Roman Breiter

Processed xenogenic cartilage as innovative biomatrix for cartilage tissue engineering: effects on chondrocyte differentiation and function

One key point in the development of new bioimplant matrices for the reconstruction and replacement of cartilage defects is to provide an adequate microenvironment to ensure chondrocyte migration and de novo synthesis of cartilage‐specific extracellular matrix (ECM). A recently developed decellularization and sterilization process maintains the three‐dimensional (3D) collagen structure of native septal cartilage while increasing matrix porosity, which is considered to be crucial for cartilage tissue engineering. Human primary nasal septal chondrocytes were amplified in monolayer culture and 3D‐cultured on processed porcine nasal septal cartilage scaffolds. The influence of chondrogenic growth factors on neosynthesis of ECM proteins was examined at the protein and gene expression levels. Seeding experiments demonstrated that processed xenogenic cartilage matrices provide excellent environmental properties for human nasal septal chondrocytes with respect to cell adhesion, migration into the matrix and neosynthesis of cartilage‐specific ECM proteins, such as collagen type II and aggrecan. Matrix biomechanical stability indicated that the constructs retrieve full stability and function during 3D culture for up to 42 days, proportional to collagen type II and GAG production. Thus, processed xenogenic cartilage offers a suitable environment for human nasal chondrocytes and has promising potential for cartilage tissue engineering in the head and neck region. Copyright

In vitro cytotoxicity and in vivo effects of a decellularized xenogeneic collagen scaffold in nasal cartilage repair.

Tissue engineering is considered a promising future option for nasal cartilage repair. However, until now, an optimal material has not been identified for this specific purpose. Therefore, the aim of this study was to analyze a recently developed decellularized collagen matrix, which has promising material properties for septal cartilage repair. A tetrazolium dye based cytotoxicity assay using rat nasal septum chondrocytes was performed to examine the cytotoxic effects of decellularized cartilage matrices. Unseeded scaffolds as well as scaffolds seeded with chondrocytes were implanted in nasal septum defects in Lewis rats to investigate the cellular and humoral inflammatory responses in the surrounding tissue as well as the effect on the formation of nasal septum perforations. Samples were analyzed histochemically and immunohistochemically after 1, 4, and 12 weeks. Although cells for the cytotoxicity assay were cultured under serum-free conditions for 24 h to increase sensitivity, no cytotoxic effects were detected. Histological and immunohistochemical evidence displayed that the implanted scaffolds induced minor macrophage and lymphocyte infiltration and were well integrated at the contact site to native cartilage and between the mucosal membranes. The biocompatibility index revealed only slightly irritating effects during the study period. Septal perforations were prevented efficiently. In summary, our results provide evidence that decellularized xenogeneic collagen scaffolds are suitable for cartilage tissue engineering. The scaffolds were integrated well into septal cartilage defects without causing a strong inflammatory reaction and prevented the development of nasal septum perforations. Therefore, we envision the possibility to use them in nasal cartilage repair in the future.

Competitive sorption of cis-DCE and TCE in silica gel as a model porous mineral solid

The competitive sorption of 1,2-cis-dichloroethene (cis-DCE) and trichloroethene (TCE) was investigated by means of column experiments using a model porous mineral solid represented by silica gel. The experimental isotherms were obtained by employing a chromatographic method. The competitive sorption isotherms were modelled with the extended Freundlich and extended Langmuir isotherms, using the parameters from single-solute experiments. The breakthrough curves were modelled with the advection-dispersion transport equation coupled with the lumped pore diffusion model. The best results were obtained when the extended Freundlich isotherm was employed. The competitive sorption was revealed with the presence of an overshoot in the breakthrough curve of cis-DCE and a decrease in the degree of sorption of cis-DCE (20%) and TCE (12%). A linear dependency of the overshoot with an increase in the concentration of cis-DCE at a fixed concentration of TCE was observed, between 16% and 20%, and at least at concentrations <6 mg L(-1) in the liquid phase. The displaced molecules of cis-DCE by TCE were accumulated through the column causing its overshoot; thus short columns may hinder its observation. Thermodynamic analysis shows an exothermic adsorption process of -34 to -41 kJ mol(-1), which is enhanced by sorption in micropores. The Gibbs free energy is positive for cis-DCE in the multi-component case, due to its displacement by TCE.

Acoustic Properties of Collagenous Matrices of Xenogenic Origin for Tympanic Membrane Reconstruction.

