Returning to overuse activity following a supraspinatus and infraspinatus tear leads to joint damage in a rat model

Authors

Katherine E. Reuther, Stephen J. Thomas, Elisabeth F. Evans, Jennica J. Tucker, Joseph J. Sarver, Sarah Ilkhani-Pour, Chancellor F. Gray, Pramod B. Voleti, David L. Glaser, Louis J. Soslowsky

Abstract

Large rotator cuff tears (supraspinatus and infraspinatus) are common in patients who perform overhead activities (laborers, athletes). In addition, following large cuff tears, these patients commonly attempt to return to pre-injury activity levels. However, there is a limited understanding of the damaging effects on the uninjured joint tissues when doing so. Therefore, the objective of this study was to investigate the effect of returning to overuse activity following a supraspinatus and infraspinatus tear on shoulder function and the structural and biological properties of the intact tendons and glenoid cartilage. Forty rats underwent 4 weeks of overuse followed by detachment of the supraspinatus and infraspinatus tendons and were then randomized into two groups: return to overuse or cage activity. Ambulatory measurements were performed over time and structural and biological properties of the adjacent tendons and cartilage were evaluated. Results demonstrated that animals returning to overuse activity did not have altered shoulder function but despite this, did have altered cartilage and tendon properties. These mechanical changes corresponded to altered transcriptional regulation of chondrogenic genes within cartilage and tendon. This study helps define the mechanical and biological mechanisms leading to joint damage and provides a framework for treating active cuff tear patients.

Link to Article

http://dx.doi.org/10.1016/j.jbiomech.2013.05.007

Eldecalcitol, a vitamin D analog, reduces bone turnover and increases trabecular and cortical bone mass, density, and strength in ovariectomized cynomolgus monkeys

Authors

Susan Y. Smith, Nancy Doyle, Marilyne Boyer, Luc Chouinard, Hitoshi Saito

Abstract

Vitamin D insufficiency is common in elderly people worldwide, and intake of supplementary calcium and vitamin D is recommended to those with a high risk of fracture. Several clinical studies and meta-analyses have shown that calcium and vitamin D supplementation reduces osteoporotic fractures, and a strong correlation exists between vitamin D status and fracture risk. Vitamin D supplementations improve calcium balance in the body; however, it remains unclear whether vitamin D directly affects bone metabolism. Recently, eldecalcitol (ELD), an active form of vitamin D analog, has been approved for the treatment of osteoporosis in Japan. A 3-year clinical trial showed ELD treatment increased lumbar spine bone mineral density (BMD) and reduced fracture risk in patients with osteoporosis. To evaluate the mechanism of ELD action in bone remodeling, ovariectomized cynomolgus monkeys were treated with 0.1 or 0.3 μg/day of ELD for 6 months. This treatment increased lumbar BMD by 4.4% and 10.2%, respectively, and suppressed ovariectomy-induced increases in bone turnover markers compared to OVX-vehicle control. Histomorphometric analysis of bone revealed that both bone formation parameters and bone resorption parameters in the trabecular bone of the lumbar vertebrae were suppressed by ELD treatment. ELD treatment also improved biomechanical properties of the lumbar vertebrae and the femoral neck in the ovariectomized cynomolgus monkeys. These results indicate that, in a bone-remodeling animal model, ELD increases BMD and improves bone biomechanical properties by normalizing bone turnover. Therefore, ELD has a direct and potentially beneficial effect on bone metabolism.

Link to Article

http://dx.doi.org/10.1016/j.bone.2013.06.005

The Effect of Implant Shape and Screw Pitch on Microdamage in Mandibular Bone

Authors

Chendi Xu BDS, MS, Zhong Wei BS, Nizhou Liu BDS, MS, Fei Sun BDS, MS, Hui Chen BDS, Tingting Lin BDS, MS, Baowei Zhang DDS, Tingting Tang MD, PhD, Eryi Lu DDS, PhD

