Genome sequencing identify chromosome 9 inversions disrupting ENG in 2 unrelated HHT families

Hereditary hemorrhagic telangiectasia (HHT), also known as Rendu-Osler-Weber disease, is a dominant inherited vascular disorder. The clinical diagnosis is based on the Curaçao criteria and pathogenic variants in the ENG and ACVRL1 genes are responsible for most cases of HHT. Four families with a negative targeted gene panel and selected by a multidisciplinary team were selected and whole-genome sequencing was performed according to the recommendations of the French National Plan for Genomic Medicine. Structural variations were confirmed by standard molecular cytogenetic analysis (FISH). In two families with a definite diagnosis of HHT, we identified two different paracentric inversions of chromosome 9, both disrupting the ENG gene. These inversions are considered as pathogenic and causative for the HHT phenotype of the patients. This is the first time structural variations are reported to cause HHT. As such balanced events are often missed by exon-based sequencing (panel, exome), structural variations may be an under-recognized cause of HHT. Genome sequencing for the detection of these events could be suggested for patients with a definite diagnosis of HHT and in whom no causative pathogenic variant was identified.

L’augmentation du pourcentage de lymphocytes Th17 est associée à un risque d’évolution vers une forme grave d’infection à SARS-CoV-2

Introduction

Depuis décembre 2019, plus de 20 millions de français ont été infectés par le SARS-CoV-2 et plus de 130 000 en sont décédés. La physiopathologie de cette infection n’est pas totalement élucidée. Il a été démontré qu’elle provoquait une importante sécrétion de cytokines pro-inflammatoires, en particulier d’interleukine-6 (IL-6) [1]. Lorsque les patients infectés sont hospitalisés, ils reçoivent généralement de la dexaméthasone et parfois un traitement anti-infectieux. Si la maladie s’aggrave, le tocilizumab peut être ajouté [2]. Actuellement, seule l’évolution clinique incite à débuter le tocilizumab, mais parfois trop tardivement. Il manque aux cliniciens un marqueur précoce leur permettant de prédire le risque d’aggravation de la maladie. Cette étude, menée chez des patients hospitalisés pour infection à SARS-CoV-2 pendant la 2^e vague, avait pour objectif de rechercher un marqueur d’aggravation de la maladie en comparant la réponse lymphocytaire entre les patients évoluant vers une forme grave et les autres.

Patients et méthodes

Les patients hospitalisés pour infection à SARS-CoV-2 prouvée par RT-PCR datant de moins d’une semaine ont été inclus prospectivement dans cette étude monocentrique. Une infection grave était définie par un transfert en soins intensifs, en réanimation ou le décès. Des prélèvements sanguins ont été obtenus à l’admission à l’hôpital et avant de débuter la corticothérapie afin d’étudier les sous-populations lymphocytaires par cytométrie en flux et doser l’IL-6 plasmatique par immunofluorimétrie. Les données sont exprimées en nombre (%) ou médiane (espace inter-quartile).

