The influence of noncollagenous matrix components on the micromechanical environment of tendon fascicles

Tendon is composed of type I collagen fibers, interspersed with proteoglycan matrix and cells. Glycosaminoglycans may play a role in maintaining the structural integrity of tendon, preventing excessive shearing between collagen components. This study tests the hypothesis that tendon extension mechanisms can be altered by modifying the composition of noncollagenous matrix. Tendon explants were treated with phosphate buffered saline (PBS) or PBS + 0.5 U ml(-1) chondroitinase ABC. Structural changes were examined using TEM and biochemical analysis, while strain response was examined using confocal microscopy and gross mechanical characterization. Chondroitinase ABC removed 90% of glycosaminoglycans from the matrix. Results demonstrated significant swelling of fibrils and surrounding matrix when incubated in either solution. In response to applied strain, PBS incubated samples demonstrated significantly less sliding between adjacent fibers than nonincubated, and a 33% reduction in maximum force. By contrast, fascicles incubated in chondroitinase ABC demonstrated a similar strain response to nonincubated. Data indicate that collagen-proteoglycan binding characteristics can be influenced by incubation and this, in turn, can influence the preferred extension mechanisms adopted by fascicles. This highlights the importance of maintaining fascicles within their natural environment to prevent structural or mechanical changes prior to subsequent analysis.