All cells exist within a 3D microenvironment where they are exposed to a multitude of mechanobiological cues, from nano-level cell/matrix interactions, to tissue-level mechanical strain. These cues are fundamental to maintaining tissue homeostasis, but when disrupted during disease, can promote pathological outcomes and impair healing. This is particularly true in tendons; 3D load bearing connective tissue structures composed of a complex arrangement of matrix proteins, organised in a highly aligned manner and maintained by tendon cells (tenocytes). When diseased or injured (termed tendinopathy), the tendon begins a journey of poor healing, characterised by mechanically inferior disorganised scar tissue which ultimately results in compromised or total loss of function. In both health and disease, the mechanobiological stimuli experienced by tenocytes will directly affect their behaviour, yet this is a poorly studied area of research. We have used decellularised tendon slices to mimic the structure of healthy tendon, and induced degradation to mimic tendinopathic tendon. We have re-seeded these slices with tenocytes or immune cells and are building a greater picture of the role that the structure and stiffness of the matrix has on cell behaviour in health and disease

Objectives. The present study describes a novel technique for revitalising allogenic intrasynovial tendons by combining cell-based therapy and mechanical stimulation in an ex vivo canine model. Methods. Specifically, canine flexor digitorum profundus tendons were used for this study and were divided into the following groups: (1) untreated, unprocessed normal tendon; (2) decellularised tendon; (3) bone marrow stromal cell (BMSC)-seeded tendon; and (4) BMSC-seeded and cyclically stretched tendon. Lateral slits were introduced on the tendon to facilitate cell seeding. Tendons from all four study groups were distracted by a servohydraulic testing machine. Tensile force and displacement data were continuously recorded at a sample rate of 20 Hz until 200 Newton of force was reached. Before testing, the cross-sectional dimensions of each tendon were measured with a digital caliper. Young’s modulus was calculated from the slope of the linear region of the stress-strain curve. The BMSCs were labeled for histological and cell viability evaluation on the decellularized tendon scaffold under a confocal microscope. Gene expression levels of selected extracellular matrix tendon growth factor genes were measured. Results were reported as mean ± SD and data was analyzed with one-way ANOVAs followed by Tukey’s post hoc multiple-comparison test. Results. We observed no significant difference in cross-sectional area or in Young’s modulus among the four study groups. In addition, histological sections showed that the BMSCs were aligned well and viable on the tendon slices after two-week culture in groups three and four. Expression levels of several extracellular matrix tendon growth factors, including collagen type I, collagen type III, and matrix metalloproteinase were significantly higher in group four than in group three (p < 0.05). Conclusion. Lateral slits introduced into de-cellularised tendon is a promising method of delivery of BMSCs without compromising cell viability and tendon mechanical properties. In addition, mechanical stimulation of a cell-seeded tendon can promote cell proliferation and enhance expression of collagen types I and III in vitro. Cite this article: J. H. Wu, A. R. Thoreson, A. Gingery, K. N. An, S. L. Moran, P. C. Amadio, C. Zhao. The revitalisation of flexor tendon allografts with bone marrow stromal cells and mechanical stimulation: An ex vivo model revitalising flexor tendon allografts. Bone Joint Res 2017;6:179–185. DOI: 10.1302/2046-3758.63.BJR-2016-0207.R1

Aims: The aim of this study was to analyze the morphological features of the human surgical specimens of normal supraspinatus tendon from patients with rotator cuff tears and glenohumeral instability. Methods: 41 subjects were recruited for the study. 20 subjects (group 1) sustained a rotator cuff tear and proceeded arthroscopic repair of the lesion. 21 subjects (group 2) underwent surgery due to glenohumeral instability. During surgery, under arthroscopic control, a full thickness supraspinatus tendon biopsy was harvested in the middle portion of the tendon. All slices were processed for histological analysis. Results: On surgical specimens of supraspinatus tendon from patients with rotator cuff tears, but not from patients with instability, we found increased preponderance of hyaline degeneration, fibrocartilaginous or chondroid metaplasia, calcification, lipoid degeneration, mucoid or myxoid. Degenerative changes were more evident on the articular side of the rotator cuff. Conclusions: The present study provides a description of the histological architecture of human surgical specimens of normal supraspinatus tendon from patients with rotator cuff tears. Preexisting degenerative change in the supraspinatus tendon seems to be the main cause of rotator cuff tears