Effect of hyaluronidase for regeneration of vascularized lymph node flap transfer in the experimental animal study

Abstract

Background and purpose: Lymphedema is a chronic, debilitating and consumptive condition of an overwhelmed lymphatic system, which affects up to 250 million individuals worldwide. Currently, although there is still no cure for lymphedema we have made some breakthroughs in surgical treatment and medication. Physiological surgical treatment for lymphedema, especially Vascularized lymph node flap (VLNF) transfer, have been proven to improve the clinical efficacy in lymphedema and promote functional recovery of the affected area, as well as reduce the incidence of cellulitis by reversing the pathological process of lymphedema. However, the transfer flap could form fibrous adhesions with the surrounding tissues and extracellular matrix deposition resulting in blocked lymphangiogenesis and lymphatic fluid obstruction, which is the biggest issue affecting the efficacy of VLNF transfer. Furthermore, hyaluronidase not only enhances lymphangiogenesis in lymphedema limbs but also reduces the level of tissue fibrosis. The purpose of this study was to evaluate the efficacy of VLNF transfer combined with hyaluronidase injection. Materials and methods: The experiment was designed to utilize 34 male adult Sprague-Dawley (SD) rats weighing 250–300 g. First, all rats were established in a model of VLNF transfer for lymphedema. Then, rats were categorized into 2 groups, the experimental group, and the control group, based on whether or not hyaluronidase was injected. Each group is divided into three parts: In part I, 6 rats were recorded weekly for forelimb volume using photographic post-software analysis and observation of lymphatic drainage patterns in NIR indocyanine green imaging. In part II, 1 rat was sacrificed every 4 weeks to redissect the surgical area under the microscope to observe the level of lymphangiogenesis and the degree of surrounding fibrosis. In addition, the velocity of lymphatic transport was calculated by NIR indocyanine green imaging system every two weeks in this group of rats. In Part III, 2 rats were sacrificed every 3 weeks for pathological examination to quantify lymphangiogenesis and limb fibrosis. After 12 weeks of the experiment, all rats were euthanized. Results: In the experimental group, the change of forelimb volume was higher than that in the control group. Moreover, with the progress of the experiment, the linear drainage pattern displayed by ICG accounted for a higher proportion in the experimental group, and the upward trend was more obvious. Similarly, in the comparison of lymph node transfer velocity, the data of the experimental group was much higher than that of the control group and was almost close to the normal lymph node metastasis rate at the later stage of treatment. what's more, the pathological results showed that the content of lymphatic vessels was more, while the content of collagen fibers was less in the experimental group. Conclusion: In animal experiments, hyaluronidase injection can optimize the therapeutic effect of VLNF transfer in lymphedema. This is because the combination treatment promotes lymphangiogenesis and reduces fibrosis around the VLNF. Despite the efficacy, its clinical application remains to do further study.