Correlation between nailfold capillaroscopy abnormalities and interleukin 13 serum levels in patients with systemic sclerosis

Background: Nailfold capillaroscopy (NC) is a non-invasive technique able to evaluate the severity of microvascular involvement in connective tissue disorders, in particular systemic sclerosis (SSc).1 Interleukin 13 (IL-13), a cytokine inhibiting proinflammatory molecules production by monocytes/macrophages, seems to modulate collagen homeostasis in human skin fibroblasts and may be responsible for early fibrotic phase of SSc.2 Also, IL-13 levels are increased in SSc3, and this cytokine is supposed to participate in the determinism of vascular lesions and is considered as a serologic indicator for the disease activity and the systemic inflammation.4 Objectives: We submitted a group a SSc patients to NC, in order to investigate the relationship between the different NC findings and IL-13 serum levels. Methods: We enrolled 32 patients [M/F:2/30; mean age: 50.7 yrs (range: 20-73); mean disease duration: 9,5 yrs (range: 1-23)] fulfilling the ACR classification criteria for SSc and 20 healthy controls matched for sex and age. NC was performed in each patient, examining capillaries of all fingers in the distal row and evaluating the following morphological parameters: presence of enlarged and giant capillaries, hemorrhages, loss of capillaries, disorganization of the vascular array, ramified/bushy capillaries, sludge of blood, large total loop, venous and arterial diameters. Clinical and laboratory data were obtained at the same time the blood samples were drawn. IL-13 serum levels were measured by ELISA. Abnormal IL-13 serum levels (>17 pg/ml) were defined as mean plus two SD of control values. Results: NC evaluation demonstrated the presence of giant loops in 17 patients (53%), hemorrhages in 16 (50%), sludge of blood in 13 (41%), loss of capillaries in 28 (87%). We found significantly higher IL-13 serum levels in SSc patients respect to controls (p<0.01), whereas the comparison of the NC features in patients with (n= 8) and without (n= 24)abnormal IL-13 serum levels showed significantly relevant differences concerning a more frequent presence of hemorrhages (p<0.0037) and sludge of blood (p<0.038), as well as larger total loop (p<0.036) and arterial diameters (p<0.03)in those patients with elevated IL-13 serum levels. Conversely, no statistically significant correlation of the main clinical-demographic and laboratory parameters with NC abnormalities and IL-13 serum levels was found. Conclusion: The evidence of a relationship between IL-13 serum levels with SSc capillaroscopic features suggests that this cytokine might sustain the immunological and fibrotic process of SSc, also playing a considerable role in inducing more severe microvascular damage in this disease.1. Maricq HR, LeRoy EC, D'Angelo WA, Medsger TA jr, Rodnan GP, Sharp GC, Wolfe JF. Diagnostic potential of in vivo capillary microscopy in scleroderma and related disorders. Arthritis Rheum 1980; 23: 183-9.2. Oriente A, Fedarko NS, Pacocha SE, Huang S, Lichtenstein LM, Essajan DM. Interleukin-13 modulates collagen homeostasis in human skin and keloid fibroblasts. J Pharmacol Exp Ther 2000; 292: 988-94.3. Spadaro A, Rinaldi T, Riccieri V, Taccari E, Valesini. Interleukin-13 in autoimmune rheumatic diseases: relationship with autoantibody profile. Clin Exp Rheumatol 2002 (in press).4. Hasegawa M, Fujimoto M, Kikuchi T, Takehara K. Elevated serum levels of interleukin 4 (IL-4), IL-10 and IL-13 in patients with systemic sclerosis. J Rheumatol 1997; 24: 328-32. 1. Maricq HR, LeRoy EC, D'Angelo WA, Medsger TA jr, Rodnan GP, Sharp GC, Wolfe JF. Diagnostic potential of in vivo capillary microscopy in scleroderma and related disorders. Arthritis Rheum 1980; 23: 183-9.2. Oriente A, Fedarko NS, Pacocha SE, Huang S, Lichtenstein LM, Essajan DM. Interleukin-13 modulates collagen homeostasis in human skin and keloid fibroblasts. J Pharmacol Exp Ther 2000; 292: 988-94.3. Spadaro A, Rinaldi T, Riccieri V, Taccari E, Valesini. Interleukin-13 in autoimmune rheumatic diseases: relationship with autoantibody profile. Clin Exp Rheumatol 2002 (in press).4. Hasegawa M, Fujimoto M, Kikuchi T, Takehara K. Elevated serum levels of interleukin 4 (IL-4), IL-10 and IL-13 in patients with systemic sclerosis. J Rheumatol 1997; 24: 328-32.