Epidermal growth factor signalling pathway in endochondral ossification: an evidence-based narrative review.

During endochondral bone development, a complex process that leads to the formation of the majority of skeletal elements, mesenchymal cells condense, differentiating into chondrocytes and producing the foetal growth plate. Chondrocytes progressively hypertrophy, induce angiogenesis and are then gradually replaced by bone. Epidermal Growth Factor (EGF), one of many growth factors, is the prototype of the EGF-ligand family, which comprises several proteins involved in cell proliferation, migration and survival. In bone, EGF pathway signalling finely tunes the first steps of chondrogenesis by maintaining mesenchymal cells in an undifferentiated stage, and by promoting hypertrophic cartilage replacement. Moreover, EGF signalling modulates bone homeostasis by stimulating osteoblast and osteoclast proliferation, and by regulating osteoblast differentiation under specific spatial and temporal conditions. This evidence-based narrative review describes the EGF pathway in bone metabolism and endochondral bone development. This comprehensive description may be useful in light of possible clinical applications in orthopaedic practice. A deeper knowledge of the role of EGF in bone may be useful in musculoskeletal conditions which may benefit from the modulation of this signalling pathway.Key messagesThe EGF pathway is involved in bone metabolism.EGF signalling is essential in the very early stages of limb development by maintaining cells in an undifferentiated stage.EGF pathway positively regulates chondrocyte proliferation, negatively modulates hypertrophy, and favours cartilage replacement by bone.EGF and EGF-like proteins finely tune the proliferation and differentiation of bone tissue cells, and they also regulate the initial phases of endochondral ossification.

Tetracycline affects abnormal properties of synthetic PrP peptides and PrP(Sc) in vitro.

Prion diseases are characterized by the accumulation of altered forms of the prion protein (termed PrP(Sc)) in the brain. Unlike the normal protein, PrP(Sc) isoforms have a high content of beta-sheet secondary structure, are protease-resistant, and form insoluble aggregates and amyloid fibrils. Evidence indicates that they are responsible for neuropathological changes (i.e. nerve cell degeneration and glial cell activation) and transmissibility of the disease process. Here, we show that the antibiotic tetracycline: (i) binds to amyloid fibrils generated by synthetic peptides corresponding to residues 106-126 and 82-146 of human PrP; (ii) hinders assembly of these peptides into amyloid fibrils; (iii) reverts the protease resistance of PrP peptide aggregates and PrP(Sc) extracted from brain tissue of patients with Creutzfeldt-Jakob disease; (iv) prevents neuronal death and astrocyte proliferation induced by PrP peptides in vitro. NMR spectroscopy revealed several through-space interactions between aromatic protons of tetracycline and side-chain protons of Ala(117-119), Val(121-122) and Leu(125) of PrP 106-126. These properties make tetracycline a prototype of compounds with the potential of inactivating the pathogenic forms of PrP.

Creutzfeldt-Jakob disease: Carnoy's fixative improves the immunohistochemistry of the proteinase K-resistant prion protein.

The neuropathological diagnosis of Creutzfeldt-Jakob disease relies on the immunohistochemical demonstration of the proteinase-K resistant form of the prion protein (PrPres) in the brain tissue. The antigenicity of PrPres is strongly reduced by the formalin solution widely used to fix the tissue, thus the PrPres immunoreactivity is inconsistently detectable in formalin-fixed tissue. A better PrPres immunostaining can be obtained by using Carnoy's fixing solution, which is composed of ethanol, chloroform and acetic acid (6:3:1). PrPres can easily be extracted from Carnoy's-fixed, paraplast-embedded tissue. Accordingly, Carnoy's-fixed tissue can prior to immunolabeling be subjected to proteinase K and guanidine thiocyanate, which respectively eliminate the normal cellular form of prion protein and promote protein denaturation. In comparison with the best protocols for formalin-fixed tissue (i.e.--hydrolytic autoclaving or autoclaving in distilled water followed by formic acid and guanidine thiocyanate), PrPres immunostaining carried out on sections cut from Carnoy's-fixed, paraplast-embedded tissue blocks and subjected to proteinase K and guanidine thiocyanate, proved more successful to detect and map both diffuse and focal PrPres immunoreactivity, and to correlate the immunoreactivity pattern with MV polymorphism at PRNP codon 129 and PrPres banding and glycosylation pattern revealed by Western blot.

Sporadic Creutzfeldt-Jakob disease: co-occurrence of different types of PrP(Sc) in the same brain.

