Identification and characterization of a novel CD2-positive cell population in the seminiferous tubule of Fischer CDF344 rats†.

We report the presence of a previously undocumented cell type in the spermatogonial stem cell niche expressing CD2 protein, using whole-mount immunofluorescence of rat seminiferous tubule preparations. Confocal imaging revealed that CD2+ cells reside interspersed within the peritubular myoid cell (PTMC) layer surrounding the seminiferous tubules. Three-dimensional reconstruction and surface rendering models revealed cellular interaction between peritubular macrophages (PTMφs) and CD2+ cells. The mono-(2-ethylhexyl) phthalate (MEHP)-induced testicular injury model was utilized to investigate the dynamics of PTMφ-CD2+ cell interaction. Fischer CDF344 male rats were exposed to 700 mg/kg-bw MEHP or corn oil via oral gavage on postnatal day (PND) 28 and euthanized at 48 h or 2 weeks post-exposure. In MEHP-exposed animals, a significant number of PTMφs encounter CD2+ cells at 48 h post-exposure, suggesting it to be an adaptive response against the MEHP-induced toxicity. Moreover, neither the vehicle group (corn oil) nor the MEHP-exposed animals show a change in the temporal division dynamics of the CD2+ cells when followed along the acute (48 h) and recovery (2 weeks) phases of post-injury, suggesting these cells as dormant cell population lacking susceptibility against MEHP-induced toxicity. Nevertheless, an increase in PTMφ-CD2+ cell interactions in response to testicular toxicity indicates a CD2+ cell-mediated link for dynamic intercellular communication between the innate immune cells and niche cells of the testis. This first report of the existence of a unique CD2+ cell population in the rat seminiferous tubules and their direct cellular interaction with PTMφs is anticipated to stimulate further research in the field of testicular immunobiology.