Poster Presentation ESA-SRB Conference 2015

Testicular activin A during the development of autoimmune orchitis in mice (#288)

Nour Nicolas 1 2 , Vera Michel 1 , Sudhanshu Bhushan 1 , David De Kretser 2 3 , Kate Loveland 2 4 , Andreas Meinhardt 1 , Mark Hedger 2 3 , Monika Fijak 1
  1. Department of Anatomy and Cell Biology, Justus Liebig University, Giessen, Hessen, Germany
  2. Hudson Institute of Medical Research, Monash Medical Centre, Melbourne, Victoria, Australia
  3. Department of Anatomy and Developmental Biology, Monash University, Melbourne, Victoria, Australia
  4. School of Clinical Sciences, Monash University, Melbourne, Victoria, Australia

Experimental autoimmune epididymo-orchitis (EAEO) is a rodent model of chronic testicular inflammation that reproduces the pathology observed in some human infertility. Activin A, a dimer encoded by the inhibin βA (Inhba) gene is a pro-inflammatory, profibrotic cytokine, but also regulates spermatogenesis and steroidogenesis. The roles of activin A, inhibin and follistatin, both endogenous activin antagonists, were examined in EAEO.

EAEO was induced in adult mice by active immunization with syngeneic testicular homogenates (3 injections, 2 weeks apart) in complete Freund’s adjuvant (CFA) and Bordetella pertussis toxin. Controls received only CFA and toxin. Testes collected 25, 50 and 80 days after the first immunization were processed for histology and immunohistochemistry or frozen for qRT-PCR.

Age-matched untreated mice and controls showed no pathology, with activin A localised to Sertoli cells and interstitial cells. All immunised mice developed EAEO by 50 days, characterised by a >50% reduction in testis weight, complete loss of germ cells, immune infiltrates (macrophages and T cells) and a marked peritubular fibrotic response. These were accompanied by increased expression of inflammatory cytokines, tumour necrosis factor (TNF), macrophage chemoattractant protein-1 (MCP-1) and interleukin-10 (IL-10). Activin A immunostaining was not detectable in the EAEO testes, but the inhibin βA (Inhba) subunit encoding activin A and follistatin mRNA levels were similar to controls. Expression of Inha mRNA and mRNAs encoding the activin receptors, Acvr1b and Acvr2b, were reduced. At 25 days, before observed testicular pathology, the testicular levels of activin A, TNF, MCP-1, IL-6 and IL-10 were increased (5 to 50 fold).

These data suggest that activin A acts as a pro-inflammatory agent in EAEO, but in mice with fully established EAEO, activin A levels decreased perhaps due to the testicular damage. Treatment with follistatin to attenuate activin A bioactivity early in testicular inflammation may reduce damage to spermatogenesis in patients with epididymo-orchitis.