Parathyroid hormone signaling in mature osteoblasts/osteocytes protects mice from age-related bone loss.

Aging is accompanied by osteopenia, characterized by reduced bone formation and increased bone resorption. Osteocytes, the terminally differentiated osteoblasts, are regulators of bone homeostasis, and parathyroid hormone (PTH) receptor (PPR) signaling in mature osteoblasts/osteocytes is essential for PTH-driven anabolic and catabolic skeletal responses. However, the role of PPR signaling in those cells during aging has not been investigated. The aim of this study was to analyze the role of PTH signaling in mature osteoblasts/osteocytes during aging. Mice lacking PPR in osteocyte (Dmp1-PPRKO) display an age-dependent osteopenia characterized by a significant decrease in osteoblast activity and increase in osteoclast number and activity. At the molecular level, the absence of PPR signaling in mature osteoblasts/osteocytes is associated with an increase in serum sclerostin and a significant increase in osteocytes expressing 4-hydroxy-2-nonenals, a marker of oxidative stress. In Dmp1-PPRKO mice there was an age-dependent increase in p16Ink4a/Cdkn2a expression, whereas it was unchanged in controls. In vitro studies demonstrated that PTH protects osteocytes from oxidative stress-induced cell death. In summary, we reported that PPR signaling in osteocytes is important for protecting the skeleton from age-induced bone loss by restraining osteoclast's activity and protecting osteocytes from oxidative stresses.

Strategies in the transfer of varying grades of vitrified-warmed blastocysts in women aged over 35 years: A propensity-matched analysis.

AIM: For in vitro fertilization, the optimal number of blastocysts to transfer according to blastocyst grade has not been well established, especially with respect to vitrified-warmed blastocyst transfer (VBT) in women aged over 35 years. This study aimed to compare the pregnancy and neonatal outcomes for three different VBT methods with variable numbers and qualities of blastocysts in women aged over 35 years. METHODS: All VBT cycles were categorized into three groups according to blastocyst grade: GG (two good-quality blastocysts transferred), GP (one good-quality blastocyst transferred with one of poor quality) and GS (one good-quality blastocyst transferred). Blastocysts graded greater than or equal to 3BB were considered good quality. We conducted three 1:1 propensity score-matched analyses (GG vs GS, GP vs GS and GG vs GP) to compare the clinical pregnancy rate (CPR), live birth rate (LBR), multiple pregnancy rate (MPR), preterm birth rate and low birthweight rate. RESULTS: Compared to GS, GG had higher CPR and LBR; however, MPR was also higher with GG. There were no significant differences, except implantation rate and MPR between GP and GS. Although implantation rate and CPR with GG were higher than those with GP, there were no significant differences in LBR and MPR. CONCLUSION: To reduce high MPR after double blastocyst transfer methods, single good-quality blastocyst transfers are recommended in the VBT of women aged over 35 years. Transferring a good blastocyst with a poor one should be avoided because it confers no advantage.

Prevalence of radiologic superior canal dehiscence in normal ears and ears with chronic otitis media.

OBJECTIVES/HYPOTHESIS: Although labyrinth fistulae are caused mostly by cholesteatoma, they can occur in long-standing chronic otitis media (COM) without cholesteatoma. We aimed to compare the prevalence of radiologic SCD on computed tomography (CT) between normal ears and contralateral COM ears in patients with unilateral COM and to assess the prevalence of superior canal dehiscence (SCD) according to the age. STUDY DESIGN: Case series with comparison performed at a tertiary care academic referral center. METHODS: We retrospectively reviewed consecutive temporal bone CT scans of 759 patients with unilateral COM between 2009 and 2011. The mean (± standard deviation) age was 48 years (±14 years). Images were independently evaluated by two otologists, and the bone overlying the superior canal was characterized as normal, suspicious, or definite SCD. RESULTS: The prevalence (3.4%) of definite SCD in COM ears was significantly higher than that (0.3%) in normal ears. The prevalence (6.6%) of suspicious or definite SCD in COM ears was also higher than that (1.2%) in normal ears. There was no correlation between the prevalence of SCD and age in either normal or COM ears. All of the normal ears with suspicious or definite SCD also showed contralateral suspicious or definite SCD (bilateral involvement). CONCLUSIONS: Our present findings suggest that the COM is related to the presence of SCD. The roof of the temporal bone may become thin by the failure of postnatal bone development and susceptible to chronic brain pulsation and pressure exerted by the temporal lobe in COM ears.

Targeted mutation of mouse skeletal muscle sodium channel produces myotonia and potassium-sensitive weakness.

Hyperkalemic periodic paralysis (HyperKPP) produces myotonia and attacks of muscle weakness triggered by rest after exercise or by K+ ingestion. We introduced a missense substitution corresponding to a human familial HyperKPP mutation (Met1592Val) into the mouse gene encoding the skeletal muscle voltage-gated Na+ channel NaV1.4. Mice heterozygous for this mutation exhibited prominent myotonia at rest and muscle fiber-type switching to a more oxidative phenotype compared with controls. Isolated mutant extensor digitorum longus muscles were abnormally sensitive to the Na+/K+ pump inhibitor ouabain and exhibited age-dependent changes, including delayed relaxation and altered generation of tetanic force. Moreover, rapid and sustained weakness of isolated mutant muscles was induced when the extracellular K+ concentration was increased from 4 mM to 10 mM, a level observed in the muscle interstitium of humans during exercise. Mutant muscle recovered from stimulation-induced fatigue more slowly than did control muscle, and the extent of recovery was decreased in the presence of high extracellular K+ levels. These findings demonstrate that expression of the Met1592ValNa+ channel in mouse muscle is sufficient to produce important features of HyperKPP, including myotonia, K+-sensitive paralysis, and susceptibility to delayed weakness during recovery from fatigue.

Decreased metallation and activity in subsets of mutant superoxide dismutases associated with familial amyotrophic lateral sclerosis.

Over 90 different mutations in the gene encoding copper/zinc superoxide dismutase (SOD1) cause approximately 2% of amyotrophic lateral sclerosis (ALS) cases by an unknown mechanism. We engineered 14 different human ALS-related SOD1 mutants and obtained high yields of biologically metallated proteins from an Sf21 insect cell expression system. Both the wild type and mutant "as isolated" SOD1 variants were deficient in copper and were heterogeneous by native gel electrophoresis. By contrast, although three mutant SOD1s with substitutions near the metal binding sites (H46R, G85R, and D124V) were severely deficient in both copper and zinc ions, zinc deficiency was not a consistent feature shared by the as isolated mutants. Eight mutants (A4V, L38V, G41S, G72S, D76Y, D90A, G93A, and E133 Delta) exhibited normal SOD activity over pH 5.5-10.5, per equivalent of copper, consistent with the presumption that bound copper was in the proper metal-binding site and was fully active. The H48Q variant contained a high copper content yet was 100-fold less active than the wild type enzyme and exhibited a blue shift in the visible absorbance peak of bound Cu(II), indicating rearrangement of the Cu(II) coordination geometry. Further characterization of these as-isolated SOD1 proteins may provide new insights regarding mutant SOD1 enzyme toxicity in ALS.