Date Published: April 01, 2018
Author(s): Ewa M. Spiesz, Chavaunne T. Thorpe, Philipp J. Thurner, Hazel R.C. Screen.
Structure-function relationships in tendons are directly influenced by the arrangement of collagen fibres. However, the details of such arrangements in functionally distinct tendons remain obscure. This study demonstrates the use of quantitative polarised light microscopy (qPLM) to identify structural differences in two major tendon compartments at the mesoscale: fascicles and interfascicular matrix (IFM). It contrasts functionally distinct positional and energy storing tendons, and considers changes with age. Of particular note, the technique facilitates the analysis of crimp parameters, in which cutting direction artefact can be accounted for and eliminated, enabling the first detailed analysis of crimp parameters across functionally distinct tendons.
This is the first study to quantify birefringence in fascicles and interfascicular matrix of functionally distinct energy storing and positional tendons. It adopts a novel method – quantitative polarised light microscopy (qPLM) to measure collagen crimp angle, avoiding artefacts related to the direction of histological sectioning, and provides the first direct comparison of crimp characteristics of functionally distinct tendons of various ages.
The structure of complex materials is closely related to their function and mechanical properties and vice versa. Collagenous tissues are no exception, therefore there is considerable interest in understanding the mechanical performance of tissues, based on studying the details of their composition and structural arrangement. Tendon is a highly ordered unidirectional fibrous composite, consisting mainly of hierarchically organised collagen type I molecules. Collagen is the most abundant protein and main load-bearing constituent of tendons and many other tissues. It attains its mechanical properties through hierarchical assembly. In tendon this spans from the tropocollagen triple helix at the molecular level, to collagen fibrils, fibres, fascicles, fascicle bundles and whole tendons . At each hierarchical level the collagenous matrix is interspersed with a non-collagenous matrix, rich in proteoglycans .
This study quantifies birefringence in fascicles and interfascicular matrix of functionally distinct energy storing and positional tendons. It additionally adopts a novel method to measure collagen crimp angle, avoiding the artefacts related to histological sectioning, and provides direct comparison of the crimp characteristics of functionally distinct tendons of various ages.