Andreas Boldt

ACE-inhibitor treatment attenuates atrial structural remodeling in patients with lone chronic atrial fibrillation.

AbstractObjectiveChronic atrial fibrillation (AF) is characterized by a remodeling process which involves the development of fibrosis. Since angiotensin II has been suspected to be involved in this process, the aim of our study was to investigate a possible influence of an ACE–I therapy in patients with chronic AF regarding the occurrence of left atrial structural remodeling.MethodsAtrial tissue samples were obtained from patients with lone chronic AF or sinus rhythm (SR). Collagen I, vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (bFGF) protein expression were measured by quantitative Western Blotting techniques and calculated as mean ± SEM. Histological tissue samples were used for calculating microvessel density (microvessel/mm2 ± SEM).ResultsIn AF, the collagen amount was higher (1.78 ± 0.21; p = 0.01) vs. SR (0.37 ± 0.07) accompanied by declining microcapillary density (AF: 145 ± 13 vs. SR: 202 ± 9; p = 0.01). Additionally, a negative correlation (p = 0.01) between collagen content and microcapillary density was observed. To investigate the influence of an ACE–I therapy on this remodeling process, patient groups were divided into AF and SR both with or without ACE–I. Interestingly, there was a significantly lower expression of collagen I in AF with ACE–I (1.04 ± 0.26) vs. AF without ACE–I treatment (2.07 ± 0.24, p = 0.02). The microcapillaries were not diminished in AF with ACE–I (180 ± 15) vs. SR with ACE–I (196 ± 9), but there was a significant rarification in AF without ACE–I (123 ± 18; p = 0.03). The expression of VEGF and bFGF did not reveal any significant differences.ConclusionIn patients undergoing ACE–I treatment: atrial structural remodeling was attenuated and the loss of atrial microcapillaries was prevented.

Eight-color immunophenotyping of T-, B-, and NK-cell subpopulations for characterization of chronic immunodeficiencies

The heterogeneity of primary and secondary immunodeficiencies demands for the development of a comprehensive flow cytometric screening system, based on reference values that support a standardized immunophenotypic characterization of most lymphocyte subpopulations.

Cytokine analysis to predict immunosuppression

Recently, it has been realized that TH1/TH2 cytokine production offer the unique possibility to predict drug efficacy. However, there is still an incessant need to explore assay conditions and techniques of analyzing cytokines, which are specific and reliable for monitoring drug efficacy.

Xenogenic Esophagus Scaffolds Fixed with Several Agents: Comparative In Vivo Study of Rejection and Inflammation

Most infants with long-gap esophageal atresia receive an esophageal replacement with tissue from stomach or colon, because the native esophagus is too short for true primary repair. Tissue-engineered esophageal conducts could present an attractive alternative. In this paper, circular decellularized porcine esophageal scaffold tissues were implanted subcutaneously into Sprague-Dawley rats. Depending on scaffold cross-linking with genipin, glutaraldehyde, and carbodiimide (untreated scaffolds : positive control; bovine pericardium : gold standard), the number of infiltrating fibroblasts, lymphocytes, macrophages, giant cells, and capillaries was determined to quantify the host response after 1, 9, and 30 days. Decellularized esophagus scaffolds were shown to maintain native matrix morphology and extracellular matrix composition. Typical inflammatory reactions were observed in all implants; however, the cellular infiltration was reduced in the genipin group. We conclude that genipin is the most efficient and best tolerated cross-linking agent to attenuate inflammation and to improve the integration of esophageal scaffolds into its surrounding tissue after implantation.

The influence of immunosuppressive drugs on T- and B-cell apoptosis via p53-mediated pathway in vitro and in vivo.

