Cx40 Is Required for, and Cx37 Limits, Postischemic Hindlimb Perfusion, Survival and Recovery

Abstract

Background/Aims: Ischemia induced by large-vessel obstruction or vascular injury induces a complex cascade of vasodilatory, remodeling and inflammatory pathways; coordination of these processes by vascular endothelium is likely to involve endothelial gap junctions. Vascular endothelium predominantly expresses two connexin (Cx) isoforms: Cx37 and Cx40. The relevance of these Cxs to postischemic limb recovery remains unclear. Methods: In this study, we use a well-established, severe femoral-saphenous artery-vein pair resection model of unilateral hindlimb ischemia to test the relevance of Cx37 and Cx40 to postischemic tissue survival and recovery of limb perfusion. Results: Cx40-deficient animals (Cx40–/–) experienced a severe reduction in limb perfusion relative to wild-type (WT) animals and exhibited profound and rapid failure of ischemic limb survival. By contrast, the deficit in limb perfusion was less severe in Cx37-ablated (Cx37–/–) animals compared to WT, corresponding with more rapid recovery of limb appearance and use. These results demonstrate that Cx40 is necessary for postischemic limb survival and reperfusion, whereas Cx37 deletion reduces the extent of ischemia in the same model. Conclusion: In summary, we present evidence demonstrating that Cx37 and Cx40 uniquely regulate postischemic limb perfusion, altering the severity of ischemic insult and consequent postischemic survival.

Compromised regulation of tissue perfusion and arteriogenesis limit, in an AT1R-independent fashion, recovery of ischemic tissue in Cx40−/−mice

“…We showed previously that tissue survival and recovery were compromised in Cx40-deficient mice subjected to the severe form of hindlimb ischemia that eliminates flow to the major collateral vessels supplying the distal hindlimb (15). Generally, survival and recovery of ischemic tissue is determined, in large part, by the magnitude and area of blood flow Ϫ/Ϫ no losartan, n ϭ 13, 3-day losartan, n ϭ 7, 8-wk losartan, n ϭ 9; mild surgery: no losartan, n ϭ 10, 8-wk losartan, n ϭ 11; use data, severe surgery: no losartan, n ϭ 11, 3-day losartan, n ϭ 7, 8-wk losartan, n ϭ 9; mild surgery: no losartan, n ϭ 10, 8-wk losartan, n ϭ 11].…”

“…Unilateral hindlimb ischemia was induced by one of two surgical strategies: femoral and saphenous artery-vein pair resection, here termed severe surgery, and femoral artery ligation, here termed mild surgery, as previously described (14,15). For the severe surgery, ligatures were placed around the femoral artery-vein pair upstream of the epigastric and gracilis artery branch-points and around the saphenous artery-vein pair midway between the knee and ankle, and the intervening lengths of vessel were resected.…”

“…For the mild surgery, ligatures were placed on the femoral artery between the epigastric and popliteal branches and the intervening length of artery was severed. After either procedure, ischemia was documented by laser Doppler perfusion imaging (see below) and mice were scored at multiple postsurgery time points for surgical limb appearance and use as previously described (14,15). In brief, ischemic limbs were ascribed, by an investigator blinded to genotype and surgical procedure, a nonparametric score based on the following descriptors for appearance (relative to the contralateral control limb): 0 ϭ no difference; Ϫ1 ϭ minor discoloration; Ϫ2 ϭ moderate discoloration; Ϫ3 ϭ severe discoloration and/or mild necrosis; Ϫ4 ϭ severe necrosis and/or distal tissue auto-amputation.…”

“…Each of these deficits in vascular function, in addition to compromising normal vascular function, could negatively impact recovery of ischemic tissue (5,16,21,30,38). Previously, we showed that Cx40 Ϫ/Ϫ mice, subjected to femoral and saphenous artery-vein pair resection (here termed severe surgery), were more likely to suffer irreversible injury than either wild-type (WT) or Cx37 Ϫ/Ϫ mice (15). We concluded from these studies that the larger reduction in distal limb perfusion evident 24 h postsevere surgery in Cx40 Ϫ/Ϫ mice led to a more extensive injury, predisposing the limb to an aggressive inflammatory response that led to distal necrosis and poor recovery of the injured limb.…”

Connexin31.1 (Gjb5) Deficiency Blocks Trophoblast Stem Cell Differentiation and Delays Placental Development

“…For instance, in endothelial cells, Cx37 and Cx40 are collectively essential for vascular development [29]. Recently, it was shown that Cx40 and Cx37 have opposite effects on postischemic limb perfusion, recovery, and tissue survival in the same mouse model [30]. Another example is the expression of Cx31 and Cx43 during preimplantation development.…”