Marco Galloni

Bovine pericardium for heart valve bioprostheses:in vitro andin vivo characterization of new chemical treatments

This study is aimed at investigating the bovine pericardium treated with different chemical procedures applied to prevent dystrophic calcification; decellularization of the fresh pericardium (samples B and C); fixation of the pericardium with glutaraldehyde (samples A, B, C, D and E); detoxification with aminoacids (samples A and B) and storage in a solution of benzoic acid esters. Pericardial sacs were harvested and delivered to the laboratories to be submitted to the chemical treatments. The samples E have been treated as the samples D but before the implantation they were exposed to the surgical lamp in order to promote some drying. The samples were tested for their mechanical properties and shrinkage temperature (at 1 week and after 36 months). Thein vivo tests were performed by means of implantation in a paravertebral subcutaneous position in rats. At the explant (2, 4 and 8 weeks) the samples were submitted to histological assay and the calcium content determined by spectroscopic atomic absorption. All the samples showed loss of tensile strength and elongation at 36 months (except for the sample A), as well as a moderate diminution of the shrinkage temperature. The histology showed that the decellularized samples (B, C) were thicker than the others and the collagen fibres were extensively homogenated. The cell colonization was macrophagic for the samples A and D while it was also composed of giant cells in the samples B, C and E at 8 weeks. The von Kossas staining was positive only for the samples D and E after 4 weeks of implantation. The calcium content of the samples D was 285.3 mg/g at 8 weeks while in E it was 44.4 mg/g dry tissue at 4 weeks; for the remaining samples the calcium content did not increase with the time (2.1–2.3 mg/g at 8 weeks). In conclusion, the pericardium decellularization and detoxification associated with its storage in a glutaraldehyde-free solution is a promising method in order to realize more durable pericardial bioprostheses. The investigated tissue treatments applied to the bovine pericardium permit removal of the calcium nucleation sites, and hence the avoidance of the severe drawback of the aldehyde crosslink, but at the same time maintain the necessary and well known tissue stability.

Endocarditis in patients with bioprostheses: pathology and clinical correlations

We studied 13 porcine bioprostheses removed from patients with endocarditis at our institute during the last 4.5 years. All bioprostheses had been removed at reoperation and were analyzed using anatomical and histological techniques. Each bioprosthesis was found to have developed rather constant lesions which were not related to the type of bioprosthesis. The stage of infection was not related to the duration of implantation. The presence of perivalvular abscesses was an ominous finding, often being the seat of persistent endocarditis. Our good clinical results of reoperation lead us to suggest that this be performed early once valvular or prosthetic malfunction is detected. Bioprostheses are, in our experience, the best choice in the surgical treatment of prosthetic valve endocarditis.

Carbon-coated stents implanted in porcine iliac and renal arteries: Histologic and histomorphometric study

PURPOSE To test in a pig model the biocompatibility and effectiveness of carbon-coated renal and iliac artery stent systems during implantation procedures and at different follow-up periods. MATERIALS AND METHODS Twenty-two miniature pigs received carbon-coated balloon-expandable stainless-steel stents in their renal and iliac arteries. Animals were killed at 7, 30, or 180 days for evaluation of acute, subacute, and chronic biologic response to the implanted devices. Histologic, histomorphometric, and scanning electron microscopy (SEM) analyses were performed to assess inflammatory reaction, endothelialization process, and neointimal growth. RESULTS Forty-four iliac stents and 42 renal stents were successfully implanted. Mural thrombi were not observed by angiography or histologic examinations. Histologically, no significant inflammatory reaction was detected: the stents appeared covered by a thin monolayer of endothelial cells even at 7-day follow-up. The neointima showed homogeneous growth and moderate thickness at 30-day and 180-day explantations (0.09 mm +/- 0.06 and 0.15 mm +/- 0.13, respectively, for renal arteries; 0.12 mm +/- 0.04 and 0.21 mm +/- 0.12, respectively, for iliac arteries). Internal and external elastic laminae were intact in 82 of 86 cases (95%) of stent-implanted arteries. Histologic validations were obtained with SEM observations for each follow-up group. CONCLUSIONS This study showed good technical results of deployment of carbon-coated renal and iliac stents and very satisfactory biologic behavior in terms of tissue and hematologic compatibility. The devices do not induce thrombus formation.

