Priming chondrocytes during expansion alters cell behavior and improves matrix production in 3D culture.

OBJECTIVE: Cartilage tissue engineering strategies that use autologous chondrocytes require in vitro expansion of cells to obtain enough cells to produce functional engineered tissue. However, chondrocytes dedifferentiate during expansion culture, limiting their ability to produce chondrogenic tissue and their utility for cell-based cartilage repair strategies. The current study identified conditions that favor cartilage production and the mechanobiological mechanisms responsible for these benefits. DESIGN: Chondrocytes were isolated from juvenile bovine knee joints and cultured with (primed) or without (unprimed) a growth factor cocktail. Gene expression, cell morphology, cell adhesion, cytoskeletal protein distribution, and cell mechanics were assessed. Following passage 5, cells were embedded into agarose hydrogels to evaluate functional properties of engineered cartilage. RESULTS: Priming cells during expansion culture altered cell phenotype and chondrogenic tissue production. Unbiased ribonucleic acid-sequencing analysis suggested, and experimental studies confirmed, that growth factor priming delays dedifferentiation associated changes in cell adhesion and cytoskeletal organization. Priming also overrode mechanobiological pathways to prevent chondrocytes from remodeling their cytoskeleton to accommodate the stiff, monolayer microenvironment. Passage 1 primed cells deformed less and had lower yes associated protein 1 activity than unprimed cells. Differences in cell adhesion, morphology, and cell mechanics between primed and unprimed cells were mitigated by passage 5. CONCLUSIONS: Priming suppresses mechanobiologic cytoskeletal remodeling to prevent chondrocyte dedifferentiation, resulting in more cartilage-like tissue-engineered constructs.

Evaluation of lesion burden in a bone-by-bone comparison of osteological and radiological methods of analysis.

OBJECTIVE: To evaluate differences in lesion identification in skeletal remains with respect to bone type and method of analysis. MATERIALS: 212 mostly 19th century adult skeletons from St. Bride's Church in London. METHODS: Using a standard protocol, an osteologist evaluated each set of remains for lesions. A radiologist used the same system to examine radiographs of the crania, humeri, pelves, tibiae, and femora. RESULTS: Osteological analysis noted more lesions per bone type. All bone types examined showed positive, statistically significant correlations between the number of lesions identified by each analytical method. The humerus, tibia, and femur exhibited the strongest correlations. The pelvis exhibited the weakest correlation. For the cranium and pelvis, males showed stronger correlations. CONCLUSIONS: Sex-related differences in correlations were likely influenced by the presence, in females, of lesions affecting the entire skeleton (e.g., osteoporosis). Greater correlations between analytical modalities were observed for long bones. SIGNIFICANCE: Our findings quantify the contexts in which radiological and osteological evaluations converge and diverge and discuss the implications of these results for lesion burden interpretation. LIMITATIONS: Generalizability, potential subjectivity of evaluative methods. SUGGESTIONS FOR FURTHER RESEARCH: Assessment of another study collection using the same methods, to determine if the similar correlations are observed.