Retinoic acid treatment alters germ cell heterogeneity and testicular echotexture in prepubescent ram lambs

Abstract

Testicular echotextural attributes are closely associated with spermatogenic development; however, precise characterisation of specific germ cell types is difficult due to tremendous germ cell heterogeneity. Recently, retinoic acid (RA) administration in neonatal mice was found to induce highly synchronised spermatogenesis as adults. A RA-treatment protocol was tested in 17 ram lambs treated with or without RA at 8 weeks of age, with scrotal ultrasonography and blood samples collected until castration 24h or 2.5 weeks later. At 8.2 weeks of age, the nuclear:seminiferous tubule (ST) area was higher in the treated compared with the control group. Serum testosterone concentrations and numerical pixel values (NPVs) of the testicular parenchyma reached a peak at 9 weeks of age in both groups of ram lambs studied. At 10.5 weeks of age, the percentage of ST cross-sections with different germ cells as the most mature germ cell type was lower and the inter-tubular heterogeneity and NPVs were also lower in the treated compared with the control animals. RA manipulation of spermatogenesis in prepubertal ram lambs may provide a suitable model for further investigation of the echotextural characteristics of specific germ cell types and critical developmental events.