The role of sclerostin/dickkopf-1 and receptor activator of nuclear factor kB ligand/osteoprotegerin signalling pathways in the development of osteoporosis in patients with haemophilia A and B: A cross-sectional study

AIM

Haemophilia A and B are associated with reduced bone mineral density (BMD). The aim of this study was to assess circulating sclerostin and dickkopf-1 (Dkk-1), (inhibitors of osteoblastic differentiation), as well as the receptor activator of nuclear factor kB ligand (RANKL)/osteoprotegerin (OPG) system (the major regulator of osteoclastogenesis), in patients with haemophilia (PWH), their possible correlations with clinical risk factors and the effect of ibandronate on these markers.

METHODS

Eighty-nine male PWH (mean age 45.9 ± 15.3 years) and 30 age-matched healthy male controls participated. BMD was assessed by DXA. Sclerostin, Dkk-1, RANKL and OPG were measured in serum of patients, controls, as well as in ten patients receiving oral ibandronate (150 mg/mo), at baseline and after 12 months.

RESULTS

Patients with haemophilia had lower circulating sclerostin (median ± IQR: 47.4 ± 26.93 vs 250 ± 250 pmol/L, P < .001), Dkk-1 (21.24 ± 17.18 vs 26.16 ± 15.32pg/mL, P = .04) and higher levels of RANKL (0.23 ± 0.03 vs 0.04 ± 0.03 pmol/L, P = .001), RANKL/OPG ratio (0.063 ± 0.25 vs 0.005 ± 0.11, P = .001) compared with controls. Patients with low BMD had higher OPG concentrations compared to those with normal BMD. Sclerostin and RANKL/OPG correlated positively with BMD. Patients with severe haemophilia had lower sclerostin concentrations compared with those with mild or moderate disease. The degree of arthropathy negatively correlated with sclerostin and Dkk-1 levels. PWH who received ibandronate showed a decrease in serum Dkk-1 without any significant effect on sclerostin and RANKL/OPG.

CONCLUSIONS

Patients with haemophilia present increased osteoclastic activity coupled with compensatory increased osteoblastic activity. Ibandronate did not affect RANKL/OPG ratio, but it decreased Dkk-1.

Mechanisms of bone destruction in multiple myeloma

Osteolytic bone disease is a frequent complication of multiple myeloma, resulting in skeletal complications that are a significant cause of morbidity and mortality. It is the result of an increased activity of osteoclasts, which is not followed by reactive bone formation by osteoblasts. Recent studies have revealed novel molecules and pathways that are implicated in osteoclast activation and osteoblast inhibition. Among them, the most important include the receptor activator of nuclear factor-kappa B ligand/osteoprotegerin pathway, the macrophage inflammatory proteins and the activin-A that play a crucial role in osteoclast stimulation in myeloma, while the wingless-type (Wnt) signalling inhibitors (sclerostin and dickkopf-1) along with the growth factor independence-1 are considered the most important factors for the osteoblast dysfunction of myeloma patients. Finally, the role of osteocytes, which is the key cell for normal bone remodelling, has also revealed during the last years through their interaction with myeloma cells that leads to their apoptosis and the release of RANKL and sclerostin maintaining bone loss in these patients. This review focuses on the latest available data for the mechanisms of bone destruction in multiple myeloma.

The presence of CD55- and/or CD59-deficient erythrocytic populations in patients with rheumatic diseases reflects an immune-mediated bone-marrow derived phenomenon

Background

Complement has the potential to provoke severe impairment to host tissues, as shown in autoimmune diseases where complement activation has been associated with diminished CD55 and/or CD59 expression on peripheral blood cell membranes. The aim of this study was to evaluate the presence of CD55- and/or CD59-deficient erythrocytic populations in patients with different rheumatic diseases and to investigate possible correlations with clinical or laboratory parameters.

Material/Methods

CD55 and CD59 expression was evaluated in erythrocytes of 113 patients with rheumatic diseases, 121 normal individuals, and 10 patients with paroxysmal nocturnal hemoglobinuria (PNH) using the Sephacryl gel microtyping system. Ham and sucrose tests were also performed.

Results

Interestingly, the majority of patients (104/113, 92%) demonstrated CD55- and/or CD59-deficient erythrocytes: 47 (41.6%) with concomitant deficiency of CD55 and CD59, 50 (44.2%) with isolated deficiency of CD55, and 6 (6.2%) with isolated deficiency of CD59. In normal individuals, only 2 (1%) had concomitant CD55/CD59 negativity and 3 (2%) had isolated CD55 or CD59 deficiency. All PNH patients exhibited simultaneous CD55/CD59 deficiency. Positive Ham and sucrose tests were found only in PNH patients. There was no association between the CD55- and/or CD59-deficient erythrocytes and hemocytopenias or undergoing treatment. However, CD55 expression significantly influenced hemoglobin values (F=6.092, p=0.015).

Conclusions

This study provides evidence supporting the presence of erythrocytes with CD55 and/or CD59 deficiency in patients with rheumatic diseases. Moreover, CD55 deficiency on red cells influences hemoglobin concentration. Further studies using molecular techniques will clarify the exact pathophysiological mechanisms of this deficiency.

