Microsphere-based gradient implants for osteochondral regeneration: a long-term study in sheep.

BACKGROUND: The microfracture technique for cartilage repair has limited ability to regenerate hyaline cartilage. AIM: The current study made a direct comparison between microfracture and an osteochondral approach with microsphere-based gradient plugs. MATERIALS & METHODS: The PLGA-based scaffolds had opposing gradients of chondroitin sulfate and ß-tricalcium phosphate. A 1-year repair study in sheep was conducted. RESULTS: The repair tissues in the microfracture were mostly fibrous and had scattered fissures with degenerative changes. Cartilage regenerated with the gradient plugs had equal or superior mechanical properties; had lacunated cells and stable matrix as in hyaline cartilage. CONCLUSION: This first report of gradient scaffolds in a long-term, large animal, osteochondral defect demonstrated potential for equal or better cartilage repair than microfracture.

Functional Reconstruction of Tracheal Defects by Protein-Loaded, Cell-Seeded, Fibrous Constructs in Rabbits.

Tracheal stenosis is a life-threatening disease and current treatments include surgical reconstruction with autologous rib cartilage and the highly complex slide tracheoplasty surgical technique. We propose using a sustainable implant, composed of a tunable, fibrous scaffold with encapsulated chondrogenic growth factor (transforming growth factor-beta3 [TGF-ß3]) or seeded allogeneic rabbit bone marrow mesenchymal stromal cells (BMSCs). In vivo functionality of these constructs was determined by implanting them in induced tracheal defects in rabbits for 6 or 12 weeks. The scaffolds maintained functional airways in a majority of the cases, with the BMSC-seeded group having an improved survival rate and the Scaffold-only group having a higher occurrence of more patent airways as determined by microcomputed tomography. The BMSC group had a greater accumulation of inflammatory cells over the graft, while also exhibiting normal epithelium, subepithelium, and cartilage formation. Overall, it was concluded that a simple, acellular scaffold is a viable option for tracheal tissue engineering, with the intraoperative addition of cells being an optional variation to the scaffolds.

An Algorithm to Analyze Cost Heterogeneity using Counterfactual Scenarios in Endovascular versus Open Repair of Abdominal Aortic Aneurysm: Predicting Costs for Subsequent Patients.

Objectives: We examined patient-specific predictors of high cost for endovascular (EVAR) and open (OPEN) repair of abdominal aortic aneurysm (AAA). Methods: Vascular Study Group of Northern New England data specific to Fletcher Allen Health Care were merged with cost data from the same source. We retrospectively analyzed 389 elective AAA repairs (230 EVAR, 159 OPEN) between 2003 and 2011 to determine clinical characteristics that contribute to membership in the upper quartile of cost (UQC) versus the remaining three quartiles. For the purpose of this exercise, it was assumed that clinical outcomes were equally good with EVAR versus OPEN repair. Results: Significant predictors of UQC for OPEN repair procedures were: history of treated chronic obstructive pulmonary disease (COPD), previous bypass surgery, transfer from hospital and age >70 (area under receiver operating curve [ROC] = 0.726). Predictors of UQC for EVAR were: presence of iliac aneurysm(s), coronary artery bypass graft surgery or percutaneous transluminal coronary angioplasty within the past 5 years, ejection fraction ≤30%, absence of beta blockers, creatinine ≥1.5mg/dL, and current use of tobacco (area under ROC = 0.784). The mean length of stay for EVAR and OPEN repair were 2.22 and 8.55 days, respectively. Costs for EVAR and OPEN repair were $32,656 (standard error of the mean [SEM] $591) and $28,183 (SEM $1,571), respectively. Conclusions: Certain risk factors at the individual patient level are predictive of UQC. Under such circumstances, it is our expectation that such algorithms may be used to select the most cost-efficient treatment.

Possible role of creatine concentrations in the brain in regulating appetite and weight.