Résultats

De septembre à décembre 2020, 37 patients (18 hommes, 19 femmes) hospitalisés pour infection à SARS-Cov2 ont été inclus : âge = 81,7 (70,3–87,5) ans, IMC = 25,7 (23,7–29) kg/m², hypertension artérielle (54 %), diabète (24 %), dyslipidémie (35 %), tabagisme (24 %), cardiopathie ischémique (8 %), maladie cérébrovasculaire (11 %). La durée de suivi était de 10 (8–15) jours. Parmi les 37 patients inclus, 11 (30 %) ont présenté une infection à SARS-CoV-2 grave dont 4 transferts en réanimation et 8 décès. À l’admission, les patients ayant une infection évoluant vers une forme grave étaient plus âgés (p = 0,021), avaient une créatininémie plus élevée (p = 0,003) et une diminution du pourcentage de lymphocytes B (p = 0,04), de lymphocytes T (p = 0,009) et de lymphocytes T CD4+ (p = 0,004) circulants parmi les lymphocytes totaux comparativement aux patients dont l’évolution était favorable. Parmi les sous-populations lymphocytaires T étudiées (mémoires, naïfs, Th1, Th2, Th17, Treg, Tc1, Tc17, T CD8 cytotoxiques), il n’y avait pas de différence significative entre les deux groupes en dehors du pourcentage de lymphocytes Th17 à l’admission qui était deux fois plus élevé chez les patients dont l’infection évoluait vers une forme grave (0,44 vs 0,23 % des LT CD4 totaux ; p = 0,028). Chez les patients ayant une infection évoluant vers une forme grave, l’IL-6 plasmatique à l’admission était plus élevée (39 vs 13,1 pg/mL ; p = 0,018) et la CRP à l’admission avait tendance à être plus élevée sans atteindre le seuil de significativité (58 vs 18,5 mg/L ; p = 0,17). En analyse multivariée (régression logistique binaire comprenant les variables : âge, créatininémie, CRP, hémoglobine, lymphocytes T CD4, Th17, Treg activés (CD4 + CD45RA-FoxP3high), lymphocytes B, IL-6 sérique), la seule variable associée au risque d’évolution vers une forme grave de l’infection était le pourcentage de lymphocytes Th17 circulants (p = 0,034). L’aire sous la courbe de la courbe ROC évaluant la sensibilité et la spécificité du pourcentage de lymphocytes Th17 pour prédire une forme grave d’infection à SARS-CoV-2 chez un patient hospitalisé était de 0,75 (intervalle de confiance à 95 % : 0,56–0,95). Enfin, le fait d’avoir un pourcentage de lymphocytes Th17 > 0,435 % des lymphocytes T CD4 totaux au moment de l’admission en hospitalisation était associé à une moins bonne survie (p = 0,024).

Conclusion

Cette étude suggère qu’une élévation du pourcentage de lymphocytes Th17 chez des patients hospitalisés pour infection à SARS-CoV-2 augmente significativement le risque d’évolution vers une forme grave de la maladie. Ce résultat est cohérent avec le fait qu’il a été démontré que le tocilizumab, qui est efficace dans le traitement des formes graves de COVID-19 [2], inhibe la réponse lymphocytaire Th17 [3]. Ces données méritent d’être confirmées chez un plus grand nombre de patients afin de confirmer ce résultat car cette mesure pourrait permettre de mieux cibler la population de patients à qui proposer précocement un traitement par tocilizumab pour diminuer le risque d’évolution vers une forme grave d’infection à SARS-CoV-2.

Immunological abnormalities associated with hereditary haemorrhagic telangiectasia

OBJECTIVE

Hereditary haemorrhagic telangiectasia (HHT) is a genetic disorder related to mutations in one of the coreceptors to the transforming growth factor-β superfamily (ALK1 or endoglin). Besides the obvious vascular symptoms (epistaxis and arteriovenous malformations), patients have an unexplained high risk of severe bacterial infections. The aim of the study was to assess the main immunological functions of patients with HHT using the standard biological tests for primary immunodeficiencies.

DESIGN, SETTING AND SUBJECTS

A prospective single-centre study of 42 consecutive adult patients with an established diagnosis of HHT was conducted at the National French HHT Reference Center (Lyon). Lymphocyte subpopulations and proliferation capacity, immunoglobulin levels and neutrophil and monocyte phagocytosis, oxidative burst and chemotaxis were assessed.

RESULTS

Innate immunity was not altered in patients with HHT. With regard to adaptive immunity, significant changes were seen in immunological parameters: primarily, a lymphopenia in patients with HHT compared with healthy control subjects affecting mean CD4 (642 cells μL(-1) vs. 832 cells μL(-1) , P < 0.001), CD8 (295 cells μL(-1) vs. 501 cells μL(-1) , P < 0.0001) and natural killer (NK) cells (169 cells μL(-1) vs. 221 cells μL(-1) , P < 0.01), associated with increased levels of immunoglobulins G and A. This lymphopenia mainly concerned naïve T cells. Proliferation capacities of lymphocytes were normal. Lymphopenic patients had a higher frequency of iron supplementation but no increase in infection rate. Lower levels of immunoglobulin M and a higher rate of pulmonary arteriovenous malformations were found amongst patients with a history of severe infection.