VTD consolidation, without bisphosphonates, reduces bone resorption and is associated with a very low incidence of skeletal-related events in myeloma patients post ASCT

We prospectively evaluated the effect of bortezomib, thalidomide and dexamethasone (VTD) consolidation on bone metabolism of 42 myeloma patients who underwent an autologous stem cell transplantation (ASCT). VTD started on day 100 post ASCT; patients received four cycles of VTD (first block), were followed without treatment for 100 days and then received another four VTD cycles (second block). During this 12-month period, bisphosphonates were not administered. Best response included stringent complete remission (sCR) in 15 (35.7%) patients, complete response (CR) in 13 (30.9%), vgPR in 7 (16.6%), PR in 4 (9.5%), while 3 (7.1%) patients developed a progressive disease (PD). Importantly, 33.3% and 47.6% of patients improved their status of response after the first and second VTD block, respectively. VTD consolidation resulted in a significant reduction of circulating C-terminal cross-linking telopeptide of collagen type I (CTX), soluble receptor activator of the nuclear factor-kappa B ligand (sRANKL) and osteocalcin (OC), whereas bone-specific alkaline phosphatase (bALP) remained stable compared with pre-VTD values. During the study period, only one patient with a PD developed a skeletal-related event (that is, radiation to bone). The median time to progression (TTP) after ASCT was 34 months and the median time of next treatment was 40 months. We conclude that VTD consolidation post ASCT reduces bone resorption and is associated with a very low incidence of skeletal-related events (SREs) despite the absence of bisphosphonates; the later do not appear to be necessary in this context.

High circulating sclerostin is present in patients with thalassemia-associated osteoporosis and correlates with bone mineral density

Osteoporosis is a severe complication of thalassemia. Sclerostin is a Wnt signaling inhibitor, which is produced by osteocytes and inhibits osteoblast function. Sclerostin is implicated in the pathogenesis of osteoporosis of different etiology. The aim of the study was to evaluate circulating sclerostin in 66 patients (median age 42 years) with thalassemia and osteoporosis who participated in a phase 2, randomized study (zoledronic acid vs. placebo) and the results were compared with those of 30 healthy controls (median age 44 years) without osteopenia/osteoporosis and 62 women with postmenopausal osteoporosis (median age 63 years). At baseline, thalassemic patients with osteoporosis had elevated circulating levels of sclerostin (median: 605 pg/ml, range: 22-1,227 pg/ml) compared to healthy controls without osteopenia/osteoporosis (250 pg/ml, 0-720 pg/ml, p<0.001) and reduced levels of sclerostin compared with postmenopausal women with osteoporosis (840 pg/ml, 181-1,704 pg/ml, p<0.001). Thalassemia patients had also increased serum dickkopf-1 (Dkk-1) and high bone turnover. Circulating sclerostin levels correlated with bone mineral density in lumbar spine (r=0.619, p<0.001), distal radius (r=0.401, p=0.001) and femoral neck (r=0.301, p=0.021). Zoledronic acid did not alter sclerostin levels after 12 months of therapy, although it reduced circulating Dkk-1. We conclude that circulating sclerostin is elevated in thalassemia patients with osteoporosis and correlated with their BMD, but it was not reduced post zoledronic acid administration. These findings suggest that high sclerostin may serve as a marker of increased osteocyte activity in thalassemia patients. Drugs targeting sclerostin may also be used in this difficult to treat disorder associated with bone loss.

Circulating activin-A is elevated in patients with advanced multiple myeloma and correlates with extensive bone involvement and inferior survival; no alterations post-lenalidomide and dexamethasone therapy

BACKGROUND

Activin-A is a transforming growth factor -β superfamily member, which seems to be implicated in the biology of osteolytic disease in multiple myeloma.

DESIGN AND METHODS

Circulating activin-A was evaluated in 98 newly diagnosed myeloma patients (85 with symptomatic disease), in 40 patients with relapsed myeloma before and after four cycles of lenalidomide and dexamethasone (RD), in 27 healthy controls and in 10 monoclonal gammopathy of undetermined significance patients.

RESULTS

Patients with newly diagnosed symptomatic myeloma had increased circulating activin-A compared with controls (P < 0.001), while patients with relapsed disease had elevated activin-A even compared with symptomatic patients at diagnosis (P < 0.001). High activin-A correlated with advanced International Staging System stage (P = 0.002), increased bone resorption (P < 0.001) and extensive bone disease (P = 0.03). Low levels of activin-A (<442 pg/ml) were associated with superior median overall survival: not reached versus 59 months (P = 0.04), while activin-A inversely correlated with survival as a continuous variable (P < 0.001). RD did not alter circulating activin-A after four cycles of treatment, even in responders.

CONCLUSIONS

High circulating activin-A correlates with advanced features of myeloma, supporting the rationale for the use of activin-A antagonists, such as sotatercept in myeloma. The inability of RD to reduce activin-A reveals RD as a good candidate for combination therapies with activin-A antagonists in myeloma.