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OBJECTIVES: Re-rupture is common after primary flexor tendon repair. Characterization of the biological changes in the ruptured tendon stumps would be helpful, not only to understand the biological responses to the failed tendon repair, but also to investigate if the tendon stumps could be used as a recycling biomaterial for tendon regeneration in the secondary grafting surgery. METHODS: A canine flexor tendon repair and failure model was used. Following six weeks of repair failure, the tendon stumps were analyzed and characterized as isolated tendon-derived stem cells (TDSCs). RESULTS: Failed-repair stump tissue showed cellular accumulation of crumpled and disoriented collagen fibres. Compared with normal tendon, stump tissue had significantly higher gene expression of collagens I and III, matrix metalloproteinases (MMPs), vascular endothelial growth factor (VEGF), platelet-derived growth factor (PDGF), and insulin-like growth factor (IGF). The stump TDSCs presented both mesenchymal stem and haematopoietic cell markers with significantly increased expression of CD34, CD44, and CD90 markers. Stump TDSCs exhibited similar migration but a lower proliferation rate, as well as similar osteogenic differentiation but a lower chondrogenic/adipogenic differentiation capability, compared with normal TDSCs. Stump TDSCs also showed increasing levels of SRY-box 2 (Sox2), octamer-binding transcription factor 4 (Oct4), tenomodulin (TNMD), and scleraxis (Scx) protein and gene expression. CONCLUSION: We found that a failed repair stump had increased cellularity that preserved both mesenchymal and haematopoietic stem cell characteristics, with higher collagen synthesis, MMP, and growth factor gene expression. This study provides evidence that tendon stump tissue has regenerative potential.Cite this article: C-C. Lu, T. Zhang, R. L. Reisdorf, P. C. Amadio, K-N. An, S. L. Moran, A. Gingery, C. Zhao. Biological analysis of flexor tendon repair-failure stump tissue: A potential recycling of tissue for tendon regeneration. Bone Joint Res 2019;8:232-245. DOI: 10.1302/2046-3758.86.BJR-2018-0239.R1.
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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.
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While utero-placental insufficiency is associated with adverse outcomes for both mother and fetus, many of the maternal-fetal adaptations during pregnancy in models of fetal compromise remain unclear. The purpose of this study was to determine if chronically reduced uterine perfusion pressure (RUPP) during days 14-19 of gestation alters feto-placental growth differentially from the cervical to ovarian ends of the uterus and generates metabolic adaptations such as increased blood lactate (BLa) concentrations and lactate transporter expression in the placenta. Fetal growth restriction was evident, placental efficiency (fetal weight/placental weight) decreased (4.7 ± 0.35 vs. 5.9 ± 0.30; P < 0.05) and fetal growth pattern within the uterus was altered in the RUPP compared to the normal pregnant (NP) rats. Blood lactate concentrations were increased (3.3 ± 0.3 vs. 2.1 ± 0.4 mmol/l; P < 0.05) in NP compared to virgin rats, and in RUPP compared to NP (5.0 ± 0.6 vs. 3.3 ± 0.3 mmol/l; P < 0.05). Lactate concentration was increased (10.0 ± 0.6 vs. 7.1 ± 0.8 mmol/l; P < 0.05) in the media from hypoxic compared to normoxic BeWo cells. No changes in expression of placental MCT1, 2, or 4 were observed between RUPP and NP rats. RUPP resulted in decreased plasma leptin (2.0 ± 0.3 vs. 3.1 ± 0.4; P < 0.05) but no change in IGF-1 compared to NP. The present data indicate chronic placental ischemia results in numerous endocrine and metabolic changes during late pregnancy in the rat and that the RUPP model has differential effects on fetal growth depending on uterine position.