Attenuation of Corpus Callosum Axon Myelination and Remyelination in the Absence of Circulating Sex Hormones

Sex differences in the structure and organization of the corpus callosum (CC) can be attributed to genetic, hormonal or environmental effects, or a combination of these factors. To address the role of gonadal hormones on axon myelination, functional axon conduction and immunohistochemistry analysis of the CC in intact, gonadectomized and hormone‐replaced gonadectomized animals were used. These groups were subjected to cuprizone diet‐induced demyelination followed by remyelination. The myelinated component of callosal compound action potential was significantly decreased in ovariectomized and castrated animals under normal myelinating condition. Compared to gonadally intact cohorts, both gonadectomized groups displayed more severe demyelination and inhibited remyelination. Castration in males was more deleterious than ovariectomy in females. Callosal conduction in estradiol‐supplemented ovariectomized females was significantly increased during normal myelination, less attenuated during demyelination, and increased beyond placebo‐treated ovariectomized or intact female levels during remyelination. In castrated males, the non‐aromatizing steroid dihydrotestosterone was less efficient than testosterone and estradiol in restoring normal myelination/axon conduction and remyelination to levels of intact males. Furthermore, in both sexes, estradiol supplementation in gonadectomized groups increased the number of oligodendrocytes. These studies suggest an essential role of estradiol to promote efficient CC myelination and axon conduction in both sexes.     

Combined MEK Inhibition and BMP2 Treatment Promotes Osteoblast Differentiation and Bone Healing in Nf1Osx−/− Mice

Neurofibromatosis type I (NF1) is an autosomal dominant disease with an incidence of 1/3000, caused by mutations in the NF1 gene, which encodes the RAS/GTPase‐activating protein neurofibromin. Non‐bone union after fracture (pseudarthrosis) in children with NF1 remains a challenging orthopedic condition to treat. Recent progress in understanding the biology of neurofibromin suggested that NF1 pseudarthrosis stems primarily from defects in the bone mesenchymal lineage and hypersensitivity of hematopoietic cells to TGFβ. However, clinically relevant pharmacological approaches to augment bone union in these patients remain limited. In this study, we report the generation of a novel conditional mutant mouse line used to model NF1 pseudoarthrosis, in which Nf1 can be ablated in an inducible fashion in osteoprogenitors of postnatal mice, thus circumventing the dwarfism associated with previous mouse models where Nf1 is ablated in embryonic mesenchymal cell lineages. An ex vivo–based cell culture approach based on the use of Nf1^flox/flox bone marrow stromal cells showed that loss of Nf1 impairs osteoprogenitor cell differentiation in a cell‐autonomous manner, independent of developmental growth plate–derived or paracrine/hormonal influences. In addition, in vitro gene expression and differentiation assays indicated that chronic ERK activation in Nf1‐deficient osteoprogenitors blunts the pro‐osteogenic property of BMP2, based on the observation that only combination treatment with BMP2 and MEK inhibition promoted the differentiation of Nf1‐deficient osteoprogenitors. The in vivo preclinical relevance of these findings was confirmed by the improved bone healing and callus strength observed in Nf1_osx^?/? mice receiving Trametinib (a MEK inhibitor) and BMP2 released locally at the fracture site via a novel nanoparticle and polyglycidol‐based delivery method. Collectively, these results provide novel evidence for a cell‐autonomous role of neurofibromin in osteoprogenitor cells and insights about a novel targeted approach for the treatment of NF1 pseudoarthrosis. © 2014 American Society for Bone and Mineral Research.     

Genetics of coronary artery disease – A clinician's perspective

Coronary artery disease (CAD) is the major cause of fatality and disability among all cardiovascular diseases (CVD). Intricate interactions of genes and environment dictate the outcomes of CAD. Technological advances in the different fields of genetics including linkage studies (LS), candidate gene studies (CGS) and genome-wide association studies (GWA studies) have augmented the knowledge of pathogenesis of CAD. LS were more successful in identifying genetic variants among monogenic disease. GWA studies were relatively popular in identification of variation in polygenic disease. Until now, GWA studies recognized about 50 loci determining around 6% of the heritability in CAD. Clinical utility of the above knowledge would result in better CAD management, but validation of the variants in native population is warranted for active adoption into the clinic. The major aim of this review is to provide an adequate perspective of our current understanding and advances of genetics in CAD.     

Aspirin and clopidogrel drug response in patients undergoing percutaneous coronary intervention: the role of dual drug resistance.

