Nanocoating with titanium reduces iC3b- and granulocyte-activating immune response against glutaraldehyde-fixed bovine pericardium: a new technique to improve biologic heart valve prosthesis durability?

OBJECTIVES: An IgG and granulocyte-activating immune response with secondary dystrophic calcification might be the reason glutaraldehyde (GA)-fixed xenograft valves fail, especially in young patients, who are more immunocompetent than the elderly. Titanium nanocoating on GA-fixed bovine pericardium was tested for its ability to prevent major immunoreactions. METHODS: The immune activity of platelets from GA-fixed bovine pericardium with different treatment procedures was evaluated using the blood from 5 human donors: group I (n = 5), GA fixed as the control; group 2 (n = 5), detoxified with 10% citric acid; group 3 (n = 5), 10% citric acid, aldehyde-dehydrogenase, and a physical plasma treatment; and group 4 (n = 5), treated the same as group 3, but with an additional titanium coat 30 nm in thickness. Titanium deposition was visualized using scanning electron microscopy. IgG deposits (iC3b) were shown by immunostaining and documented as colored pixels (red). The pixels were evaluated electronically. Attracted granulocytes (polymorphonuclear leukocytes) were counted in front of the titanium-coated surface. RESULTS: IC3b deposits and polymorphonuclear leukocytes within control group 1 were defined as 100%; in group 2, iC3b was 149% ± 34% and polymorphonuclear leukocytes were 89%, in group 3, IC3b was 102% ± 24% and polymorphonuclear leukocytes were 47%; and in group 4, IC3b had decreased to 38.49% ± 21% (P < .05) and polymorphonuclear leukocyte activation had decreased to 6.3% (P ≤ .01). CONCLUSIONS: Titanium coating significantly reduced the iC3b and granulocyte activating immune response of GA-fixed pericardium. Therefore, it might prevent relevant immunorejection and increase the durability of GA-fixed bioprosthetic heart valves.

Impact of valves in a biomechanical heart model assisting failing hearts.

Experimental valveless muscular blood pumps (biomechanical hearts) in goats can pump more than 1 L.min(-1), but due to a high pendulum volume, no significant flow contribution to the circulation is gained. Thus valved and valveless biomechanical hearts were compared for efficacy. Heart failure was induced in 5 adult Bore goats by repeated intracoronary embolization. A valved and balloon-equipped pumping chamber was integrated into the descending aorta, simulating standard biomechanical circulatory support. The valveless biomechanical heart supported a failing heart with a baseline cardiac output of 2,670 +/- 710 mL.min(-1) by contributing additional flow of 113 +/- 37 mL.min(-1). The biomechanical heart model incorporating an outlet valve offered an additional 304 +/- 126 mL.min(-1), and the use of 2 valves significantly enhanced pulmonary blood flow by 1,235 +/- 526 mL.min(-1). The use of 2 valves in biomechanical hearts seems to be essential to achieve adequate circulatory support. Double-valved biomechanical hearts driven by an appropriate skeletal muscle ventricle may contribute to the therapy of heart failure.

Detoxification and endothelialization of glutaraldehyde-fixed bovine pericardium with titanium coating: a new technology for cardiovascular tissue engineering.

