[A new autosomal-recessive hereditary syndrome. Multiple peripheral pulmonary stenosis, brachytelephalangia, inner-ear deafness, ossification or calcification of cartilages]

Inhibition of endothelial histone deacetylase 2 shifts endothelial-mesenchymal transitions in cerebral arteriovenous malformation models

Cerebral arteriovenous malformations (AVMs) are the most common vascular malformations worldwide and the leading cause of hemorrhagic strokes that may result in crippling neurological deficits. Here, using recently generated mouse models, we uncovered that cerebral endothelial cells (ECs) acquired mesenchymal markers and caused vascular malformations. Interestingly, we found that limiting endothelial histone deacetylase 2 (HDAC2) prevented cerebral ECs from undergoing mesenchymal differentiation and reduced cerebral AVMs. We found that endothelial expression of HDAC2 and enhancer of zeste homolog 1 (EZH1) was altered in cerebral AVMs. These alterations changed the abundance of H4K8ac and H3K27me in the genes regulating endothelial and mesenchymal differentiation, which caused the ECs to acquire mesenchymal characteristics and form AVMs. This investigation demonstrated that the induction of HDAC2 altered specific histone modifications, which resulted in mesenchymal characteristics in the ECs and cerebral AVMs. The results provide insight into the epigenetic impact on AVMs.

Specific heterozygous variants in MGP lead to endoplasmic reticulum stress and cause spondyloepiphyseal dysplasia

Matrix Gla protein (MGP) is a vitamin K-dependent post-translationally modified protein, highly expressed in vascular and cartilaginous tissues. It is a potent inhibitor of extracellular matrix mineralization. Biallelic loss-of-function variants in the MGP gene cause Keutel syndrome, an autosomal recessive disorder characterized by widespread calcification of various cartilaginous tissues and skeletal and vascular anomalies. In this study, we report four individuals from two unrelated families with two heterozygous variants in MGP, both altering the cysteine 19 residue to phenylalanine or tyrosine. These individuals present with a spondyloepiphyseal skeletal dysplasia characterized by short stature with a short trunk, diffuse platyspondyly, midface retrusion, progressive epiphyseal anomalies and brachytelephalangism. We investigated the cellular and molecular effects of one of the heterozygous deleterious variants (C19F) using both cell and genetically modified mouse models. Heterozygous 'knock-in' mice expressing C19F MGP recapitulate most of the skeletal anomalies observed in the affected individuals. Our results suggest that the main underlying mechanism leading to the observed skeletal dysplasia is endoplasmic reticulum stress-induced apoptosis of the growth plate chondrocytes. Overall, our findings support that heterozygous variants in MGP altering the Cys19 residue cause autosomal dominant spondyloepiphyseal dysplasia, a condition distinct from Keutel syndrome both clinically and molecularly.

Regulating the cell shift of endothelial cell-like myofibroblasts in pulmonary fibrosis

Pulmonary fibrosis is a common and severe fibrotic lung disease with high morbidity and mortality. Recent studies have reported a large number of unwanted myofibroblasts appearing in pulmonary fibrosis, and shown that the sustained activation of myofibroblasts is essential for unremitting interstitial fibrogenesis. However, the origin of these myofibroblasts remains poorly understood. Here, we create new mouse models of pulmonary fibrosis and identify a previously unknown population of endothelial cell (EC)-like myofibroblasts in normal lung tissue. We show that these EC-like myofibroblasts significantly contribute myofibroblasts to pulmonary fibrosis, which is confirmed by single-cell RNA sequencing of human pulmonary fibrosis. Using the transcriptional profiles, we identified a small molecule that redirects the differentiation of EC-like myofibroblasts and reduces pulmonary fibrosis in our mouse models. Our study reveals the mechanistic underpinnings of the differentiation of EC-like myofibroblasts in pulmonary fibrosis and may provide new strategies for therapeutic interventions.

Auditory Profile of Children With Some Rare Neurodevelopmental Disorders

Neurodevelopmental disorder is an umbrella term comprising many muscular, skeletal, metabolic, endocrinal, systemic, and immune-related diseases, which are caused due to the improper/inaccurate development of the central nervous system. Most of these disorders are highly prevalent, but some express rarely in human beings. Such disorders with least prevalence rates are known as rare neurodevelopmental disorders. The sensory system is affected in all individuals with these rare neurodevelopmental disorders, although to a varying extent. Sensory processing in terms of hearing loss is reported by many researchers in many rare neurodevelopmental disorders, but the pathophysiology of audiological findings are seldom investigated. In this chapter, the authors highlight the possible relationship between underlying cause and the resultant audiological symptoms in some of the rare neurodevelopmental disorders. Further, the research studies on the audiological profiling in such disorders are discussed.

