The future of computer-aided sperm analysis

Abstract

Computer-aided sperm analysis (CASA) technology was developed in the late 1980s for analyzing sperm movement characteristics or kinematics and has been highly successful in enabling this field of research. CASA has also been used with great success for measuring semen characteristics such as sperm concentration and proportions of progressive motility in many animal species, including wide application in domesticated animal production laboratories and reproductive toxicology. However, attempts to use CASA for human clinical semen analysis have largely met with poor success due to the inherent difficulties presented by many human semen samples caused by sperm clumping and heavy background debris that, until now, have precluded accurate digital image analysis. The authors review the improved capabilities of two modern CASA platforms (Hamilton Thorne CASA-II and Microptic SCA6) and consider their current and future applications with particular reference to directing our focus towards using this technology to assess functional rather than simple descriptive characteristics of spermatozoa. Specific requirements for validating CASA technology as a semi-automated system for human semen analysis are also provided, with particular reference to the accuracy and uncertainty of measurement expected of a robust medical laboratory test for implementation in clinical laboratories operating according to modern accreditation standards.

Figure 1

The upper panel shows the reconstructed sperm tracks in one analysis field of the IVOS-II system (1 s @ 60 Hz), purple tracks are ones that have passed the Boolean sort argument for being hyperactivated. The lower panel shows the zoomed image of one of these tracks including the spermatozoon at the start of the track; note the high curvature wave, characteristic of a hyperactivated spermatozoon, present in the proximal region of the tail. The cell's kinematic values are shown at the bottom of the figure, including the fractal dimension, D, clearly confirming hyperactivation.⁶⁰

Figure 2

Spermatozoa from an Angus bull hyperactivated in capacitating medium with 10 mmol l-1 caffeine analyzed using the SCA (a). The numerous starspin patterns in the upper panel can be easily selected and their individual kinematic values can be recorded (b).

Figure 3

(a) SCA analysis of ram spermatozoa showing three columns of paired images of spermatozoa, in each of which the left sub-column is the original image and the right sub-column is the automated analysis of each spermatozoon; yellow = acrosome; blue = rest of head; green = anterior part of midpiece. (b) Ram spermatozoa stained with SpermBlue; (c) screen shot of the entire spermatozoon including its tail as analyzed by the SCA.

Figure 4

Percentages of rapidly progressive human spermatozoa from three PureSperm fractions (Fractions 1 to 3 = 40%, 60% and 80% respectively) compared when incubated with increasing concentrations of caffeine; Treatment 1 = control; Treatments 2–4 increasing concentrations of caffeine from 2 to 10 mmol l-1.

Figure 5

Comparison of methods for classification of capacitating sperm trajectories as HA or non-HA (Mortimer, unpublished data).