Spermatozoal DNA damage in patients with B thalassaemia syndromes.

OBJECTIVE: to determine whether sperm DNA damage is increased in patients with beta-thalassaemia syndromes. DESIGN: prospective comparative assessment of sperm genomic integrity in thalassaemia patients and donor controls and correlation of sperm DNA damage with other measures of semen quality, reproductive hormones, ferritin, zinc and vitamin E levels. SETTING: Thalassaemia Centre of Paediatric and Adolescent Unit, Ferrara, Italy and Academic Research Institutions in the UK. SUBJECTS: twenty-eight thalassaemia major and thalassaemia intermedia patients attending the clinic for regular treatment. INTERVENTIONS: assessment of the degree of spermatozoa undergoing apoptosis by terminal deoxynucleotidyl transferase mediated assay (TUNEL) and measurement of the degree of those with compromised structural integrity as measured by the sperm chromatin structure assay (SCSA) using flow cytometry. MAIN OUTCOME MEASURES: the degree of spermatozoal DNA damage by TUNEL and SCSA and the correlation between these measures and sperm motility, concentration, morphology and serum FSH, LH, sex hormone binding globulin, free and total testosterone, ferritin, zinc and vitamin E using regression analysis and Student t-test. RESULTS: comparative analysis showed that beta-thalassaemia patients had significantly more sperm DNA damage (mean TUNEL=18.5%, SCSA=0.28) than controls (mean TUNEL=11.4%, mean SCSA=0.18) (p<0.001). Among thalassaemia patients there was a negative correlation between itchromatin structure damage and sperm concentration (r2=0.3, p<0.006). There was a significant negative correlation between serum ferritin levels and abnormal sperm morphology (r2=0.2, p<0.05). CONCLUSIONS: compared to controls there was a higher degree of DNA damage in spermatozoa of beta-thalassaemia patients. Thalassaemic patients with low sperm concentrations were more likely to have a higher degree of defective chromatin packaging. The negative association between ferritin levels and abnormal sperm morphology suggests a possible detrimental effect on spermatogenesis by the iron chelator desferrioxamine, which is used to reduce iron overload. Thalassaemic patients especially those being considered for assisted conception procedures should be counselled accordingly.

Sperm DNA damage in potentially fertile homozygous beta-thalassaemia patients with iron overload.

BACKGROUND: To test the hypothesis that human sperm DNA could sustain iron-induced oxidative damage and reduce its fertilizing ability, we studied patients with homozygous beta-thalassaemia major (HbTh) as a model of iron overload. METHODS: Sperm from six thalassaemic patients and five age-matched controls were assessed by the sperm chromatin structure assay (SCSA) and terminal deoxynucleotidyl transferase-mediated dUTP nick-end labelling (TUNEL) assay. Semen parameters, endocrine markers of testicular function, iron profiles and the presence of organ dysfunction were also determined. RESULTS: All patients with HbTh were iron overloaded (median ferritin: 2251 microg/l) and had evidence of spontaneous spermatogenesis. Thalassaemic patients had more sperm DNA damage than the controls (P < 0.01). The sperm DNA damage by SCSA and TUNEL were positively correlated (P < 0.05). Sperm motility and TUNEL results were negatively correlated (P < 0.05), while the age of onset of chelation and sperm DNA damage were positively associated with both SCSA (R(2) = 0.80, P = 0.016) and TUNEL data (R(2) = 0.67, P < 0.044). No other biochemical or clinical data were associated with sperm DNA damage. CONCLUSIONS: The increase in sperm DNA damage and the negative correlation between sperm motility and DNA damage suggest that iron overload in HbTh predisposes sperm to oxidative injury. This finding has important implications in assisted reproductive procedures such as ICSI where there is increased risk of transmitting defective DNA to the offspring.