Persistent ischemia impairs myofibroblast development in wound granulation tissue: A new model of delayed wound healing

Abstract

We describe a new animal model designed to assess the impact of ischemia on wound healing. Eight patterns of arterial lesion in the limb were first tested in 24 Wistar rats. Resection of the external iliac artery down to the femoral artery at the level of the knee was chosen as the reference model and performed on the left limb of 45 rats; the right limb was used as the control. Skin wounds measuring 1.2 x 0.8 cm were created on both feet. Ischemia was assessed by blood flow measurement, which decreases dramatically in the ischemic limb. A significant delay in wound closure with a decrease in wound contraction was observed in the ischemic limb. Myofibroblast quantification showed a significant delay in appearance as well as a decrease in the number of these cells in the ischemic wound. Vascular endothelial growth factor-A appearance and evolution were qualitatively similar in both situations. However, collagen type I mRNA was markedly decreased in ischemic granulation tissue 10 days after wounding. These findings suggest that decreased wound contraction plays an important role in delayed ischemic wound healing, probably due to reduced myofibroblast development and activity.

Hypoxia Impairs Skin Myofibroblast Differentiation and Function

“…These data support the notion of acute low O 2 as a positive stimulator of wound healing (Frangogiannis et al, 2000). The upregulation of TGFb1 in hypoxic dermal rat wounds (Alizadeh et al, 2007) is consistent with our results showing increased levels of active and total TGFb1 in response to the low-O 2 switch. The absence of effects of TGFb1 in these conditions may be partly due to the concomitant downregulation of the TGFb-RII shown here, possibly by a negative TGFb1 feedback loop.…”

“…Our previous work using a rat hind-limb ischemic wound model suggested that reduced wound contraction in ischemic conditions is related to decreased myofibroblast differentiation (Alizadeh et al, 2007). Conversely, hypoxic culture has been shown to stimulate fibrosis and myofibroblast activity in vessels (Das et al, 2002;Krick et al, 2005;Zhang et al, 2005), lung (Short et al, 2004;Leufgen et al, 2005;Jiang et al, 2006), liver, and kidney (Manotham et al, 2004;Shi et al, 2007).…”

“…In this model of ischemic limb by total resection of the external iliac artery, decreased ischemic wound contraction correlated with reduced myofibroblast development (Alizadeh et al, 2007). Several mechanisms have been suggested to decrease myofibroblast occurrence in nonhealing wounds, including reduced TGFb1 expression and/or activation, impaired angiogenesis, and delayed revascularization (Ahn and Mustoe, 1990;Wu et al, 1999;Tandara and Mustoe, 2004).…”

Hemoglobin vesicles improve wound healing and tissue survival in critically ischemic skin in mice

“…An increased oxygen demand is necessary for normal tissue repair, which is not sufficiently covered under hypoxic conditions, and wound healing may be attenuated due to the suppression of essential oxygen-dependent processes such as fibroblast and myofibroblast activity, angiogenesis, and collagen synthesis (2,9). An ameliorated oxygen supply was most likely responsible for the improved midline suture healing in the HbV-treated animals in our study.…”

The Role of Hypoxia-Inducible Factor in Wound Healing

“…Using an ischemic limb model, persistent hypoxia was shown to reduce production of collagenous matrix and retard granulation tissue formation as well as reduce contraction in a cutaneous wound. 40 On the other hand, defective granulation tissue formation and delayed dermal regeneration in diabetic mice wounds were improved by increasing the stabilization of HIF-1. 1 Additionally, HIF-1a gene transcription was found to be impaired in dermal fibroblasts of aged mice resulting in delayed angiogenic responses in ischemic wounds.…”