Cobaltic protoporphyrin IX (CoPP) is a synthetic heme analog which can elicit profound and prolonged decreases in appetite and body weight in several different animal species. Intracerebroventricular administration of CoPP in rats was found, by differential display and confirmed by Real-Time PCR, to result in an increase in expression of the creatine transporter when compared to vehicle-treated fed or vehicle-treated fasted control animals. In situ hybridization studies showed that creatine transporter mRNA concentrations were increased in several areas of the brain involved in the regulation of food intake, but creatine concentrations were decreased in hypothalamic homogenates in CoPP-treated animals compared to controls. Intracerebroventricular administration of beta-guanidinopropionic acid, a compound known to decrease intracellular creatine concentration by competition for uptake, resulted in decreased food intake and body weight and increased Fos expression in the hypothalamus. Taken together, these findings suggest that creatine concentrations in the brain may play a role in regulating food intake and body weight.

The weight loss elicited by cobalt protoporphyrin is related to decreased activity of nitric oxide synthase in the hypothalamus.

Administration of cobaltic protoporphyrin IX (CoPP) into the third ventricle of the brain by intracerebroventricular injection in rodents is known to result in transient hypophagia and remarkably prolonged weight loss. The mechanism of action of CoPP in eliciting these effects is unknown. It is known that nitric oxide plays a role in food intake and that the hyperphagia that results from a wide variety of genetic, physiological, and pharmacological stimuli can be blocked by the administration of inhibitors of the enzyme nitric oxide synthase (NOS). We demonstrate that intracerebroventricular administration of compounds that alter nitrergic tone can also change food ingestion and weight gain patterns in normophagic rats. We also demonstrate that CoPP decreases NOS activity but that it paradoxically increases neuronal NOS transcript expression and increases neuronal NOS protein content on Western blotting.

Advancing age and other factors influencing the balance between amino acid requirements and toxicity.

As the average human lifespan increases, so does the recognition that advancing age is associated with changes in nutrient intake and requirements as a consequence of biological, social, and pathological factors. Studies show that whereas protein requirements may not differ significantly between younger and older adults, the adaptive mechanisms and responses to nutritional or pathological stressors may differ and alter the balance between requirement and toxicity of specific amino acids (AAs). As an individual gets older, cardiovascular disease and cancer become the leading causes of morbidity and mortality. Advancing age is also associated with changes in appetite, food intake, and physical activity, all of which can influence protein and AA metabolism. The sulfur amino acids (SAAs) methionine and cysteine recently attracted attention because of their pivotal roles in methyl group metabolism and maintenance of the cellular redox state. Methionine, an indispensable AA, is important for methylation reactions and as a precursor for cysteine, which is the rate-limiting AA for glutathione (GSH) synthesis. On one hand, high intake levels or blood concentrations of methionine are associated with adverse consequences such as hyperhomocysteinemia and endothelial dysfunction, which are risk factors for cardiovascular disease. On the other hand, methionine deficiency is reported to lower the threshold of chemical-induced toxicity and play a role in carcinogenesis. Therefore, it is evident that understanding the biological significance of the interrelationship between SAAs, GSH, and methyl group metabolism is key to determining optimal dietary intakes of SAAs in older individuals.

Prolonged retention of the anorectic cobalt protoporphyrin in the hypothalamus and the resulting expression of Fos.

The anorectic cobalt protoporphyrin (CoPP) is known to elicit short-term hypophagia and long-term weight loss through unknown mechanisms in the brains of experimental animals. The goal of this work was to determine 1) if the prolonged duration of action of CoPP is related to its prolonged retention within the brain; and 2) with the use of immunohistochemical detection of Fos, the product of the early-immediate gene c-fos, which cells are activated after exposure to CoPP. These studies were carried out in male rats after intracerebroventricular administration of CoPP, 0.4 micromol/kg body wt, given under light halothane anesthesia. Residence of CoPP in the brain was determined by residual counts in dissected brains of (57)CoPP-injected rats. Fos immunoreactivity was mapped in coronal sections of rat brains 4-6 h after injection with CoPP. The results showed that (57)CoPP was retained in the hypothalamus preferentially compared with the cortex of the brain and could be detected in the hypothalamus for in excess of 5 wk. Fos activation was increased by CoPP, detected predominantly in neuronal rather than glial cells, and was markedly more robust in the hypothalamus than in other brain areas. Thus CoPP remains in the hypothalamus for prolonged periods and activates Fos expression in the hypothalamus.