In Vitro Analysis of the Cytocompatibility of a Novel Porcine Aortic Patch for Vascular Reconstruction.

BACKGROUND/AIM: Cardiovascular diseases are one of the most common causes of morbidity and mortality in the world. In the case of severe arteriosclerotic damage, surgical treatment is necessary. Although the use of autologous vessels is still considered to be the gold standard, sufficient autologous vessels for transplantation are lacking. MATERIALS AND METHODS: In the present study, histological examination and in vitro cytotoxicity analysis according to DIN EN ISO 10993-5 were performed on a newly developed porcine vascular graft from a decellularized aorta. A conventional bovine graft was used as control. RESULTS: The ex vivo-histological analysis revealed the effectiveness of a new purification process on the microstructure and the removal of xenogeneic antigen-bearing structures in the new vessels. Furthermore, cell viability and cytotoxicity assays revealed full cytocompatibility. CONCLUSION: The novel graft shows no structural damage and gets completely decellularized by the purification process. Superior cytocompatibility, compared with the bovine-derived vascular graft, was demonstrated.

Novel Histomorphometrical Approach to Evaluate the Integration Pattern and Functionality of Barrier Membranes.

GBR (guided bone regeneration) is a standard procedure for building up bony defects in the jaw. In this procedure, resorbable membranes made of bovine and porcine collagen are increasingly being used, which, in addition to many possible advantages, could have the potential disadvantage of a shorter barrier functionality, especially when augmenting large-volume defects. Thus, it is of importance to evaluate the integration behavior and especially the standing time of barrier membranes using specialized methods to predict its respective biocompatibility. This study is intended to establish a new histomorphometrical analysis method to quantify the integration rate of collagen-based barrier membranes. Three commercially available barrier membranes, i.e., non-crosslinked membranes (BioGide® and Jason® membrane), a ribose-crosslinked membrane (Ossix® Plus), and a newly developed collagen-hyaluronic acid-based (Coll-HA) barrier membrane were implanted in the subcutaneous tissue of 48 6-8-week-old Wistar rats. The explants, after three timepoints (10, 30, and 60 days), were processed and prepared into histological sections for histopathological (host tissue response) and histomorphometrical (cellular invasion) analyses. 10 days after implantation, fragmentation was not evident in any of the study groups. The sections of the Coll-HA, Jason® and BioGide® membranes showed a similar mild inflammatory reaction within the surrounding tissue and an initial superficial cell immigration. Only in the Ossix® Plus group very little inflammation and no cell invasion was detected. While the results of the three commercially available membranes remained intact in the further course of the study, only fragments of the Coll-HA membrane were found 30 and 60 days after implantation. Histomorphometrically, it can be described that although initially (at 10 days post-implantation) similar results were found in all study groups, after 30 days post-implantation the cellular penetration depth of the hyaluronic acid-collagen membrane was significantly increased with time (**** p < 0.0001). Similarly, the percentage of cellular invasion per membrane thickness was also significantly higher in the Coll-HA group at all timepoints, compared to the other membranes (**** p < 0.0001). Altogether, these results show that the histomorphometrical analysis of the cellular migration can act as an indicator of integration and duration of barrier functionality. Via this approach, it was possible to semi-quantify the different levels of cellular penetration of GBR membranes that were only qualitatively analyzed through histopathological approaches before. Additionally, the results of the histopathological and histomorphometrical analyses revealed that hyaluronic acid addition to collagen does not lead to a prolonged standing time, but an increased integration of a collagen-based biomaterial. Therefore, it can only partially be used in the dental field for indications that require fast resorbed membranes and a fast cell or tissue influx such as periodontal regeneration processes.

Ex Vivo and In Vivo Analysis of a Novel Porcine Aortic Patch for Vascular Reconstruction.