Phenotypic heterogeneity of sporadic Creutzfeldt-Jakob disease (CJD) has been linked to biochemically distinct types of the protease-resistant form of the prion protein (type 1 and type 2 PrP(Sc)). We investigated 14 cases of sporadic CJD and found that both type 1 and type 2 PrP(Sc) coexisted in 5 subjects. The distinct PrP(Sc) isoforms were associated with different patterns of PrP deposition and severity of spongiform changes, suggesting that the PrP(Sc) type plays a central role in determining the neuropathologic profile of CJD.

A betaPP peptide carboxyl-terminal to Abeta is neurotoxic.

Extracellular Abeta-amyloid and intraneuronal paired helical filaments (PHFs) composed of tau protein are the neuropathological hallmark of Alzheimer's disease. Abeta is a 39- to 43-residue peptide derived by cleavage of a 695- to 770-amino-acid membrane-associate glycoprotein (termed beta-protein precursor, betaPP). Following the observation that an antiserum to an epitope located between residues 713 and 723 of betaPP770 (ie, the transmembrane region of the betaPP distal to Abeta) labels PHFs and that a synthetic peptide homologous to residues 713 to 730 of betaPP770 (betaPP713-730) is highly fibrillogenic and interacts with tau in vitro, it has been hypothesized that betaPP fragments other than Abeta may feature in the pathogenesis of Alzheimer's disease concurring with neuronal degeneration. To investigate this issue, we have analyzed the effects of the exposure of primary neuronal cultures to the synthetic peptide betaPP713-730. Cultures were prepared from rat hippocampus on embryonic day 17 and incubated with the peptide at 2.5 to 30 micromol/L concentration for 1 to 4 days. Cell viability was compared with that of control cultures exposed to a scrambled sequence of the peptide. A 4-day exposure to 20 micromol/L betaPP713-730 resulted in almost complete neuronal loss, whereas no changes were observed with the scrambled peptide. Degenerating neurons showed DNA fragmentation by agarose gel electrophoresis and apoptotic changes by light and electron microscopy. These findings support the view that betaPP sequences other than Abeta may play a role in nerve cell degeneration in Alzheimer's disease.

Effectiveness of anthracycline against experimental prion disease in Syrian hamsters.

Prion diseases are transmissible neurodegenerative conditions characterized by the accumulation of protease-resistant forms of the prion protein (PrP), termed PrPres, in the brain. Insoluble PrPres tends to aggregate into amyloid fibrils. The anthracycline 4'-iodo-4'-deoxy-doxorubicin (IDX) binds to amyloid fibrils and induces amyloid resorption in patients with systemic amyloidosis. To test IDX in an experimental model of prion disease, Syrian hamsters were inoculated intracerebrally either with scrapie-infected brain homogenate or with infected homogenate coincubated with IDX. In IDX-treated hamsters, clinical signs of disease were delayed and survival time was prolonged. Neuropathological examination showed a parallel delay in the appearance of brain changes and in the accumulation of PrPres and PrP amyloid.

[Initial and final changes in the signal-averaged QRS in the time and frequency domain in a case of hypertrophic myocardiopathy]. / Alterazioni iniziali e finali del "signal-averaged" QRS nel dominio del tempo e nel dominio della frequenza in un caso di miocardiopatia ipertrofica.

We report on a patient suffering from asymmetrical hypertrophic cardiomyopathy, with alterations occurring in the signal-averaged electrocardiogram (SAQRS). Recordings of 3-lead orthogonal ECG were obtained and analyzed by a Del Mar Avionics 750A Innovator device. The time domain analysis showed late potentials and a slow inscription of the initial portion of the SAQRS, that we called "early potentials". On the frequency domain there was a high degree of spectral turbulence at the beginning and at the end of the SAQRS. We discuss the possibility that the slow and fragmented conduction of the initial portion of the SAQRS could be related to the electrical instability of the disease.

Right ventricular cardiomyopathy in identical and nonidentical young twins.

We describe the first sets of identical and nonidentical twins with right ventricular cardiomyopathy (RVC). Pair A: A 12-year-old boy was referred because of palpitation and syncope. Clinical and instrument examinations revealed an enlarged and depressed right ventricle (end-diastolic volume = 110 ml/m2; ejection fraction = 44%), spontaneous ventricular tachycardia, and fatty-fibrous infiltrates in the biopsy specimens. His asymptomatic, monozygotic twin showed localized involvement of the right ventricle with isolated, ventricular extrasystoles. Pair B: These 18-year-old nonidentical twin boys showed diffuse right ventricular involvement (end-diastolic volume = 110 ml/m2 and 114 ml/m2; ejection fraction = 30% and 24%, respectively), induction of sustained and nonsustained ventricular tachycardia, respectively, and fibrosis on endomyocardial biopsy. One of the boys died suddenly at rest after documented ventricular fibrillation. These cases support the hypothesis of a genetic etiology with a minor role for genotype and point to the important influence of environmental factors in determining the clinical features of the disease.