CONCLUSIONS

Patients with HHT exhibit immunological abnormalities including T CD4, T CD8 and NK cell lymphopenia and increased levels of immunoglobulins G and A. The observed low level of immunoglobulin M requires further investigation to determine whether it is a specific risk factor for infection in HHT.

[Tartrate-resistant acid phosphatases (TRAP) and cytology of pseudosynovial membranes]

Pseudo-synovial membranes are found at the interface between bone and aseptically lost prostheses. They are supposed to be due to the release of material debris at the interface with bone. They are mostly composed of macrophages and giant cells, and some fibrocytes in the deep layer of the membrane. The different histological structures present in these membranes have been largely described. Very recently, Kadoya et al. have demonstrated that a lot of giant cells present in the pseudo-synovial membranes show a tartrate resistant acid phosphatase activity in the presence of more than 100 mM tartrate. They have also shown that some of these cells were responsible for bone degradation. We have studied the tartrate acid phosphatase activity of a series of 10 membranes containing various material debris: titanium alloy, stainless steel, polymethylmethacrylate, polyethylene. Many mono or multinucleated cells showed a TRAP activity in their lysosomes in the presence of a 400 mM tartrate concentration. In certain membranes, these cells showed a TRAP activity located in the nucleus. This study shows that the macrophage population is very heterogeneous and the difference between osteoclasts and giant cells may be unclear.

[Engineering of osseous cells and bioartificial tissues]

The association of osteogenic stem cells to a synthetic carrier makes possible the elaboration of bioartificial tissue. Numerous phosphocalcic ceramics does not trigger a foreign body reaction when implanted in bone tissue and thus, a number of materials are available osteogenic stem cell carriers to replace the bone tissue. Several methods can be used to harvest these cells. Their multiplication in vitro can lead to the appearance of anomalies of their metabolism or their karyotype. The culture method also seems to have a major influence on their appearance. The presence of these anomalies could explain the variability of results in terms of bone extracellular matrix synthesis after cell reimplantation. The surgical technique used for the implantation is also of influence. A method suppressing the in vitro period has been developed to avoid any cell metabolism modification. This method allows for a very reproducible bone synthesis in ectopic site. The availability of human embryonic stem cells could help to develop cell graft techniques for bone reconstruction.

Degradation of hydroxylapatite, fluorapatite, and fluorhydroxyapatite coatings of dental implants in dogs

Calcium phosphate coatings on dental implants enhance integration of the material. Resorption of the ceramic coatings has raised some concern about the behavior of the bone-implant interfaces after the coating disappearance. Substitution of the OH- ions by fluoride in the hydroxylapatite (HA) lattice makes the calcium phosphate more stable. We investigated the degradation rate of dental implants with 50- and 100-microm coatings of HA, fluorapatite (FA), or fluorhydroxylapatite (FHA). The implants were inserted in dog jaws and retrieved for histological analysis after 3, 6, and 12 months. The thickness of the calcium phosphate coatings was evaluated using an image analysis device. A relative resorption index and its standard deviation were studied. HA and FA coatings (even at 100-microm thickness) were almost totally degraded within the implantation period. In contrast, the FHA coatings did not show significant degradation during the same period. The standard deviation showed that the resorption process for FHA with thicknesses of 50 or 100 microm was the same. Such a difference was not observed between the 50- and 100-microm thick coatings of FA and HA. In conclusion, the FHA coatings showed good integration in the bone tissue and lasted much longer than classic calcium phosphate coatings.

