While cell morphology has been recognized as a fundamental regulator of cell behavior, few studies have measured the complex cell morphological changes of chondrocytes using quantitative cell morphometry descriptors in relation to inflammation and phenotypic outcome.

Acute vs. persistent exposure to IL-1β and how IL-1β modulated dynamic changes in cell morphology in relation to the phenotype, donor and OA grade in healthy and osteoarthritis (OA) chondrocytes was investigated. A panel of quantitative cell morphometry descriptors was measured using an automated high-throughput method. Absolute quantification of gene expression was measured by ddPCR followed by correlation analyses.

In OA chondrocytes, chronic IL-1β significantly decreased COL2A1, SOX9, and ACAN, increased IL-6 and IL-8 levels and caused chondrocytes to become less wide, smaller, longer, slimmer, less round and more circular, consistent with a de-differentiated phenotype. In healthy chondrocytes, 3 days after acute (72 h) IL-1β exposure, COL1A2 and IL-6 significantly increased but had minor effects on cell morphology. However, in healthy chondrocytes, persistent IL-1β led to more profound effects in all cell morphology descriptors and chondrocytes expressed significantly less COL2A1 and more IL-6 and IL-8 vs. controls and acutely-stimulated chondrocytes. In both OA and healthy chronically-stimulated chondrocytes, area, width and circularity were sensitive to the persistent presence of the IL-1β cytokine. Moreover, there were many significant and strong correlations among the measured parameters, with several indications of an IL-1β-mediated mechanism.

Cell morphology combined with gene expression analysis could guide researchers interested in understanding inflammatory effects in the complex domain of cartilage/chondrocyte biology. Use of quantitative cell morphometry could complement classical approaches by providing numerical data on a large number of cells, thereby providing a biological fingerprint for describing chondrocyte phenotype, which could help to understand how changes in cell morphology lead to disease progression.

As stem cells and primary cells hold potential for improving disease outcomes and patient lives, methods for steering cell fate are of considerable importance. In this context, an emerging method is directing cell function through controlling cellular shape. The talk will discuss how cell functions are based on mechano-transduction events related to the balance of intra- and extracellular forces. The talk will explore the multiple biophysical cues that affect cell shape and present methods for directly generating cell shape, e. g. micro-contact printing used for directing the differentiation lineage of stem cells. Based on our own work, the talk will introduce the novel concept that specific biomaterial types and stiffnesses can be chosen for generating specific cellular “baseline shapes” and associated function. As our cells are exposed to continuously changing biomechanical forces, the talk will also report how specific forces can be used for engineering shape. The talk will explore how biomaterial stiffness and biomechanical forces act together on cellular shape, and whether one of the two stimuli is able to override the other. The novel insights reported here are fundamental for designing cell shape-instructive 3D biomaterials in the context of steering cell function in situ for regenerative medicine.

Summary

In adult articular cartilage, the pericellular matrix (PCM) mediates chondrocyte-matrix-interactions and is associated with the spatial cellular organization. Immunofluorescence microscopy, multiphoton-induced autofluorescence and second harmonic generation (SHG) imaging, as well as point pattern analyses revealed that both PCM and spatial organization were absent in fetal chondrocytes.

We attempted to characterise the biological quality and regenerative potential of chondrocytes in osteochondritis dissecans (OCD). Dissected fragments from ten patients with OCD of the knee (mean age 27.8 years (16 to 49)) were harvested at arthroscopy. A sample of cartilage from the intercondylar notch was taken from the same joint and from the notch of ten patients with a traumatic cartilage defect (mean age 31.6 years (19 to 52)). Chondrocytes were extracted and subsequently cultured. Collagen types 1, 2, and 10 mRNA were quantified by polymerase chain reaction. Compared with the notch chondrocytes, cells from the dissecate expressed similar levels of collagen types 1 and 2 mRNA. The level of collagen type 10 message was 50 times lower after cell culture, indicating a loss of hypertrophic cells or genes. The high viability, retained capacity to differentiate and metabolic activity of the extracted cells suggests preservation of the intrinsic repair capability of these dissecates. Molecular analysis indicated a phenotypic modulation of the expanded dissecate chondrocytes towards a normal phenotype. Our findings suggest that cartilage taken from the dissecate can be reasonably used as a cell source for chondrocyte implantation procedures.