The effects of increased ischemic times on adipose tissue: a histopathologic study using the epigastric flap model in rats

The Effect of Locally Delivered Apocynin on Fat Graft Survival in an Experimental Rat Animal Model

OBJECTIVES

We aimed to investigate the efficacy of locally delivered apocynin on fat graft survival in an experimental autologous fat grafting (AFG) model created in rats.

METHODS

Twenty-one Wistar albino male rats were included in this study. The 0.647 g mean weight grafts were harvested from the inguinal region and transferred to the nape of every rat. The subjects were randomly separated into three groups. Saline, dimethyl sulfoxide (DMSO) and apocynin, a dose of 20 mg/kg, solutions were applied once a day for 2 weeks. After 3 months, the rats were sacrificed. The evaluation of physical measurements (weight and volume) and survival rates of the grafts for volume (SRV) and weight (SRW), the viable cell count (VC) with the MTT assay, and histopathological parameters were done.

RESULTS

All biophysical parameters were found to be significantly higher in the apocynin group compared to other groups (p < .05). In the MTT test, the saline group was normalized to 100%. According to this, DMSO and apocynin groups' means were 106% and 163%, respectively. The VC was significantly higher in the apocynin group than the other groups (p < .05). The VC was significantly higher in the DMSO group than in the saline group (p < .05). No significant difference was found in other comparisons performed according to biophysical and histopathological parameters (p > .05).

CONCLUSION

The locally delivered apocynin decreases fat graft volume loss in an experimental AFG model. Consequently, apocynin can be used as an effective substance to increase graft survival.

Adipose tissue remodeling under ischemia: death of adipocytes and activation of stem/progenitor cells

BACKGROUND

Following various types of plastic surgery, such as adipose grafting and flap elevation, adipose tissue undergoes ischemia, leading to hypoxia and nutrient depletion. However, few studies have examined ischemic and/or hypoxic changes in adipose tissue.

METHODS

The authors established surgically induced ischemia models by severing blood vessels supplying the inguinal fat pads in mice. The partial pressure of oxygen in adipose tissue was measured with an oxygen monitor, and ischemic changes were analyzed by whole-mount staining, immunohistochemistry, flow cytometry, and Western blotting. The authors also examined cell survival under a hypoxic condition in vitro.

RESULTS

Models for three degrees (mild, intermediate, and severe) of ischemia showed approximately 75, 55, and 20 percent of the partial pressure of oxygen level in normal adipose tissue (50.5±1.3 mm Hg), respectively. Adipose tissue atrophy with substantial fibrosis on day 28 was seen, depending on the severity of ischemia. Intermediate and severe ischemia induced elevated expression of hypoxia-inducible factor 1α and fibroblast growth factor 2 on day 1 and degenerative changes (i.e., apoptosis, necrosis, and macrophage infiltration and phagocytosis) in adipose tissue. Dead cells included adipocytes, vascular endothelial cells, and blood-derived cells, but not adipose-derived stem/progenitor cells. Subsequent to degenerative changes, regenerative changes were seen, including angiogenesis, adipogenesis, and proliferation of cells (adipose-derived stem/progenitor cells, vascular endothelial cells, and blood cells). The authors found that, in vitro, the experimentally differentiated adipocytes underwent apoptosis and/or necrosis under severe hypoxia, but adipose-derived stem/progenitor cells remained viable.

CONCLUSIONS

Severe ischemia/hypoxia induces degenerative changes in adipose tissue and subsequent adaptive tissue remodeling. Adipocytes die easily under ischemic conditions, whereas adipose-derived stem/progenitor cells are activated and contribute to adipose tissue repair.

Critical ischemic time for the rat ovary: experimental study evaluating early histopathologic changes

The aim of the present study was to determine a critical ischemic time for ovary in an experimental study in rats. An experimental model using slip-knot tying of all ovarian arteries and veins in cycling female rats was developed. Rat ovaries were tied using the technique through an explorative laparotomy. Complete ischemia times of 1, 2 and 3 h were used for the study. At the end of the ischemic times, the ovaries were harvested following 1 h of reperfusion. Histology indicated a gradually increased congestion correlating with the respective increased ischemic times. According to the present findings 2 h complete ischemia yields a significant injury. The model used in the present study may be used for complete ischemia-reperfusion injury of the rat ovary.