Identification of Sperm Oxidative Stress from Routine Semen Analysis

Semen analysis is a cornerstone of assessment of the infertile male. While direct measurement of sperm oxidative stress is not presently part of the routine WHO semen analysis [151], the clinician can often make a presumptive diagnosis of oxidative stress from a routine semen analysis (Table 16.1). As described above, MAGI may cause sperm oxidative stress. A diagnosis of past or present MAGI can be made when there is a alteration in normal semen viscosity (increase or decrease), discolouration of the semen or an increase in semen pH above the normal range (pH > 8). Hyperviscosity of seminal plasma is associated with increased levels of seminal plasma MDA [152] and reduced seminal plasma antioxidant status [153], making impaired viscosity a reasonable surrogate marker of oxidative stress. Infection of the semen with U. urealyticum is associated with increased seminal plasma viscosity [154] and an increase in ROS production [55]. It is possible that these infections may damage the prostate and seminal vesicle, altering the substrates required for creation of normal semen viscosity.

Furthermore, the presence of large numbers of round cells may suggest oxidative stress caused by leukocytospermia [73]. However, round cells may also be immature sperm rather than leukocytes, so formal identification of leukocytes requires ancillary tests such as the peroxidase test, CD45 staining or measurement of seminal elastase [151, 155, 156]. Poor sperm motility, especially in the absence of any features of antisperm antibody generation (sperm "clumping"), is highly suggestive of the presence of sperm oxidative damage. Sperm with abnormal morphology, especially those with excess residual cytoplasm and cytoplasmic "droplets" are cardinal features of pathological sperm producing high levels of ROS. In addition, the more severe the semen defect is, the higher the chance that sperm oxidative stress will be present. Finally, poor sperm membrane integrity assessed by the hypo-osmolar swelling test (HOST) has been linked with the presence of sperm oxidative stress [157].

Advanced ancillary semen assays may also indirectly suggest the presence of oxidative stress. High levels of the neutrophil activation marker elastase in seminal plasma have been linked with sperm oxidative stress [155, 156]. More recently, the

Table 16.1 Cardinal signs of sperm oxidative stress seen in a routine semen analysis

♦ Altered semen viscosity

♦ Discolouration of semen

♦ High number of round cells in semen

♦ Leukocytospermia on the Endtz or immuno-cytochemical analysis

♦ Poor sperm motility, especially in the absence of anti-sperm antibodies

♦ High number of morphologically abnormal sperm (especially cytoplasmic droplets)

♦ Severe OAT "triple semen defect"

♦ Low hypo-osmolar swelling test (HOST) results presence of the macrophage activity marker neopterin in seminal plasma has been linked with sperm oxidative stress [158]. Sperm DNA integrity tests such as TUNEL or SCSA may suggest the possibility of sperm oxidative stress if high levels of DNA fragmentation are recorded [6, 47]. However, as sperm DNA fragmentation can also be caused by non-oxidative processes (abortive apoptosis, DNA nicks made during DNA remodelling), neither is conclusive evidence for the presence of sperm oxida-tive damage.

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