Purpose: Previously we found that the trophinin-binding peptide GWRQ (glycine, tryptophane, arginine, glutamic acid) activated human trophoblastic cells. Although trophinin is expressed in human sperm, to our knowledge the function of this protein is not known. In this study we tested the effect of GWRQ on human sperm to evaluate whether the peptide enhances human sperm motility.
Materials and methods: Immunohistochemistry was performed using monoclonal antibodies specific to trophinin, bystin or tastin. GWRQ-MAPS (multivalent 8-branched GWRQ peptide) was chemically synthesized. Human sperm from 4 volunteers with a mean +/- SD age of 35.75 +/- 3.4 years was suspended in buffer with GWRQ or control peptides. In 23 volunteers with a mean age of 25.5 +/- 2.5 years the number of immotile sperm was counted and subtracted from the total number of sperm to determine the number of motile sperm. A Transwell assay was used to measure swim-down motility. Levels of adenosine triphosphate and intracellular calcium in sperm cells incubated with GWRQ or control peptide were measured using a luminescent cell viability assay and a fluo-4 calcium assay, respectively.
Results: The presence of trophinin and the trophinin associated proteins bystin and tastin in human sperm was confirmed by immunohistochemistry. Human sperm incubated with GWRQ-MAPS showed enhanced motility on sperm count assay and swim-down Transwell assay. Sperm cells incubated with GWRQ-MAPS showed decreased adenosine triphosphate and increased intracellular calcium.
Conclusions: Results suggest that GWRQ-MAPS may facilitate optimized in vitro fertilization outcomes and help avert the need for intracytoplasmic sperm injection in cases of severely low sperm motility. Trophinin may have a role in regulating adenosine triphosphatase in human sperm.