Abstract

The aim of this study was to investigate the effect of implant shape and screw pitch on microdamage in bone during insertion of dental implants. Thirty custom-made implants (length, 10 mm; diameters, 4.1 mm; cylindrical, tapered, and taper-cylindrical shapes; screw pitches, 1.25 and 0.8 mm; classified as 1.25C, 0.8C, 1.25T, 0.8T, 1.25TC, 0.8TC) were placed with a surgical device in the mandibles of eight goats. Two implant sites were prepared in the edentulous area on each side of the mandible. Implants were placed in a randomized order. Immediately after placement of the implants, the bone blocks with the implants were collected, bulk stained with basic fuchsin, embedded in methyl methacrylate, and sectioned. Histomorphometric quantification of the microcrack length (Cr.Le, μm); microcrack surface density (Cr.Le/B.Ar, μm/mm2), and damaged bone area fraction (DB.Ar/B.Ar, %) were measured. The Cr.Le, Cr.Le/B.Ar, and DB.Ar/B.Ar values of 0.8TC group were 80.96 ± 17.55, 478.75 ± 51.85, and 4.40 ± 0.36, respectively. All these parameters of microdamage induced by 0.8TC were significantly lower than those induced by other five types of implants (p < .05). Taper-cylindrical implants with 0.8 mm screw pitch caused the least microdamage to the bone in comparison with the other five types of implants during placement of implants.

Link to Article

http://dx.doi.org/10.1111/cid.12100

Effects of menopausal hormonal therapy on occult breast tumors

Authors

Richard J. Santen, Yan Song, Wei Yue, Ji-Ping Wang, Daniel F. Heitjan

Abstract

An estimated 7% of 40–80 year old women dying of unrelated causes harbor occult breast tumors at autopsy. These lesions are too small to be detected by mammography, a method which requires tumors to be approximately 1 cm in diameter to be diagnosed. Tumor growth rates, as assessed by “effective doubling times” on serial mammography range from 10 to >700 days with a median of approximately 200 days. We previously reported two models, based on iterative analysis of these parameters, to describe the biologic behavior of undiagnosed, occult breast tumors. One of our models is biologically based and includes parameters of a 200 day effective doubling time, 7% prevalence of occult tumors in the 40-80 aged female population and a detection threshold of 1.16 cm and the other involves computer based projections based on age related breast cancer incidence. Our models facilitate interpretation of the Women's Health Initiative (WHI) and anti-estrogen prevention studies. The biologically based model suggests that menopausal hormone therapy with conjugated equine estrogens plus medroxyprogesterone acetate (MPA) in the WHI trial primarily promoted the growth of pre-existing, occult lesions and minimally initiated de novo tumors. The paradoxical reduction of breast cancer incidence in women receiving estrogen alone is consistent with a model that this hormone causes apoptosis in women deprived of estrogen long term as a result of the cessation of estrogen production after the menopause. Understanding of the kinetics of occult tumors suggests that breast cancer “prevention” with anti-estrogens or aromatase inhibitors represents early treatment rather than a reduction in de novo tumor formation. Our in vivo data suggest that the combination of a SERM, bazedoxifene (BZA), with conjugated equine estrogen (CEE) acts to block maturation of the mammary gland in oophorectomized, immature mice. This hormonal combination is defined by the generic term, tissue selective estrogen complex or TSEC. Xenograft studies with the BZA/CEE combination show that it blocks the growth of occult, hormone dependent tumors in nude mice. These pre-clinical data suggest that the BZA/CEE TSEC combination may prevent the growth of occult breast tumors in women. Based on the beneficial effects of this TSEC combination on symptoms and fracture prevention in menopausal women, the combination of BZA/CEE might be used as a means both to treat menopausal symptoms and to prevent breast cancer.

