Depth-varying Density and Organization of Chondrocytes in Immature and Mature Bovine Articular Cartilage Assessed by 3D Imaging and Analysis

Abstract

S U M M A R Y Articular cartilage is a heterogeneous tissue, with cell density and organization varying with depth from the surface. The objectives of the present study were to establish a method for localizing individual cells in three-dimensional (3D) images of cartilage and quantifying depth-associated variation in cellularity and cell organization at different stages of growth. Accuracy of nucleus localization was high, with 99% sensitivity relative to manual localization. Cellularity (million cells per cm 3 ) decreased from 290, 310, and 150 near the articular surface in fetal, calf, and adult samples, respectively, to 120, 110, and 50 at a depth of 1.0 mm. The distance/angle to the nearest neighboring cell was 7.9 m/31 Њ , 7.1 m/31 Њ , and 9.1 m/31 Њ for cells at the articular surface of fetal, calf, and adult samples, respectively, and increased/decreased to 11.6 m/31 Њ , 12.0 m/30 Њ , and 19.2 m/ 25 Њ at a depth of 0.7 mm. The methodologies described here may be useful for analyzing the 3D cellular organization of cartilage during growth, maturation, aging, degeneration, and regeneration.

Computational investigation of in situ chondrocyte deformation and actin cytoskeleton remodelling under physiological loading

“…A side length of 60 µm for the cuboidal ECM is chosen in order to give an approximate representation of chondrocyte volume per unit cartilage volume. This was determined by considering that the volume fraction of chondrocytes in cartilage tissue varies from 1-10% [40,46], and cellularity decreases with tissue depth from 150 × 10 6 cells/cm 3 at the surface to 50 × 10 6 cells/cm 3 at 500 μm below the surface [47]. Additionally, the ratio of cell volume to ECM volume in the current study is comparable to previous finite element models incorporating chondrocytes embedded in an ECM [15,17,18,48].…”

Distinct horizontal patterns in the spatial organization of superficial zone chondrocytes of human joints

“…The observed patterns were not due to a random distribution of chondrocytes but rather represented a significant grouping of cells in the context of a statistical analysis of point patterns. Although a few studies of the superficial zone reported clusters in human cartilage , pairs in bovine cartilage (Jadin et al, 2005) and incidentally symmetrical rows in rabbit cartilage (Clark and Rudd, 1991), to the author's knowledge, the present study is the first to identify complex patterns in the arrangement of human chondrocyte groups in the superficial zone of non-degenerated cartilage.…”

“…Each can be distinguished based on differences in morphology (Aydelotte and Kuettner, 1988;Jadin et al, 2005;Kuettner et al, 1991), content of glycosaminoglycans , collagen (Nieminen et al, 2001), water , and mineral (Burr, 2004). The zonal differences in organization and biochemical content are directly associated with depth-dependant changes in biomechanical and bioelectrical tissue properties (Chen et al, 2001;Klein et al, 2007;Krishnan et al, 2003;Schinagl et al, 1997).…”

“…Studies that were undertaken to further clarify the unique role of the superficial zone thus far have concentrated on cell shape (Hunziker et al, 2002;Jadin et al, 2005), cell density (Bywaters, 1937;Hunziker et al, 2002;Jadin et al, 2005;Quinn et al, 2005;Stockwell, 1971), cytoskeletal organization (Kim and Spector, 2000), growth-related changes in the bovine chondrocyte organization (Jadin et al, 2007), single cell mechanical properties (Jurvelin et al, 1996), gene expression (Darling et al, 2004;Jay et al, 2001;Khan et al, 2001;Schumacher et al, 1994), and metabolism (Eger et al, 2002). While it is widely accepted that the organization of human chondrocytes of the radial zones occur in vertical columns and the transitional zone in small "random" groups (Aydelotte and Kuettner, 1988;Brighton et al, 1984;Kuettner et al, 1991), it remains unclear how the human chondrocytes of the superficial zone are organized.…”

Current Applications of Mesenchymal Stem Cells for Cartilage Tissue Engineering

“…Hyaline or articular cartilage is heterologous, with varying density and organization according to the depth of its zones [9]. Articular cartilage is predominantly avascular, aneural, and alymphatic, so the main route for nutrition is through synovial luid and assisted by mechanical compression forces [10].…”