Correlation study between osteoporosis and hematopoiesis in the context of adjuvant chemotherapy for breast cancer

Bone Density and Trabecular Bone Score Decline Rapidly in the First Year After Bone Marrow Transplantation with a Marked Increase in 10-Year Fracture Risk

As outcomes from allogeneic bone marrow transplantation (BMT) have improved, prevention of long-term complications, such as fragility fractures, has gained importance. We aimed to assess areal bone mineral density (aBMD) and trabecular bone score (TBS) changes post BMT, and determine their relationship with fracture prevalence. Patients who attended the Royal Melbourne Hospital (RMH) BMT clinic between 2005-2021 were included. Patient characteristics and dual-energy X-ray absorptiometry (DXA) values were collected from the electronic medical record and a survey. TBS iNsight™ was used to calculate TBS for DXA scans performed from 2019 onwards. 337 patients with sequential DXAs were eligible for inclusion. Patients were primarily male (60%) and mean age ± SD was 45.7 ± 13.4 years. The annualised decline in aBMD was greater at the femoral neck (0.066g/cm2 (0.0038-0.17)) and total hip (0.094g/cm2 (0.013-0.19)), compared to the lumbar spine (0.049g/cm2 (- 0.0032-0.16)), p < 0.0001. TBS declined independently of aBMD T-scores at all sites. Eighteen patients (5.3%) sustained 19 fractures over 3884 person-years of follow-up post-transplant (median follow-up 11 years (8.2-15)). This 5.3% fracture prevalence over the median 11-year follow-up period is higher than what would be predicted with FRAX® estimates. Twenty-two patients (6.5%) received antiresorptive therapy, and 9 of 18 (50%) who fractured received or were on antiresorptive therapy. In BMT patients, aBMD and TBS decline rapidly and independently in the first year post BMT. However, FRAX® fracture probability estimates incorporating these values significantly underestimate fracture rates, and antiresorptive treatment rates remain relatively low.

A Novel Mechanism for Bone Loss: Platelet Count Negatively Correlates with Bone Mineral Density via Megakaryocyte-Derived RANKL

A potential association between hematopoietic stem cell status in bone marrow and surrounding bone tissue has been hypothesized, and some studies have investigated the link between blood count and bone mineral density (BMD), although their exact relationship remains controversial. Moreover, biological factors linking the two are largely unknown. In our present study, we found no clear association between platelet count and BMD in the female group, with aging having a very strong effect on BMD. On the other hand, a significant negative correlation was found between platelet count and BMD in the male group. As a potential mechanism, we examined whether megakaryocytes, the source of platelet production, secrete cytokines that regulate BMD, namely OPG, M-CSF, and RANKL. We detected the production of these cytokines by megakaryocytes derived from bone marrow mononuclear cells, and found that RANKL was negatively correlated with BMD. This finding suggests that RANKL production by megakaryocytes may mediate the negative correlation between platelet count and BMD. To our knowledge, this is the first report to analyze bone marrow cells as a mechanism for the association between blood count and BMD. Our study may provide new insights into the development and potential treatment of osteoporosis.

Differential blood counts do not consistently predict clinical measurements of bone mineral density and microarchitecture at homeostasis

The hematopoietic stem cell niche constitutes a complex bone marrow (BM) microenvironment. Osteoporosis is characterized by both reduced bone mineral density (BMD) and microarchitectural deterioration, constituting the most frequent alteration of the BM microenvironment. It is unclear to which extent modifications of the BM microenvironment, including in the context of osteoporosis, influence blood cell production. We aimed to describe the association between lumbar spine and total hip BMD and microarchitecture (assessed by trabecular bone score [TBS]) and differential blood counts. Data were collected at two time points from 803 (first assessment) and 901 (second assessment) postmenopausal women participating in the CoLaus/OsteoLaus cohort, a population‐based sample in Lausanne, Switzerland. Participants with other active disease or treatment that could influence hematopoiesis or osteoporosis were excluded. Bivariate and multivariate associations between each peripheral blood cell count and BMD or TBS were performed. Additionally, participants in the highest BMD and TBS tertiles were compared with participants in the lowest BMD and TBS tertiles. At first assessment, only neutrophils were significantly different in the lowest BMD and TBS tertile (3.18 ± 0.09 versus 3.47 ± 0.08 G/L, p = 0.028). At the second assessment, leucocytes (5.90 ± 0.11 versus 5.56 ± 0.10 G/L, p = 0.033), lymphocytes (1.87 ± 0.04 versus 1.72 ± 0.04 G/L p = 0.033), and monocytes (0.49 ± 0.01 versus 0.46 ± 0.1 G/L, p = 0.033) were significantly different. Power analysis did not identify quasi‐significant associations missed due to sample size. Although significant associations between blood counts and BMD or TBS were found, none was consistent across bone measurements or assessments. This study suggests that, at homeostasis and in postmenopausal women, there is no clinically significant association between the osteoporotic microenvironment and blood production output as measured by differential blood counts. In the context of conflicting reports on the relationship between osteoporosis and hematopoiesis, our study represents the first prospective two time‐point analysis of a large, homogenous cohort at steady state. © 2022 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.

Changes in trabecular bone score and bone mineral density following allogeneic hematopoietic stem cell transplantation

PURPOSE

It has been demonstrated that bone mineral density (BMD) loss is substantial within the first 12 months after allogeneic hematopoietic stem cell transplantation (alloHSCT). Declines in BMD showed a disproportionate cortical bone loss even though trabecular bone is metabolically more active than cortical bone. This finding suggests a unique mechanism. However, the structural bone deficits after alloHSCT have not been well characterized. The trabecular bone score (TBS) has emerged as a method to assess bone microarchitecture. The aim of this study was to evaluate the changes in BMD and TBS in patients who received alloHSCT with follow-up of two years.

METHODS

All patients 18 years and older who received alloHSCT between 2009 and 2015 at Seoul St. Mary's Hospital, Korea were included. They were segregated into a first group (A, n = 24) that was evaluated for BMD at the time of alloHSCT and 12 months posttransplant and a second group (B, n = 44) that was evaluated for BMD at 12 and 24 months following alloHSCT.

RESULTS

Subjects in group A experienced a decrease in BMD at the femoral neck and total hip between the time of transplantation and 12 months posttransplantation: 0.056 ± 0.057 (5.48%) and 0.072 ± 0.063 (6.84%), respectively. Subjects in group B experienced an increase in BMD at the lumbar spine and total hip between 12 and 24 months post-alloHSCT: 0.047 ± 0.064 (4.90%) and 0.017 ± 0.045 (2.16%), respectively. In group A, TBS at 12 months post-alloHSCT decreased 0.028 ± 0.067 (1.92%) from the baseline (p = 0.086). In group B, TBS at 24 months post-alloHSCT increased 0.010 ± 0.049 (0.78%) from the 12 months post-alloHSCT evaluation (p = 0.149). TBS change was positively associated with BMD changes at all measured sites. The cumulative dose of glucocorticoid therapy was associated with loss of BMD at all measured sites and TBS. In addition, the dose of total body irradiation (TBI) was negatively associated with TBS.

CONCLUSIONS

In summary, this study delineated longitudinal microarchitectural changes in bone structure occurring in the context of alloHSCT. TBS change per 12 months was insignificant during the two years following alloHSCT. Therefore, our data represented disproportionate cortical bone loss in the context of the microarchitecture.