Clinical profile of concealed form of arrhythmogenic right ventricular cardiomyopathy presenting with apparently idiopathic ventricular arrhythmias.

In 24 subjects presenting with apparently idiopathic ventricular arrhythmias, a final diagnosis of arrhythmogenic right ventricular cardiomyopathy was formulated following global evaluation of the clinical, cross-sectional echocardiography and angiographic findings, and the observation of myocardial atrophy with fibrous-fatty substitution in right ventricular endomyocardial biopsy. All patients had good effort tolerance, and a normal cardiac silhouette. Ventricular arrhythmias with a left bundle branch block pattern were present in 23 cases (sustained ventricular tachycardia, nonsustained ventricular tachycardia, ventricular couplets, and ventricular premature complexes); 1 patient experienced an episode of ventricular fibrillation. A nearly constant electrocardiographic feature was T wave negativity in the right precordial leads. Cross-sectional echocardiography and hemodynamic studies showed that right ventricular impairment consisted only of localized structural and dynamic abnormalities; in a few cases the left ventricle was segmentally involved. Familial occurrence was present in 29% of the cases. No case of sudden death was observed during follow-up. These findings confirm that the concealed form of arrhythmogenic right ventricular cardiomyopathy is a cause of so-called "idiopathic" ventricular arrhythmias in subjects with apparently "normal hearts". Echocardiographic and angiographic investigations may lead to the correct diagnosis.

A casual spontaneous mutation as possible cause of the familial form of arrhythmogenic right ventricular cardiomyopathy (arrhythmogenic right ventricular dysplasia).

In a family affected by arrhythmogenic right ventricular cardiomyopathy (ARVC) the familial occurrence was investigated. All 14 members of two generations were investigated carefully, and only 2 (father and one son) members were affected. Both subjects had a massive form of the disease with relevant ventricular arrhythmias. Apart from the limitations of having investigated few subjects, this behavior suggests a genetic mutation appearing in the father and transmitted via an autosomal dominant trait.

Arrhythmia development in a young subject with right ventricular cardiomyopathy (right ventricular dysplasia).

In right ventricular cardiomyopathy the relationship between the progression of structural abnormalities and arrhythmia development is not yet well known. This report describes a case in which severe ventricular arrhythmias appeared 3 years after the demonstration of right ventricular (RV) structural and dynamic abnormalities. In this interval of time structural changes were not detectable with the commonly used diagnostic methods, but endocavitary RV late fractionated QRS potentials appeared suggesting the development of an arrhythmic component of the disease.

Coexistence of kent accessory pathway, enhanced AV node conduction, and various conduction disturbances in a young athlete with tricuspid valve dysplasia.

An asymptomatic 19-year-old top-level athlete had electrocardiographic evidence of intermittent cardiac preexcitation and intermittent left bundle branch block. The electrophysiologic study demonstrated the presence of a direct accessory pathway and enhanced atrioventricular node conduction that resulted in infrahisian and intraventricular conduction disturbances. The echocardiogram disclosed tricuspid valve dysplasia.

[Analysis of the mode of transmission of right ventricular dysplasia]. / Analyse du mode de transmission de la dysplasie ventriculaire droite.

A formal analysis of the mode of transmission of right ventricular cardiomyopathy was performed in seven families with this condition. Ninety-six subjects (81 family members, 15 connected) were studied. The index cases were family members who had died suddenly in their youth with autopsy evidence of massive fibrous-adipose right ventricular myocardial replacement. Pedigree analysis showed that 58 per cent of the family members were affected, with a male predominance (63% of men vs 53% of women). The kindreds were all normal and in none of the families were both parents affected. Carrier states were observed in both males and females and vertical transmission was demonstrated. Clinically, the disease was very variable with some cases showing widespread right ventricular involvement with or without cardiomegaly, and other cases showing localised right ventricular abnormalities. These data are consistent with a congenital disease with an autosomal dominant mode of inheritance with incomplete penetrance and variable expression.

[Electro-vectorcardiographic study of ventricular extrasystole in arrhythmogenic dysplasia of the right ventricle]. / Etude électro-vectocardiographique des extrasystoles ventriculaires dans la dysplasie arythmogène du ventricule droit.

