Relative safety of various spermatogenic stem cell purification methods for application in spermatogenic stem cell transplantation

Background

Spermatogonial stem cell (SSC) transplantation technology as a promising option for male fertility preservation has received increasing attention, along with efficient SSC purification technology as a necessary technical support; however, the safety of such application in patients with tumors remains controversial.

Methods

In this study, we used a green fluorescent protein mouse xenograft model of B cell acute lymphocytic leukemia. We isolated and purified SSCs from the testicular tissue of model mice using density gradient centrifugation, immune cell magnetic bead separation, and flow cytometry. The purified SSCs were transplanted into convoluted seminiferous tubules of the nude mice and C57BL/6 male mice subjected to busulfan. The development and proliferation of SSCs in the recipient testis were periodically tested, along with whether B cell acute lymphocytic leukemia was induced following SSC implantation. The genetic characteristics of the offspring obtained from natural mating were also observed.

Results

In testicular leukemia model mice, a large number of BALL cells infiltrated into the seminiferous tubule, spermatogenic cells, and sperm cells in the testis tissue decreased. After spermatogonial stem cell transplantation, the transplanted SSCs purified by immunomagnetic beads and flow cytometry methods colonized and proliferated extensively in the basement of the seminiferous tubules of mice; a large number of spermatogenic cells and sperm were found in recipient testicular tissue after 12 weeks of SSC transplantation. In leukemia detection in nude mice after transplantation in the three SSC purification groups, a large number of BALL cells could be detected in the blood of recipient mice 2–3 weeks after transplantation in the density gradient centrifugation group, but not in the blood of the flow cytometry sorting group and the immunomagnetic bead group after 16 weeks of observation.

Conclusions

In this study, we confirmed that immunomagnetic beads and flow cytometry methods of purifying SSCs from the testicular tissue of the testicular leukemia mouse model could be safely applied to the SSC transplantation technology without concomitant tumor implantation. The results thus provide a theoretical basis for the application of tumor SSC cryopreservation for fertility preservation in patients with tumors.

[Construction of a mouse model of spermatogonial stem cell transplant recipient by high-temperature heat stress]

OBJECTIVE

To investigate the feasibility of constructing a mouse model of spermatogonial stem cell (SSC) transplant recipient by high-temperature heat stress.

METHODS

Four-week-old C57BL/6 male mice and B6(Cg)-Tyrc-2J/J coat color gene homozygous mutant male mice were heat-treated at 43 ℃ for an hour in the incubator. The best transplantation time was determined by HE staining, immunohistochemistry and TUNEL and the SSCs were transplanted into the seminiferous tubules of the mice followed by regular observation of the proliferation, differentiation and spermiogenesis of the SSCs in the testis of the recipient mice. Then the recipients were mated with age-matched normal female mice and the epigenetic features of their offspring were observed.

RESULTS

After 3－5 days of high-temperature heat stress, the spermatogenic cells in the testicular seminiferous tubules of the recipient mice showed obviously decreased layers, disordered and loose arrangement, massive deletion, significant apoptosis, reduced mesenchymal cells and increased autophagy, which were basically recovered in about 12 days. At 8 weeks after transplantation, the isolated and purified SSCs were differentiated into spermatogenic cells and sperm with genetic function in the testicular seminiferous tubules of the recipient mice, and normal offspring were reproduced after natural mating.

CONCLUSIONS

High-temperature heat stress can be used as an efficient method for rapid construction of the mouse model of spermatogonial stem cell transplantation recipient.

[Rho/ROCK signaling pathway and anti-cryodamage ability of human sperm]

OBJECTIVE

To investigate the influence of the Rho/ROCK signaling pathway on the anti-cryodamage ability of human sperm and provide some theoretical evidence for the development of high-efficiency semen cryoprotectants.

METHODS

We collected semen samples from 25 healthy males, each divided into a fresh, a normal cryopreservation control and an Rho-inhibition group. Before and after freezing, we detected sperm motility, viability, membrane integrity, morphology, DNA fragmentation index (DFI), acrosomal enzyme activity (AEA) and mitochondrial membrane potential (MMP) and determined the expressions of RhoA and ROCK proteins in the sperm by immunofluorescence staining.

RESULTS

Compared with the normal cryopreservation control, the frozen-thawed sperm of the Rho-inhibition group showed significantly increased sperm motility （ ［51.20 ± 7.70］% vs ［57.50 ± 6.83］%, P = 0.002), survival rate ( ［52.87 ± 5.07］% vs ［60.24 ± 5.53］%, P = 0.001), membrane integrity (［59.78±5.56］% vs ［67.10 ± 4.43］%, P = 0.001), percentage of morphologically normal sperm (［4.83 ± 1.11］% vs ［7.46 ± 1.28］, P = 0.001) and MMP (56.30 ± 4.28 vs 63.11 ± 2.97, P = 0.001), but decreased DFI (［27.64 ± 6.64］% vs ［18.87 ± 4.07］%, P = 0.001). There was no statistically significant difference in the AEA of the frozen-thawed sperm between the control and Rho-inhibition groups (97.65 ± 9.31 vs 98.30 ± 11.33, P > 0.05). Immunofluorescence staining revealed extensive expressions of RhoA and ROCK proteins in the head and neck of the sperm.

CONCLUSIONS

The Rho/ROCK signaling pathway plays a role in the cryodamage to human sperm, and inhibiting the activity of Rho/ROCK can significantly improve the ability of sperm to resist cryodamage.