Improvements in human sperm quality by long-term in vitro co-culture with isolated porcine Sertoli cells

BACKGROUND: Spermatogenesis is a complex process where spermatogonial germ cells become spermatozoa with the indispensable support of Sertoli cells (SCs), which provide 'ad hoc' structural and nutritional support. Unfortunately, for most sperm dysfunctions, no therapies are yet available except assisted reproductive technologies (ART) that are based on the use of different culture media to preserve sperm in vitro. However, sperm culture is only possible for short periods of time, since long-term culture would invariably and irreversibly damage the cells with negative impact on their fertilization potential. METHODS: Fresh sperm cells (5 ml of 20 x 10(6)/ml) were co-cultured with SCs layers, derived from prepubertal pig testes or incubated in cell free SC medium or BWW (Biggers, Whitten and Whittingham) medium for 2, 4 or 7 days. Sperm viability, motility, mitochondrial status, DNA fragmentation, chromatin integrity, intracellular calcium and acrosome status were assessed after every co-culture or incubation time, but capacitation and induction of acrosome reaction (AR) with progesterone was only evaluated after 7 days. RESULTS: SCs layers derived from prepubertal pig testes (co-culture of sperm and SC feeder, CCSCF) were able to preserve normal sperm viability, motility and normal mitochondrial function, after 7 days of culture; CCSCF did not induce AR or hyperactivation of spermatozoa, keeping the sperm in a quiescent state for 7 days of culture. Nevertheless, the sperm were readily able to initiate AR after stimulation with progesterone. CONCLUSIONS: CCSCF maintained good sperm viability and motility for 7 days. This approach could improve retention of sperm viability and motility during ART procedures and maintain sperm viability, during transfer between two distant Centres, avoiding the need for cryopreservation.