Comparison of global gene expression between porcine testis tissue xenografts and porcine testis in situ

Testis tissue from immature mammalian donor animals, grafted ectopically to immunodeficient mouse hosts, can undergo complete spermatogenesis with the production of fertilization-competent spermatozoa. To further characterize testis tissue xenografts as a model for testis function in situ, the objective of this study was to compare gene expression between porcine testis tissue xenografts and testis tissue in situ. Pieces of testis tissue from 1-week-old piglets were grafted onto immunodeficient male mice and a littermate piglet was raised for comparison as control. Complete spermatogenesis was present in the testis tissue xenografts at 8 months after transplantation into mouse hosts and in the 8-month-old control porcine testis tissue. Total RNA was isolated from xenografts and control tissue, and the RNA was labeled and hybridized to the porcine genome array. By analyzing the expression of 23,256 transcripts, we found that 71 genes were differentially expressed with at least a fourfold difference between xenografts and control tissue. Interestingly, none of the 56 transcripts present on the array that were annotated in porcine testis showed differential expression between xenografts and control testis. This analysis indicates that global gene expression in porcine testis xenografts appears comparable to testis tissue in situ. These findings support the hypothesis that testis tissue xenografts can provide a representative model to study mammalian spermatogenesis.