Transgender individuals who pursue alignment with their gender identity, through medical treatments or surgery face challenges to family building because the medical community lacks the understanding or infrastructure to serve the reproductive needs of transgender or non-binary people. Fertility preservation (FP) offers a crucial opportunity for the transgender community, enabling individuals to exercise autonomy over their reproductive choices. While fertility preservation has been extensively studied in other populations such as cancer patients, the unique biology and clinical care of the transgender and gender non-binarydiverse (TGD) individuals has challenged direct translation of what can be offered for cisgender individuals. Additionally, the FP services in transgender communities are reportedly under-utilized, despite the prevalent desire of TGD individuals to have children. This review aims to provide up-to-date information on the current standard of care and experimental FP options available to TGD individuals and their potential reproductive outcomes. We will also discuss the barriers to the success of FP utilization, from both the biology/medical aspect and the perspectives of TGD population. By recognizing the unique family building challenges faced by TGD people and potential areas of improvement, appropriate adjustments can be made to better support fertility preservation in the TGD community.

Spermatogonial stem cells (SSCs) maintain spermatogenesis throughout the reproductive life of mammals. While A_single spermatogonia comprise the rodent SSC pool, the identity of the stem cell pool in the primate spermatogenic lineage is not well established. The prevailing model is that primate spermatogenesis arises from A_dark and A_pale spermatogonia, which are considered to represent reserve and active stem cells respectively. However, there is limited information about how the A_dark and A_pale descriptions of nuclear morphology correlate with the clonal (A_single, A_paired, and A_aligned), molecular (e.g. GFRα1 (GFRA1) and PLZF), and functional (SSC transplantation) descriptions of rodent SSCs. Thus, there is a need to investigate primate SSCs using criteria, tools, and approaches that have been used to investigate rodent SSCs over the past two decades. SSCs have potential clinical application for treating some cases of male infertility, providing impetus for characterizing and learning to manipulate these adult tissue stem cells in primates (nonhuman and human). This review recounts the development of a xenotransplant assay for functional identification of primate SSCs and progress dissecting the molecular and clonal characteristics of the primate spermatogenic lineage. These observations highlight the similarities and potential differences between rodents and primates regarding the SSC pool and the kinetics of spermatogonial self-renewal and clonal expansion. With new tools and reagents for studying primate spermatogonia, the field is poised to develop and test new hypotheses about the biology and regenerative capacity of primate SSCs.