['To study the ability of human spermatogonial stem cells (hSSCs) to proliferate in\xa0vitro under mouse spermatogonial stem cell (mSSC) culture conditions.', 'Experimental basic science study.', 'Reproductive biology laboratory.', 'Cryopreserved testicular tissue with normal spermatogenesis obtained from three donors subjected to orchiectomy due to a prostate cancer treatment.', 'Testicular cells used to create in\xa0vitro cell cultures corresponding to the following groups: [1] unsorted human testicular cells, [2] differentially plated human testicular cells, and [3] cells enriched with major histocompatibility complex class 1 (HLA', 'Analyses and characterization including immunocytochemistry and quantitative reverse-transcription polymerase chain reaction for somatic and germ cell markers, testosterone and inhibin B quantification, and TUNEL assay.', 'Putative hSSCs appeared in singlets, doublets, or small groups of up to four cells in\xa0vitro only when testicular cells were cultured in StemPro-34 medium supplemented with glial cell line-derived neurotrophic factor (GDNF), leukemia inhibitory factor (LIF), basic fibroblast growth factor (bFGF), and epidermal growth factor (EGF). Fluorescence-activated cell sorting with HLA'] Do human spermatogonial stem cells display limited proliferation in vitro under mouse spermatogonial stem cell culture conditions?