The effect of stromal vascular fraction cells derived from epididymal and inguinal adipose tissues on <i>in vitro</i> spermatogenesis

Infertility affects 10-20% of sexually active couples and male-related factors contribute to 30-50% of all cases of infertility. The development of three-dimensional in vitro approaches to promote the differentiation of spermatogonial stem cells (SSCs) into functional spermatozoa is an essential step for the treatment of male infertility. Stromal vascular fraction (SVF) cells derived from adipose tissue are known to have a regenerative effect on spermatogenesis and testicular regeneration after testicular damage. The study assessed the effect of SVF cells from epididymal and inguinal adipose tissue on in vitro spermatogenesis. Testicular cells from prepubertal mice were cultured alone as control and co-cultured with SVF cells from epididymal (ESVF) and inguinal (ISVF) adipose tissue in experimental groups by an air-liquid interface system. Spermatogenic progression was evaluated histomorphometrically and immunohistochemically at weeks 1, 3, 4, and 6. ESVF increased formation of tubule-like structures at week 1 and ISVF had a similar effect at week 4. The ISVF group showed higher numbers of ID4(+) (Inhibitor of DNA Binding 4) SSCs than control at all time points. At weeks 3 and 4, the ISVF exhibited increased number of SCP3(+) (Synaptonemal Complex Protein 3) spermatocytes compared to the control group and the ESVF showed a similar increase at week 6. The presence of ACR(+) (Acrosin) spermatids was observed in all groups at week 3. At week 4, the ISVF group had more ACR(+) spermatids than the control and ESVF groups. Our findings demonstrated that SVF cells effectively supported in vitro spermatogenesis. Notably, inguinal-derived SVF cells led to a higher production of ACR(+) spermatids than edidiymal-derived SVF cells. In conclusion, inguinal derived SVF cells can be used as a new co-culture method to preserve the SSC pool and promote in vitro spermatogenesis in infertile patients.