Defining matrix Gla protein expression in the Dunkin-Hartley guinea pig model of spontaneous osteoarthritis

BACKGROUND

Matrix Gla (γ-carboxyglutamate) protein (MGP) is considered a strong inhibitor of ectopic calcification, and it has been associated with OA severity, although not conclusively. We utilized male Dunkin-Hartley (DH) guinea pigs to investigate the expression of MGP throughout aging and disease pathogenesis in a spontaneous model.

METHOD

Twenty-five male DH guinea pigs were obtained and nurtured to several timepoints, and then randomly and equally divided by age into five subgroups (1-, 3-, 6-, 9-, and 12-months, with the 1-month group as the reference group). DH guinea pigs in each group were euthanized at the designated month-age and the left or right medial tibial plateaus cartilages were randomly excised. OA severity was described by modified Mankin Score (MMS) at microscopy (Safranin O/Fast Green stain). Proteomic evaluation using isobaric tags for relative and absolute quantification (iTRAQ) was performed to validate the age-related changes in the MGP profiles, and immunohistochemistry (IHC) methods were applied for semi-quantitative determination of MGP expression in articular cartilage.

RESULTS

The histopathologic findings validated the increasing severity of cartilage degeneration with age in the DH guinea pigs. The MMS showed significant, stepwise (every adjacent comparison P < 0.05) disease progression with month-age. The iTRAQ indicated that MGP levels increased significantly with advancing age (P < 0.05), as supported by the IHC result (P < 0.05).

CONCLUSION

Increased expression of MGP in male DH guinea pigs was present throughout aging and disease progression and may be link to increased OA severity. Further studies are needed to investigate and confirm the association between MGP levels and OA severity.

Keutel Syndrome, a Review of 50 Years of Literature

Keutel syndrome (KS) is a rare autosomal recessive genetic disorder that was first identified in the beginning of the 1970s and nearly 30 years later attributed to loss-of-function mutations in the gene coding for the matrix Gla protein (MGP). Patients with KS are usually diagnosed during childhood (early onset of the disease), and the major traits include abnormal calcification of cartilaginous tissues resulting in or associated with malformations of skeletal tissues (e.g., midface hypoplasia and brachytelephalangism) and cardiovascular defects (e.g., congenital heart defect, peripheral pulmonary artery stenosis, and, in some cases, arterial calcification), and also hearing loss and mild developmental delay. While studies on Mgp -/- mouse, a faithful model of KS, show that pathologic mineral deposition (ectopic calcification) in cartilaginous and vascular tissues is the primary cause underlying many of these abnormalities, the mechanisms explaining how MGP prevents abnormal calcification remain poorly understood. This has negative implication for the development of a cure for KS. Indeed, at present, only symptomatic treatments are available to treat hypertension and respiratory complications occurring in the KS patients. In this review, we summarize the results published in the last 50 years on Keutel syndrome and present the current status of the knowledge on this rare pathology.

A Rare Diagnosis: Keutel Syndrome

Tracheobronchial cartilage calcification is a rare finding in the pediatric population. Keutel syndrome (OMIM 245150) is a very rare syndrome characterized with diffuse calcification of cartilage, brachytelephalangia, pulmonary stenosis, midline defects, stippled epiphysis in infancy, and hearing loss accompanied by recurrent respiratory infections and asthma-like attacks. Here, we present a 14-year-old patient who was followed up with the diagnosis of asthma, but did not respond to appropriate asthma treatment. She was subsequently diagnosed as having Keutel syndrome with cartilage calcification on the tracheobranchial tree and auricula, atypical facial features, recurrent otitis media, hearing loss, and recurrent asthma-like symptoms.

The Role of Vitamin K and Its Related Compounds in Mendelian and Acquired Ectopic Mineralization Disorders

Ectopic mineralization disorders comprise a broad spectrum of inherited or acquired diseases characterized by aberrant deposition of calcium crystals in multiple organs, such as the skin, eyes, kidneys, and blood vessels. Although the precise mechanisms leading to ectopic calcification are still incompletely known to date, various molecular targets leading to a disturbed balance between pro- and anti-mineralizing pathways have been identified in recent years. Vitamin K and its related compounds, mainly those post-translationally activated by vitamin K-dependent carboxylation, may play an important role in the pathogenesis of ectopic mineralization as has been demonstrated in studies on rare Mendelian diseases, but also on highly prevalent disorders, like vascular calcification. This narrative review compiles and summarizes the current knowledge regarding the role of vitamin K, its metabolism, and associated compounds in the pathophysiology of both monogenic ectopic mineralization disorders, like pseudoxanthoma elasticum or Keutel syndrome, as well as acquired multifactorial diseases, like chronic kidney disease. Clinical and molecular aspects of the various disorders are discussed according to the state-of-the-art, followed by a comprehensive literature review regarding the role of vitamin K in molecular pathophysiology and as a therapeutic target in both human and animal models of ectopic mineralization disorders.

