Protamine deficiency as a cause or effect of decreased semen quality
Introduction: Sperm chromatin is a highly organized structure constituting of DNA and heterogeneous nucleoproteins including histones and Protamines. Protamines make a higher compaction in chromatin of sperm than that found in somatic cells. Sperm chromatin packaging anomalies are associated with poor fertility outcomes. Furthermore, human sperm protamine deficiency correlates significantly with diminished sperm functional ability. Recently, protamine deficiency is evaluated by staining with chromomycin A3. Nevertheless, threshold for protamine deficiency affecting semen quality has been not reported up to now. Therefore, the objective of this study was to determine threshold for protamine deficiency that affects semen parameters. Materials and Methods: Semen samples from 150 oligoasthenoteratospermic (OAT, case group) and 180 normospermic men (control group) were collected from infertile couples attending to Avicenna infertility clinic, affiliated to Avicenna Research Institute (ARI). Semen analysis was performed according to WHO criteria. Washed sperms (with PBS) of samples were spread on slides and after fixation were stained with Fluorochrome CMA3. Stained sperms (bright green-yellow cells as protamine deficient) were counted using fluorescent microscopy. Results: Protamine deficiency as a percent of CMA3 positive sperm in OAT group was significantly higher than normospermic group (43.67±17.20% against 24.71±13.08%, p<0.001). Also increased in percent of CMA3 positive sperm had a negative correlation with semen parameters including sperm concentration, motility and morphology (R = –0.425, –0.393, –0.461 respectively, p<0.001). In addition considering of the mean percent of CMA3 positive sperm in each groups, ideal cut-off value for CMA3 positive sperm was 35% that have 62.9% and 80.3% sensitivity and specificity. According to 35% and several else cut-off (25, 30, 40, 45 and 50%) semen parameters in protamine deficient men were significantly decreased in comparison to men with normal sperm protamination (p<0.001). Conclusion: According to CMA3 staining of sperm, protamine deficiency could be the cause or effect of low quality sperm parameters. But in OAT group with a wide range of sperm protamination it is obvious that concentration, motility and normal morphology of sperms decreased significantly in protamine deficient men and this support the role of protamine deficiency as a cause of diminished semen quality.