Carbofilm ™: Present and future applications in biomedical devices

Abstract Carbofilm is a thin film of pyrolytic carbon that can be deposited on materials, such as polymers and metals, suitable for implantable-prosthesis production. In this way, the coated material acquires the well-known biocompatibility characteristics of pyrolytic carbon. In critical applications such as heart-valve prostheses, the Carbofilm coating has proved to be effective in reducing those blood and tissue reactions that can negatively affect the implanted prosthesis functionality. Carbofilm can be applied on different biomedical devices in order to improve their biocompatibility: a summary of experimental results obtained with vascular grafts, plastic-surgery devices, and orthopaedic and maxillofacial prostheses will be reported. In particular, the most recent results concerning the osteocompatibility of titanium-alloy coated and uncoated samples will be presented: Carbofilm-coated cylinders implanted in the cubital bone of sheep, histologically evaluated at three and twelve months, showed a better biological response (lower osteoclastic erosion and connective-tissue formation) than uncoated ones.

Short-, mid-, and long-term effects of a polymer-free tacrolimus-eluting stent in a porcine coronary model

Stent-based delivery of tacrolimus has shown neointimal hyperplasia and restenosis reduction; FK506 is a water insoluble macrolide immunosuppressant. The purpose of this study was to evaluate acute and chronic tissue response to a polymer-free FK506 drug-eluting stent implantation in a porcine coronary artery model. Seventy-eight nonatherosclerotic minipigs underwent successful placement of 134 stents (control n = 56; FK506 (1.5 microg/mm(2)) n = 44; FK506 (2.6 microg/mm(2)) n = 34) at 7, 15, 30, 90, or 180 days. Endothelialisation was almost complete at 7 days, complete at 15 days. At 30 and 90 days, mean neointimal thickness, neointimal area, and % stenosis was significantly less for drug-eluting stents compared with controls. At 180 days, histomorphometric values were similar for eluting and control stents. The FK506-eluting stent allows for a complete re-endothelialisation at 15 days and favorably moderate neointimal hyperplasia at 30 and 90 days in the porcine coronary model. Because of a possible limited bioavailability of FK506, long-term inhibition of neointimal formation was not sustained at the considered follow-up.

Angelo Mosso (1846-1910)

Angelo Mosso was born on the May 30, 1846, in Turin, Italy. His modest family was from Chieri, a town near Turin. Mosso spent a large part of his childhood in Chieri and would for the rest of his life consider himself a citizen of this small town [1]. In school, he was not always a model pupil: on one occasion, for example, his mother had to intercede in order to have him re-admitted after he had been put to work in his father’s carpenter shop [1]. Though he spent his childhood and adolescence in poverty, his brilliant results in secondary school helped him to obtain grants and his diploma. Thanks to his family’s savings and his earnings as an assistant-teacher in Chieri, Mosso could pay the academic fees and study medicine. In 1870, he graduated from the University of Turin magna cum laude. As a young physician in Florence, he devoted himself to research in the physiology laboratory directed by Moritz Schiff (1823–1896), where he studied the mechanics of esophageal contraction. He then moved to Leipzig, to the laboratory of Carl Ludwig (1816–1895), and subsequently to Paris, where he worked with Claude Bernard (1813–1878) and Étienne-Jules Marey (1830–1904). During his European tour, he focused on graphical methods to investigate the dynamics of physiological phenomena. On his return to Turin, he applied the graphical method to the circulation in the human brain. Mosso’s most well-known contribution to neurology is his study of subjects with skull defects [2, 3]. The ‘Mosso method’ consisted of measuring changes in cerebral blood flow in these patients by recording brain pulsations—a phenomenon normally observed in the fontanelles of newborns—by means of the special plethysmograph he developed for this purpose. By converting brain pulsations into plethysmographic waves he could quantify the S. Sandrone M. Bacigaluppi G. Martino Vita-Salute San Raffaele University, 20132 Milan, Italy

Anatomic, histologic, and two-dimensional- echocardiographic evaluation of mitral valve anatomy in dogs