(1) Background: The aim of the present study was the biocompatibility analysis of a novel xenogeneic vascular graft material (PAP) based on native collagen won from porcine aorta using the subcutaneous implantation model up to 120 days post implantationem. As a control, an already commercially available collagen-based vessel graft (XenoSure®) based on bovine pericardium was used. Another focus was to analyze the (ultra-) structure and the purification effort. (2) Methods: Established methodologies such as the histological material analysis and the conduct of the subcutaneous implantation model in Wistar rats were applied. Moreover, established methods combining histological, immunohistochemical, and histomorphometrical procedures were applied to analyze the tissue reactions to the vessel graft materials, including the induction of pro- and anti-inflammatory macrophages to test the immune response. (3) Results: The results showed that the PAP implants induced a special cellular infiltration and host tissue integration based on its three different parts based on the different layers of the donor tissue. Thereby, these material parts induced a vascularization pattern that branches to all parts of the graft and altogether a balanced immune tissue reaction in contrast to the control material. (4) Conclusions: PAP implants seemed to be advantageous in many aspects: (i) cellular infiltration and host tissue integration, (ii) vascularization pattern that branches to all parts of the graft, and (iii) balanced immune tissue reaction that can result in less scar tissue and enhanced integrative healing patterns. Moreover, the unique trans-implant vascularization can provide unprecedented anti-infection properties that can avoid material-related bacterial infections.

In Vitro and In Vivo Biocompatibility Analysis of a New Transparent Collagen-based Wound Membrane for Tissue Regeneration in Different Clinical Indications.

BACKGROUND/AIM: For the treatment of different tissue defects such as jawbone defects, open wound defect, chronic ulcers, dura mater defects and corneal defects, different biomaterials are available. The use of collagen-based materials for these applications has been significantly increased over the past decades due to its excellent biocompatibility and degradability. However, no transparent collagen-based biomaterial is available until now. Thus, a newly developed transparent collagen membrane (TCM) based on natural derived porcine pericardium, which offers numerous application possibilities, was developed. The present study aimed to analyze the in vitro and in vivo biocompatibility using established methods. MATERIALS AND METHODS: The new TCM membrane and a commercially available collagen membrane (CM, Jason membrane, botiss biomaterials GmbH, Zossen, Germany) were tested for its in vitro cytocompatibility. Furthermore, the in vivo biocompatibility was analyzed using sham operations as control group. In vitro, cytocompatibility was tested in accordance with EN ISO 10993-5/-12 regulations and Live-Dead-stainings. In vivo, a subcutaneous implantation model in BALB/c mice was used and explants were prepared for analyses by established histological, immunohistochemical and histomorphometrical methods. RESULTS: In vitro, both membranes showed promising cytocompatibility with a slightly better direct cell response in the Live-Dead staining assay for the TCM. In vivo, TCM induced a comparable inflammatory immune response after 10 and 30 days with comparable numbers of M1- and M2-macrophages as also found in the control group without biomaterial insertion. CONCLUSION: The newly transparent collagen membrane is fully biocompatible and is supporting safe clinical application in tissue repair and surgery.

The Condensation of Collagen Leads to an Extended Standing Time and a Decreased Pro-inflammatory Tissue Response to a Newly Developed Pericardium-based Barrier Membrane for Guided Bone Regeneration.

BACKGROUND/AIM: A new manufacturing process has been established for the condensation of collagen derived from porcine pericardium to develop a new dental barrier membrane (CPM) that can provide a long barrier functionality. A native collagen membrane (PM) was used as control. MATERIALS AND METHODS: Established in vitro procedures using L929 and MC3T3 cells were used for cytocompatibility analyses. For the in vivo study, subcutaneous implantation of both membrane types in 40 BALB/c mice and established histological, immuno histochemical and histomorphometrical methods were conducted. RESULTS: Both the in vitro and in vivo results revealed that the CPM has a biocompatibility profile comparable to that of the control membrane. The new CPM induced a tissue reaction including more M2-macrophages. CONCLUSION: The CPM is fully biocompatible and seems to support the early healing process. Moreover, the new biomaterial seems to prevent cell ingrowth for a longer period of time, making it ideally suited for GBR procedures.

Degradation, Bone Regeneration and Tissue Response of an Innovative Volume Stable Magnesium-Supported GBR/GTR Barrier Membrane.

