Background/Purpose: To decipher the phenotype of endothelial cells (ECs) derived from circulating progenitors issued from patients with rheumatoid arthritis (RA).

Methods: Proliferation capacities between RA and control ECs was compared using the xCELLigence™ RTCA System. rh-TNFa-induced EC activation was analyzed by adhesion cell expression, VEGF synthesis and stress fiber formation. Angiogenic properties of ECs were assessed in vitroby tube formation on Matrigel and migration capacities through VEGF stimulation in modified Boyden chambers, and in vivoin a mouse model of tumoral neovascularization. Microarray experiments were then performed on Affymetrix GeneChip® Human Exon 1.0 ST Arrays in ECs issued from 18 RA patients and 11 age and sex-matched healthy controls. Expression of identified candidates was assessed by RT-PCR and western blots in ECs and by immunohistochemistry in the synovium. Their functional importance was then evaluated in vitroafter gene invalidation by siRNA and adenoviral gene overexpression, and in vivoin the mouse model of methyl-BSA-induced arthritis.

Results: RA ECs displayed higher proliferation rate, greater sensitization to TNF-α,with increased VEGF production, ICAM/VCAM expression, and more prominent stress fiber formation, as well as enhanced angiogenic capacities, characterized by accelerated tube formation and increased migration capacities through VEGF stimulation, compared co control ECs. The subcutaneous transplantation of murine colon carcinoma (CT-26) cells with RA ECs in CB17-SCID mice markedly amplified tumor growth and intra-tumoral neovessel density, compared to the transplantation of control ECs.

Supervised microarray analyses identified the NAD-dependent protein deacetylase sirtuin-1 (SIRT1) as a relevant gene candidate. A strikingly decreased SIRT1 gene / protein expression and enzyme activity was detected in RA ECs upon the regulation of miR217 and miR181. A markedly decreased SIRT1 expression was also observed in synovial vessels of RA patients.

Invalidation of SIRT1 with specific siRNA in control ECs was associated with a proliferative and activated profile upon TNFa stimulation, trough the acetylation of p53 and p65, and with the development of proangiogenic capacities through the upregulation of the matricellular protein CYR61. Conditional deletion of SIRT1 in ECs through a Cre-LoxP recombination system increased angiogenesis and worsened signs of arthritis in methyl-BSA-induced arthritis.Conversely, adenoviral overexpression of SIRT1 in RA ECs reversed the activated and proangiogenic phenotype of RA ECs, and activation of SIRT1 with resveratrol alleviated signs of experimental methyl-BSA-induced arthritis.

Conclusion: SIRT1 expression is reduced in synovial vessels of RA patients. SIRT1 invalidation in ECs reproduces the proliferative, activated and proangiogenic profile of RA ECs and exacerbate experimental arthritis. These effects were reversed by SIRT1 activation. These results support the implication of SIRT1 in RA synovial neoangiogenesis and may have direct therapeutic implications, since targeting angiogenesis, and especially SIRT1, might be used as a complementary therapeutic approach in RA.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/activation-of-the-desacetylase-sirtuin-1-counteracts-the-activated-and-proangiogenic-profile-of-endothelial-cells-in-rheumatoid-arthritis-and-alleviates-experimental-arthritis/