Therapeutic warfarin use and the extrahepatic functions of vitamin K-dependent proteins

The impact of warfarin therapy on the functions of extrahepatic vitamin K-dependent proteins (VKDP) is less clearly understood and less widely recognised in clinical practice than that on the hepatic counterparts (clotting factors II, VII, IX and X). Warfarin inhibits osteocalcin, an abundant extrahepatic VKDP involved in the mineralisation and maturation of bone and thus, primarily by this mechanism, may have an adverse effect on bone health. Whilst some studies do link warfarin use to an increase in osteoporosis and fracture risk others have not. Warfarin also inhibits the extrahepatic VKDP matrix gla protein (MGP) which acts to prevent ectopic calcification of the vasculature. Studies have consistently found a correlation between warfarin use and vascular calcification with inhibition of MGP believed to be the main cause. Inhibition of MGP also appears to explain warfarin's well established teratogenic effect. Further adverse effects may also arise from warfarin's inhibition of other known extrahepatic VKDPs. The available evidence is intriguing, and suggests that the impact of warfarin on the extrahepatic functions of vitamin K-dependent proteins warrants further careful consideration.

Calcification of Vascular Smooth Muscle Cells and Imaging of Aortic Calcification and Inflammation

Cardiovascular disease is the leading cause of morbidity and mortality in the world. Atherosclerotic plaques, consisting of lipid-laden macrophages and calcification, develop in the coronary arteries, aortic valve, aorta, and peripheral conduit arteries and are the hallmark of cardiovascular disease. In humans, imaging with computed tomography allows for the quantification of vascular calcification; the presence of vascular calcification is a strong predictor of future cardiovascular events. Development of novel therapies in cardiovascular disease relies critically on improving our understanding of the underlying molecular mechanisms of atherosclerosis. Advancing our knowledge of atherosclerotic mechanisms relies on murine and cell-based models. Here, a method for imaging aortic calcification and macrophage infiltration using two spectrally distinct near-infrared fluorescent imaging probes is detailed. Near-infrared fluorescent imaging allows for the ex vivo quantification of calcification and macrophage accumulation in the entire aorta and can be used to further our understanding of the mechanistic relationship between inflammation and calcification in atherosclerosis. Additionally, a method for isolating and culturing animal aortic vascular smooth muscle cells and a protocol for inducing calcification in cultured smooth muscle cells from either murine aortas or from human coronary arteries is described. This in vitro method of modeling vascular calcification can be used to identify and characterize the signaling pathways likely important for the development of vascular disease, in the hopes of discovering novel targets for therapy.

Characterization of vitamin K-dependent carboxylase mutations that cause bleeding and nonbleeding disorders

Vitamin K-dependent coagulation factors deficiency is a bleeding disorder mainly associated with mutations in γ-glutamyl carboxylase (GGCX) that often has fatal outcomes. Some patients with nonbleeding syndromes linked to GGCX mutations, however, show no coagulation abnormalities. The correlation between GGCX genotypes and their clinical phenotypes has been previously unknown. Here we report the identification and characterization of novel GGCX mutations in a patient with both severe cerebral bleeding disorder and comorbid Keutel syndrome, a nonbleeding malady caused by functional defects of matrix γ-carboxyglutamate protein (MGP). To characterize GGCX mutants in a cellular milieu, we established a cell-based assay by stably expressing 2 reporter proteins (a chimeric coagulation factor and MGP) in HEK293 cells. The endogenous GGCX gene in these cells was knocked out by CRISPR-Cas9-mediated genome editing. Our results show that, compared with wild-type GGCX, the patient's GGCX D153G mutant significantly decreased coagulation factor carboxylation and abolished MGP carboxylation at the physiological concentration of vitamin K. Higher vitamin K concentrations can restore up to 60% of coagulation factor carboxylation but do not ameliorate MGP carboxylation. These results are consistent with the clinical results obtained from the patient treated with vitamin K, suggesting that the D153G alteration in GGCX is the causative mutation for both the bleeding and nonbleeding disorders in our patient. These findings provide the first evidence of a GGCX mutation resulting in 2 distinct clinical phenotypes; the established cell-based assay provides a powerful tool for studying the clinical consequences of naturally occurring GGCX mutations in vivo.

