In-vitro studies of ineffective erythropoiesis in rheumatoid arthritis

Platelet and Red Blood Cell Volume Indices in Patients with Rheumatoid Arthritis: A Systematic Review and Meta-Analysis

Alterations in the volume of platelets (mean platelet volume, MPV; platelet distribution width, PDW) and erythrocytes (red blood cell distribution width, RDW) have been reported in rheumatoid arthritis (RA) and might serve as diagnostic biomarkers. We conducted a systematic review and meta-analysis of the MPV, PDW, and RDW in RA patients and healthy controls. Relevant articles were searched in PubMed, Web of Science, Scopus, and Google Scholar from inception to June 2022. Risk of bias was assessed using the Joanna Briggs Institute Critical Appraisal Checklist and certainty of evidence was assessed using GRADE. In 23 studies (2194 RA patients and 1565 healthy controls), the RDW, but not MPV or PDW, was significantly higher in RA patients (standardized mean difference, SMD = 0.96, 95% CI 0.78 to 1.15, p < 0.001; moderate certainty of evidence). The substantial heterogeneity observed (I2 = 75.1%, p < 0.001) was virtually removed in a subgroup of prospective studies. In sensitivity analysis, the magnitude of the effect size was not substantially modified by sequentially removing individual studies. There was no significant publication bias. No significant associations were observed between the effect size and pre-defined study or patient characteristics. The results of our study suggest that the RDW might be a useful biomarker for the diagnosis of RA, and complement the clinical information provided by other patient characteristics and laboratory parameters (PROSPERO registration number: CRD42022349432).

Immature cell populations and an erythropoiesis gene-expression signature in systemic juvenile idiopathic arthritis: implications for pathogenesis

Introduction

Previous observations suggest that active systemic juvenile idiopathic arthritis (sJIA) is associated with a prominent erythropoiesis gene-expression signature. The aim of this study was to determine the association of this signature with peripheral blood mononuclear cell (PBMC) subpopulations and its specificity for sJIA as compared with related conditions.

Methods

The 199 patients with JIA (23 sJIA and 176 non-sJIA) and 38 controls were studied. PBMCs were isolated and analyzed for multiple surface antigens with flow cytometry and for gene-expression profiles. The proportions of different PBMC subpopulations were compared among sJIA, non-sJIA patients, and controls and subsequently correlated with the strength of the erythropoiesis signature. Additional gene-expression data from patients with familial hemophagocytic lymphohistiocytosis (FHLH) and from a published sJIA cohort were analyzed to determine whether the erythropoiesis signature was present.

Results

Patients with sJIA had significantly increased proportions of immature cell populations, including CD34⁺ cells, correlating highly with the strength of the erythropoiesis signature. The erythropoiesis signature strongly overlapped with the gene-expression pattern in purified immature erythroid precursors. The expansion of immature cells was most prominently seen in patients with sJIA and anemia, even in the absence of reticulocytosis. Patients with non-sJIA and anemia did not exhibit the erythropoiesis signature. The erythropoiesis signature was found to be prominent in patients with FHLH and in a published cohort of patients with active sJIA, but not in patients with inactive sJIA.

Conclusions

An erythropoiesis signature in active sJIA is associated with the expansion of CD34⁺ cells, also is seen in some patients with FHLH and infection, and may be an indicator of ineffective erythropoiesis and hemophagocytosis due to hypercytokinemia.

The role of erythropoietin in the anaemia of chronic disease in rheumatoid arthritis

We reviewed studies on the role of erythropoietin (Epo) in the anaemia of chronic disease (ACD) in rheumatoid arthritis (RA). A relatively impaired Epo response to the anaemia was found in a number of studies although in others serum Epo level was the same as in other types of anaemia. Some arguments are found in favor of a reduced bone marrow-Epo sensitivity although these reflect results mainly from in vitro experiments. It is not yet established whether bone marrow macrophage Epo production is impaired in ACD. In two cases Epo administration to RA patients resulted in increased erythropoiesis. It was concluded that impaired Epo production or reduced bone marrow Epo sensitivity might be associated with ACD but it is not certain whether these factors are causally linked with ACD or side phenomena of RA disease activity. Future Epo treatment in RA and ACD will possibly solve this question.

The pathogenesis of anemia in rheumatoid arthritis: a clinical and laboratory analysis

Principal concepts concerning the anemia of RA are summarized in Tables 7 and 8. These concepts have been validated by our analysis of 93 anemic RA patients and by our review of the literature. The fact that anemia in RA may have one or more etiologies, occasionally in the same patient, mandates a reasoned approach to the analysis of anemia in every RA patient in whom it may occur. In particular, iron deficiency is common and determination of bone marrow iron content via an aspirate may be required for a definitive diagnosis. In those RA patients with anemia of chronic disease, the best therapy remains control of the underlying disease, most commonly with second line drugs and/or corticosteroids. The place for recombinant erythropoietin in the therapy of this anemia has not been defined; one specific role for erythropoietin may be in the preparation of RA patients for elective surgery, particularly hip arthroplasty, where correction of the anemia may either obviate the need for transfusion or may allow for donation of blood for purposes of autologous transfusion perioperatively. The pathogenesis of the anemia of chronic disease, as seen in RA anemia, is not completely understood. Inflammatory mediators, particularly the cytokines, appear to be important factors in the impairment of erythropoiesis. The mechanism by which these cytokines impair erythroid progenitor growth and hemoglobin production in developing erythrocytes is an important area for future study.

