Sperm content of TXNDC8 reflects sperm chromatin structure, pregnancy establishment, and incidence of multiple births after ART

ABSTRACT

Male germline-specific thioredoxin domain containing 8 (TXNDC8; alias SPTRX3) accumulates indefective human spermatozoa. We assessed the efficiency of two-step semen purification inremoving spermatozoa carrying TXNDC8, and examined the relationship of TXNDC8 with theoutcomes of assisted reproductive therapy (ART), conventional semen parameters, and sperm DNA integrity in sperm chromatin structure assay (SCSA). Semen samples (n = 255) from 91 ART couples were screened in two independent trials, both including a two-step, gradient-and-swim-up separation procedure yielding A-samples (raw semen), B-samples (gradient separated), and C-samples (gradient-and-swim-up). The C-samples were used for intracytoplasmic sperm injection (ICSI) with morphologically selected spermatozoa (IMSSI). Percentage of TXNDC8-positive spermatozoaincreased progressively from A to B/C-samples in both trials. In the first trial (35 couples), the TXNDC8 correlated positively with sperm DNA fragmentation index (%DFI; r = 0.66) measured before separation, and negatively with sperm concentration (r = −0.57) and motility (r = −0.67), also taken before separation. The high DNA stainability index (%HDS) correlated with the percentage of spermatozoa lacking TXNDC8 (r = 0.68). Both SCSA and TXNDC8 parameters showed moderate correlations (r = 0.33–0.66) with blood serum levels of hCG on day 11 (Beta 1) and day13 (Beta 2) after oocyte retrieval. In the second trial (56 couples), fathers of multiplets had a significantly lower percentage of TXNDC8-positive spermatozoa in B-sample (gradient separationonly) compared to men who conceived a singleton pregnancy (p = 0.01) and those who produced no pregnancy (p = 0.02). Those multiplets’ fathers also had a significantly higher sperm concentration while their SCSA parameters did not differ from others. It is concluded that theTXNDC8 levels correlate with SCSA and conventional raw semen parameters, and are predictive of pregnancy outcome and multiple births after ART. Two-step purification does not efficiently remove TXNDC8 carrying spermatozoa.

Abbreviations

ART– assisted reproductive therapy; DFI- DNA fragmentation index; FC- flow cytometry (FC); hCG: human chorionic gonadotropin; HDS: high DNA stainability index; HEPES- (4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid); HTF- human tubal fluid; ICSI- intracytoplasmic sperm injection; IgG- immunoglobulin G; IMSSI- ICSI with morphologically selected spermatozoa; IVF- in vitro fertilization; IU-: intrauterine insemination; NGS- normal goat serum; PBS- phosphate buffered saline; PVP- polyvinylpyrrolidone; SAB- spontaneous abortion; SCSA- sperm chromatin structure assay; SPTRX3- spermatid specific thioredoxin 3; SSS- synthetic serum substitute; TRITC- tetramethyl rhodamine isothiocyanate; TX-100- Triton X-100; TXNDC- thioredoxin domain-containing proteins; TXNDC8- thioredoxin domain containing 8; TUNEL- Terminal deoxynucleotidyl transferase dUTP nick end labeling

KEYWORDS:

• Sperm
• infertility
• flow cytometry
• biomarker
• thioredoxin
• TXNDC8
• SPTRX3

Authors’ contributions

Conceptualized and supervised the study, and co-wrote the article: PS, PA; clinician working with patients: PA; embryologist performing sperm preparation and assessment, and ICSI/IMSSI: DG; processed the sperm samples after purification and prepared them for shipping and flow cytometric analysis: KB; labeled and analyzed samples for flow cytometry and light microscopy: MS; developed and validated the TXNDC8 antibody, and contributed to study design: AMV.

Ethical approval

Both male and female partners signed informed consent and the samples were coded as to make the study subjects unidentifiable to research team at the University of Missouri, wherein all samples were handled and processed strictly as stipulated by an approved Internal Review Board (MU IRB) protocol.

Acknowledgments

We appreciate the generosity of anonymous ART patients whom consented to donate the sperm samples for this research. We thank the staff of Cell & Immunology Core, School of Medicine, University of Missouri, for assistance with FC.

Disclosure statement

PA is the founder and owner of MCRM, Chesterfield, MO. PS is the co-founder and chief scientific officer of AndroLabb LLC, Columbia MO, and chief scientific officer of International Boar Semen Inc., Eldora, IA.

Supplementary material

Supplemental data for this article can be accessed here.

Additional information

Funding

This work was supported by award no. [1R21HD066333-01] from NIH-NICHD and by seed funding from the F21C Program, University of Missouri to PS. AMV was supported by the Instituto de Salud Carlos III [Projects PI050065 and PI080557, co-financed by the Fondo Social Europeo, FEDER] and Junta de Andalucía [Projects P07-CVI-02697 and P08-CVI-03629], Spain.