The use of modern technologies of cryopreservation of testicular tissue samples in prepubertal patients is one of the ways to maintain their fertility in the future. The purpose of the study was to investigate the proliferative potential, morphological characteristics and expression of specific markers of cell culture obtained from cryopreserved and vitrified fragments of seminiferous tubules (FSTs) of rats' testis. Materials and methods. The isolation of cells from native, cryopreserved and vitrified FSTs of immature rats was performed by incubation in a solution of collagenase type IV (1 mg/mL) + DNase (500 μg/mL). Cell viability was determined by Trypan blue staining. Monoclonal antibodies CD9-FITC, CD24-PE, CD45-FITC, CD90-FITC were used for immunophenotype analysis. Morphological characteristics, proliferative activity (MTT assay), relative number of cells positive for MAGE-B1 and vimentin were assessed in the obtained cultures. Results. The analysis of phenotypic characteristics showed that cells from native, cryopreserved and vitrified FSTs were characterized by high expression level of CD9 (≥ 40 %), CD24 (≥ 70 %), CD90 (≥ 70 %) and low expression of the CD45 (≤ 1 %). In cell culture in vitro, the studied cells from cryopreserved and vitrified rat's FSTs had the ability to adhere and proliferate while maintaining a cells population positive for MAGE-B1 and vimentin. Conclusions. The results can be the basis for the development of effective protocols for the cultivation and cryopreservation of testicular spermatogonial stem cells in order to restore fertility in men.

Today, transplantation of cryopreserved fragments of immature testis is a non-alternative method of preserving the fertility of pre-adolescent patients who undergo cytotoxic therapy.The purpose of the study is to compare the effectiveness of the use of biopolymers (bovine serum albumin and fibrin gel) as the bases of cryoprotective media at low temperature preservation of the fragments of the convoluted seminiferous tubules of prepubertal rats’ testis.Materials and methods. Convoluted seminiferous tubules of prepubertal rats’ testis (75 ± 3 mg and 6-8 mm3), after a 30-minute exposure at 4 °C in cryoprotective media based on Hanks’ solution with 50 g/L of bovine serum albumin (BSA) or fibrin gel (FG) supplemented with 0.6 M DMSO or 0.7 M glycerol, were cryopreserved according to the program: 1 °C/min to -8 °C; stop for 10 minutes; 10 °C/min to -70 °C; stored in liquid nitrogen. After thawing, the histological structure was evaluated and the metabolic activity of the spermatogenic epithelium cells was determined.Results. According to the results of the histological study, there was a positive tendency of FG application, which had the maximum expressiveness in combination with 0,7 M glycerol. In this case, 68.8 ± 15.7 % of cell nuclei remained morphologically intact, and changes in the spermatogenic epithelium were slightly pronounced. The metabolic activity of the rats’ seminiferous convoluted tubules cells after freezing and thawing remained at a significantly higher level when using FG in combination with 0.6 M DMSO than with 0.7 M glycerol compared to the corresponding cryoprotectant based on the Hanks’ solution with BSA.Conclusions. The use of fibrin gel in the protocols of cryopreservation provide to preserve the histological structure and metabolic activity of the spermatogenic epithelium.