The effects of hypothyroidism on the proximal femoral physis in miniature swine.

As a potential means of comparing hypothyroidism in humans, this work intended to establish a defined hypothyroid state in immature miniature swine and evaluate specific molecular, cellular, and extracellular responses of their growth plates. Two male, 11-week-old Sinclair miniature swine were given 6-propyl-2-thiouracil (PTU) in their water and two other like animals (controls) were provided water without PTU. Blood levels of thyroid stimulating hormone (TSH), triiodothyronine (T3), and thyroxin (T4) were monitored weekly. At 25 weeks of age, the hind limb proximal femoral physes were harvested and divided into portions for histology and reverse transcription-quantitative polymerase chain reaction (RT-qPCR) analysis. Compared to controls, swine administered PTU exhibited increased TSH and decreased T3 and T4 serum levels during the study period, features consistent with a hypothyroid state. Compared to controls, hypothyroid swine exhibited structurally altered physes and demonstrated significantly decreased gene expression of aggrecan (p < 0.05) and type X collagen (p ≤ 0.1). This is the first hypothyroid model established in miniature swine and represents a potentially important advance for understanding the condition in humans, in which, like this swine model, there are changes critical to growth plate molecular biology, biochemistry and structure.

New biomaterial as a promising alternative to silicone breast implants.

One in eight American women develops breast cancer. Of the many patients requiring mastectomy yearly as a consequence, most elect some form of breast reconstruction. Since 2006, only silicone breast implants have been approved by the FDA for the public use. Unfortunately, over one-third of women with these implants experience complications as a result of tissue-material biocompatibility issues, which may include capsular contracture, calcification, hematoma, necrosis and implant rupture. Our group has been working on developing alternatives to silicone. Linear triblock poly(styrene-b-isobutylene-b-styrene) (SIBS) polymers are self-assembling nanostructured thermoplastic rubbers, already in clinical practice as drug eluting stent coatings. New generations with a branched (arborescent or dendritic) polyisobutylene core show promising potential as a biomaterial alternative to silicone rubber. The purpose of this pre-clinical research was to evaluate the material-tissue interactions of a new arborescent block copolymer (TPE1) in a rabbit implantation model compared to a linear SIBS (SIBSTAR 103T) and silicone rubber. This study is the first to compare the molecular weight and molecular weight distribution, tensile properties and histological evaluation of arborescent SIBS-type materials with silicone rubber before implantation and after explantation.

Serum folate: a pharmacodynamic biomarker of intracellular nitrosylcobalamin activity following intravenous administration in dogs.

BACKGROUND/AIM: Cobalamin and folate are interdependent co-factors of the methionine synthase pathway. This study evaluated the effect of intravenously-administered nitrosylcobalamin (NO-Cbl), a vitamin B12 analog, on serum folate concentrations in healthy dogs. MATERIALS AND METHODS: Four dogs received a 10-mg/kg, 20-mg/kg and 40-mg/kg intravenous bolus dose of NO-Cbl, with a 14-day washout period between doses. Blood samples were collected at baseline and post-dosing, and serum cobalamin and folate concentrations were measured. RESULTS: For each dose, serum cobalamin concentrations were inversely correlated with serum folate concentrations. Spearman rank correlation co-efficient values were -0.976 (10 mg/kg, p<0.0096), and -1.0 (20 mg/kg, p<0.008; 40 mg/kg, p<0.0046). CONCLUSION: Cellular uptake of NO-Cbl, following intravenous administration exerted a biological effect on folate, similar to that previously described for other vitamin B12 analogs. Serum folate concentration may serve as a pharmacodynamic biomarker of intracellular nitrosylcobalamin activity following intravenous administration.

Pharmacokinetics of intravenous nitrosylcobalamin, an antitumor agent, in healthy Beagle dogs: a pilot study.

BACKGROUND/AIM: Nitrosylcobalamin (NO-Cbl) is a cobalamin-based anti-tumor agent. This study evaluated the pharmacokinetic parameters of NO-Cbl following intravenous administration in dogs. MATERIALS AND METHODS: Four dogs received 10 mg/kg, 20 mg/kg and 40 mg/kg intravenous bolus doses of NO-Cbl, with a 14-day washout period between doses. Blood samples were collected at baseline and post-dosing, and noncompartmental pharmacokinetic parameters were determined. RESULTS: Average peak serum concentrations of 2265, 5523 and 13,866 pg/mL were achieved following single-dose bolus intravenous administration of 10 mg/kg, 20 mg/kg and 40 mg/kg of NO-Cbl respectively. The average area under the curve was 12,697 h × pg/mL, 24,497 h × pg/mL and 44,976 h × pg/mL respectively, with an average elimination half-life of 16.2 h, 13.5 h and 13.1 h respectively. CONCLUSION: These results can be used to determine the dose and dosing intervals for clinical trials evaluating NO-Cbl in humans and companion animals.

