The relative viability of human spermatozoa from the vas deferens, epididymis and testis before and after cryopreservation

Abstract

Testicular and epididymal spermatozoa are routinely used with in-vitro fertilization (IVF) and intracytoplasmic sperm injection (ICSI) to achieve pregnancies. In addition, excess cryopreserved spermatozoa can be thawed and used for ICSI. However, information on the recovery of epididymal and testicular spermatozoa after freeze–thaw is lacking. This is important to determine the feasibility of using previously cryopreserved aspirated spermatozoa for ICSI. We prospectively compared the viability of fresh and frozen–thawed spermatozoa from the vas deferens, epididymis and testicle by several measures. Testis spermatozoa were obtained from men with non-obstructive azoospermia (n = 5), epididymal spermatozoa from men with obstructive azoospermia (n = 8), and vasal spermatozoa from fertile men by vasal irrigation at vasectomy (n = 5). The viability of fresh spermatozoa was assessed by motility, two vital stains (carboxyfluorescein, 0.08 mg/ml and propidium iodide, 20 mg/ml) and the hypo-osmotic swelling assay (HOS; 100 mmol/l citrate and fructose). After cryopreservation, spermatozoa were thawed and all viability measures repeated. Although fresh vasal spermatozoa were the most motile, testicular spermatozoa exhibited similar, high viability (91 and 86% respectively) by vital stain. Spermatozoa from testis, epididymis and vas deferens survived cryopreservation equally well by vital stain, but not by motility. As a selection measure, the HOS assay identified significantly more viable epididymal and testicular spermatozoa than did motility in both fresh and frozen–thawed populations. It appears feasible to use frozen–thawed extracted spermatozoa for ICSI when motility and a selection measure such as the HOS assay are used. With fresh testis spermatozoa, selection methods may not be necessary prior to ICSI, as cell viability is high.