We evaluated the response to clopidogrel among aspirin-resistant versus aspirin-sensitive patients undergoing elective coronary stenting. Patients (n = 150) treated with aspirin but not clopidogrel had blood samples drawn at baseline and 24 h after clopidogrel loading. Depending on the definition used, 9% to 15% were resistant to aspirin and 24% to clopidogrel. About half of the aspirin-resistant patients were also resistant to clopidogrel. As a group, aspirin-resistant patients had lower response to clopidogrel (assessed by platelet aggregation and activation markers) than aspirin-sensitive patients. Both aspirin- and clopidogrel-resistant patients had higher incidence of creatine kinase-MB elevation than the respective sensitive patients. OBJECTIVES: We sought to evaluate the response to clopidogrel among aspirin-resistant versus aspirin-sensitive patients undergoing percutaneous coronary intervention (PCI). BACKGROUND: Wide variability has been reported in response to aspirin and clopidogrel. There are limited data on the simultaneous responses to both drugs. METHODS: Elective PCI patients (n = 150) who received aspirin for > or = 1 week but not clopidogrel were included. All patients received bivalirudin during PCI. Blood samples were drawn at baseline and 20 to 24 h after a 300-mg clopidogrel dose. Aspirin resistance was defined by > or = 2 of 3 criteria: rapid platelet function analyzer-ASA score > or = 550, 5 micromol/l adenosine diphosphate (ADP)-induced aggregation > or = 70%, and 0.5 mg/ml arachidonic acid-induced aggregation > or = 20%. Clopidogrel resistance was defined as baseline minus post-treatment aggregation < or = 10% in response to 5 and 20 micromol/l ADP. RESULTS: Nineteen (12.7%) patients were resistant to aspirin and 36 (24%) to clopidogrel. Nine (47.4%) of the aspirin-resistant patients were also clopidogrel resistant. Aspirin-resistant patients were more likely to be women and have diabetes than were aspirin-sensitive patients. They also had lower response to clopidogrel, assessed by platelet aggregation and activation markers (flow cytometry-determined PAC-1 binding and P-selectin expression). Elevation of creatine kinase-myocardial band after stenting occurred more frequently in aspirin-resistant versus aspirin-sensitive patients (38.9% vs. 18.3%; p = 0.04) and in clopidogrel-resistant versus clopidogrel-sensitive patients (32.4% vs. 17.3%; p = 0.06). CONCLUSIONS: Aspirin-resistant patients as a group have reduced response to clopidogrel. Furthermore, we have identified a unique group of dual drug-resistant patients who may be at increased risk for thrombotic complications after PCI.     

Rho kinase regulates the survival and transformation of cells bearing oncogenic forms of KIT, FLT3, and BCR-ABL

We show constitutive activation of Rho kinase (ROCK) in cells bearing oncogenic forms of KIT, FLT3, and BCR-ABL, which is dependent on PI3K and Rho GTPase. Genetic or pharmacologic inhibition of ROCK in oncogene-bearing cells impaired their growth as well as the growth of acute myeloid leukemia patient-derived blasts and prolonged the life span of mice bearing myeloproliferative disease. Downstream from ROCK, rapid dephosphorylation or loss of expression of myosin light chain resulted in enhanced apoptosis, reduced growth, and loss of actin polymerization in oncogene-bearing cells leading to significantly prolonged life span of leukemic mice. In summary we describe a pathway involving PI3K/Rho/ROCK/MLC that may contribute to myeloproliferative disease and/or acute myeloid leukemia in humans.     

Resistance to antiplatelet therapy

Cardiovascular mortality continues to be high and events continue to occur in patients taking antiplatelet medications. Aspirin and clopidogrel have become integral parts of management in patients with coronary artery disease and after percutaneous angioplasty. However, the platelet responses to aspirin and clopidogrel are not uniform. Diminished or lack of response to these agents has been termed aspirin resistance and clopidogrel resistance. These phenomena have tremendous clinical significance as together they may occur in more than 50% of all patients on chronic therapy with aspirin or clopidogrel. Postulated mechanisms of aspirin and clopidogrel resistance include alterations in genetic, pharmacokinetic, and platelet properties. There is a dearth of information in regard to their clinical significance, methods to test them, and strategies to treat them. Further research is necessary in these areas to identify these patients and treat them appropriately.     

Delayed deformation of self-expanding stents after carotid artery stenting for postendarterectomy restenoses

Carotid artery stenting has become an acceptable alternative for treating patients with severe atherosclerotic lesions, particularly those with significant surgical risks, such as recurrent stenosis after endarterectomy. Stent deformation, a phenomenon primarily associated with balloon-expandable stents, is largely avoided by exclusively using self-expanding stents in treating carotid artery stenosis. Nonetheless, we herein report two patients who presented with delayed Wallstent deformation after carotid artery stenting for postendarterectomy restenosis. Our cases highlight the need for caution because delayed deformation of self-expanding stents can occur, particularly during treatment of patients with postendarterectomy stenosis. Furthermore, poststent surveillance is imperative in identifying patients with severe restenosis after carotid artery stenting who need reintervention.     

Histopathologic diversity of Gorlin's cyst: a study of four cases and review of literature

AIM: The purpose of the present article is to discuss four different case reports of the so-called calcifying odontogenic cyst and highlight the histopathological diversity of the same. BACKGROUND: Calcifying odontogenic cyst was first described by Gorlin et al in 1962. Ever since, its identification as a specific odontogenic lesion, controversies and confusions have existed regarding the relationship between cystic lesions and solid tumor masses that share cellular and histomorphologic features. Although several classifications were proposed, dilemma still persists regarding the nature of these lesions as cysts, neoplasms and even malignancies. CONCLUSION AND CLINICAL SIGNIFICANCE: The classifications discussed for the so-called calcifying odontogenic cyst by various authors have only added to further confusion rather than enlightening. Though many authors state that classifications remain only an academic exercise, it definitely has significance in treatment planning. Emphasis should, therefore, be laid on a universally accepted classification.