Experimental Study On The Ischemic Wound Treated By VAC In Rabbit Ear

Chronic and hard to healing wound means that the wound didn’t heal bythrough the normal healing course and come to a pathological inflammatorycondition because of various internal or external factors. The pathogeny ofchronic wound is of various kinds and with complicated pathogenesis. To date,people still do not create an ideal animal model conform to the character ofchronic wound in human being,and the ischemiec wound in animal may becomethe best representative.The efficacy of treating chronic wound by VAC technique alreadyachieved general consensus, but how to exert pressure can achieve the besttherapeutic results didn’t coincide in opinion, and also didn’t provide a basis forit by experiments. In this experiment, we drawed up a plan to explore that.ExperimentⅠ: A fullthickness skin defect,2.5cm in diameter,3-3.5cmaway from the ear root was created in bilateral dorsal ear skin of rabbit and the central neurovascular bundle was ligated with the perichondrium retained. Afterstop bleeding the animal was placed in a specially made wooden box.42rabbitwith84ischemic wounds were randomly divided into3major groups-50mmHg,-75mmHg,-100mmHg negative pressure(NP) group, and respectivelysubjected to intermittent negative pressure treatment(2minutes on,1minute off,4hrs/d) or continuous treatment(4hrs/d). In1,3,7,10,14,20d after wounding,the wound healing was evaluated, and taking the7d tissue samples for westernblotting, HE staining, VEGF expression, and histological examination forepithelial regeneration, granulation formation, and apoptosis detection.Results: All the wounds treated by intermittent NP healed more faster than thatof the continuous NP groups. The wounds treated by-50mmHg NP healedfastest, the-75mmHg group second, and the-100mmHg group, slowest. At thesame time point, in-50mmHg NP group, the VEGF expression, granulationtissue formation, and capillary members significantly lager than that in the other2groups, also the cell apoptosis significantly reduced.Experiment Ⅱ: Except that the wound was covered respectively withplexiglass hood in combination with gauze or sponge, the experimental methodsincluding experimental material, wound formation, evaluation index, treatingmethod with negative pressure and groups were the same with experiment Ⅰ.The plexiglass hood is2.5cm in diameter and2.5cm hight. There is a hole at thetop for connecting to negative pressure tube. Results:（1） Since7th day, thehealing rate has been increased significantly. In-50mmHg and-75mmHgintermittent or continuous groups, the healing rates were superior to-100mmHggroup and also the-50mmHg group was best. In the-100mmHg group, all thewounds appeared necrosis.(2) In the3d and7d, regardless of gauze or spongegroup, and whatever intermittent or continuous negative pressure were used, a double apoptotic peak emerged and with the posterior was more higher than thatin experiment Ⅰ.