Influence of Inseminate Components on Porcine Leucocyte Migration In Vitro and In Vivo after Pre- and Post-Ovulatory Insemination

A post-breeding migration of leucocytes (PMN) into the uterus is considered to be an important reason for sperm losses. Minimizing such effects may be necessary for successful insemination with low sperm numbers, as required with sex-sorted spermatozoa. We examined the magnitude of PMN influx 3 h after pre- or post-ovulatory insemination with various combinations of seminal plasma (SP), semen extender Androhep[trade mark sign] (AH; Minitüb, Tiefenbach, Germany) and sperm preparations (S). Pre-ovulatory inseminations with preparations containing 98% AH caused a massive influx of PMN, independent of whether spermatozoa were present (628 ± 189 x 10⁶ leucocytes/uterine horn) or not (580 ± 153 x 10⁶). Post-ovulatory, 98% AH caused a comparable immigration only in the absence of sperm cells (AH: 569 ± 198 x 10⁶, AH+S: 162 ± 102 x 10⁶). The presence of SP significantly dampened the numbers of recruited uterine leucocytes. The reaction to all inseminates containing 98% SP both with and without spermatozoa, used before ovulation (SP: 14 ± 6 x 10⁶, SP+S: 73 ± 27 x 10⁶) and after ovulation (SP: 60 ± 32 x 10⁶, SP+S: 51 ± 33 x 10⁶) did not differ significantly from controls using phosphate buffered saline (PBS) (pre-ovulatory: 1 ± 1 x 10⁶, post-ovulatory: 11 ± 9 x 10⁶). Quantitative in vitro transmigration assays with blood-derived PMN proved that AH-induced leucocyte migration into the uterus to be not as a result of direct chemotaxis, because, on account of the chelator citrate, AH significantly inhibited the transmigration towards recombinant human Interleukin-8 (rhCXCL8) (AH: 14 ± 5% migration rate vs controls: 37 ± 6%, p < 0.05). Supernatants of spermatozoa incubated in PBS for 1, 12 or 24 h showed neither chemoattractive nor chemotaxis-inhibiting properties. SP at greater-than-or-equal0.1% [v/v] significantly inhibited the in vitro transmigration of PMN. With respect to in vivo migration of neutrophils, the striking difference in the results between semen extender and seminal plasma suggests that adaptation of extender composition is needed to reflect more closely the in vivo regulatory potential of natural seminal plasma.