OBJECTIVE To compare echocardiographic variables of dogs with postmortem anatomic measurements and histologic characteristics of the mitral valve (MV). ANIMALS 21 cardiologically normal dogs. PROCEDURES The MV was measured echocardiographically by use of the right parasternal 5-chamber long-axis view. Dogs were euthanized, and anatomic measurements of the MV annulus (MVa) were performed at the level of the left circumflex coronary artery. Mitral valve leaflets (MVLs) and chordae tendineae were measured. Structure of the MVLs was histologically evaluated in 3 segments (proximal, middle, and distal). RESULTS Echocardiographic measurements of MVL length did not differ significantly from anatomic measurements. A positive correlation was detected between body weight and MVa area. There was a negative correlation between MVa area and the percentage by which the MVL area exceeded the MVa area. Anterior MVLs had a significantly higher number of chordae tendineae than did posterior MVLs. Histologically, layering of MVLs was less preserved in the distal segment, whereas the muscular component and adipose tissue were significantly more diffuse in the proximal and middle segments. CONCLUSIONS AND CLINICAL RELEVANCE The MV in cardiologically normal dogs had wide anatomic variability. Anatomic measurements of MVL length were correlated with echocardiographic measurements.

Preclinical evaluation of a novel abluminal surface coated sirolimus eluting stent with biodegradable polymer matrix.

BACKGROUND Second generation of drug eluting stents (DES) has attempted to improve safety using abluminal sirolimus drug delivery with biodegradable polymers matrix. The present preclinical study was designed to investigate the safety and efficacy profile of Abluminus™ stents (SES). This is a new coronary stent with sirolimus and biodegradable polymer matrix coated on abluminal stent and balloon surface. METHODS SES were compared with two controls: bare metal stent (BMS) and BMS + polymer coated stents (PC). All devices (40 stents) were implanted in porcine coronary arteries with primary endpoint of endothelialization at 7 days and subsequent histological and morphometric evaluations at 7, 30 and 90 days. RESULTS Early endothelialization at seven days was complete in all stents. Histology at 30 days revealed minimum inflammation in all groups and increased at 90 days in PC group while it was absent at 180 days. Thirty day morphometry showed significantly reduction of neointimal area in Abluminus™ (SES 0.96±0.48 mm(2); BMS 1.83±0.34 mm(2); PC 1.76±0.55 mm(2); P<0.05); after 90 days neointimal area was 1.10±0.54 mm(2) for SES; 1.92±0.36 mm(2) for BMS; and 1.94±0.48 mm(2) for PC; P<0.05). Neointimal thickness at 30 and 90 days respectively was 0.15±0.07 and 0.18±0.10 mm for SES, 0.57±0.08 and 0.61±0.09 mm for BMS and 0.52±0.09 and 0.59±0.08 mm, P<0.001 for PC group. CONCLUSIONS The most significant experimental evidence appears to be earlier endothelialization at 7 days for SES which led to safety of the device. Efficacy of the device was also observed by a reduced neointimal thickness and minimized inflammatory score at all follow-ups. Termination of antiplatelet at 30 days has not shown any further complications. Polymer thickness was almost in negligible amount at 180 days with no inflammation.

Cytostatic drugs differentially affect phenotypic features of porcine coronary artery smooth muscle cell populations

By promoting SMC quiescence and differentiation imatinib and curcumin may represent valid candidates for restenosis preventive and therapeutic strategies.

Calcification of chemically treated bovine pericardium.

One of the most important problems arising in cardiac bioprostheses made with bovine pericardium and, more generally, with biologically-derived tissues is tissue calcification. The present study assessed four chemical treatments on patches of bovine pericardium, intended to avoid or minimize calcification. Pericardium specimens were treated with: A) 0.5% glutaraldehyde; B) 0.5% glutaraldehyde + 4% formaldehyde; C) same as A, but with a further neutralization treatment; D) acylation of fresh bovine pericardium. Circular samples of 1 cm diameter were subcutaneously implanted in the abdominal region of three groups of six rats. The explants were retrieved after 2, 4 and 8 weeks. The calcium content and the histological results showed better behaviour for C and D samples than with the commonly used fixation methods (A and B). The lowest calcification was observed with treatment D, even though its morphological structures were somewhat modified with homogenation of collagen bundles. Among the glutaraldehyde-based treatments, treatment C appears to be the most promising because the pericardium shows slower calcium accumulation with a diffusive pattern.