Link to Article

http://dx.doi.org/10.1016/j.jsbmb.2013.05.008

Short-courses of dexamethasone abolish bisphosphonate-induced reductions in bone toughness

Authors

Tianyi D. Luo and Matthew R. Allen

Abstract

Atypical femoral fractures, which display characteristics of brittle material failure, have been associated with potent remodeling suppression drugs. Given the millions of individuals treated with this class of drugs it is likely that other factors play a role in these fractures. Some evidence suggests concomitant use of corticosteroids may contribute to the pathogenesis although data in this area is lacking. The goal of this study was to assess the combined role of bisphosphonates and dexamethasone on bone mechanical properties. Skeletally mature beagle dogs were either untreated controls, or treated with zoledronic acid (ZOL), dexamethasone (DEX), or ZOL + DEX. Zoledronic acid (0.06 mg/kg) was given monthly via IV infusion for 9 months. DEX (5 mg) was administered daily for one week during each of the last three months of the 9 month experiment. Ribs were harvested and assessed for bone geometry, mechanical properties, and remodeling rate (n=3-6 specimens per group). DEX significantly suppressed intracortical remodeling compared to vehicle controls while both ZOL and the combination of DEX+ZOL nearly abolished intracortical remodeling. ZOL treatment resulted in significantly lower bone toughness, determined from 3-point bending tests, compared to all other treatment groups while the toughness in ZOL+DEX animals was identical to those of untreated controls. These findings suggest not only that short-courses of dexamethasone do not adversely affect toughness in the setting of bisphosphonates, they actually reverse the adverse effects of its treatment. Understanding the mechanism for this tissue-level effect could lead to novels approaches for reducing the risk of atypical femoral fractures.

Link to Article

http://www.iupui.edu/~bonelab/BONE-accepted%20version.pdf

Epithelial 11β-hydroxysteroid dehydrogenase type II deletion inhibits Apc+/min mouse tumorigenesis via COX-2 pathway inhibition and induction of G1 cell cycle arrest

Authors

Li Jiang, Shilin Yang, Huiyong Yin, Xiaofeng Fan, Suwan Wang, Bing Yao, Ambra Pozzi, Xiaoping Chen, Raymond C. Harris, and Ming-Zhi Zhang

Abstract

Cyclooxygenase-2 (COX-2)-derived prostaglandin E2 (PGE2) promotes colorectal tumorigenesis. Glucocorticoids are endogenous and potent COX-2 inhibitors, and their local actions are down-regulated by 11beta-hydroxysteroid dehydrogenase type II (11ßbetaHSD2)-mediated metabolism. We previously reported that 11betaHSD2 increased in human colonic and Apc+/min mouse intestinal adenomas and correlated with increased COX-2 expression and activity, and 11betaHSD2 inhibition suppressed the COX-2 pathway and decreased tumorigenesis. 11betaHSD2 is expressed in Apc+/min mouse intestinal adenoma stromal and epithelial cells. We generated Apc+/min mice with selective deletion of 11betaHSD2 in intestinal epithelial cells (Vil-HSD2-/- Apc+/min). 11betaHSD2 deletion in intestinal epithelia led to marked inhibition of Apc+/min mouse intestinal tumorigenesis. Immunostaining indicated decreased 11ßHSD2 and COX-2 expression in adenoma epithelia, while stromal COX-2 expression was intact in Vil-HSD2-/- Apc+/min mice. In Vil-HSD2-/- Apc+/min mouse intestinal adenomas, both p53 and p21 mRNA and protein levels were increased, with concomitant decrease in phosphorylation of retinoblastoma protein, indicating glucocorticoid-mediated G1 cell cycle arrest. Regulated in development and DNA damage responses 1 (REDD1), a novel stress-induced gene that inhibits mammalian target of rapamycin (mTOR) signaling pathway, was increased, while the mTOR signaling pathway was inhibited. Therefore, in Vil-HSD2-/- Apc+/min mice, epithelial cell 11betaHSD2 deficiency leads to inhibition of adenoma initiation and growth by attenuation of COX-2 expression, increased G1 cell cycle arrest and inhibition of mTOR signaling as a result of increased tumor intracellular active glucocorticoids. 11betaHSD2 inhibition may represent a novel approach for colorectal cancer chemoprevention by increasing tumor glucocorticoid activity, which in turn inhibits tumor growth by multiple pathways.

Link to Article

http://dx.doi.org/10.1158/1541-7786.MCR-13-0084-T