proximal vessels. Conclusions: Noradrenaline contractile responses in skeletal muscle resistance arteries are predominantly mediated by α1-adrenoceptors. Both α1- and α2-adrenoceptor-mediated responses are increased in the arteries from ischemic regions that may aggravate the decreased blood flow to the limbs due to arterial occlusion