A study of structure and degradation of nonpolymeric biomaterials implanted in bone using reflected and transmitted light microscopy

Orthopedic biomaterials currently are made of metal alloy coated with one or more thin layers of dense or porous ceramic or metal. Sections of these materials implanted in human bone were made without altering the implant or bone-implant interfaces. Bone containing an implant was fixed and then embedded in polymethylmethacrylate. Thick sections were made using a cooled, low speed diamond saw, then ground and polished. Some were stained by fuchsin-toluidine staining solution, others were acid etched to reveal the structure of the metal contained in the prosthesis. Observation by reflected and transmitted light microscopy revealed microstructure of the implant material as well as features of the surrounding tissues.

New observations on middle term hydroxyapatite-coated titanium alloy hip prostheses

HA-coated hip prostheses were retrieved from elderly patients after death. Histological analysis, scanning electron microscopy and microanalysis by energy-dispersive X-ray spectrometry were performed on the same sections. These revealed good osseointegration of the implant material and evolution of bone and material.

Bonding of hydroxyapatite-coated femoral prostheses. Histopathology of specimens from four cases

We examined specimens of hydroxyapatite-coated femoral prostheses from four patients who had died within nine months of implantation for fractured neck of femur. Histology showed newly formed immature bone overlying the hydroxyapatite coating with new trabeculae bridging to the endosteal bone layer. In the diaphysis, where there had been contact between the hydroxyapatite and the cortex, there was dense, firmly anchored bone with an haversian architecture. In other places the newly formed bone had a trabecular structure, containing bone marrow tissue with normal cellularity. It appeared that biological osseointegration had taken place.

Physicochemical characterization of deposits associated with HA ceramics implanted in nonosseous sites

Pellets of well-characterized microporous hydroxyapatite (HA) ceramic were implanted in hamsters in two nonosseous sites: (1) in the fatty tissue of the gingival crease, far from bony tissue and (2) in intraperitoneal sites. The implants in site 1 were placed directly in contact with tissues, cells, and extracellular fluids while the implants in site 2 were placed in special chambers made of plexiglass cylinders covered in both ends with millipore filters, preventing contact with tissues and cells, but not with extracellular fluids. The hamsters were sacrificed and the implants recovered after 8, 16, 30, 150, and 365 days. The pellets were characterized using x-ray diffraction, infrared absorption, thermogravimetry, scanning and transmission electron microscopy, and calcium and phosphate analyses before and after implantation. Physicochemical analyses of HA ceramic implants before and after implantation demonstrated the formation of new material which was significantly different from the HA ceramic in terms of the following: (a) morphology (size of shape) of crystals; (b) intimate association of the inorganic phase of the new material with an organic phase similar to inorganic/organic association in bone; (c) the inorganic phase of the new material is a CO3-apatite, similar to that of bone, while the HA in ceramic is CO3-free; (d) electron diffraction of apatite of new material is similar to that of bone apatite. This study also demonstrated that the new material associated with the HA ceramics implanted in two different nonosseous sites were identical in spite of the differences in their microenvironment (cellular and acellular).

[Make-up of the posterior branches of the spinal nerves]

By opposition to the anterior branches of spinal nerves which are constituted by motor, sensitive and autonomic fibers, some of the posterior branches have not or have few of sensitive territory: C1, C5, C6, C7, D1, L4, L5 are like that. This particularity ought to be reflected in their histogram. In a first analyse authors study number of fibers, in a second their caliber.

Influence of 3-methoxy 5,7,3',4'-tetrahydroxyflavan (ME) on experimental periodontitis in the golden hamster

Experimental periodontal disease was induced in golden hamsters by feeding the animals with a Keyes 2 000 diet. The aim of the present study was to investigate the effect of 3-methoxy 5,7,3',4'-tetrahydroxyflavan (ME), a flavanoid derivative, on periodontally induced changes by this diet which was fed ad libitum to half of the animals for 2 months prior to the start of drug therapy. The animals were then divided into 4 groups: A) control animals on normal diet; B) ME-treated (200 mg/kg 3 times a week i.p.) animals on normal diet; C) animals on Keyes 2 000 diet; D) ME-treated (200 mg/kg 3 times a week i.p.) animals on Keyes 2 000 diet. ME inhibited the diminution of bone volume as measured morphometrically. The growth of dental plaque as evaluated by a sensitive index (PII) appeared to be retarded by ME. The average PII in the ME-treated animals reached after 2 months of diet remained unchanged during the drug therapy period (4 months); whereas it was significantly increased in the group C hamsters. The biochemical data further suggest that the resorption process of the alveolar bone was decreased by ME.

