Decreased Mechanical Strength and Collagen Content in SPARC‐Null Periodontal Ligament Is Reversed by Inhibition of Transglutaminase Activity

The periodontal ligament (PDL) is a critical tissue that provides a physical link between the mineralized outer layer of the tooth and the alveolar bone. The PDL is composed primarily of nonmineralized fibrillar collagens. Expression of secreted protein acidic and rich in cysteine (SPARC/osteonectin), a collagen‐binding matricellular protein, has been shown to be essential for collagen homeostasis in PDL. In the absence of SPARC, PDL collagen fibers are smaller and less dense than fibers that constitute WT PDL. The aim of this study was to identify cellular mechanisms by which SPARC affected collagen fiber assembly and morphology in PDL. Cross‐linking of fibrillar collagens is one parameter that is known to affect insoluble collagen incorporation and fiber morphology. Herein, the reduction in collagen fiber size and quantity in the absence of SPARC expression was shown to result in a PDL with reduced molar extraction force in comparison to that of WT mice (C57Bl/6J). Furthermore, an increase in transglutaminase activity was found in SPARC‐null PDL by biochemical analyses that was supported by immunohistochemical results. Specifically, collagen I was identified as a substrate for transglutaminase in PDL and transglutaminase activity on collagen I was found to be greater in SPARC‐null tissues in comparison to WT. Strikingly, inhibition of transglutaminase activity in SPARC‐null PDL resulted in increases in both collagen fiber thickness and in collagen content, whereas transglutaminase inhibitors injected into WT mice resulted in increases in collagen fiber thickness only. Furthermore, PDL treated with transglutaminase inhibitors exhibited increases in molar extraction force in WT and in SPARC‐null mice. Thus, SPARC is proposed to act as a critical regulator of transglutaminase activity on collagen I with implications for mechanical strength of tissues. © 2015 American Society for Bone and Mineral Research     

Multidisciplinary team meeting for complex bone and joint infections diagnosis: The PHICTOS study

Background

In France, the most severe bone and joint infections (BJI), called “complex” (CBJI), are assessed in a multidisciplinary team meeting (MTM) in a reference center. However, the definition of CBJI, drawn up by the Health Ministry, is not consensual between physicians. The objective was to estimate the agreement for CBJI classification.

Midterm Outcomes of Embolisation of Internal Iliac Artery Aneurysms

ObjectivesThere is no standardised technique for internal iliac artery aneurysm (IIAA) embolisation and results of long-term prevention of rupture are unknown.DesignWe retrospectively evaluated technical aspects and results of IIAA embolisation in a multicentre study.MethodsAneurysm morphology and embolisation techniques were reviewed. Aneurysm-related death, rupture, diameter increase, endoleak, secondary procedure and complication related to the IIA occlusion were recorded.ResultsBetween 2001 and 2011, 53 patients with 57 IIAA were treated. Mean diameter of IIAA was 41 mm (range: 25–88 mm). Embolisation techniques were distal and proximal occlusion (n = 24), proximal occlusion (n = 18) and sac packing (n = 15). Cumulative overall survival rate was 92% at 1 year, 83% at 3 years and 59% at 5 years. No cause of deaths was related to aneurysm. Aneurysm diameter increased in five patients and endoleak was observed in 11 patients. One secondary open conversion and five secondary endovascular procedures were performed for increase of diameter or proximal endoleak. Two patients experienced a disabling buttock claudication.ConclusionsEmbolisation of IIAA is safe in the short- and midterm. However, endoleak and aneurysm diameter increases are not rare. Yearly post-procedure computed tomography angiography seems appropriate.     

Viscoelastic properties of human arteries methodology and preliminary results

In order to study the biomechanical properties of the arterial wall and to compare arteries with different histologic structures, we designed a device that allows testing of arterial segments under near-physiologic conditions. A hydrodynamic generator simulates systolo-diastolic pressures in an open loop. An intraarterial pressure sensor and a sonomicrometer connected to two piezoelectric crystals placed in diametric opposition on the arterial wall allow computer calculation of compliance, stiffness, midwall radial arterial stress, Young modulus, and incremental modulus for a given arterial segment at a given pressure setting. Seven healthy common carotid artery (CCA) segments and seven healthy (superficial) femoral artery (FA) segments were studied immediately after removal from brain-dead donors between the ages of 18 and 35 years. Histologic examination was performed to determine the density of elastic fibers in the arterial wall. Hysteresis was observed in all segments regardless of pressure settings. Compliance was greater and modulus values and stiffness were lower in CCA than in FA. No evidence of structural change was noted after testing in the circulation loop. These preliminary results open the way to a wide variety of applications for our hydrodynamic circulation loop. Experiments will be undertaken to compare the mechanical properties of arteries before and after cryopreservation.

