Correlation between distribution of cytoskeletal proteins and release of alkaline phosphatase-rich vesicles by epiphyseal chondrocytes in primary culture
✍ Scribed by Hale, John E. ;Chin, Jia E. ;Ishikawa, Yoshinori ;Paradiso, Peter R. ;Wuthier, Roy E.
- Publisher
- Wiley (John Wiley & Sons)
- Year
- 1983
- Weight
- 817 KB
- Volume
- 3
- Category
- Article
- ISSN
- 0271-6585
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✦ Synopsis
Matrix vesicles, extracellular microstructures known to be involved in endochondral calcification, are rich in alkaline phosphatase and have been shown to contain actin. The mechanism of matrix vesicle formation in chondrocytes is not well understood. Chondrocytes from the epiphyseal growth plate, when grown in primary culture, elaborate alkaline phosphatase-rich vesciles. We examined the distribution of the cytoskeletal proteins actin, myosin, tubulin, and vinculin at various time-points during culture using indirect immunofluorescent labeling. Concomitantly, the production of alkaline phosphatase-containing matrix vesicles was also followed. Cell morphology changed noticeably at two distinct stages during the 22-day culture period: Immediately after release from the growth plate the cells were rounded, but after 4 days of culture they began to spread out and acquire irregular shapes with distinct filopodia. By 13 days, as the cells attained confluency, they reacquired a rounded, polygonal appearance. At all time-points, tubulin was seen as a dense network of microtubules radiating from the perinuclear region throughout the cytoplasm toward the cell periphery. Initially actin was seen in filamentous form, but displayed a punctate distribution focused at contact points during the cell-spreading stage of culture. After confluency, actin was concentrated at cell-cell junctions. Initially, vinculin was diffusely distributed, but became focused in multiple adhesion plaques and at the termini of filopodia during the cell-spreading stage of culture. Following confluency vinculin became concentrated at cell-cell junctions. Myosin was observed at all time-points in small, intensely localized focal points in the cytoplasmic region of the cells and was