Comprehensive assessment of tissue and serum parameters of bone metabolism in a series of orthopaedic patients

Associations of serum sclerostin levels with body composition, pulmonary function, and exacerbations in COPD patients

BACKGROUND

In COPD, the bronchial epithelium shows a pathologically activated Wnt pathway. Sclerostin (SOST) is a secreted glycoprotein that is associated with bone metabolism and blocks the Wnt pathway. We hypothesized that low sclerostin levels might be associated with lung function and COPD exacerbations in patients.

METHODS

We studied 139 outpatients with stable COPD and normal kidney function. We assessed the serum levels of SOST and bone metabolism parameters, body composition, clinical characteristics and lung function at baseline. We followed the patients prospectively for 12 months after enrolment. Moderate exacerbations and hospital admissions were recorded during follow-up.

RESULTS

The serum SOST levels were 23.98±7.6 pmol/l (men: 25.5±7.7 pmol/l, women: 20.3±5.9 pmol/l (p < 0.001)). SOST showed correlations with age (r = 0.36), FFMI (r = 0.38), FEV1 (r = 0.27), DLCO (r = 0.39), 6MWD (r = 0.19) and CAT (r = -0.24). In multivariate linear regression analysis, only age (beta=0.264) and FFMI (beta=1.241) remained significant. SOST showed a significant negative correlation with serum phosphorus (r = -0.29). Cox proportional risk analysis indicated that patients in the lower tertile of SOST levels were at higher risk of moderate COPD exacerbation (HR 2.015, CI95% 1.136-3.577, p = 0.017) and hospital admission due to COPD (HR 5.142, CI95% 1.380-19.158, p = 0.015) than the rest of the patients.

CONCLUSIONS

SOST levels are associated with body composition and lung function in patients with COPD. Furthermore, lower SOST levels predict a higher risk of exacerbations and hospitalization.

Explanted Skull Flaps after Decompressive Hemicraniectomy Demonstrate Relevant Bone Avitality-Is Their Reimplantation Worth the Risk?

BACKGROUND

Reimplantations of autologous skull flaps after decompressive hemicraniectomies (DHs) are associated with high rates of postoperative bone flap resorption (BFR). We histologically assessed the cell viability of explanted bone flaps in certain periods of time after DH, in order to conclude whether precursors of BRF may be developed during their storage.

METHODS

Skull bone flaps explanted during a DH between 2019 and 2020 were stored in a freezer at either -23 °C or -80 °C. After their thawing process, the skulls were collected. Parameters of bone metabolism, namely PTH1 and OPG, were analyzed via immunohistochemistry. H&E stain was used to assess the degree of avital bone tissue, whereas the repeated assays were performed after 6 months.

RESULTS

A total of 17 stored skull flaps (8 at -23 °C; 9 at -80 °C) were analyzed. The duration of cryopreservation varied between 2 and 17 months. A relevant degree of bone avitality was observed in all skull flaps, which significantly increased at the repeated evaluation after 6 months (p < 0.001). Preservation at -23 °C (p = 0.006) as well as longer storage times (p < 0.001) were identified as prognostic factors for higher rates of bone avitality in a linear mixed regression model.

CONCLUSIONS

Our novel finding shows a clear benefit from storage at -80° C, which should be carefully considered for the future management and storage of explanted skull flaps. Our analysis also further revealed a significant degree of bone avitality, a potential precursor of BFR, in skull flaps stored for several weeks. To this end, we should reconsider whether the reimplantation of autologous skull flaps instead of synthetic skull flaps is still justified.

New Generation of Meso and Antiprogestins (SPRMs) into the Osteoporosis Approach

Receptor activator of nuclear factor κB (RANK) and its ligand (RANKL) play key roles in bone metabolism and the immune system. The RANK/RANKL complex has also been shown to be critical in the formation of mammary epithelia cells. The female hormones estradiol and progesterone closely control the action of RANKL with RANK. Blood concentration of these sex hormones in the postmenopausal period leads to an increase in RANK/RANKL signaling and are a major cause of women's osteoporosis, characterized by altered bone mineralization. Knowledge of the biochemical relationships between hormones and RANK/RANKL signaling provides the opportunity to design novel therapeutic agents to inhibit bone loss, based on the anti-RANKL treatment and inhibition of its interaction with the RANK receptor. The new generation of both anti- and mesoprogestins that inhibit the NF-κB-cyclin D1 axis and blocks the binding of RANKL to RANK can be considered as a potential source of new RANK receptor ligands with anti-RANKL function, which may provide a new perspective into osteoporosis treatment itself as well as limit the osteoporosis rise during breast cancer metastasis to the bone.

Atherosclerosis and Bone Loss in Humans-Results From Deceased Donors and From Patients Submitted to Carotid Endarterectomy

Background and Aims: Atherosclerosis and osteoporosis share common risk factors, as well as inflammatory mechanisms. Our aim was to understand how atherosclerotic lesions are related with disturbances in bone.

Methods: Gene expression of pro-inflammatory and bone metabolism related proteins (IL-1β, IL-6, IL-17A, TNF, RANKL, OPG, COL1, CTSK, OCL, TRAP, CBFA1, DKK1, SOST, ADIPOQ, and ADIPOR1) were analyzed in arteries and bones from 45 deceased donors and adipose tissue was used as control. Additionally, in 139 patients with advanced atherosclerosis submitted to carotid endarterectomy we compared calcium content (Alizarin red) and plaque inflammatory scores (CD3⁺, CD68⁺, and adiponectin) of patients with normal bone mineral density (BMD) with those with low BMD and explored the associations between gene expression in atherosclerotic plaques and BMD. Serum levels of pro-inflammatory and bone related proteins were measured both in donors and patients. Associations were investigated by the Pearson or Spearman correlation tests, and multivariate regression analyzes were performed when justified.

Results: Gene expression of bone remodeling and pro-inflammatory proteins correlated positively in bone and aorta, independently of age and sex of donors, but not in adipose tissue. The expression of bone formation genes was significantly higher in atheroma plaques from endarterectomized patients with normal vs. low BMD as well as inflammatory CD68⁺ scores, regardless of patients' age and sex, but not of body mass index. No relationship was observed between serum levels and gene expression levels of pro-inflammatory or bone remodeling proteins.

Conclusions: Our results suggest that the relationship between bones and vessels in the context of atherosclerotic disease and osteoporosis may rely on the intrinsic connection between the tissues involved, independently of disease stage. Serum measurements of pro-inflammatory and bone-remodeling proteins do not accurately translate tissue pathologic processes.

Circulating bioactive sclerostin levels in an Austrian population-based cohort

Background

Circulating serum sclerostin levels are supposed to give a good estimation of the levels of this negative regulator of bone mass within bone. Most studies evaluating total serum sclerostin found different levels in males compared to females and in older compared to younger subjects. Besides an ELISA detecting total sclerostin an ELISA determining bioactive sclerostin has been developed. The aim of this study was to investigate serum levels of bioactive sclerostin in an Austrian population-based cohort.

Methods

We conducted a cross-sectional observational study in 235 healthy subjects. Using the bioactive ELISA assay (Biomedica) bioactive sclerostin levels were evaluated.

Results

Serum levels of bioactive sclerostin were higher in men than in women (24%). The levels correlated positively with age (r = 0.47). A positive correlation could also be detected with body mass index and bone mineral density.

Conclusion

Using the ELISA detecting bioactive sclerostin our results are consistent with data in the literature obtained by different sclerostin assays. The determination of sclerostin concentrations in peripheral blood thus appears to be a robust parameter of bone metabolism.