Jul 1, 1986

Extracellular compartments in tendon morphogenesis: collagen fibril, bundle, and macroaggregate formation

The Journal of Cell Biology
David E Birk, R L Trelstad


The formation of collagen fibrils, fibril bundles, and tissue-specific collagen macroaggregates by chick embryo tendon fibroblasts was studied using conventional and high voltage electron microscopy. During chick tendon morphogenesis, there are at least three extracellular compartments responsible for three levels of matrix organization: collagen fibrils, bundles, and collagen macroaggregates. Our observations indicate that the initial extracellular events in collagen fibrillogenesis occur within narrow cytoplasmic recesses, presumably under close cellular regulation. Collagen fibrils are formed within these deep, narrow recesses, which are continuous with the extracellular space. Where these narrow recesses fuse with the cell surface, it becomes highly convoluted with folds and processes that envelope forming fibril bundles. The bundles laterally associate and coalesce, forming aggregates within a third cell-defined extracellular compartment. Our interpretation is that this third compartment forms as cell processes retract and cytoplasm is withdrawn between bundles. These studies define a hierarchical organization within the tendon, extending from fibril assembly to fascicle formation. Correlation of different levels of extrac...Continue Reading

Mentioned in this Paper

Macromolecular Compounds
Specimen Type - Fibroblasts
Extracellular Space
Tendons, Para-Articular
Extracellular Matrix
Collagen Fibril
Cell Process Structure
High Voltage Electron Microscopy
Plasma Protein Binding Capacity

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