Investigations for retinopathy in an avian model for systemic sclerosis

Systemic Sclerosis (SSc) is a connective tissue disease affecting the skin and internal organs. Retinopathy has been described in patients with SSc, but cannot be distinguished from secondary changes due to concomitant hypertension. UCD 200 chickens, a well-established animal model for SSc, were used in this study to investigate the posterior ocular segment for manifestations of SSc. Terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labelling was applied to detect endothelial cell (EC) apoptosis, a condition previously shown to represent the first step in SSc pathogenesis in humans and to be present in the skin and the involved internal organs of UCD 200 chickens in the acute stage. Our study showed a complete absence of EC apoptosis in the pecten and choroidal vessels of UCD 200 chickens in the acute stage. Ophthalmoscopy, biomicroscopy and histology revealed normal structures of the pecten, retina and choroid in the chronic stage. In summary, we showed that there is no primary involvement of the posterior ocular segment in avian SSc. SSc of UCD 200 chickens closely mimics human SSc, presenting all the clinical, serological and histological disease manifestations seen in the human counterpart. Therefore, our data raise serious doubts about primary posterior ocular involvement in human SSc. However, fundal examinations in patients with SSc may have their justification for assessment of hypertensive retinopathy.