The Relationship between Radial Bone Properties and Disease Activity and Physical Function in Individuals with Rheumatoid Arthritis

Association between forearm cortical bone properties and handgrip strength in women with distal radius fractures: A cross-sectional study

OBJECTIVES

Mechanical and biochemical bone properties are influenced by muscles. However, the muscle-bone interaction has not been fully elucidated regarding the upper extremities. The objective of the present study was to evaluate the mechanical muscle-bone interaction at the forearm by evaluating the relationship between the properties of three-dimensional (3D) forearm cortical bone models derived from conventional computed tomography (CT) images and handgrip strength (HGS).

METHODS

A total of 108 women (mean age, 75.2 ± 9.4 years; range, 62-101 years) with a distal radius fracture who took conventional CT scans for the assessment of the fracture were included in this study. Distal radius 3D models were reconstructed and the average cortical bone density (Cd) and thickness (Ct) of the region of interest (ROI), which might be affected by the forearm flexor muscles, were calculated using a 3D modeling software. Clinical parameters including HGS, lumbar and hip bone mineral densities (BMDs), and other demographic factors were also obtained. A multivariate linear regression analysis was performed to identify relevant factors associated with HGS.

RESULTS

HGS was found to be independently associated with height and Cd, but no significant difference was found between HGS and Ct, age, weight, as well as lumber and hip BMDs.

CONCLUSIONS

Cortical bone density might be associated with HGS, which is generated by the forearm flexor muscles. Hence, the mechanical muscle-bone interaction in the upper extremities could be supported by the present study.

Construction of a Bcl-2-shRNA expression vector and its effect on the mitochondrial apoptosis pathway in SW982 cells

Apoptosis is considered to serve an important role in the pathogenesis of rheumatoid arthritis. The aim of the present study was to construct Bcl-2-short hairpin (sh)RNA expression vectors and transfect them into human synovial sarcoma SW982 cells, in order to screen for an effective interference sequence and analyze the effects of this interference on the expression levels of Bcl-2 and other molecules associated with the mitochondrial apoptosis pathway. Three different shRNAs (Bcl-2-sh1, 2 and 3) were designed according to the human Bcl-2 mRNA target sequence and were transformed into competent DH5α Escherichia coli cells following the construction of an expression vector, which was then transfected into SW982 cells. SW982 cells were grouped into a control group (transfected with a negative control shRNA), and Bcl-2-sh1, Bcl-2-sh2 and Bcl-2-sh3 groups (transfected with Bcl-2-sh1, 2 and 3, respectively). The expression levels of Bcl-2 mRNA were detected using reverse transcription-quantitative PCR (RT-qPCR). Bcl-2-sh1 was identified as the most effective shRNA sequence for interference, and was used for subsequent experiments. The mRNA and protein expression levels of Bcl-2, Bax, CytC and Caspase-3 were detected in SW982 cells by RT-qPCR and western blotting at various time-points (48 and 72 h) following transfection with Bcl-2-sh1, in order to observe the effectiveness of this interference. Compared with the control group, the expression levels of Bcl-2 were decreased, while those of Bax, CytC and Caspase-3 were increased in Bcl-2-sh1-transfected cells (P<0.01). The interference effect was greater at 48 h than at 72 h. In summary, an effective shRNA sequence (Bcl-2-sh1) targeting the Bcl-2 gene was identified from three candidates, and was demonstrated to significantly interfere with the expression of Bcl-2, Bax, CytC and Caspase-3 when transfected into SW982 cells. The interference effect of Bcl-2-sh1 was more pronounced at 48 h than at 72 h post-transfection.

Influence of bisphosphonate therapy on bone geometry, volumetric bone density and bone strength of femoral shaft in postmenopausal women with rheumatoid arthritis

BACKGROUND

There is evidence that postmenopausal women with rheumatoid arthritis (RA) on glucocorticoid (GC) therapy and bisphosphonate (BP) have an increased risk for atypical subtrochanteric and atypical diaphyseal femoral fracture (AFF). The underlying mechanism has not been elucidated so far. Using peripheral quantitative computed tomography (pQCT), the aim of the present study was to compare bone geometry, volumetric bone mineral density (vBMD) and bone strength of femoral shaft in BP-treated and BP-naïve postmenopausal women with RA.

METHODS

Prospective cross-sectional pQCT scans were taken at 33 % of total femur of BP-treated and BP-naïve RA patients. Bone parameters of the two groups were compared and correlated to disease characteristics and muscle cross-sectional area (CSA).

RESULTS

A total of 60 consecutive postmenopausal RA patients, 20 with BP therapy and 40 BP-naïve, were included in the study. The median age of the subjects was 63.5 years (range 48-85 years), and median disease duration (RA) was 12.0 years (range 2-47 years). Height and weight of the patients of the two groups were comparable. Women in the BP group were on average 4.3 years older (p = 0.044), and duration since menopause was on average 5.76 years longer (p = 0.045). In the BP group, there was a 13.31 % reduced muscle cross-sectional area around the proximal thigh (p = 0.013); cortical CSA was smaller by 5.3 % (p = 0.043); however, total and medullary CSA, as well as cortical vBMD and the polar bone stress-strain index of the femoral shaft were similar in the two groups. In regression analysis, age, time since menopause and muscular CSA were significant factors determining cortical CSA, cortical thickness and femoral index (p < 0.05). Regression model showed no significant effect of BP therapy on bone geometry and density of the femoral diaphysis at 33 %.

CONCLUSION

Differences in cortical CSA between BP-treated and BP-naïve postmenopausal RA patients were found to be associated only with differences in age, time since menopause and muscle cross-sectional area around the proximal thigh. In interpreting our results, it should be kept in mind that BP was given only to patients with increased fracture risk. This fact might have a confounding effect on our findings of differences between the two groups.