Reparative regeneration of thymus under the exposure to ionizing radiation: histomorphometric and immunomorphological study

The aim of this study was to evaluate the time-related changes in histomorphometric and immunomorphological parameters of rat thymus under a single ionizing radiation exposure in sublethal dose of 5 Gray on the background of correction by parenteral administration of xenogenic cerebrospinal fluid.
An experiment with radiation injury of rats at a dose of 5 Gray without correction and with parenteral administration of xenogenic cerebrospinal fluid was carried out. The structural organization of the thymus was assessed by descriptive histological analysis, histomorphometric and immunohistochemical methods (Ki-67 and CD68 markers) followed by statistical analysis of the results.
The revealed changes in structural organization of thymus after radiation injury has shown significant morphological transformations of both histological and cytological structural arrangements of the organ observed on 3rd and 7th days after irradiation, and with the restoration of cell population up to the 30th day of the experiment. A single injection of the cerebrospinal fluid at a dose of 10 mL/kg has excessive and short
effect, resulting in aggravation of reactive changes in microvasculature during the early postradiation period followed by the peak of restoration process on the 14th day of the experiment. Repeated administrations of cerebrospinal fluid in a dose of 2 mL/kg result in a peak of intrathymic proliferation, elimination of cells with signs of destruction, restoration of the ratio of structural-functional zones and their cellular composition on
the 7th day after irradiation with a constant reparative processes on the 14th and 30th days of the experiment.
Reparative regeneration of the thymus in postradiation period without correction is characterized by the two-wave kinetics with recession on the 3rd and 14th days and relative restoration on the 7th and 30th days after irradiation. Parenteral administration of cerebrospinal fluid has a pronounced effect on thymus histoarchitectonics during the postradiation period. Revealed changes are linear and are aimed at restoring the histological and cytological structure of the thymus, largely depending on the dose and frequency of cerebrospinal fluid administration.