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While Wnt-activation is less effective, BMP-4/-7 heterodimer stimulation approximated native cartilage features in less than 50% of standard culture time representing a promising strategy for functional cartilage TE to improve biomechanical parameters of engineered cartilage.

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This study investigates the effects of seeding a chondrogenic and osteogenic scaffold with a bone marrowderived cell concentrate (BMCC) and reports the histological and mechanical properties 3 months after implantation in the miniature pig. Twenty defects (7 · 10 mm) were created in the femoral condyles of 10 miniature pigs. The defects were left empty (E), filled with the grafted cylinder upside down (U) or with a combined scaffold (S) containing a spongious bone cylinder (Tutobone Ò ) covered with a collagen membrane (Chondrogide Ò ). In a fourth group, the same scaffolds were implanted but seeded with a stem cell concentrate (S + BMCC). The animals were stained with calcein green after 2 weeks and xylenol orange after 4 weeks. After 3 months, the animals were sacrificed, and a mechanical analysis (Young's modulus), macroscopic, and histologic (ICRS Score) examination of the specimens was conducted. Young's modulus in the periphery was significantly lower for group E (67.5 -15.3 kPa) compared with untreated controls (171.7 -21.6 kPa, p < 0.04). Bone defects were smaller in group S (10% -8%) compared with E (27% -7%; p < 0.05). There was a trend toward smaller bony defects on comparing groups E and S + BMCC (11% -8%; p = 0.07). More red fluorescence was detected in group S + BMCC (2.3% -1.1%) compared with groups E (0.4% -0.2%) and U (0.5% -0.2%, p < 0.03). ICRS scores were higher for groups S (25.3 -3.8) and S + BMCC (26.2 -5.2, p < 0.01). In this animal model of osteochondral defects, stem cell concentrates enhance new bone apposition but fail to improve mechanical properties or histological appearance of cartilage regenerates in critical-sized defects.

Purpose:To assess the electromechanical properties of human knee articular cartilage with compression-induced streaming potentials for reliability among users and correlation with macroscopic and histological evaluation tools and sulfated glycosaminoglycan (sGAG) content.Methods:Streaming potentials are induced in cartilage in response to loading when mobile positive ions in the interstitial fluid temporarily move away from negatively charged proteoglycans. Streaming potential integrals (SPIs) were measured with an indentation probe on femoral condyles of 10 human knee specimens according to a standardized location scheme. Interobserver reliability was measured using an interclass correlation coefficient (ICC). The learning curves of 3 observers were evaluated by regression analysis. At each SPI measurement location the degradation level of the tissue was determined by means of the International Cartilage Repair Society (ICRS) score, Mankin score, and sGAG content.Results:The computed ICC was 0.77 (0.70-0.83) indicating good to excellent linear agreement of SPI values among the 3 users. A significant positive linear correlation of the learning index values was observed for 2 of the 3 users. Statistically significant negative correlations between SPI and both ICRS and Mankin scores were observed (r = 0.502, P < 0.001, and r = 0.255, P = 0.02, respectively). No correlation was observed between SPI and sGAG content (r = 0.004, P = 0.973).Conclusions:SPI values may be used as a quantitative means of cartilage evaluation with sufficient reliability among users. Due to the significant learning curve, adequate training should be absolved before routine use of the technique.

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The quantitative description of the biomechanical function of diarthrodial joint cartilage is a particularly challenging task due to the unique load bearing, load distribution and tribological properties of the tissue,which have their origin in the unique structure and biochemical composition. In the course of recent decades,different material models and testing methods have been published which claim to meet this challenge in one way or another. The goal of this paper is to provide an overview of the basic principles involved in the most important of these material models and testing methods. The relationship between the material models and the relevant testing methods will be illustrated in a comprehensible manner. As practical use of these methods is also associated with the amount of time required to perform them, particular attention will be paid to experimental approaches requiring only one test modality to be performed.

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