INTRODUCTION: Bioresorbable collagenous barrier membranes are used to prevent premature soft tissue ingrowth and to allow bone regeneration. For volume stable indications, only non-absorbable synthetic materials are available. This study investigates a new bioresorbable hydrofluoric acid (HF)-treated magnesium (Mg) mesh in a native collagen membrane for volume stable situations. MATERIALS AND METHODS: HF-treated and untreated Mg were compared in direct and indirect cytocompatibility assays. In vivo, 18 New Zealand White Rabbits received each four 8 mm calvarial defects and were divided into four groups: (a) HF-treated Mg mesh/collagen membrane, (b) untreated Mg mesh/collagen membrane (c) collagen membrane and (d) sham operation. After 6, 12 and 18 weeks, Mg degradation and bone regeneration was measured using radiological and histological methods. RESULTS: In vitro, HF-treated Mg showed higher cytocompatibility. Histopathologically, HF-Mg prevented gas cavities and was degraded by mononuclear cells via phagocytosis up to 12 weeks. Untreated Mg showed partially significant more gas cavities and a fibrous tissue reaction. Bone regeneration was not significantly different between all groups. DISCUSSION AND CONCLUSIONS: HF-Mg meshes embedded in native collagen membranes represent a volume stable and biocompatible alternative to the non-absorbable synthetic materials. HF-Mg shows less corrosion and is degraded by phagocytosis. However, the application of membranes did not result in higher bone regeneration.

Acute and chronic local inflammatory reaction after implantation of different extracellular porcine dermis collagen matrices in rats.

Two cross-linked acellular porcine dermal collagen matrices (Permacol and NRX) were implanted into rats and the acute and chronic local inflammatory tissue reactions were investigated after 7, 14, 28, and 112 days. Both membranes were stable in vivo for up to 112 days. All investigated immune cell populations (CD68+ macrophages, CD163+ macrophages, T lymphocytes, MHC class II positive cells, mast cells, and NK cells) were present. Their amount decreased significantly over time compared to day 7 after implantation. A change from an acute to a chronic inflammation and an associated shift from proinflammatory M1-like to anti-inflammatory M2-like macrophages were observed. In the early phase there was a significant correlation of T cells to CD68+ (M1-like) macrophages, whereas in the chronic phase T lymphocytes were positively correlated with CD163+ (M2-like) macrophages. The material NRX showed an enhanced inflammatory reaction in comparison to Permacol possibly caused by material characteristics such as a twofold higher thickness of the membrane, roughness, and water absorption capacity. Nevertheless, a more pronounced regenerative process as, for example, indicated by nestin expression demonstrated its possible suitability for applications as wound repair material.

Electronic modification of an aminotroponiminate zinc complex leading to an increased reactivity in the hydroamination of alkenes.

The electronically modified zinc complex 5-phenylsulfanyl-N-isopropyl-2-(isopropylamino)troponiminate zinc methyl, [(PhS-ATI(iPr)2)ZnMe], was synthesized. It showed an increased reactivity in the intramolecular hydroamination reaction of non-activated alkenes compared to a previously-reported, non-substituted complex.

Intramolecular hydroamination with homogeneous zinc catalysts: evaluation of substituent effects in N,N'-disubstituted aminotroponiminate zinc complexes.

A series of symmetrical and unsymmetrical N,N'-disubstituted aminotroponimines (ATIHs) have been prepared. Substituents ranging from linear to cyclic alkyl groups, chelating ethers, and aryl groups were employed. The corresponding aminotroponiminate zinc complexes were then synthesized and characterized by a number of techniques, including by X-ray crystallography. Herein we report on the investigations into their activity in the intramolecular hydroamination of nonactivated alkenes. We also demonstrate that complexes bearing ligands with cyclic alkyl groups show superior activity in a number of selected reactions with functionalized aminoalkenes.

A new homogeneous zinc complex with increased reactivity for the intramolecular hydroamination of alkenes.

The new zinc compound N-cyclohexyl-2-(cyclohexylamino)troponiminate zinc methyl, [(Cy)2ATI]ZnMe, was synthesized and showed a superior reactivity in the intramolecular hydroamination reaction of non-activated alkenes compared to previously reported homogeneous zinc complexes.