Expression of selected human endogenous retroviral sequences in skin and peripheral blood mononuclear cells in morphea

INTRODUCTION: Morphea or localized scleroderma is a relatively rare disease whose main symptom is excessive skin fibrosis. Here we focus on the involvement of human endogenous retroviruses (HERVs) in morphea. The HERVs are a vast and intensely growing field in genomics. HERVs are of special interest as far as autoimmune disorders are concerned, yet little effort has been made until now to assess the possible changes of their expression in morphea. MATERIAL AND METHODS: Six sequences of particular interest were chosen for this study. Real-time polymerase chain reaction was performed on samples derived from peripheral blood mononuclear cells (PBMCs) and skin biopsies. The results were normalized to the level of glyceraldehyde 3-phosphate dehydrogenase (GAPDH) transcription. RESULTS: In PBMCs we found a statistically significant decrease of transcription of HERV-E pol, while HERV-K env, HERV-R pol-env, and HERV-W env were found to be up-regulated. In skin biopsies HERV-K env was strongly up-regulated. On the other hand, we noted a decrease of transcription of HERV-H env 62, HERV-K10 gag, HERV-R pol-env, and HERV-W env. In PBMCs we found a statistically significant decrease of transcription of HERV-E pol (-81.8%, p < 0.001), while HERV-K env (+94.1%, p = 0.010), HERV-R pol-env (+140.0%, p < 0.001), and HERV-W env (+97.7%, p < 0.001) were found to be up-regulated. In skin biopsies HERV-K env was strongly up-regulated (+713.0%, p = 0.003). On the other hand, we noted a decrease of transcription of HERV-H env 62 (-83.5%, p < 0.001, HERV-K10 gag (-33.7%, p = 0.044), HERV-R pol-env (-71.3%, p < 0.001), and HERV-W env (-59.3%, p = 0.029). CONCLUSIONS: The studied HERV sequences generally show an increase of transcription in PBMCs of morphea patients, while being down-regulated in their skin, with some exceptions for both types of tissue.