Background. This study was designed to assess the effects of calcineurin and inosine-5-monophosphate-dehydrogenase inhibitors on p53-mediated-apoptosis in T- and B-cells in vitro and in human heart-transplanted recipients (HTx-R). Methods. For in vitro experiments, peripheral blood from healthy volunteers was collected and treated either with 1 &mgr;M cyclosporin A (CsA; n=6), 10 &mgr;M mycophenolic acid (MPA; n=6) or 100 nM tacrolimus (TRL; n=6). For the second part, peripheral blood was collected from HTx-R undergoing CsA-MPA (n=11) or TRL-MPA (n=11) therapy before (0 hr) and after (2 hr) acute drug application and from healthy volunteers (n=11) without drug therapy. Whole blood (part 1+2) was stimulated (24 hr) with eight different concentrations of actinomycin-D (0–800 nM), an apoptosis inductor acting via p53-pathway. Apoptotic lymphocytes were measured by TUNEL and expression of Annexin-V using FACS. Drug effects were calculated by taking the effects of actinomycin-D as baseline values. Results. In vitro drug treatment with CsA, MPA, and TRL significantly (P<0.05) decreased the apoptotic effect of actinomycin-D in T-cells in a noncompetitive manner. In HTx-R undergoing drug therapy, there was a similar antiapoptotic effect observed in both T- and B-cells (P<0.05). Differences between 0 hr and 2 hr after acute drug application did not exist. Apoptosis induced by actinomycin-D can be completely blocked by caspase-inhibitor zVAD-FMK. Conclusion. Our results suggest that, in vitro and in HTx-R, an inhibition of calcineurin and inosine-5-monophosphate-dehydrogenase by CsA, TRL, or MPA lead to an inhibition of T-and B-cell apoptosis via p53-pathway. This assay may be helpful to provide insights into mechanisms of immunosuppressive drugs in regulation of apoptosis in lymphocytes.

Do Cells Contribute to Tendon and Ligament Biomechanics

Introduction Acellular scaffolds are increasingly used for the surgical repair of tendon injury and ligament tears. Despite this increased use, very little data exist directly comparing acellular scaffolds and their native counterparts. Such a comparison would help establish the effectiveness of the acellularization procedure of human tissues. Furthermore, such a comparison would help estimate the influence of cells in ligament and tendon stability and give insight into the effects of acellularization on collagen. Material and Methods Eighteen human iliotibial tract samples were obtained from nine body donors. Nine samples were acellularized with sodium dodecyl sulphate (SDS), while nine counterparts from the same donors remained in the native condition. The ends of all samples were plastinated to minimize material slippage. Their water content was adjusted to 69%, using the osmotic stress technique to exclude water content-related alterations of the mechanical properties. Uniaxial tensile testing was performed to obtain the elastic modulus, ultimate stress and maximum strain. The effectiveness of the acellularization procedure was histologically verified by means of a DNA assay. Results The histology samples showed a complete removal of the cells, an extensive, yet incomplete removal of the DNA content and alterations to the extracellular collagen. Tensile properties of the tract samples such as elastic modulus and ultimate stress were unaffected by acellularization with the exception of maximum strain. Discussion The data indicate that cells influence the mechanical properties of ligaments and tendons in vitro to a negligible extent. Moreover, acellularization with SDS alters material properties to a minor extent, indicating that this method provides a biomechanical match in ligament and tendon reconstruction. However, the given protocol insufficiently removes DNA. This may increase the potential for transplant rejection when acellular tract scaffolds are used in soft tissue repair. Further research will help optimize the SDS-protocol for clinical application.

Gender-Specific Remodeling in Atrial Fibrillation?

BACKGROUND The authors wanted to investigate whether the remodeling process in AF regarding gap junction proteins, collagen I, and amyloid may be gender dependent in humans. METHODS In total, 123 patients with sinus rhythm (SR, n = 41) or atrial fibrillation (AF, n = 82) suffering from mitral valve disease undergoing cardiac surgery were included. Of the 123 patients, 66 patients (SR: n = 17, AF: n = 49) were investigated biochemically for the expression of the atrial gap junction proteins connexin40 (Cx40), connexin43 (Cx43) and collagen I and 57 patients (SR: n = 24; AF: n = 33) using histochemical methods for possible amyloid depositions. RESULTS AF led to increased levels of Cx40, Cx43, and collagen I protein. Regarding Cx40 this upregulation was significantly higher in female than in male patients. For AF-induced changes in collagen or Cx43, there were no significant gender-dependent differences. Amyloid depositions were found with increasing age, but were not significantly related to AF or gender. CONCLUSIONS Remodeling in AF seems to be similar in men and women, with a tendency for women exhibiting somewhat stronger AF-induced changes in Cx40, which is probably a secondary effect because there is nothing known about hormone sensitivity of the Cx40 promoter, and a not significant tendency for higher Cx43 and collagen I.

