Stage-specific embryonic antigen-1 expression by undifferentiated spermatogonia in the prepubertal boar testis

The objective of this study was to use fluorescence-activated cell sorting (FACS) and spermatogonial stem cell (SSC) xenotransplantation to identify cell surface markers of putative porcine SSC. Analysis of porcine testis cells enriched for spermatogonia using FACS indicated that nearly half of stage-specific embryonic antigen-1 (SSEA-1) expressing testis cells expressed the undifferentiated spermatogonia marker protein gene product 9.5 (PGP 9.5) whereas significantly fewer (P < 0.05) cells selected for thymus cell antigen-1 (Thy-1), also known as cluster of differentiation 90 (CD90), cluster of differentiation 9 (CD9), or other SSC markers expressed PGP 9.5. Immunocytochemical analysis indicated that promyelocytic leukemia zinc finger (PLZF) protein and germ cell lineage marker VASA homolog (VASA), also known as DEAD box protein 4 (DDX4), were expressed by SSEA-1 expressing germ cells. Spermatogonial stem cell xenotransplantation of testis cell populations enriched for cells expressing SSEA-1 generated significantly (P < 0.05; greater than 15-fold) more colonies of donor derived germ cells than unselected testis cells. In conclusion, these data indicate that SSC markers identified in rodents are likely not entirely conserved in pigs and that SSEA-1 is a marker for porcine undifferentiated spermatogonia including SSC in prepubertal boars and its expression may serve as a target for the further study of porcine germ cells.