The effect of radiotherapy given to the anterior chest wall on stromal vascular fraction injected latissimus dorsi muscle in rats

Objective: The use of the latissimus dorsi muscle flap in the reconstruction of thoracic region had been mentioned since the ancient times. The infectivity of the wound bed and the effects of radiotherapy given to this region after oncological processes are some of the difficulties that may be encountered while using this muscle flap. Although many treatment strategies have been described to enhance wound healing by eliminate the negative local effects of radiotherapy, there is no consensus regarding the definite treatment modality. Mesenchymal stem cells are one of the basic building blocks of the connective tissue and responsible of releasing several trophic factors which induce wound healing and tissue regeneration. In this study, we aimed to investigate the resistance of mesenchymal stem cell- enriched latissimus dorsi muscle flap against the adverse side effects of radiation in terms of histopathological and electrophysiological evaluations. Materials and Methods: This study was carried out on 30 rats by forming 3 groups with 10 (n=10) rats in each group. After the omental adipose tissue of the rats was taken, cellular pellets of mesenchymal stem cell- enriched stromal vascular fraction was obtained by the Department of Histology. This cellular pellet was homogeneously injected into the latissimus dorsi muscle, which was brought to the anterior chest wall by the surgical team. Group I: The latissimus dorsi muscle was transposed to the subcutaneous pocket on the anterior chest wall, with the preservation of the neurovascular connections. Group II: after transposing the latissimus dorsi muscle to the subcutaneous pocket on the anterior chest wall, 20 Gy external radiotherapy was applied in a single fraction 10 days after the transposition. Group III: after transposing the latissimus dorsi muscle to the subcutaneous pocket on the anterior chest wall, Stromal vascular fraction was injected into the transposed muscle. 10 days after this procedure, external radiotherapy of 20 Gy was applied in a single fraction. At the postoperative 3rd month, amplitude and latency values of all the muscles in the 3 groups were obtained by EMG test. After the rats were sacrificed, samples taken from the latissimus dorsi muscle were evaluated by histopathological examinations. The median latency values were: 1.09 (0.96-1.35), 1.05 (0.91-1.45) and1.08 (0.81-1.59) for Group I, II and III, respectively. However, the median amplitude values were: 7.14 (2.49-11.55), 3.65 (2.12-16.20) and 7.10 (2.60-22.96) for Group I, II and III, respectively. The distribution of EMG results between Group I and Group II was found to be statistically similar (p>0.05). There was no statistically significant difference in the distribution of EMG parameters between Group II and Group III (p>0.05) Results: The degree of atrophy and fibrosis were found to be statistically significantly lower in Group I compared to Group II in the comparisons made by considering the averages of histopathological parameters within the groups (p=0.019; p=0.015, respectively). There was no statistically significant difference between Group I and Group II in terms of vascularization, fatty change and inflammation (p>0.05). The degree of atrophy and fibrosis were found to be statistically significantly lower in Group III compared to Group II (p=0.007; p=0.029, respectively). There was no statistically significant difference between Group II and Group III in terms of vascularization, fatty change and inflammation (p>0.05). Conclusions: It was revealed by histopathological evaluation that stromal vascular fraction- enriched latissimus dorsi muscle gained resistance against radiotherapy-induced atrophy and fibrosis in this experimental study. The positive effects of clinical application of stromal vascular fraction in soft tissue reconstruction of the anterior chest wall on reducing the side effects of radiotherapy can be supported by further research.