Cartilage repair using tissue engineering is the most advanced clinical application in regenerative medicine, yet available solutions remain unsuccessful in reconstructing native cartilage in its proprietary form and function. Previous investigations have suggested that the combination of specific bioactive elements combined with a natural polymer could generate carrier matrices that enhance activities of seeded stem cells and possibly induce the desired matrix formation. The present study sought to clarify this by assessing whether a chitosan-hyaluronic-acid-based biomimetic matrix in conjunction with adipose-derived stem cells could support articular hyaline cartilage formation in relation to a standard chitosan-based construct. By assessing cellular development, matrix formation, and key gene/protein expressions during in vitro cultivation utilizing quantitative gene and immunofluorescent assays, results showed that chitosan with hyaluronic acid provides a suitable environment that supports stem cell differentiation towards cartilage matrix producing chondrocytes. However, on the molecular gene expression level, it has become apparent that, without combinations of morphogens, in the chondrogenic medium, hyaluronic acid with chitosan has a very limited capacity to stimulate and maintain stem cells in an articular chondrogenic state, suggesting that cocktails of various growth factors are one of the key features to regenerate articular cartilage, clinically.

The importance of decellularized medical products has significantly increased during the last years. In this paper, we evaluated the effects of selected physical and procedural decellularization (DC) factors with the aim to systematically assess their influence on DC results. 72 porcine aortic walls (AW) were divided into three groups and exposed to a DC solution for 4 h and 8 h, either continuously or in repeated cycles. The AW were rocked (90bpm), whirled (10 l/min), sonicated (120W, 45 kHz) or exposed to a combination of these treatments, followed by 10 washing cycles. Defining successful DC as removal of nuclei while keeping an intact extracellular matrix (ECM), we equalized the efficiency to the penetration depth (PD), obtained by DAPI fluorescence and H&E staining. Additionally, we performed scanning electron microscopy (SEM), Pentachrome and Picrosirius-Red staining. Results showed that significantly higher DC depths are achieved on outer compared to inner surfaces (61 ± 7%; p < 0.001). Furthermore, the PD showed a high time dependency for all samples. Compared to continuous rocking, we achieved a significant increase in the DC efficiency through cyclic treatments ( ∼ 43%), whirling ( ∼ 19%) and sonication ( ∼ 49%). The combined treatment supported these results. In all procedures, a skeletonized but intact Collagen fibrous network was obtained as confirmed by SEM analysis. In conclusion, we systematically identified essential factors to significantly enhance DC procedures. We highly recommend considering these factors in future DC protocols. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 153-162, 2018.

Heart valve disease (HVD) is a globally increasing problem and accounts for thousands of deaths yearly. Currently end-stage HVD can only be treated by total valve replacement, however with major drawbacks. To overcome the limitations of conventional substitutes, a new clinical approach based on cell colonization of artificially manufactured heart valves has been developed. Even though this attempt seems promising, a confluent and stable cell layer has not yet been achieved due to the high stresses present in this area of the human heart. This study describes a bioreactor with a new approach to cell conditioning of tissue engineered heart valves. The bioreactor provides a low pulsatile flow that grants the correct opening and closing of the valve without high shear stresses. The flow rate can be regulated allowing a steady and sensitive conditioning process. Furthermore, the correct functioning of the valve can be monitored by endoscope surveillance in real-time. The tubeless and modular design allows an accurate, simple and faultless assembly of the reactor in a laminar flow chamber. It can be concluded that the bioreactor provides a strong tool for dynamic pre-conditioning and monitoring of colonized heart valve prostheses physiologically exposed to shear stress.

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