Cross-calibration of 45calcium kinetics against dynamic histomorphometry in a rat model to determine bone turnover

An overview of de novo bone generation in animal models

Some of the earliest success in de novo tissue generation was in bone tissue, and advances, facilitated by the use of endogenous and exogenous progenitor cells, continue unabated. The concept of one health promotes shared discoveries among medical disciplines to overcome health challenges that afflict numerous species. Carefully selected animal models are vital to development and translation of targeted therapies that improve the health and well-being of humans and animals alike. While inherent differences among species limit direct translation of scientific knowledge between them, rapid progress in ex vivo and in vivo de novo tissue generation is propelling revolutionary innovation to reality among all musculoskeletal specialties. This review contains a comparison of bone deposition among species and descriptions of animal models of bone restoration designed to replicate a multitude of bone injuries and pathology, including impaired osteogenic capacity.

Soy isoflavones prevent bone resorption and loss, a systematic review and meta-analysis of randomized controlled trials

BACKGROUND

Osteoporosis is a common bone disease characterized by reduced bone mass resulting from continuous bone resorption.

METHODS

PubMed, Scopus, and Embase were searched to find published trials on the effect of soy isoflavones on bone mineral density (BMD) and bone turnover markers (bone-specific alkaline phosphatase, osteocalcin, osteoprotegerin, pyridinoline, deoxypyridinoline, C-telopeptide, and N-telopeptide). Random-effects inverse-variance model was used to calculate the pooled effects.

RESULTS

A total of 5313 articles were found, screened, and assessed for eligibility, and finally 52 trials were included in the meta-analysis. Consumption of soy isoflavones caused significant improvement in BMD of lumbar spine (mean difference (MD) = 0.76%; 95% CI: 0.09, 1.42%; p = 0.03), hip (MD = 0.22%; 95% CI: 0.02, 0.42%; p = 0.04), and femoral neck (MD = 2.27%; 95% CI: 1.22, 3.31%; p < 0.001). Subgroup analysis showed that in all 3 sites, the improvement was significant in normal weight subjects and interventions longer than a year, although trial location and dosage were also factors influencing isoflavones' impact on BMD. Among markers of bone turnover, osteoprotegerin (MD = 5.79; 95% CI: 3.08, 8.51 pg/ml; p < 0.001), pyridinoline (MD = -5.13; 95% CI: -7.76, -2.50 nmol/mmol; p < 0.001), and C-telopeptides (MD = -0.08; 95% CI: -0.16, -0.00 ng/ml; p = 0.04) were favorably affected by isoflavones while osteocalcin and bone alkaline phosphatase did not change. Subgroup analysis of bone markers showed that in overweight/obese individuals and dosages <90 mg/day, isoflavones are more effective.

CONCLUSIONS

Soy isoflavones prevent osteoporosis-related bone loss in any weight status or treatment duration. They increase BMD in normal weight subjects and diminish bone resorption in overweight/obese individuals. Although bone resorption may be decelerated over short-term isoflavone consumption, periods longer than a year are probably needed to affect BMD. Isoflavones also appear benefits on bone in any dose or subjects' ethnicity.

Skeletal remodeling following clinically relevant radiation-induced bone damage treated with zoledronic acid

Our aim was to determine if zoledronic acid (ZA) changes (45)Ca pharmacokinetics and bone microstructure in irradiated, ovary-intact (I) and irradiated, ovariectomized mice (OVX), two groups with different patterns of skeletal damage. The hind limbs of I and OVX BALB/c mice received a single 16-Gy radiation dose, simulating pre- and postmenopausal female cancer patients undergoing radiation treatment. All I and OVX mice were radiolabeled with 15 μCi (45)Ca. Mice were treated with or without a 0.5 mg/kg injection of ZA. The time course of bone mineral remodeling was evaluated using a fecal (45)Ca assay, measured by liquid scintillation. A group of nonirradiated, intact mice were used for the longitudinal evaluation of (45)Ca biodistribution. Distal femur bone histomorphometric parameters were measured using microCT at 50 days post-ZA intervention. Most (45)Ca was incorporated into the skeleton and eliminated from the soft tissues within 3-5 days postirradiation, attaining a steady state of excretion at 25-30 days. ZA intervention in both groups resulted in a rapid decrease in fecal (45)Ca excretion. There was a significant difference in (45)Ca excretion in the OVX ± ZA (P = 0.005) group but not in the I ± ZA (P = 0.655) group. The rate of excretion of fecal (45)Ca was slower in the OVX + ZA compared to the I + ZA group (P = 0.064). (45)Ca assay is useful to monitor the time course of bone mineral remodeling after an antiresorptive intervention in irradiated mice, providing a basis to investigate bone effects of cancer therapy protocols. For equivalent doses of ZA, recovery may depend on the nature and degree of skeletal damage.

Liquid scintillation based quantitative measurement of dual radioisotopes (3H and 45Ca) in biological samples for bone remodeling studies

Acute and prolonged bone complications associated with radiation and chemotherapy in cancer survivors underscore the importance of establishing a laboratory-based complementary dual-isotope tool to evaluate short- as well as long-term bone remodeling in an in vivo model. To address this need, a liquid scintillation dual-label method was investigated using different scintillation cocktails for quantitative measurement of (3)H-tetracycline ((3)H-TC) and (45)Ca as markers of bone turnover in mice. Individual samples were prepared over a wide range of known (45)Ca/(3)H activity ratios. Results showed that (45)Ca/(3)H activity ratios determined experimentally by the dual-label method were comparable to the known activity ratios (percentage difference ∼2%), but large variations were found in samples with (45)Ca/(3)H activity ratios in range of 2-10 (percentage difference ∼20-30%). Urine and fecal samples from mice administered with both (3)H-TC and (45)Ca were analyzed with the dual-label method. Positive correlations between (3)H and (45)Ca in urine (R=0.93) and feces (R=0.83) indicate that (3)H-TC and (45)Ca can be interchangeably used to monitor longitudinal in vivo skeletal remodeling.