[Kurloff's thymic inclusion : action on rat gonads in culture]

Thymic and splenic extracts rich in FOA-KURLOFF (F.K.) body cells, obtained from guinea-pigs treated with oestrogen, were added to rat testis or ovaries in culture. Controls were prepared with extracts from thymus and spleen of non treated animals and from kidneys of treated or non treated animals. After five hours the level of sexual hormones and the germinal cells were studied. The F.K. substance has no effect on germinal cells and on progesterone and testosterone secretion. The F.K. substance induces a significative decrease of oestrogen secretion. In an other paper we established that F.K. bodies induced a hyperactivity of internal theca folliculi and of ovarian interstitial cells. It is a false image of activity in connection with a hypersecretion of FSH. The F.K. substance inhibits oestrogen synthesis.

[Neoplasm-resistance of guinea pigs: demonstration of a principle ensuring destruction of human cancer cells in culture]

The thymus and the spleen of guinea Pigs treated with oestrogen were rich in cells showing a special inclusion, the Foa-Kurloff body cell (F.K.). Thymic, spleen and renal cellular extracts were obtained by tissue crushing and ultra-centrifugation from healthy or oestrogen treated animals. The extracts were added to carcinomatous (HeLa) or to non-carcinomatous cells (MRC5 fibroblasts or foetal human lung cells). The thymic extracts in the non-treated animals and the splenic extracts rich in F.K. body cells induced an inhibition in the growth of carcinomatous cells. These effects were increased with the thymus extracts rich in F.K. bodies. The thymic inclusion of F.K. seems therefore to concentrate tumorous thymic fractions.

[Action of thymic extracts on the growth of different cell populations in vitro]

Thymic, splenic and renal cellular extracts were obtained by tissular grinding and ultra centrifugation, from animals having undergone diverse hormonal treatments. These extracts were added to different cellular populations in culture (carcinomatous HeLa strain, established MRCs strain, primo-culture of human foetal lung strain). The thymic extracts of non treated animals and the splenic extracts rich in FK substance from intact guinea pigs treated by oestrogenes or FSH, provoque an inhibition of tumoral cell growth. The most important effects are obtained with thymus extracts rich in FK substance. The FK substance seems capable of concentrating certain antitumoral thymic fractions.

[Thymic Kurloff inclusion. Action on the ovogenesis of the rat]

Grafts and injections of cellular extracts from thymus and spleen of guinea pigs, were carried out in puberal and impuberal female rats. These organs are especially rich in Foa-Kurloff cells after oestrogentherapy. Kidney served as a reference material for the same experimental conditions. Controls received cellular injections and grafts from guinea pig organs without treatment. In all cases, ovarian histological and biometric study of recipient animals shows no alteration of the ovarian cycle. On the other hand, grafts and injections of cellular extracts from organs with high concentration of Foa-Kurloff cells induced hyperactivity of internal theca folliculi and of ovarian interstitial cells, only in puberal female rats.

Study of light-, electron- and immunofluorescence microscopy of urinary sediment in amyloidosis

Urinary sediment of 11 patients with amyloidosis and 12 without (with proteinuria or in good health) have been sutdied by different morphological techniques. By light microscopy, an amyloid-related substance was occasionally demonstrated both in patients with amyloidosis and in control subjects. Immunofluorescence (IF) showed substance A (amyloid component) to be present in some cases of amyloidosis and in controls. On electron-microscopy, fibrils with characteristic appearance of amyloid substance were found in some cases of amyloidosis (4 out of 11), but were also found in controls. It therefore seems difficult to establish the diagnosis of amyloidosis by microscopic studies of the urinary sediment.