The morphology of ventricular extrasystole (VES) in 46 cases of arrhythmogenic dysplasia of the right ventricle (ADRV) was correlated with the point of origin located by intracavitary mapping. The cases concerned 41 of left bundle-branch block (LBB) with various axes on the frontal plane (FP), 4 of right bundle-branch block (RBB), and 5 of atypical morphology (frontal plane shifted inferiorly and increased R from V1 to V6; on the horizontal plane, clockwise rotation of the loop oriented anteriorly and leftward). There is a good correlation with the site of origin: VESs which were LBB in appearance originated in the right ventricle (apex, septum, infundibulum); VESs which were RBB in appearance originated in the apex of the left ventricle, while the atypical VESs started in the upper posterior septum. A study of morphology may therefore also give an indication of the location of the disease.

Monomorphic repetitive rhythms originating from the outflow tract in patients with minor forms of right ventricular cardiomyopathy.

We studied in detail 17 patients presenting with monomorphic repetitive ventricular rhythms having left bundle branch block morphology and right axis deviation. All had an apparently normal heart at physical examination. At chest radiography, three patients had mild cardiomegaly, and at electrocardiography, five patients had inverted T waves beyond V2. Five patients had syncope or near syncope. In seven patients the tachycardia occurred on effort. One patient died suddenly. The patients were extensively investigated, using cross-sectional echocardiography, complete haemodynamic and angiographic studies, electrophysiology and histology, to search for any structural basis of the arrhythmias. Tachycardia was sustained in 8 patients, nonsustained in 3, and consistent with accelerated idioventricular rhythm and repetitive paroxysmal ventricular tachycardia in 5 and 1 patients, respectively. Despite the differences in clinical and arrhythmologic features, similar abnormalities of right ventricular structure and/or wall motion were detected in all patients, consistent with localized forms of right ventricular cardiomyopathy. Different antiarrhythmic drugs were successfully used in twelve patients (the four patients with accelerated idioventricular rhythm were not treated). The patient who died suddenly had previously had a sustained ventricular tachycardia and was being treated by beta-blockade. Postmortem study revealed massive fibro-adipose substitution of the right ventricular free wall and pulmonary infundibulum.

[Contribution of electrovectorcardiography in the diagnosis of hypertrophic cardiomyopathy. Comparative study with an echocardiographic score]. / Apport de l'électro-vectocardiographie dans le diagnostic de la myocardiopathie hypertrophique. Etude comparative avec un "score" échocardiographique.

The object of the study was to define spreading and quantitative criteria of left ventricular hypertrophy in echocardiography by using a "score"--for this, the left ventricle has been divided into 11 regions and a "score" attributed to each one of them--and to find the correlation with the vectocardiogram (VCG) in 42 patients with hypertrophic myocardiopathy (HM). The results obtained show the following: 1) the left ventricular hypertrophy aspect on the ECG and the VCG is very sensitive for the identification of a diffuse HM; 2) the necrosis, hemiblock or septal hypertrophy indicate a hypertrophy located in the forepart septum or the whole of the septum; 3) the giant T waves indicate a hypertrophy of the apex; 4) a left ventricular hypertrophy associated with a necrosis or a hemiblock indicate a global myocardiopathy, with the basal region of the septum largely affected.

Giant P wave in a patient with right ventricular cardiomyopathy.

A P wave of 7.5 mm in lead I and 12.5 in V1 was detected in a 28-year-old man, with a progressive cardiomegaly since the age of 14 years. At last admission he had minor symptoms, and a systolic murmur consistent with tricuspid regurgitation. The electrocardiogram showed an extremely tall P wave and a QRS of a very low amplitude; T waves were inverted on the precordial leads. These ECG features, and subsequent investigations, were consistent with right ventricular cardiomyopathy with massive tricuspid regurgitation, and right atrial abnormality.

[Arrhythmogenic myocardiopathy of the left ventricle: dynamic ECG. Morphologic data and age of the patient in the prediction of the onset of arrhythmic events]. / Miocardiopatia aritmogena del ventricolo destro: ECG dinamico. Dati morfologici ed età dei pazienti nel predire l'insorgenza di eventi aritmici.

In 57 patients with arrhythmogenic right ventricular cardiomyopathy, 34 males 23 females, aged 5 to 60 average 27.93 years, arrhythmias recorded during the whole clinical history have been compared with the 24 hours ECG ambulatory monitoring data, age and anatomic extension of the disease. In 77.77% of patients with history of sustained ventricular tachycardia Holter monitoring showed Lown class less than or equal to 3 arrhythmias, in 75% of patients with ventricular fibrillation Holter monitoring showed no arrhythmias. 55.88% of patients whose Holter monitoring documented Lown class less than or equal to 3 arrhythmias had more severe arrhythmias in their history. There is not a close relation between Holter data and arrhythmias that occurred during the whole history; however, Holter monitoring is a useful tool in evaluating risk when it shows complex arrhythmias.