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Propriétés visco-élastiques des artères humaines. Méthodologie et résultats préliminaires

Résumé Dans le but d'étudier les propriétés mécaniques de la paroi artérielle et de pouvoir établir des comparaisons entre des segments artériels de structure histologique différente, nous avons mis au point un banc d'essai hydrodynamique permettant de tester des segments artériels dans des conditions voisines de la réalité physiologique. Un générateur hydrodynamique permettait d'obtenir dans un circuit ouvert un régime de pressions de type systolo-diastolique. Un capteur de pression intra-artériel, ainsi qu'un sonomicromètre relié à des cristaux piézo-électriques placés de façon diamétralement opposée sur la paroi artérielle, permettaient de calculer, pour un régime de pressions donné et grâce à l'acquisition de données dans un système informatique, la compliance, la rigidité, la contrainte trans-pariétale, le module de Young, le module incrémentiel d'un segment artériel. Nous avons étudié sept artères carotides communes (CC), et sept artères fémorales (superficielles) (F) fraîchement prélevées chez des sujets sains âgés de 18 à 35 ans. Des corrélations avec la richesse en fibres élastiques de la paroi artérielle ont été établies. Nous avons mis en évidence un phénomène d'hystérésis pour chaque artère testée quel que soit le niveau de pression considéré. La compliance des artères CC a été plus importante, les modules et la rigidité ont été moins importants et ce de façon significative par rapport aux artères F. Aucune altération histologique n'a été mise en évidence après passage des segments artériels au banc d'essai. Ces résultas préliminaires nous permettent d'envisager de nombreuses applications à ce travail dont l'une d'entre elles sera la mesure comparative des propriétés mécaniques des artères avant et après cryopréservation.

     

Mesenchymal stem cells in bone and cartilage repair: current status

The progression of rheumatoid pathologies, degenerative diseases, traumatologies, and their cortege of increasing medical, social and economical needs, has mandated the development of tissue repair and engineering technologies in orthopedic medicine. Mesenchymal stem cells (MSCs) are multipotent cells that can be extracted from large and relatively easily accessible compartments of the body, especially the bone marrow, and such cells are able to differentiate into adipogenic, chondrogenic and osteogenic precursors. The concept of using MSCs to repair tissues has progressively evolved, and the goal of cell-mediated therapy is to prolong the natural physiological abilities of healing, or substitute them, when these are lacking, failing or progressing too slowly. In recent years, the first clinical trials on the utility of MSCs, with or without scaffolds and/or growth factors, have been initiated. In this review, the authors focus on findings from preclinical research, clinical trials and case reports involving bone and cartilage repairs. New perspectives are considered regarding uses of cell types, cell delivery approaches and growth factors. They also consider the stringent conditions, constraints and considerations necessary to take cell-mediated therapy from bench to bedside.     

Inverse variations of plasma renin activity and renin substrate in normal man

Abstract. In the control subject, plasma angiotensin production is a linear function of plasma renin content. Upon incubation of this same plasma in the presence of an excess of homologous renin, angiotensin production is finally limited by the plasma content of renin substrate (PRS). By this method, PRS levels were measured and compared with levels of plasma renin activity (PRA), urinary aldosterone excretion, and sweat sodium and potassium content, in sixteen normal human subjects, aged twenty-five to thirty years, under three defined metabolic conditions: unrestricted sodium intake, salt depletion, constant sodium intake plus administration of desoxycorticosterone acetate (DOCA). 1) Unrestricted Sodium Intake. In these control subjects, in perfect health, there exist important individual differences in PRS levels. The PRS levels seem to be quite constant for a given subject under a given metabolic condition: the levels remained the same after a four month interval for a given subject. 2) Salt Depletion. Activation of the renin-angiotensinaldosterone system (RAAS), as shown by an elevation of PRA and of urinary aldosterone excretion, is accompanied by a decrease in PRS levels. 3) Constant Sodium Intake Plus Administration of DOCA. Inactivation of the RAAS, as shown by lowering of PRA and of urinary aldosterone excretion, is accompanied by a marked elevation of PRS levels. It would appear that, in human control subjects there exists an inverse relationship between PRS and PRA levels.     

Cryopreserved arterial allografts for in situ reconstruction of abdominal aortic native or secondary graft infection

Objective

The objective of this study was to evaluate the early and long-term outcome of cryopreserved arterial allografts (CAAs) used for in situ reconstruction of abdominal aortic native or secondary graft infection and to identify predictors of mortality.

A study on the venom of Bothrops alternatus Duméril, Bibron and Duméril, from different regions of Argentina

We report a comparison of toxic and enzymatic activities of Bothrops alternatus venoms collected from specimens of different regions of Argentina with a pool of these same venoms. We determined lethal, hemorrhagic and pro-coagulant (plasma and fibrinogen) doses, as well as indirect hemolysis, hydrolysis of gelatin and fibrinogen. The electrophoretic pattern of the venoms and that of fibrinogen incubated with each of the venoms was studied by SDS-PAGE. The toxic activities were consistent with those reported for these venoms but with noticeable differences between samples which do not seem related to geographical or climatic characteristics. In some cases the pooled venom showed values close to the individual samples, but it was not representative since at least the half of the venoms (4/9) exhibited very different patterns of toxicity. The potency of some activities in the individual venoms ranged from much higher to much lower than those determined in the pooled venom (0.1 to 3 fold). Not all venoms exhibited thrombin-like activity but all hydrolyzed α and β chains of fibrinogen; however, degradation patterns were not always similar. Variation in activities and toxicities do not seem to be related to geographical or climatic characteristics.