Vascular Calcification in Uremia: New-Age Concepts about an Old-Age Problem

A hallmark of aging, and major contributor to the increased prevalence of cardiovascular disease in patients with chronic kidney disease (CKD), is the progressive structural and functional deterioration of the arteries and concomitant accrual of mineral. Vascular calcification (VC) was long viewed as a degenerative age-related pathology that resulted from the passive deposition of mineral in the extracellular matrix; however, since the discovery of "bone-related" protein expression in calcified atherosclerotic plaques over 20 years ago, a plethora of studies have evoked the now widely accepted view that VC is a highly regulated and principally cell-mediated phenomenon that recapitulates many features of physiologic ossification. Central to this theory are changes in vascular smooth muscle cell (VSMC) phenotype and viability, thought to be driven by chronic exposure to a number of dystrophic stimuli characteristics of the uremic state. Here, dedifferentiated synthetic VSMCs are seen to spawn calcifying matrix vesicles that actively seed mineralization of the arterial matrix. This review provides an overview of the major epidemiological, histological, and molecular aspects of VC in the context of CKD, and a counterpoint to the prevailing paradigm that emphasizes the primacy of VSMC-mediated mechanisms. Particular focus is given to the import of protein and small molecule inhibitors in regulating physiologic and pathological mineralization and the emerging role of mineral nanoparticles and their interplay with proinflammatory processes.

Animal Models to Study Links between Cardiovascular Disease and Renal Failure and Their Relevance to Human Pathology

The close association between cardiovascular pathology and renal dysfunction is well documented and significant. Patients with conventional risk factors for cardiovascular disease like diabetes and hypertension also suffer renal dysfunction. This is unsurprising if the kidney is simply regarded as a “modified blood vessel” and thus, traditional risk factors will affect both systems. Consistent with this, it is relatively easy to comprehend how patients with either sudden or gradual cardiac and or vascular compromise have changes in both renal hemodynamic and regulatory systems. However, patients with pure or primary renal dysfunction also have metabolic changes (e.g., oxidant stress, inflammation, nitric oxide, or endocrine changes) that affect the cardiovascular system. Thus, cardiovascular and renal systems are intimately, bidirectionally and inextricably linked. Whilst we understand several of these links, some of the mechanisms for these connections remain incompletely explained. Animal models of cardiovascular and renal disease allow us to explore such mechanisms, and more importantly, potential therapeutic strategies. In this article, we review various experimental models used, and examine critically how representative they are of the human condition.

From variome to phenome: Pathogenesis, diagnosis and management of ectopic mineralization disorders

Ectopic mineralization - inappropriate biomineralization in soft tissues - is a frequent finding in physiological aging processes and several common disorders, which can be associated with significant morbidity and mortality. Further, pathologic mineralization is seen in several rare genetic disorders, which often present life-threatening phenotypes. These disorders are classified based on the mechanisms through which the mineralization occurs: metastatic or dystrophic calcification or ectopic ossification. Underlying mechanisms have been extensively studied, which resulted in several hypotheses regarding the etiology of mineralization in the extracellular matrix of soft tissue. These hypotheses include intracellular and extracellular mechanisms, such as the formation of matrix vesicles, aberrant osteogenic and chondrogenic signaling, apoptosis and oxidative stress. Though coherence between the different findings is not always clear, current insights have led to improvement of the diagnosis and management of ectopic mineralization patients, thus translating pathogenetic knowledge (variome) to the phenotype (phenome). In this review, we will focus on the clinical presentation, pathogenesis and management of primary genetic soft tissue mineralization disorders. As examples of dystrophic calcification disorders Pseudoxanthoma elasticum, Generalized arterial calcification of infancy, Keutel syndrome, Idiopathic basal ganglia calcification and Arterial calcification due to CD73 (NT5E) deficiency will be discussed. Hyperphosphatemic familial tumoral calcinosis will be reviewed as an example of mineralization disorders caused by metastatic calcification.

[The matrix-gla protein awakening may lead to the demise of vascular calcification]

Matrix-gla-protein (MGP) is mainly secreted by chondrocytes and smooth vascular muscle cells. This potent inhibitor of vascular calcification need to undergo 2 post-transcriptional steps to be fully active: one phosphorylation of 3 serine residues (on 5) and a carboxylation of 5 glutamate residues (on 9). Like other "Gla" proteins, this carboxylation is vitamin K dependant. Several forms of MGP thus circulate in the plasma, some of them being totally inactive (the unphosphorylated and uncarboxylated MGP), some others being partially or fully active, according to the number of phosphorylated or carboxylated sites. A theoretical link exists between MGP, vitamin K, vascular calcifications and cardiovascular diseases. This link is even more evident in patients suffering from chronic kidney diseases (CKD), and notably hemodialysis patients. If this link has been demonstrated in different experimental studies, clinical studies are mainly observational and their results must be interpreted accordingly. MGP concentrations are definitely not yet a surrogate to estimate the levels of vascular calcification, but could allow the monitoring of vitamin K treatment. Modulation of MGP concentrations may reduce vascular calcification in hemodialyzed patients, if the large ongoing trials show an efficiency of this treatment. In this review, we will summarize the role of MGP in the vascular calcifications process, describe the problems linked to the analytical determination of MGP in plasma and finally describe the different clinical studies on MGP and vascular calcifications in the general population and in CKD patients.

