Background Systemic sclerosis (SSc) is a chronic autoimmune inflammatory disease characterized by vascular and fibrotic changes in the skin and internal organs. Aberrant accumulation of the extracellular matrix (ECM) is a well characterized feature of SSc. A major component of most ECM is hyaluronan (HA), a glycosaminoglycan. HA is a large polysaccharide produced by three hyaluronan synthase (HAS1-3) and degraded by predominantly 2 major hyaluronidase 1-2 (HYAL 1-2). HYAL1 degrades high molecular weight HA, whereas HYAL 2 degrades low molecular weight HA. HA is known to play critical roles in response to tissue injury, inflammation, and remodeling according to molecular weight.
Objectives This study aimed to assess serum and tissue levels of hyaluronan in skin biopsies of patients with SSc and also to investigate the type of HASs and HYALs expression in the skin tissue.
Methods Women who met 2013 ACR/EULAR criteria for the classification of SSc and age matched healthy controls were included into the study. Serum samples of the patients and controls were obtained. Punch biopsies of the effected skin were obtained in 10 patients and 4 healthy controls from the same skin region. Serum levels of hyaluronan were assessed by ELISA technique and skin levels were semiquantitatively assessed by immunofluorescence staining. Hematoxylin eosin staining of tissue was also obtained. First, HYALs and HASs mRNA expression were assessed by conventional PCR, then positive expressions were confirmed by real-time PCR.
Results Twenty-five patients were included (13 (52%) had diffuse cutaneous, 10 (40%) had limited cutaneous and 1 (4%) had SSc sine scleroderma). Mean symptom duration was 10.2±9.5 years and mean modified Rodnan skin score was 13.2±7.0. Serum levels of hyaluronan were 82.3±50.1 ng/ml in patients with SSc and 26.6±17.4ng/ml in controls (p<0.0001). Serum hyaluronan levels in postmenopausal women with SSc were higher than premenopausal patients (102.2±49.2 ng/ml, 46.9±28.1 ng/ml, p=0.005). Mean pulmonary arterial pressure (PAP) was 35.1±10.6 mmHg in patients with SSc. Mean serum levels of hyaluronan in patients with or without pulmonary involvement and PAP levels more or less than 35 mmHg were similar. Semiquantitative evaluation of tissue staining (Image J pixel quantification) revealed more dense hyaluronan accumulation in patients with SSc than healthy controls (p=0.0004). Only HAS-2 mRNA expression but not HAS-1 was seen in the skin samples by using conventional PCR. HAS-2 mRNA expression was higher in patients with SSc than healthy controls (8.33±4.48 and 2.39±1.59, respectively, p=0.026), whereas HYAL-2 mRNA expression was higher in healthy controls than patients with SSc (1614.11±1251.59 and 125.56±101.91, respectively, p=0.0018).
Conclusions Our study revealed that serum and tissue levels of hyaluronan increased in SSc and the increase in tissue samples might be related with the increased HAS-2 enzyme activity and decreased HYAL-2 enzyme activity. The role of HAS-2 inhibitors and HYAL-2 enzyme activity to prevent fibrosis in patients with SSc needs to be further investigated.
Disclosure of Interest None declared