Re The effect of photodynamic therapy and surgical treatment of experimental breast cancer on the relationship of microRNAs (-21, -27a, -221, -429) of thymic mRNA with the thymus structure

Abstract

Aim. To identify the effect of photodynamic therapy (PDT) and its combination with surgical treatment of breast cancer on the relationship of thymic microRNA (‑21, ‑27a, ‑221, ‑429) with the thymus structure in female Wistar rats. Methods. The study was conducted on 80 anesthetized mature female Wistar rats. The relationship between the thymus structure and the amount of microRNA in the thymus was assessed after PDT for breast cancer (intramammary administration of N-methyl-N-nitrosourea) and after PDT and surgical treatment for breast cancer. Results. After PDT, relationships were found only between pro-oncogenic microRNAs (‑21, ‑27a, ‑221) and cells in the corticomedullary zone and the central part of the medulla compared with the intact group and with breast cancer without treatment. Morphological changes in the thymus indicated the effect of PDT on the processes of both positive and negative selection. The relationships between thymic microRNAs and morphological changes in the thymus may indicate the effect of PDT on the attenuation of proliferative activity, differentiation and migration of T lymphocytes from the thymus compared to untreated breast cancer. PDT and subsequent surgical treatment of breast tumor, as compared to the PTD therapy, induced a significant increase in thymic microRNAs (‑21, ‑27a, ‑429). The following relationships were found: in the subcapsular zone, immunoblasts with microRNA‑21 and small lymphocytes with microRNA‑429; in the corticomedullary zone, small lymphocytes with microRNA‑27a; in the central part of the medulla, immunoblasts with microRNA‑21. Compared with PDT, the number of immunoblasts and medium lymphocytes decreased in the subcapsular zone and the central part of the cortical substance. The number of small lymphocytes increased in the central part of the cortical substance, and the number of small lymphocytes decreased in the central medulla and the corticomedullary zone. The number of epithelial reticular cells in the central part of the cortical substance and medullary substance was reduced. Conclusion. This study revealed relationships of cells in thymus structural components with quantitative changes in thymic microRNA after PDT and surgical removal of the tumor, in comparison with PDT alone and along with morphological data. These relationships may be due to a decrease in the thymus proliferative activity, the activity of the processes of both positive and negative selection of T cells, as well as decreased activity of the processes of differentiation and migration of T lymphocytes from the thymus.