Selective Sexual Dimorphisms in Musculoskeletal and Cardiopulmonary Pathologic Manifestations and Mortality Incidence in the Tumor Necrosis Factor–Transgenic Mouse Model of Rheumatoid Arthritis

Abstract

Objective To examine and quantify the sexual dimorphism in pathologic features manifested in the musculoskeletal and cardiopulmonary systems and incidence of mortality in the tumor necrosis factor–transgenic (TNF‐Tg; Tg3647 strain) mouse model of inflammatory erosive arthritis. Methods Kaplan‐Meier survival estimates were determined in male and female Tg3647 mice and sex‐matched wild‐type (WT) littermate mice. Longitudinal and cross‐sectional pathologic outcomes in the musculoskeletal and cardiopulmonary systems were assessed via ultrasound, micro–computed tomography, grip strength measurements, histologic and serologic analyses, flow cytometry, and skeletal muscle physiologic measures. Results Compared to male Tg3647 mice (n = 30), female Tg3647 mice (n = 34) had significantly shorter lifespans (P < 0.001) and exhibited the following pathologic features (n = 4–6 per group; P < 0.05 versus male Tg3647 littermates): gross deficits in body mass and muscle weight, early‐onset inflammatory arthritis with severity of end‐stage arthritis that was as severe as that seen in male transgenic mice, and early onset and increased severity of inflammatory interstitial lung disease (ILD). Histologically, the ILD observed in Tg3647 mice was characterized by inflammatory cell accumulation and pulmonary arteriole thickening, which was concomitant with the presence of right ventricular hypertrophy, a feature that was also more severe in the female compared to male Tg3647 mice (P < 0.05). No sexual dimorphisms in TNF‐induced deficient grip strength, axial skeletal growth, or bone loss were found. Globally, the extent of the pathologic changes observed in female Tg3647 mice was greater than that observed in male Tg3647 mice when each group was compared to their sex‐matched WT littermates. Conclusion These findings indicate that TNF selectively drives the early onset of arthritis and progression of pathologic changes in the cardiopulmonary system in female Tg3647 mice. These results in the Tg3647 mouse identify it as a suitable model to better understand the mechanisms underlying sexual dimorphism and cardiopulmonary disease in the setting of inflammatory arthritis and other connective tissue diseases.

iNOS dependent and independent phases of lymph node expansion in mice with TNF-induced inflammatory-erosive arthritis

“…All studies were performed with littermate wild-type or iNOS −/− controls. Due to the observed temporal differences in male and female TNF-Tg pathology [11], male and female animals were studied at different ages to match disease phenotype. Longitudinal analysis (ultrasound and near-infrared lymphatic imaging) was performed in female mice at 2, 3, and 4 months of age and in male mice at 3, 4, 5, and 6 months.…”

“…Histology and micro-computed tomography analyses show that severe knee synovitis and bone erosion do not occur until the PLN collapses, indicating PLN collapse is a biomarker for severe knee arthritis [7, 8, 10]. Importantly, all of these studies were performed in male mice, but when we investigated female mice, we found significantly altered progression indicating that in the TNF-Tg mouse model, these lymphatic and arthritis phenotypes are sexually dimorphic [11]. Female mice show an earlier peak expansion (~ 4 months of age) and collapse (~ 6 months of age) of their popliteal lymph node concomitant with earlier starting synovitis and bone erosions (3 months of age).…”

Ex vivo Demonstration of Functional Deficiencies in Popliteal Lymphatic Vessels from TNF-Tg Mice with Inflammatory Arthritis

“…We have focused on the synovial lymphatic system during arthritic progression and flare (10,12,16,20,25,26,35,43,44), and the effects of interventions that specifically target lymphatic contractions, whose physiologic importance in supporting lymphatic drainage and subsequent onset of lymphedema have been established in preclinical and clinical studies (7,29,45,46). We have also performed transmission electron microscopy studies on WT, Expanding and Collapsed PLVs (42).…”

“…We have also recently demonstrated that PLN expansion during arthritic progression is dependent on iNOS by longitudinally monitoring PLN volumes with PD-US in TNF-Tg versus TNF-Tg x iNOS -/mice (25). Global ablation of iNOS preserved PLV contraction frequency assessed by in vivo NIR-ICG imaging, which was associated with significantly reduced synovitis in female TNF-Tg mice that typically exhibit an accelerated disease course (25,26). Thus, the specific features associated with nitric oxide signaling and PLV contractility in TNF-Tg mice warrants further investigation.…”

Altered Lymphatic Vessel Anatomy and Markedly Diminished Lymph Clearance in Affected Hands of Patients With Active Rheumatoid Arthritis

“…The lymphatic system provides homeostatic turnover of interstitial fluid and trafficking of immune cells to the closest lymph node (4,5). Multiple studies on murine RA models have demonstrated dramatic changes in both lymphatic vessel (LV) contractions and the joint-draining lymph node volume with disease progression (6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17). During the early and middle phases of musculoskeletal inflammation, the joint-draining lymph node undergoes a rapid increase in volume to several fold greater than unaffected lymph nodes.…”