BACKGROUND: Endothelial cell seeding of glutardialdehyde-fixed biological heart valves is hypothesized to improve biocompatibility and durability; however, the toxicity of glutardialdehyde prevents its use as a biological coating. Therefore, different detoxification strategies are applied, including surface coating with titanium, before in vitro endothelialization of glutaraldehyde-fixed bovine pericardium as the base material for prosthetic heart valves. METHODS AND RESULTS: Bovine pericardium was fixed with 0.25% glutardialdehyde. Detoxification was performed with citric acid, aldehyde dehydrogenase, and plasma deposition with titanium at low temperatures of 30 degrees C to 35 degrees C. Toxic glutaraldehyde ligands were quantified photometrically, and the vitality of seeded cells was tested to validate detoxification methods. Detoxification agents and titanium coating were applied before seeding with human endothelial cells. Endothelial cells were visualized by electron microscopic surface scanning. To evaluate cell adhesion, shear stress was applied by a flow of 5 L/min over 24 hours. Compared with untreated glutaraldehyde-fixed samples, treatment with the different agents reduced free aldehyde groups gradually (citric acid 5% < citric acid 10% < titanium < aldehyde dehydrogenase). A combination of citric acid 10%, aldehyde dehydrogenase, and titanium coating resulted in a reduction of free aldehyde ligands to 17.3+/-4.6% (P < or = 0.05) and demonstrated a vitality of seeded cells of 94+/-6.7% (P < or = 0.05). This procedure yielded a completely confluent layer of regular human endothelial cells (n=5). After application of shear stress for 24 hours on these endothelial layers, cell vitality was 81%. CONCLUSIONS: Titanium coating combined with chemical procedures yielded significant detoxification and complete endothelialization of conventional glutaraldehyde-fixed pericardium. This new technique might improve glutardialdehyde-fixed cardiovascular bioimplants for better biocompatibility and longer durability.

Towards a pragmatic strategy for regenerating infarcted myocardium with glandular stem cells.

We have recently reported that the in vitro differentiation of human glandular stem cells into cardiac-like cells can be enhanced by co-culture with small myocardial biopsies. These results suggest that implantation of such cells directly into infarcted myocardium may facilitate the regeneration of the heart. As a preliminary to testing this approach in a goat model, pilot in vitro tests for these experiments have been performed and are presented here. Stem cells, isolated from the glandula submandibularis of Boer goats (SuSCs), have been co-cultured either directly or indirectly with heart biopsies from various species (Boer goat, rattus norwegicus, human) or heart conditioned medium for 48h. We found a substantial increase in the number of cells expressing heart-specific marker proteins (Troponin I, Troponin T, sarcomeric myosin) regardless of the source organism of the heart biopsy. The proliferation of SuSCs also increased significantly under co-culture conditions. To benefit from these results in vivo, the stem cells must be delivered to the infarcted region in the heart and held securely in place over lengthy periods of time. Therefore, we repeated the co-culture experiments with SuSCs grown on biodegradable Vicryl-meshes. The cells demonstrated good proliferation on the meshes and likewise, the expression of heart-specific marker proteins could be enhanced through co-culture with heart biopsies.

Bio-technologies for a glandular stem cell cardiomyopexy.

The glandular stem cell cardiomyopexy should become a treatment option for end-stage heart failure. It combines an expected regenerative potential of transformed adult glandular stem cells into cardiomyocytes within the myocardium or onto the myocardium of the recipient and the potential of a hypercapillarized latissimus dorsi muscle (LDM) wrapped around the heart for stem cell nutrition and girdling.

Seventy-five years' survival in partial atrioventricular septal defect.

Long-term survival of patients with partial atrioventricular septal defect (PAVSD) without operative therapy is very rare. The case is reported of a 75-year-old man who presented with dyspnea and decline of general condition. A heart defect was known but not investigated as the patient refused to undergo invasive cardiologic diagnosis. Hence, treatment was conservative. At autopsy, a huge (3 cm diameter) ostium primum atrial septal defect (ASD) was found, together with deformation of the right and left atrioventricular valves and extreme dilatation of the heart. Pulmonary arteriosclerosis indicating pulmonary hypertension was present, but there was no lung fibrosis. Life expectancy in patients with PAVSD ranges from 3 to 37.5 years. The present patient showed very late onset pulmonary hypertension, which may be a critical parameter for survival.

Development of muscular blood pumps performed in a one-step operation.

Up to now, the employment of skeletal muscle ventricles (SMVs) has required a two-step operation, that is, first, the construction followed by a vascular delay and electrical conditioning, and second, the integration into circulation by a second operation. As shown previously, clenbuterol increased the power of electrically conditioned SMVs wrapped around a mock system. These clenbuterol-supported SMVs pumped successfully from construction to several months against a pressure of 60-70 mm Hg. Due to these successful former experiments, a muscular blood pump has been employed via a one-step procedure, trained within the circulation under the support of clenbuterol. It appeared to be hemodynamically relevant and is expected to become clinically practicable for the treatment of end-stage heart failure.