Inhibition of bone morphogenetic protein signal transduction prevents the medial vascular calcification associated with matrix Gla protein deficiency

OBJECTIVE

Matrix Gla protein (MGP) is reported to inhibit bone morphogenetic protein (BMP) signal transduction. MGP deficiency is associated with medial calcification of the arterial wall, in a process that involves both osteogenic transdifferentiation of vascular smooth muscle cells (VSMCs) and mesenchymal transition of endothelial cells (EndMT). In this study, we investigated the contribution of BMP signal transduction to the medial calcification that develops in MGP-deficient mice.

APPROACH AND RESULTS

MGP-deficient mice (MGP(-/-)) were treated with one of two BMP signaling inhibitors, LDN-193189 or ALK3-Fc, beginning one day after birth. Aortic calcification was assessed in 28-day-old mice by measuring the uptake of a fluorescent bisphosphonate probe and by staining tissue sections with Alizarin red. Aortic calcification was 80% less in MGP(-/-) mice treated with LDN-193189 or ALK3-Fc compared with vehicle-treated control animals (P<0.001 for both). LDN-193189-treated MGP(-/-) mice survived longer than vehicle-treated MGP(-/-) mice. Levels of phosphorylated Smad1/5 and Id1 mRNA (markers of BMP signaling) did not differ in the aortas from MGP(-/-) and wild-type mice. Markers of EndMT and osteogenesis were increased in MGP(-/-) aortas, an effect that was prevented by LDN-193189. Calcification of isolated VSMCs was also inhibited by LDN-193189.

CONCLUSIONS

Inhibition of BMP signaling leads to reduced vascular calcification and improved survival in MGP(-/-) mice. The EndMT and osteogenic transdifferentiation associated with MGP deficiency is dependent upon BMP signaling. These results suggest that BMP signal transduction has critical roles in the development of vascular calcification in MGP-deficient mice.

Premature calcifications of costal cartilages: a new perspective

Background. Calcifications of the costal cartilages occur, as a rule, not until the age of 30 years. The knowledge of the clinical significance of early and extensive calcifications is still incomplete. Materials and Methods. A search was made to find patients below the age of 30 years who showed distinct calcifications of their lower costal cartilages by viewing 360 random samples of intravenous pyelograms and abdominal plain films. The histories, and clinical and laboratory findings of these patients were analyzed. Results. Nineteen patients fulfilled the criteria of premature calcifications of costal cartilages (CCCs). The patients had in common that they were frequently referred to a hospital and were treated by several medical disciplines. Nevertheless many complaints of the patients remained unsolved. Premature CCCs were often associated with rare endocrine disorders, inborn errors of metabolism, and abnormal hematologic findings. Among the metabolic disorders there were 2 proven porphyrias and 7 patients with a suspected porphyria but with inconclusive laboratory findings. Conclusion. Premature CCCs are unlikely to be a normal variant in skeletal radiology. The findings in this small group of patients call for more intensive studies, especially in regard to the putative role of a porphyria.

Long term follow-up of four patients with Keutel syndrome

Keutel syndrome (KS) [OMIM 245150] is an autosomal recessive hereditary syndrome characterized by multiple peripheral pulmonary stenoses (PPS), brachytelephalangia, inner ear deafness, and abnormal cartilage ossification or calcification. Mutations in the matrix Gla protein (MGP) gene have been reported in different unrelated families with KS previously. MGP is an extracellular matrix protein and calcification inhibitor; mutations in its encoding gene result in cartilage ossification or calcification, the main presenting feature of KS. This report describes the findings of four sisters with KS born to consanguineous parents were followed for 26 years in an irregular fashion. During follow-up of the patients over the years the complications appear to be mostly involving the respiratory system. Permanent skin rashes, papillary microcarcinoma of the thyroid, asthma, massive bullous pulmonary emphysema, severe systemic arterial hypertension, and short term memory loss were observed during long term follow-up. The fertility status of the patients were also observed and infertility was observed in one of three married patients.