Hypothesis: The acoustic properties of scaffolds made from decellularized extracellular cartilage matrices of porcine origin are comparable to those of the human tympanic membrane. Background: Currently, the reconstruction of tympanic membrane in the context of chronic tympanic membrane defects is mostly performed using autologous fascia or cartilage. Autologous tissue may be associated with lack of graft material in revision patients and requires more invasive and longer operative time. Therefore, other materials are investigated for reconstruction. An increasingly important role could be played by scaffolds from different materials, which are known to induce constructive tissue remodeling. Methods: To analyze the acoustic properties, the vibrations of the scaffolds, cartilage, perichondrium and tympanic membrane were measured by laser scanning doppler vibrometry under different static pressures. Results: The analysis of volume velocities serves as an indicator for sound transmission. The results of the average volume velocities at atmospheric pressure show a similar frequency response of the tympanic membrane and the scaffolds with a peak at about 800 Hz. After changing the artificial ear-canal pressure from atmospheric pressure to negative pressure (−100, −200, and −300 daPa) the vibration characteristics of the different membranes remain fairly constant, whereas the results of the perichondrium show a decrease after changing the pressure into the negative range in the frequencies 1 to 3 kHz. Conclusion: The present study showed that the vibration characteristics of the scaffolds under atmospheric and negative pressure can be interpreted as similar to those of thin cartilage (<0.5 mm) and human tympanic membranes. However, in relation to the behavior of these scaffolds made from decellularized extracellular cartilage matrices in vivo, further investigations should be carried out.

Laser surface modification of decellularized extracellular cartilage matrix for cartilage tissue engineering

The implantation of autologous cartilage as the gold standard operative procedure for the reconstruction of cartilage defects in the head and neck region unfortunately implicates a variety of negative effects at the donor site. Tissue-engineered cartilage appears to be a promising alternative. However, due to the complex requirements, the optimal material is yet to be determined. As demonstrated previously, decellularized porcine cartilage (DECM) might be a good option to engineer vital cartilage. As the dense structure of DECM limits cellular infiltration, we investigated surface modifications of the scaffolds by carbon dioxide (CO2) and Er:YAG laser application to facilitate the migration of chondrocytes inside the scaffold. After laser treatment, the scaffolds were seeded with human nasal septal chondrocytes and analyzed with respect to cell migration and formation of new extracellular matrix proteins. Histology, immunohistochemistry, SEM, and TEM examination revealed an increase of the scaffolds’ surface area with proliferation of cell numbers on the scaffolds for both laser types. The lack of cytotoxic effects was demonstrated by standard cytotoxicity testing. However, a thermal denaturation area seemed to hinder the migration of the chondrocytes inside the scaffolds, even more so after CO2 laser treatment. Therefore, the Er:YAG laser seemed to be better suitable. Further modifications of the laser adjustments or the use of alternative laser systems might be advantageous for surface enlargement and to facilitate migration of chondrocytes into the scaffold in one step.

Transplantation of Chemically Processed Decellularized Meniscal Allografts: A Pilot Sheep Study

Objective The aim of this study was to evaluate the chondroprotective effect of chemically decellularized meniscal allografts transplanted into the knee joints of adult merino sheep. Methods Lateral sheep meniscal allografts were chemically processed by a multistep method to yield acellular, sterile grafts. The grafts were transplanted into the knee joints of sheep that were treated by lateral meniscectomy. Joints treated by meniscectomy only and untreated joints served as controls. The joints were analyzed morphologically 6 and 26 weeks after surgery by the macroscopical and histological OARSI (Osteoarthritis Research Society International) score. Additionally, the meniscal grafts were biomechanically tested by cyclic indentation. Results Lateral meniscectomy was associated with significant degenerative changes of the articular cartilage of the lateral joint compartment. Transplanted lateral meniscal allografts retained their integrity during the observation period without inducing significant synovitis or foreign body reactions. Cellular repopulation of the grafts was only present on the surface and the periphery of the lateral meniscus, but was still completely lacking in the center of the grafts at week 26. Transplantation of processed meniscal allografts could not prevent degenerative changes of the articular cartilage in the lateral joint compartment. Compared with healthy menisci, the processed grafts were characterized by a significantly reduced dynamic modulus, which did not improve during the observation period of 26 weeks in vivo. Conclusion Chemically decellularized meniscal allografts proved their biocompatibility and durability without inducing immunogenic reactions. However, insufficient recellularization and inferior stiffness of the grafts hampered chondroprotective effects on the articular cartilage.