Background Excess activation of the complement system is involved in the development and progression of systemic lupus erythematosus (SLE). Allogeneic umbilical cord mesenchymal stem cells (UC-MSC) transplantation has achieved good clinical efficacy for refractory SLE, however, the exact mechanism is unclear. Our previous work found that deposits of C5a and C5b-9 were significantly enhanced in severe lupus nephritis (LN), which suggested that antagonists of C5 might contribute to the treatment of LN, in other words, effective therapy for LN may be involved in inhibiting the activation of C5.
Objectives To observe the clinical effect of UC-MSC on SLE model mice (B6.lpr), and explore the mechanism of MSC inhibiting the activation of complement C5 in lupus mice.
Methods 26-week-old female B6.lpr mice were randomly allocated in four groups, which were given the following treatments, CTX (200mg/kg), UC-MSC (1x106), C5aRa (W-54011, 1mg/kg), and an equal volume of 0.5%DMSO. 24 hours urine and peripheral blood were collected periodically. All mice were sacrificed at 40 weeks of age.Urine protein to creatinine ratio was used to estimate daily urine protein excretion. Plasma creatinine was measured by a biochemical analyzer. Plasma levels of C3, C5a, soluble C5b-9, and anti-dsDNA antibody were determined by ELISA. Histopathological evaluation of renal lesions was undertaken by HE, PAS, PASM and Masson staining under light microscopy. Podocyte foot processes were assayed by the transmission electron microscopy. Depositions of C5a, C5b-9, and MBL were detected by immunohistochemistry assay. Immunofluorescence was utilized to detect the expression of C5aR1, IgG, IgM, IgA, C3, C1q, and properdin in the glomeruli.
Results At the end point, proteinuria of mice in the former three groups was significantly reduced when compared with the control mice, and renal function was also improved in both MSCT and CTX groups. Plasma level of C3 was significantly elevated in mice of MSCT and C5aRA groups. Furthermore, mice in MSCT group appeared a remarkably decreased C5a in the circulation. Compared to control mice, no significant difference was found in plasma levels of anti-dsDNA and SC5b-9, although there were decline trends in other three groups. Pathological analysis showed that the proliferation of glomerular cells and foot process fusion were significantly inhibited in MSCT treated mice. Immunohistochemistry showed that deposits of C5a and C5b-9 were significantly decreased in the MSCT group. Immunofluorescence examination showed that the expression of IgG, C3, C1q, and properdin was significantly decreased in MSCT treated mice, meanwhile, the expression of MBL was also significantly reduced in these mice.
Conclusions The activation of the complement system was obviously involved in the glomerulonephritis in lupus mice. Allogeneic UC-MSC transplantation can effectively improve the clinical outcome of lupus mice. Possible mechanism of MSCT might be related to inhibit the activation of complement C5 in the circulation and local kidney via interrupting the classical, alternative, and lectin pathways. The potential involved contributors of UC-MSC are currently under study.
Vignesh P, et al. Clin Chim Acta. 2016.
Disclosure of Interest None declared