Keutel syndrome: report of two novel MGP mutations and discussion of clinical overlap with arylsulfatase E deficiency and relapsing polychondritis

Keutel syndrome is a rare, autosomal recessive disorder characterized by diffuse cartilage calcification, peripheral pulmonary artery stenosis, midface retrusion, and short distal phalanges. To date, 28 patients from 18 families have been reported, and five mutations in the matrix Gla protein gene (MGP) have been identified. The matrix Gla protein (MGP) is a vitamin K-dependent extracellular protein that functions as a calcification inhibitor through incompletely understood mechanisms. We present the clinical manifestations of three affected siblings from a consanguineous Turkish family, in whom we detected the sixth MGP mutation (c.79G>T, which predicts p.E27X) and a fourth unrelated patient in whom we detected the seventh MGP mutation, a partial deletion of exon 4. Both mutations predict complete loss of MGP function. One of the patients presented initially with a working diagnosis of relapsing polychondritis. Clinical features suggestive of Keutel syndrome were also observed in one additional unrelated patient who was later found to have a deletion of arylsulfatase E, consistent with a diagnosis of X-linked recessive chondrodysplasia punctata. Through a discussion of these cases, we highlight the clinical overlap of Keutel syndrome, X-linked chondrodysplasia punctata, and the inflammatory disease relapsing polychondritis.

Warfarin induces cardiovascular damage in mice

OBJECTIVE

Vascular calcification is an independent risk factor for cardiovascular disease. Once thought to be a passive process, vascular calcification is now known to be actively prevented by proteins acting systemically (fetuin-A) or locally (matrix Gla protein). Warfarin is a vitamin K antagonist, widely prescribed to reduce coagulation by inhibiting vitamin K-dependent coagulation factors. Recently, it became clear that vitamin K antagonists also affect vascular calcification by inactivation of matrix Gla protein. Here, we investigated functional cardiovascular characteristics in a mouse model with warfarin-induced media calcification.

APPROACH AND RESULTS

DBA/2 mice received diets with variable concentrations of warfarin (0.03, 0.3, and 3 mg/g) with vitamin K1 at variable time intervals (1, 4, and 7 weeks). Von Kossa staining revealed that warfarin treatment induced calcified areas in both medial layer of aorta and heart in a dose- and time-dependent fashion, which could be inhibited by simultaneous vitamin K2 treatment. With ongoing calcification, matrix Gla protein mRNA expression decreased, and inactive matrix Gla protein expression increased. TdT-mediated dUTP-biotin nick end labeling-positive apoptosis increased, and vascular smooth muscle cell number was concomitantly reduced by warfarin treatment. On a functional level, warfarin treatment augmented aortic peak velocity, aortic valve-peak gradient, and carotid pulse-wave velocity.

CONCLUSION

Warfarin induced significant calcification with resulting functional cardiovascular damage in DBA/2 wild-type mice. The model would enable future researchers to decipher mechanisms of vascular calcification and may guide them in the development of new therapeutic strategies.

Resolving candidate genes of mouse skeletal muscle QTL via RNA-Seq and expression network analyses

Background

We have recently identified a number of Quantitative Trait Loci (QTL) contributing to the 2-fold muscle weight difference between the LG/J and SM/J mouse strains and refined their confidence intervals. To facilitate nomination of the candidate genes responsible for these differences we examined the transcriptome of the tibialis anterior (TA) muscle of each strain by RNA-Seq.

Results

13,726 genes were expressed in mouse skeletal muscle. Intersection of a set of 1061 differentially expressed transcripts with a mouse muscle Bayesian Network identified a coherent set of differentially expressed genes that we term the LG/J and SM/J Regulatory Network (LSRN). The integration of the QTL, transcriptome and the network analyses identified eight key drivers of the LSRN (Kdr, Plbd1, Mgp, Fah, Prss23, 2310014F06Rik, Grtp1, Stk10) residing within five QTL regions, which were either polymorphic or differentially expressed between the two strains and are strong candidates for quantitative trait genes (QTGs) underlying muscle mass. The insight gained from network analysis including the ability to make testable predictions is illustrated by annotating the LSRN with knowledge-based signatures and showing that the SM/J state of the network corresponds to a more oxidative state. We validated this prediction by NADH tetrazolium reductase staining in the TA muscle revealing higher oxidative potential of the SM/J compared to the LG/J strain (p<0.03).

Conclusion

Thus, integration of fine resolution QTL mapping, RNA-Seq transcriptome information and mouse muscle Bayesian Network analysis provides a novel and unbiased strategy for nomination of muscle QTGs.

