Introduction & Objectives: Human Spermatozoa are characterized by certain features that differentiate them from simple Flagella. One of these features is the presence of outer dense fibers (ODFs). ODFs are nine fibers surrounding Axoneme in the midpiece and extend to variable length through the principal piece. They represent about 30% of the protein portion of human spermatozoa and accordingly they are affected by any pathology that can affect protein content of spermatozoa as in the case of oxidative stress (OS). ODFs are thought to have a role in sperm motility and support. In this study we detect the abnormalities in outer dense fibers in iOAT patients and correlate these abnormalities with measurements of Carbonyl Protein which is the most recent reliable and stable indicator for oxidative stress. Moreover we correlate these results with the percentage of forward progressive sperm motility and the percentage of midpiece anomalies to find the relation between OS, ODFs anomalies and sperm function.

Material & Methods: 20 patients with iOAT syndrome (group 1) and 10 normal subjects with proven fertility, as controls, (group 2) were included in this study. Carbonyl Protein was measured by ELISA as an indicator for oxidative stress. Semen analysis was done according WHO parameters. Abnormalities of outer dense fibers were determined by transmission electron microscopy (TEM).

Results: Sperm parameters showed a statistically significant difference between iOAT patients and normal controls. CP values were significantly higher in iOAT patients than in Normal controls (p<0.001). A highly significant difference was found between iOAT patients and normal

controls regarding abnormalities in outer dense fibers (p<0.001). Abnormalities in Outer dense  fibers have been found to be positively correlated with CP values (r²= 0,851) and MP anomalies

(r²= 0,431) and negatively correlated with forward progressive motility (r²= -0,762).

Conclusions: In our study, we found a higher percentage of ODFs anomalies in iOAT patientsthan in normal controls. Abnormalities in ODFs are positively correlated with CP values which may indicate the effect of OS as underlying pathology for those anomalies. Moreover, ODFs anomalies are correlated positively with midpiece anomalies and negatively with progressive sperm motility. This correlation indicates the possible role of ODFs in sperm functions. Interestingly, ODFs anomalies, found in our study, were always associated with anomalies in the outer doublets tubules (Ods) of the axoneme. This may lead to the thinking that both ODFs and ODs are structurally and functionally related.