Towards Understanding Male Infertility After Spinal Cord Injury Using Quantitative Proteomics

Barbara Ferreira Da Silva,Chen Meng,Dominic Helm,Fiona Pachl,Jürgen Schiller,Emad Ibrahim,Charles M Lynne,Nancy L Brackett,Ricardo Pimenta Bertolla,Bernhard Kuster

doi:10.1074/mcp.m115.052175

Abstract

The study of male infertility after spinal cord injury (SCI) has enhanced the understanding of seminal plasma (SP) as an important regulator of spermatozoa function. However, the most important factors leading to the diminished sperm motility and viability observed in semen of men with SCI remained unknown. Thus, to explore SP related molecular mechanisms underlying infertility after SCI, we used mass spectrometry-based quantitative proteomics to compare SP retrieved from SCI patients to normal controls. As a result, we present an in-depth characterization of the human SP proteome, identifying ∼2,800 individual proteins, and describe, in detail, the differential proteome observed in SCI. Our analysis demonstrates that a hyper-activation of the immune system may influence some seminal processes, which likely are not triggered by microbial infection. Moreover, we show evidence of an important prostate gland functional failure,i.e.diminished abundance of metabolic enzymes related to ATP turnover and those secreted via prostasomes. Further we identify the main outcome related to this fact and that it is intrinsically linked to the low sperm motility in SCI. Together, our data highlights the molecular pathways hindering fertility in SCI and shed new light on other causes of male infertility.

Highlights

From the ‡Human Reproduction Section, Division of Urology, Department of Surgery Sao Paulo Federal University, Brazil; §Chair for Proteomics and Bioanalytics, Technische Universitat Munchen, Freising, Germany; ¶Medical Department, Institute of Medical Physics, Universitat Leipzig, Leipzig, Germany; ʈThe Miami Project to Cure Paralysis,University of Miami Miller School of Medicine, Miami, Florida; **Department of Urology, University of Miami Miller School of Medicine, Miami, Florida; ‡‡Center for Integrated Protein Science Munich (CIPSM), §§Bavarian Biomolecular Mass Spectrometry Center, Technische Universitat Munchen, Freising, Germany
By studying semen of men with spinal cord injury (SCI), who become infertile after a traumatic injury and often present with an unusual seminal profile characterized by normal sperm concentration but extremely impaired sperm motility and viability, Brackett et al demonstrated how seminal plasma (SP) can impair sperm function leading to infertility [6]
A variety of proteins including apolipoproteins (e.g. APOB) and immunoglobulins (e.g. IGHG2) were found exclusively in samples from SCI patients. These findings suggested a deviation from homeostasis occurring in the SP of SCI patients, presumably altering its function and accounting for the poor seminal quality, which is typical of these individuals [12]

Summary

Introduction

Seminal samples from 12 SCI patients and 11 controls were collected, analyzed and further prepared for proteomic analysis. Normalized ratios were used for the differential expression analysis and statistical significance was assessed using paired t test on proteins that are quantified all replicates of the pool experiment and in at least two samples of the individual experiment.

Results

Conclusion