The role of vitamin K in soft-tissue calcification

Seventeen vitamin K-dependent proteins have been identified to date of which several are involved in regulating soft-tissue calcification. Osteocalcin, matrix Gla protein (MGP), and possibly Gla-rich protein are all inhibitors of soft-tissue calcification and need vitamin K-dependent carboxylation for activity. A common characteristic is their low molecular weight, and it has been postulated that their small size is essential for calcification inhibition within tissues. MGP is synthesized by vascular smooth muscle cells and is the most important inhibitor of arterial mineralization currently known. Remarkably, the extrahepatic Gla proteins mentioned are only partly carboxylated in the healthy adult population, suggesting vitamin K insufficiency. Because carboxylation of the most essential Gla proteins is localized in the liver and that of the less essential Gla proteins in the extrahepatic tissues, a transport system has evolved ensuring preferential distribution of dietary vitamin K to the liver when vitamin K is limiting. This is why the first signs of vitamin K insufficiency are seen as undercarboxylation of the extrahepatic Gla proteins. New conformation-specific assays for circulating uncarboxylated MGP were developed; an assay for desphospho-uncarboxylated matrix Gla protein and another assay for total uncarboxylated matrix Gla protein. Circulating desphospho-uncarboxylated matrix Gla protein was found to be predictive of cardiovascular risk and mortality, whereas circulating total uncarboxylated matrix Gla protein was associated with the extent of prevalent arterial calcification. Vitamin K intervention studies have shown that MGP carboxylation can be increased dose dependently, but thus far only 1 study with clinical endpoints has been completed. This study showed maintenance of vascular elasticity during a 3-y supplementation period, with a parallel 12% loss of elasticity in the placebo group. More studies, both in healthy subjects and in patients at risk of vascular calcification, are required before conclusions can be drawn.

Circulating matrix γ-carboxyglutamate protein (MGP) species are refractory to vitamin K treatment in a new case of Keutel syndrome

BACKGROUND AND OBJECTIVES

 Matrix γ-carboxyglutamate protein (MGP), a vitamin K-dependent protein, is recognized as a potent local inhibitor of vascular calcification. Studying patients with Keutel syndrome (KS), a rare autosomal recessive disorder resulting from MGP mutations, provides an opportunity to investigate the functions of MGP. The purpose of this study was (i) to investigate the phenotype and the underlying MGP mutation of a newly identified KS patient, and (ii) to investigate MGP species and the effect of vitamin K supplements in KS patients.

METHODS

 The phenotype of a newly identified KS patient was characterized with specific attention to signs of vascular calcification. Genetic analysis of the MGP gene was performed. Circulating MGP species were quantified and the effect of vitamin K supplements on MGP carboxylation was studied. Finally, we performed immunohistochemical staining of tissues of the first KS patient originally described focusing on MGP species.

RESULTS

 We describe a novel homozygous MGP mutation (c.61+1G>A) in a newly identified KS patient. No signs of arterial calcification were found, in contrast to findings in MGP knockout mice. This patient is the first in whom circulating MGP species have been characterized, showing a high level of phosphorylated MGP and a low level of carboxylated MGP. Contrary to expectations, vitamin K supplements did not improve the circulating carboxylated mgp levels. phosphorylated mgp was also found to be present in the first ks patient originally described.

CONCLUSIONS

 Investigation of the phenotype and MGP species in the circulation and tissues of KS patients contributes to our understanding of MGP functions and to further elucidation of the difference in arterial phenotype between MGP-deficient mice and humans.

Partial cricotracheal resection for congenital subglottic stenosis in children: the effect of concomitant anomalies

OBJECTIVE

To review the surgical outcomes of partial cricotracheal resection in children with severe congenital subglottic stenosis and define the effect of concomitant anomalies or syndromes affecting outcome.

METHODS

Forty-one children with subglottic stenosis of congenital and mixed (acquired on congenital) etiologies who underwent partial cricotracheal resection were identified from a prospectively collected database. Children with congenital subglottic stenosis and concomitant anomalies/syndromes were compared to children with congenital subglottic stenosis with no syndromes or concomitant anomalies. Operation-specific decannulation rates and complication rates were the primary outcome measures. We performed a two-sample test of proportion using the STATA-10 software for categorical variables to detect differences in proportions. Significance was set at p value<0.05.

RESULTS

Twenty-seven (66%) of 41 children had concomitant anomalies/syndromes and 14 (34%) had congenital subglottic stenosis without concomitant anomalies/syndromes. Four patients needed revision surgery in the concomitant anomaly group and two patients needed revision surgery in the non concomitant anomaly group before achieving decannulation. The operation-specific decannulation rate in the concomitant anomaly group was 85% and 86% in the non anomaly group. When compared to children without concomitant anomaly, children with concomitant anomalies were more likely to have delayed decannulation following partial cricotracheal resection. However, this difference was not found to be statistically significant. The complication and operation-specific decannulation rates after partial cricotracheal resection were comparable to children without concomitant anomalies. Mortality rate was 11% (three of 27 patients) in the group with associated congenital anomalies or syndromes. Two patients succumbed to the primary pathology and one patient died due to tracheostomy-tube obstruction. There was no post-operative death in the non anomaly group.

