Quantification of axonal ingrowth and functional recovery in a myocutaneous flap model in rats with strong clinical implications

AT2R Activation Improves Wound Healing in a Preclinical Mouse Model

Abnormal skin healing resulting in chronic wounds or hypertrophic scarring remains a major healthcare burden. Here, the antifibrotic angiotensin II type 2 receptor (AT2R) signaling pathway was modulated to determine its impact on cutaneous wound healing. Balb/c mice received two splinted full-thickness wounds. Topical treatments with the selective AT2R agonist compound 21 (C21) and/or selective antagonist PD123319 or saline vehicle were administered until sacrifice on post-wounding days 7 or 10. The rate of wound re-epithelialization was accelerated by PD123319 and combination treatments. In vitro, C21 significantly reduced human fibroblast migration. C21 increased both collagen and vascular densities at days 7 and 10 post-wounding and collagen I:III ratio at day 10, while PD123319 and combination treatments decreased them. Genes associated with regeneration and repair were upregulated by C21, while PD123319 treatment increased the expression of genes associated with inflammation and immune cell chemotaxis. C21 treatment reduced wound total leukocyte and neutrophil staining densities, while PD123319 increased these and macrophage densities. Overall, AT2R activation with C21 yields wounds that mature more quickly with structural, cellular, and gene expression profiles more closely approximating unwounded skin. These findings support AT2R signal modulation as a potential therapeutic target to improve skin quality during wound healing.

Exploiting synergistic effect of CO/NO gases for soft tissue transplantation using a hydrogel patch

Autologous skin flap transplantation is a common method for repairing complex soft tissue defects caused by cancer, trauma, and congenital malformations. Limited blood supply range and post-transplantation ischemia-reperfusion injury can lead to distal necrosis of the flap and long-term functional loss, which severely restricts the decision-making regarding the optimal surgical plan. To address this issue, we develop a hydrogel patch that releases carbon monoxide and nitric oxide gases on demand, to afford a timely blood supply for skin flap transplantation during surgery. Using an ischemia-reperfusion dorsal skin flap model in rats, we show that the hydrogel patch maintains the immediate opening of blood flow channels in transplanted tissue and effective blood perfusion throughout the perioperative period, activating perfusion of the hemodynamic donor site. We demonstrate that the hydrogel patch promotes distal vascularization and long-term functional reconstruction of transplanted tissues by inhibiting inflammatory damage and accelerating blood vessel formation.

Impact of Diameter of Perforator in Pedicle and Different Managements of Intermediate Non-Pedicle Perforator on Flap Survival in Rats

BACKGROUNDS

The quantified relationship between perforator diameter and flap length can be supported, and the impact of different strategies of managements of a non-pedicled perforator with two major subfascial divisions on flap survival has never been explored.

MATERIALS AND METHODS

This study was divided into two parts. In Part I, 48 Sprague-Dawley rats underwent flap harvesting based on six perforators with a diameter gradient. Then, the flap length and perforator diameter were measured for establishment of an equation. In Part II, 32 rats underwent harvest of a transverse flap based on the right superficial epigastric perforator. In 16 rats the right intermediate iliolumbar perforator was severed in a distal-to-division approach, whereas, in the other 16 rats, it was severed with in a proximal-to-division approach. Necrosis rates and blood perfusion were also compared.

RESULTS

The equation y = 13.02 × x + 2.29 could be established between the perforator diameter in the pedicle (x) and the flap length (y) that could be supported with R²=0.8963 and P < 0.001.The transverse flap with a distal-to-division management of the intermediate iliolumbar perforasome was weaker in perfusion and had a necrosis rate of 49±4%, whereas the flap with a proximal-to division management had a significantly stronger perfusion and a lower necrosis rate of 21±2% (P<0.001).

CONCLUSIONS

The safe flap length that can be estimated based on a perforator with a known diameter can be calculated using y=13.02× x +2.29. A short segment of the stem of an intermediate perforator with two major subfascial branches should be preserved to augment flap survival.