Acellularization-Induced Changes in Tensile Properties Are Organ Specific - An In-Vitro Mechanical and Structural Analysis of Porcine Soft Tissues.

Introduction Though xenogeneic acellular scaffolds are frequently used for surgical reconstruction, knowledge of their mechanical properties is lacking. This study compared the mechanical, histological and ultrastructural properties of various native and acellular specimens. Materials and Methods Porcine esophagi, ureters and skin were tested mechanically in a native or acellular condition, focusing on the elastic modulus, ultimate tensile stress and maximum strain. The testing protocol for soft tissues was standardized, including the adaption of the tissue’s water content and partial plastination to minimize material slippage as well as templates for normed sample dimensions and precise cross-section measurements. The native and acellular tissues were compared at the microscopic and ultrastructural level with a focus on type I collagens. Results Increased elastic modulus and ultimate tensile stress values were quantified in acellular esophagi and ureters compared to the native condition. In contrast, these values were strongly decreased in the skin after acellularization. Acellularization-related decreases in maximum strain were found in all tissues. Type I collagens were well-preserved in these samples; however, clotting and a loss of cross-linking type I collagens was observed ultrastructurally. Elastins and fibronectins were preserved in the esophagi and ureters. A loss of the epidermal layer and decreased fibronectin content was present in the skin. Discussion Acellularization induces changes in the tensile properties of soft tissues. Some of these changes appear to be organ specific. Loss of cross-linking type I collagen may indicate increased mechanical strength due to decreasing transverse forces acting upon the scaffolds, whereas fibronectin loss may be related to decreased load-bearing capacity. Potentially, the alterations in tissue mechanics are linked to organ function and to the interplay of cells and the extracellular matrix, which is different in hollow organs when compared to skin.

Tissue Engineering of Ureteral Grafts: Preparation of Biocompatible Crosslinked Ureteral Scaffolds of Porcine Origin

The surgical reconstruction of ureteric defects is often associated with post-operative complications and requires additional medical care. Decellularized ureters originating from porcine donors could represent an alternative therapy. Our aim was to investigate the possibility of manufacturing decellularized ureters, the characteristics of the extracellular matrix (ECM) and the biocompatibility of these grafts in vitro/in vivo after treatment with different crosslinking agents. To achieve these goals, native ureters were obtained from pigs and were decellularized. The success of decellularization and the ECM composition were characterized by (immuno)histological staining methods and a DNA-assay. In vitro: scaffolds were crosslinked either with carbodiimide (CDI), genipin (GP), glutaraldehyde, left chemically untreated or were lyophilized. Scaffolds in each group were reseeded with Caco2, LS48, 3T3 cells, or native rat smooth muscle cells (SMC). After 2 weeks, the number of ingrown cells was quantified. In vivo: crosslinked scaffolds were implanted subcutaneously into rats and the type of infiltrating cells were determined after 1, 9, and 30 days. After decellularization, scaffold morphology and composition of ECM were maintained, all cellular components were removed, DNA destroyed and strongly reduced. In vitro: GP and CDI scaffolds revealed a higher number of ingrown 3T3 and SMC cells as compared to untreated scaffolds. In vivo: at day 30, implants were predominantly infiltrated by fibroblasts and M2 anti-inflammatory macrophages. A maximum of MMP3 was observed in the CDI group at day 30. TIMP1 was below the detection limit. In this study, we demonstrated the potential of decellularization to create biocompatible porcine ureteric grafts, whereas a CDI-crosslink may facilitate the remodeling process. The use of decellularized ureteric grafts may represent a novel therapeutic method in reconstruction of ureteric defects.

Novel apoptosis assay to analyze immunosuppression

We developed a novel whole blood assay to assess the effects of immunosuppressants on lymphocyte apoptosis.