Engineering of fibrillar decorin matrices for a tissue-engineered trachea.

Decorin is a structural and functional proteoglycan (PG) residing in the complex network of extracellular matrix (ECM) proteins in many connective tissues. Depending on the protein core and the glycosaminoglycan chain, PGs support cell adhesion, migration, proliferation, differentiation, ECM assembly and growth factor binding. For applications in tissue engineering, it is crucial to develop reliable, ECM-mimicking biomaterials. Electrospinning is a suitable method for creating three-dimensional (3D), fibrillar scaffolds. While there are numerous reports on the electrospinning of proteins including collagen, to date, there are no reports on the electrospinning of PGs. In the following study, we used electrospinning to generate decorin-containing matrices for tracheal tissue engineering applications. The electrospun scaffolds were analyzed using scanning electron microscopy, atomic force microscopy, contact angle measurements and dynamic mechanical analysis. Additionally, we confirmed PG functionality with immunostaining and 1,9-dimethylmethylene blue. To determine cell-matrix-interactions, tracheal cells (hPAECs) were seeded and analyzed using an FOXJ1-antibody. Moreover, interactions of the electrospun scaffolds with immune-mediated mechanisms were analyzed in detail. To conclude, we demonstrated the feasibility of electrospinning of decorin to generate functional 3D scaffolds with low immunogenicity for hPAEC expansion. Our data suggest that these hybrid materials may be suitable as a substrate for tracheal tissue engineering.

Skin tissue engineering--in vivo and in vitro applications.

Significant progress has been made over the years in the development of in vitro-engineered substitutes that mimic human skin, either to be used as grafts for the replacement of lost skin or for the establishment of human-based in vitro skin models. This review summarizes these advances in in vivo and in vitro applications of tissue-engineered skin. We further highlight novel efforts in the design of complex disease-in-a-dish models for studies ranging from disease etiology to drug development and screening.

Depth profiling of gold nanoparticles and characterization of point spread functions in reconstructed and human skin using multiphoton microscopy.

Multiphoton microscopy has become popular in studying dermal nanoparticle penetration. This necessitates studying the imaging parameters of multiphoton microscopy in skin as an imaging medium, in terms of achievable detection depths and the resolution limit. This would simulate real-case scenarios rather than depending on theoretical values determined under ideal conditions. This study has focused on depth profiling of sub-resolution gold nanoparticles (AuNP) in reconstructed (fixed and unfixed) and human skin using multiphoton microscopy. Point spread functions (PSF) were determined for the used water-immersion objective of 63×/NA = 1.2. Factors such as skin-tissue compactness and the presence of wrinkles were found to deteriorate the accuracy of depth profiling. A broad range of AuNP detectable depths (20-100 µm) in reconstructed skin was observed. AuNP could only be detected up to ∼14 µm depth in human skin. Lateral (0.5 ± 0.1 µm) and axial (1.0 ± 0.3 µm) PSF in reconstructed and human specimens were determined. Skin cells and intercellular components didn't degrade the PSF with depth. In summary, the imaging parameters of multiphoton microscopy in skin and practical limitations encountered in tracking nanoparticle penetration using this approach were investigated.

The physiological performance of a three-dimensional model that mimics the microenvironment of the small intestine.

Our focus was to develop a three-dimensional (3D) human dynamic in vitro tissue model that mimics the natural microenvironment of the small intestine. We co-cultured human Caco-2 cells with primary-isolated human microvascular endothelial cells (hMECs) on decellularized porcine jejunal segments within a custom-made dynamic bioreactor system that resembles the apical and basolateral side of the intestine for up to 14 days. The obtained data were compared to results generated using routine static Caco-2 assays. We performed histology and immunohistochemistry. Permeability was measured using directed transport studies. Histological analyses revealed that in tissue-engineered segments, which had been cultured under dynamic conditions, the Caco-2 cells showed a high-prismatic morphology, resembling normal primary enterocytes within their native environment. We further identified that the transport of low permeable substances, such as fluorescein and desmopressin increased within the dynamic bioreactor cultures. Immunohistochemical staining showed a significantly higher expression of the efflux transport p-glycoprotein (p-gp) under dynamic culture conditions when compared to the static cultures. We conclude that the integration of physiological parameters is crucial for the establishment of a reliable 3D intestinal in vitro model, which enables the simulation of drug transport over the gut-blood-barrier in a simplified way.

Skin tissue engineering--in vivo and in vitro applications.

Significant progress has been made over the years in the development of in vitro-engineered substitutes that mimic human skin, either to be used as grafts for the replacement of lost skin or for the establishment of human-based in vitro skin models. This review summarizes these advances in in vivo and in vitro applications of tissue-engineered skin. We further highlight novel efforts in the design of complex disease-in-a-dish models for studies ranging from disease etiology to drug development and screening.

Impact of neo-adjuvant radiochemotherapy on bronchial tissue viability.

OBJECTIVE: In the treatment of advanced stages of lung cancer, increasingly more multimodality approaches applying radiotherapy and/or chemotherapy in a neo-adjuvant setting are being introduced. The impact of induction therapy, especially radiotherapy, on bronchial tissue viability has not been investigated so far. METHODS: In 2008, we determined the tissue viability of bronchial segments obtained during surgery in 45 consecutive patients, including patients after neo-adjuvant radiochemotherapy (RCTX). Bronchial tissue viability was analysed by histology, life-dead assay and cell proliferation in tissue-specific culture media. Biomedical findings were compared with the clinical course of the patients. RESULTS: Tissue samples of 44 patients were included into this study. Fourteen patients (32%) had undergone neo-adjuvant RCTX. Histology and life-dead assay of the bronchial segments did not show significant differences. While patient age, sex, tumour entity and site of resection had no influence on cell proliferation in vitro, previous RCTX resulted in a 46% decrease of bronchial tissue viability (P=0.01). However, this effect was not reflected by the clinical course of the operated patients. CONCLUSIONS: Neo-adjuvant RCTX reduces bronchial tissue viability substantially. However, this impairment does not necessarily translate into an increased rate of postoperative bronchial insufficiencies. Standard histological work-up is not sensitive enough to characterise changes in bronchial tissue viability following RCTX.

Clinical tracheal replacement: transplantation, bioprostheses and artificial grafts.

The replacement of significant lengths of tracheal tissue still remains the unrivalled 'holy grail' of thoracic surgery. As a result of continuous developments and improvements in tracheal surgery throughout the last five decades, most tracheal lesions can now be resected and primary reconstruction effected safely. Today, very few patients present extensive tracheal lesions that necessitate tracheal replacement. The spectrum of tracheal substitutes ranges from autologous tissue flaps and patches to synthetic stents and prostheses to tissue-engineered scaffolding. In this review, the clinical achievements and conceivable developments of applying human allografts and biological and artificial prostheses will be discussed.