Anaemia in rheumatoid arthritis: pathogenesis, diagnosis and treatment

The pathogenesis, diagnosis and treatment of the anaemia of chronic disorders (ACD) in rheumatoid arthritis (RA) were reviewed. Causes of anaemia other than ACD frequently present in RA. Decreased iron absorption was shown to be the result of active RA rather than a cause of ACD or iron deficiency. It has been hypothesized that bone marrow iron availability decreases due to decreased iron release by the mononuclear phagocyte system or that the anaemia in ACD is due to ineffective erythropoiesis; these remain controversial theories. Studies considering a decreased erythropoietin responsiveness have not produced consistent results. Erythroid colony growth is suppressed in vitro by interleukins and tumour necrosis factor but their role in vivo in ACD is unknown. The diagnosis of ACD is made by exclusion. Iron deficiency is detected by transferrin, ferritin, and cellular indices after adaptation of their normal values. Treatment of the anaemia consists merely of antirheumatic treatment. Iron administration is counterproductive since iron chelators or exogenous erythropoietin administration might increase erythropoiesis.

Does active rheumatoid arthritis affect intestinal iron absorption?

One of the causes of anaemia in rheumatoid arthritis is thought to be defective iron absorption. In this study the 59Fe absorption in patients with active rheumatoid arthritis is measured and correlated with the results for bone marrow iron stores (and in some cases with the iron stores in the terminal duodenum), which were assessed simultaneously with semiquantitative methods, and with the serum ferritin concentration. In 11 patients with rheumatoid arthritis and increased bone marrow iron stores, iron absorption was decreased. In five patients it was normal and in three further patients, whose bone marrow iron stores were depleted, iron absorption was maximally increased. According to the results both intestinal malabsorption and defective iron absorption can be excluded as causes.

Immunological aspects of the anemia of rheumatoid arthritis

In order to investigate the cause of the anemia concomitant with rheumatoid arthritis (RA), we examined, using the erythroid colony assay of human bone marrow colony-forming units-erythroid (CFU-e) and burst-forming units-erythroid (BFU-e), the effects of the patients' serum and peripheral blood T lymphocytes on the CFU-e-derived colonies. The counts of erythroid colonies of RA patients were markedly lower than those of human control subjects [CFU-e: control 152.9 +/- 30.6 (n = 19), RA 51.1 +/- 13.6 (n = 7), t = 7.66567, p less than 0.01; BFU-e: control 25.2 +/- 5.9 (n = 5), RA 12.6 +/- 2.6 (n = 7), t = 4.574, p less than 0.01]. The serum from two out of seven RA patients slightly inhibited the formation of CFU-e-derived colonies of human control subjects (t = 2.31, 0.05 less than p less than 0.1); however, the serum from the other five RA patients did not significantly inhibit human control erythroid colony formation as compared with human control serum (t = 0.981, 0.3 less than p less than 0.4). On the other hand, peripheral blood T lymphocytes of the patients markedly inhibited the formation of CFU-e-derived colonies of the control subjects as compared with peripheral blood T lymphocytes from human control subjects (t = 4.24, p less than 0.01). The above-mentioned results suggest that the peripheral blood T lymphocytes of RA patients might play a role as one of the causes of the concomitant anemia of RA patients.

Anaemia in juvenile chronic arthritis: serum inhibition of normal erythropoiesis in vitro

Serum from patients with juvenile chronic arthritis (JCA) was shown to inhibit colony formation by normal erythropoietic progenitor cells cultured in vitro. The inhibition was proportional to the degree of anaemia and to certain indices of activity of the arthritis and systemic disease. It occurred in a dose dependent manner with increasing serum concentration and was independent of previous blood transfusion or administered drugs. Erythropoietic progenitor cells from the bone marrows of anaemic patients with JCA showed normal requirements for accessory cells (T lymphocytes and macrophages) in culture, and autologous accessory cells were not deficient in providing normal growth requirements.

Serum ferritin and free erythrocyte protoporphyrin in rheumatoid arthritis

In this prospective study 20 newly diagnosed patients with definite or classical rheumatoid arthritis were followed with serial measurements of serum ferritin and erythrocyte-free protoporphyrin at the beginning of the trial and at 3 and 6 months. The values were correlated with clinical disease activity ad with various laboratory parameters. It was shown that free erythrocyte protoporphyrin has a constant negative correlation with erythrocyte haemoglobin concentration independent of disease activity, while serum ferritin behaves like an acute phase protein. Initial serum ferritin or free erythrocyte protoporphyrin values or their early changes appeared to have no prognostic value as evaluated by the development of new erosions or by the response of the patient to the therapy.

The mechanism of the anaemia in rheumatoid arthritis: effects of bone marrow adherent cells and of serum on in-vitro erythropoiesis

Clonal assays for erythroid progenitors (BFU-e and CFU-e) were used to study 20 patients with rheumatoid arthritis, 15 of whom had anaemia of chronic disease and five of whom were haematologically normal. The numbers of bone marrow BFU-e and CFU-e in the anaemic patients did not differ significantly from those in normal controls. Macrophages were removed from the bone marrow by a combination of adherence and buoyant density centrifugation over a sucrose gradient and the resulting fractions were cultured alone or together with autologous adherent cells in BFU-e assays. Co-culture with adherent cells significantly increased colony growth in both the controls and in seven of eight anaemic patients studied. Serum from 14 anaemic patients and from five non-anaemic patients was added to cultures of bone marrow or to control peripheral blood 'null' cells. Anaemic serum uniformly either inhibited or failed to stimulate BFU-e growth under these conditions. Serum from non-anaemic patients and from 10 healthy controls stimulated BFU-e growth from 'null' cells to an equal degree.