CONCLUSION

Partial cricotracheal resection can be done safely and effectively in children with concomitant anomalies/syndromes to achieve decannulation. The post-operative course may be prolonged but the decannulation and the complication rates are comparable to those children with congenital subglottic stenosis without concomitant anomalies.

Vitamin K and thrombosis

Vitamin K was discovered in the 1930s during cholesterol metabolism experiments in chickens. It is a fat-soluble vitamin which occurs naturally in plants as phylloquinone (vitamin K1) and is produced by gram-negative bacteria in the human gastrointestinal tract as menaquinone (vitamin K2). This vitamin was found to be essential for normal functioning of hemostasis. In addition, a number of clinical conditions in which vitamin K deficiency was found to be the underlying pathophysiologic problem were discovered. These conditions include hemorrhagic disease of the newborn, obstructive jaundice, and malabsorption syndromes. The importance of this vitamin has become more apparent with the discovery of the anticoagulant warfarin which is a vitamin K antagonist. There are millions of patients on this therapy for a variety of thrombogenic conditions such as atrial fibrillation, deep vein thrombosis, pulmonary embolism, and prosthetic cardiac valves. The wide use of this narrow therapeutic index drug has resulted in significant risk for major bleeding. Vitamin K serves as one of the major reversing agent for patients over-anticoagulated with warfarin. In the past few years, research has focused on new areas of vitamin K metabolism, which include bone and endovascular metabolism; cell growth, regulation, migration, and proliferation; cell survival, apoptosis, phagocytosis, and adhesion. These new areas of research highlight the significance of vitamin K but raise new clinical questions for patients who must be maintained on long-term warfarin therapy.

Testicular cancer in a patient with Primrose syndrome

A mentally retarded, adult man was found to have joint contractures, sparse body hair, hearing loss, dysmorphic facial features, large calcified pinnae and a huge torus palatinus. All features are similar to those earlier described in patients with Primrose syndrome. In addition he developed a germ cell tumour of his right testicle at age 27 years. A comparison is provided between the main findings in the four previously reported cases with Primrose syndrome and the current patient. Calcification of the pinnae is an infrequent symptom in the general population, and a torus palatinus of limited size is commonly found but a torus of the size reported here is extremely unusual. Both symptoms are excellent handles for diagnosing this entity. It remains as yet uncertain whether an increased risk to malignancies forms part of this syndrome or is only a consequence of cryptorchidism in this patient.

Tracheobronchial stenosis in Keutel syndrome

In 1971 Keutel et al. described a new syndrome in two siblings presenting with peripheral pulmonary stenoses, brachytelephalangism, neural hearing loss and abnormal cartilage calcification. Recent investigations provided evidence that mutations in the gene encoding the human matrix GLA protein cause Keutel syndrome. With these new insights in the disease the symptomatology of Keutel syndrome was reassessed. The follow-up of the two siblings was studied by clinical and post mortem examination. As a new feature of Keutel syndrome tracheobronchial stenosis and concentric calcification of pulmonary, coronary, hepatic, renal, meningeal and cerebral arteries were described. Complementary to the results in molecular genetics the symptomatology of Keutel syndrome could be revised by clinical and post mortem examination.

Skeletal and cardiac malformations with thrombocytopenia: a new syndrome?

We describe a female patient with multiple anomalies suggestive of a new syndrome. Manifestations include: VSD and ASD, mild developmental delay, conductive hearing loss, minor facial anomalies, thrombocytopenia, and radiological findings (including carpal fusion). Some of these manifestations may be present in the Keutel syndrome, IVIC syndrome, and the 10qter deletion syndrome. However, none of these syndromes can explain the spectrum of anomalies seen in our patient.

Premature tracheobronchial, laryngeal and costochondral cartilage calcification in children

Two children with premature tracheobronchial, laryngeal and costochondral cartilage calcification are described. Both patients had associated congenital cardiovascular anomalies; one of them having features of Keutel syndrome.

Keutel syndrome: a report of four cases

We report four new cases of Keutel syndrome. Clinical manifestation included abnormal cartilage ossification, multiple peripheral pulmonary stenosis (PPS), brachytelephalangism, subnormal IQ, repeated respiratory infections, otitis media and hearing loss. All four children have a typical facial appearance and are of consanguineous parents. Father and the fifth offspring exhibit a normal phenotype; the mother has pulmonary stenosis. This observation confirms Keutel syndrome as a distinct autosomal recessive syndrome.