Study question: Can transplanted primate testicular cells form seminiferous tubules de novo, supporting complete spermatogenesis?
Summary answer: Cryopreserved testicular cells from a prepubertal monkey can reorganize in an adult monkey recipient testis forming de novo seminiferous tubular cords supporting complete spermatogenesis.
What is known already: De novo morphogenesis of testicular tissue using aggregated cells from non-primate species grafted either subcutaneously or in the testis can support spermatogenesis.
Study design, size, duration: Two postpubertal rhesus monkeys (Macaca mulatta) were given testicular irradiation. One monkey was given GnRH-antagonist treatment from 8 to 16 weeks after irradiation, while the other received sham injections. At 16 weeks, cryopreserved testicular cells from two different prepubertal monkeys [43 × 106 viable (Trypan-blue excluding) cells in 260 μl, and 80 × 106 viable cells in 400 μl] were transplanted via ultrasound-guided injections to one of the rete testis in each recipient, and immune suppression was given. The contralateral testis was sham transplanted. Testes were analyzed 9 months after transplantation.
Participants/materials, setting, methods: Spermatogenic recovery was assessed by testicular volume, weight, histology and immunofluorescence. Microsatellite genotyping of regions of testicular sections obtained by LCM determined whether the cells were derived from the host or transplanted cells.
Main results and the role of chance: Transplanted testis of the GnRH-antagonist-treated recipient, but not the sham-treated recipient, contained numerous irregularly shaped seminiferous tubular cords, 89% of which had differentiating germ cells, including sperm in a few of them. The percentages of donor genotype in different regions of this testis were as follows: normal tubule, 0%; inflammatory, 0%; abnormal tubule region, 67%; whole interior of abnormal tubules, >99%; adluminal region of the abnormal tubules, 92%. Thus, these abnormal tubules, including the enclosed germ cells, were derived de novo from the donor testicular cells.
Large scale data: Not applicable.
Limitations, reasons for caution: The de novo tubules were observed in only one out of the two monkeys transplanted with prepubertal donor testicular cells.
Wider implications of the findings: These findings may represent a promising strategy for restoration of fertility in male childhood cancer survivors. The approach could be particularly useful in those exposed to therapeutic agents that are detrimental to the normal development of the tubule somatic cells affecting the ability of the endogenous tubules to support spermatogenesis, even from transplanted spermatogonial stem cells.
Study funding/competing interest(s): This work was supported by research grants P01 HD075795 from Eunice Kennedy Shriver National Institute of Child Health & Human Development (NICHD/NIH) to K.E.O and Cancer Center Support Grant P30 CA016672 from NCI/NIH to The University of Texas MD Anderson Cancer Center. The authors declare that they have no competing interests.