Sperm-lectin agglutination combined with swim-up leads to an efficient selection of highly motile, viable and heterogeneous ram spermatozoa

Lectins, high molecular weight glycoproteins with different sugar-binding s pecificity, are able to agglutinate different cell types. The recovery of h igh-quality spermatozoa can be facilitated by the agglutination induced by the lectin binding. The objective of this study was to combine sperm-lectin agglutination with a dextran/swim-up procedure for developing a new select ion technique for ram spermatozoa. To study sperm quality, cell viability ( plasma membrane integrity), the HOS-test response and progressive individua l motility were assessed. Simultaneously, centrifugal countercurrent distri bution (CCCD) in an aqueous two-phase system was carried out to analyze spe rm surface heterogeneity. Semen from 3 mature Saltz rams was pooled, and 0.5-mL aliquots were incubat ed with 4 fluorescein-labelled lectins (ECL, JAC, PSA, RCA). Then, a dextra n solution was gently added and overlaid with medium. The top layer of the medium containing the spermatozoa was collected and replaced by careful add ition of fresh medium. The incubation sequence was repeated 3 times at 10-m in intervals. The consecutive 4 top layers obtained were pooled to give the swim-up combined sample. The highest rate of improvement in sperm quality was obtained after incubat ion with RCA, with a 50% increase in progressive individual motility, 21.6% in HOS value and 39.5% in viability. Total cell recovery was 64% (1.56 x 1 0(9) cells), with a viable cell recovery rate of 86%. The obtained sample s howed 82% motility, 80% HOS score and 77% viability, up from the pre-swim-u p values of 51, 60 and 57 %, respectively. Comparative CCCD analysis reveal ed a very high heterogeneous population in the RCA/swim-up sample obtained, while a much more homogeneous population was obtained in the sample after the dextran/swim-up procedure previously developed by us With this simple method, a large proportion of highly-motile spermatozoa wi th preserved plasma membrane and high heterogeneity can be obtained. These results strongly suggest that this selection procedure could result in a hi gh fertility rate. (C) 1999 by Elsevier Science Inc.