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Title: A descriptive study of the ultrastucture of the equine superficial digital flexor tendon
Author: Ali, Othman Jalal
ISNI:       0000 0004 6059 607X
Awarding Body: University of Liverpool
Current Institution: University of Liverpool
Date of Award: 2016
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The aim of this study was to describe three-dimensional (3D) anatomy and the histological features of equine superficial digital flexor tendon (SDFT), specifically to determine the organisation of the individual sub-units (fascicles) and how this may vary between individuals and in tendinopathy. For macroscopic 3D study, 17 frozen SDFT (n=13) were sectioned transversely (2-3mm), photographed and processed for 3D reconstruction. In microscopic 3D reconstruction, SDFT from foetal, one-year-old and 9-years-old were fixed in 4% paraformaldehyde solution, paraffin blocked, cut into series sections (5μm), H&E stained and processed for 3D reconstruction. Histologically a novel scoring method was devised using ImageJ to describe the cellular morphology and extracellular matrix (ECM) organisation and quantification (n=24). Tertiary fascicles were defined as being delineated by a well-defined inter-fascicular septum (IFM) (30.45μm ± 9.78 SD) with a range of 4.09μm-174.11μm, which is further subdivided into secondary fascicles with a thinner IFM (9.78μm ± 2.64 SD) with a range of 2μm-27.43μm in mature horses (n=3). Fascicles were heterogeneous regionally, diverged, converged and inter-connected with each other. Moreover, fascicle showed a twisted configuration when running from the proximal to the distal aspect of the 3D reconstruction. In histological scoring, it was shown that a number of fascicles and the IFM were angulated with a range of 0.2° to 40°. The IFM thickness between the secondary fascicles was significantly decreased during ageing. Intra-fascicular nuclear morphometry (density and lengths) were altered during ageing. Moreover, a number of intra-fascicular chondroid-like bodies were present in elderly horses (17- 20 years), that appeared as an individual or a cluster of large rounded cells, which stained positively for GAG and proteoglycans. In injured SDFT, 3D reconstruction displayed how the disrupted ECM extends in different planes and there was up-regulation of all histological scoring parameters. We conclude that the secondary and tertiary fascicles display a complex 3D organisation not reflected in current models of the hierarchical organisation of equine tendon. Understanding the 3D anatomy of the tendon will facilitate understanding of tendon structure-function relationships and injury predisposition. Histological parameters including IFM and nucleus morphology were altered with ageing. In particular in aged animal chondroid-like cells were present which may be indicative of chondroid metaplasia in tendon.
Supervisor: Clegg, Peter ; Comerford, Eithne ; Canty-Laird, E. G. Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral