Morphometric assessment of mature and diminished-maturity human spermatozoa: sperm regions that reflect differences in maturity

As part of our studies on sperm maturity and function, we examined the head , midpiece and tail of human spermatozoa using computerized morphometry in order to determine which regions reflect the differences between mature spe rmatozoa and spermatozoa of diminished cellular maturity. We studied 20 men , who were divided into two groups based on their lower (LCKM: 14.6 +/- 7.0 %, n = 8) and higher sperm creatine kinase (CK-M) isoform ratios (HCKM: 48. 0 +/- 4.3%, it = 12) in the initial semen. Using a sequential centrifugatio n method which relies on the lower density of immature spermatozoa with ret ained extra cytoplasm, we prepared three sperm fractions with progressively declining maturity, as confirmed with CK-M isoform ratio measurements. Fol lowing the sequential fractionation, we affixed the spermatozoa to glass sl ides, stained the midpiece and the sperm contour, and photographed 25 sperm atozoa in each of the 60 fractions (1509 spermatozoa in all). The spermatoz oa were then individually digitized on the Image-1 system, and the dimensio ns of the head, midpiece, and tail were determined. While the data showed s ignificant differences in the midpiece and tail dimensions between the matu re and diminished-maturity sperm fractions, the head dimensions were simila r and did not reflect sperm maturity. We postulated that the relationship b etween the biochemical markers of sperm maturity and sperm morphology is ba sed on common spermiogenic events. The data support this idea. In immature spermatozoa in which cytoplasmic extrusion, CK-M isoform expression, and ta il sprouting are all diminished, the retained extra cytoplasm in the midpie ce and shorter tail length contribute to the morphological variations that we identified by morphometry and considered in sperm morphology. These morp hometric features, in association with fluorochrome-coupled biochemical pro bes, can facilitate the identification of mature spermatozoa in computer-as sisted semen analysis.