A study in vivo of the effects of a static compressive load on the proximal tibial physis in rabbits.

BACKGROUND: The effect of compression on the physis is generally defined by the Hueter-Volkmann principle, in which decreased linear growth of the physis results from increased compression. This investigation examined whether mechanically induced compression of rabbit physes causes changes in gene expression, cells, and extracellular components that promote physeal resilience and strength (type-II collagen and aggrecan) and cartilage hypertrophy (type-X collagen and matrix metalloprotease-13). METHODS: Static compressive loads (10 N or 30 N) were applied for two or six weeks across one hind limb proximal tibial physis of thirteen-week-old female New Zealand White rabbits (n = 18). The contralateral hind limb in all rabbits underwent sham surgery with no load to serve as an internal control. Harvested physes were divided into portions for histological, immunohistochemical, and quantitative reverse transcription-polymerase chain reaction analysis. Gene expression was statistically analyzed by means of comparisons between loaded samples and unloaded shams with use of analysis of variance and a Tukey post hoc test. RESULTS: Compared with unloaded shams, physes loaded at 10 N or 30 N for two weeks and at 10 N for six weeks showed histological changes in cells and matrices. Physes loaded at 30 N for six weeks were decreased in thickness and had structurally disorganized chondrocyte columns, a decreased extracellular matrix, and less intense type-II and X collagen immunohistochemical staining. Quantitative reverse transcription-polymerase chain reaction analysis of loaded samples compared with unloaded shams yielded a significantly (p ≤ 0.05) decreased gene expression of aggrecan and type-II and X collagen and no significant (p > 0.05) changes in the matrix metalloprotease-13 gene expression with increasing load. CONCLUSIONS: Compressed rabbit physes generate biochemical changes in collagens, proteoglycan, and cellular and tissue matrix architecture. Changes potentially weaken overall physeal strength, consistent with the Hueter-Volkmann principle, and lend understanding of the causes of pathological conditions of the physis.

Beta-adrenoceptor stimulation of alveolar fluid clearance is increased in rats with heart failure.

The alveolar epithelium plays a critical role in resolving pulmonary edema. We thus hypothesized that its function might be upregulated in rats with heart failure, a condition that severely challenges the lung's ability to maintain fluid balance. Heart failure was induced by left coronary artery ligation. Echocardiographic and cardiovascular hemodynamics confirmed its development at 16 wk postligation. At that time, alveolar fluid clearance was measured by an increase in protein concentration over 1 h of a 5% albumin solution instilled into the lungs. Baseline alveolar fluid clearance was similar in heart failure and age-matched control rats. Terbutaline was added to the instillate to determine whether heart failure rats responded to beta-adrenoceptor stimulation. Alveolar fluid clearance in heart failure rats was increased by 194% after terbutaline stimulation compared with a 153% increase by terbutaline in control rats. To determine the mechanisms responsible for this accelerated alveolar fluid clearance, we measured ion transporter expression (ENaC, Na-K- ATPase, CFTR). No significant upregulation was observed for these ion transporters in the heart failure rats. Lung morphology showed significant alveolar epithelial type II cell hyperplasia in heart failure rats. Thus, alveolar epithelial type II cell hyperplasia is the likely explanation for the increased terbutaline-stimulated alveolar fluid clearance in heart failure rats. These data provide evidence for previously unrecognized mechanisms that can protect against or hasten resolution of alveolar edema in heart failure.

Type VI collagen induces cardiac myofibroblast differentiation: implications for postinfarction remodeling.

Cardiac fibroblast (CF) proliferation and differentiation into hypersecretory myofibroblasts can lead to excessive extracellular matrix (ECM) production and cardiac fibrosis. In turn, the ECM produced can potentially activate CFs via distinct feedback mechanisms. To assess how specific ECM components influence CF activation, isolated CFs were plated on specific collagen substrates (type I, III, and VI collagens) before functional assays were carried out. The type VI collagen substrate potently induced myofibroblast differentiation but had little effect on CF proliferation. Conversely, the type I and III collagen substrates did not affect differentiation but caused significant induction of proliferation (type I, 240.7 +/- 10.3%, and type III, 271.7 +/- 21.8% of basal). Type I collagen activated ERK1/2, whereas type III collagen did not. Treatment of CFs with angiotensin II, a potent mitogen of CFs, enhanced the growth observed on types I and III collagen but not on the type VI collagen substrate. Using an in vivo model of myocardial infarction (MI), we measured changes in type VI collagen expression and myofibroblast differentiation after post-MI remodeling. Concurrent elevations in type VI collagen and myofibroblast content were evident in the infarcted myocardium 20-wk post-MI. Overall, types I and III collagen stimulate CF proliferation, whereas type VI collagen plays a potentially novel role in cardiac remodeling through facilitation of myofibroblast differentiation.