The Effects of Microgravity on Human Sperm

Primary outcomes

1. Change in Sperm motility

   Time frame: In earth gravity g=1(<4 hours before Parabolic flight) and after simulated microgravity exposure (<4 hours Post Parabolic Flight)

   The percentage of normal spermatozoa in terms of motility grades a,b,c according to WHO

2. Change Sperm Morphology

   Time frame: In earth gravity g=1(<4 hours before Parabolic flight) and after simulated microgravity exposure (<4 hours Post Parabolic Flight)

   The percentage of normal spermatozoa in terms of morphology is assessed by staining. The lower reference limit for normal forms is 4% (WHO 2010).

3. Change Sperm Vitality

   Time frame: In earth gravity g=1(<4 hours before Parabolic flight) and after simulated microgravity exposure (<4 hours Post Parabolic Flight)

   The percentage of live spermatozoa is assessed by identifying those with an intact cell membrane, from dye exclusion. The lower reference limit for vitality (membrane-intact spermatozoa) is 58% (WHO 2010).

4. Change in Sperm DNA Fragmentation

   Time frame: In earth gravity g=1(<4 hours before Parabolic flight) and after simulated microgravity exposure (<4 hours Post Parabolic Flight)

   Sperm DNA fragmentation is evaluated by Halosperm® kit, based on the SCD technique, patented by Halotech. This kit is based on a controlled DNA denaturation process to facilitate the subsequent removal of the proteins contained in each spermatozoon. In this way, normal spermatozoa create halos formed by loops of DNA at the head of the sperm, which are not present in those with damaged DNA.

   Thresholds for frequency of Sperm DNA Fragmentation (SDF) have been suggested by Dr. Evenson et al. (Evenson and Nixon, Reprod Biomed Online 12:466-472, 2006). The authors reported that couples with no known infertility problems were more likely to achieve a pregnancy/delivery if the DNA fragmentation index (DFI) was <30%.

5. Change Sperm APOPTOSIS (Annexin V )

   Time frame: In earth gravity g=1(<4 hours before Parabolic flight) and after simulated microgravity exposure (<4 hours Post Parabolic Flight)

   Annexin V recognizes an antigen (externalized phosphatidylserine, EPS) in the plasma membrane of apoptotic cells. Apoptotic cell depletion begins with the magnetic labeling of apoptotic cells by the MACS® ART Annexin V Reagent. The labeled cells are then passed through a separation column located in a fixed magnetic field. Unwanted cells are selectively retained in the column. Living spermatozoa are not labeled by the reagent, so they pass through the column and are collected for later use.

   In our study, after collecting living spermatozoa we also collected the retained apoptotic spermatozoa for comparing the concentration (M/ml) of apoptotic vs no apoptotic cells.