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- Dietrich-Zagonel, Franciele, et al.
(författare)
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Stimulation of Tendon Healing With Delayed Dexamethasone Treatment Is Modified by the Microbiome
- 2018
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Ingår i: American Journal of Sports Medicine. - : Sage Publications. - 0363-5465 .- 1552-3365. ; 46:13, s. 3281-3287
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Tidskriftsartikel (refereegranskat)abstract
- Background:The immune system reflects the microbiome (microbiota). Modulation of the immune system during early tendon remodeling by dexamethasone treatment can improve rat Achilles tendon healing. The authors tested whether changes in the microbiota could influence the effect of dexamethasone treatment.Hypothesis:A change in microbiome would influence the response to dexamethasone on regenerate remodeling, specifically tendon material properties (peak stress).Study Design:Controlled laboratory study.Methods:Specific opportunist and pathogen-free female rats were housed separately (n = 41) or together with specific pathogen-free rats carrying opportunistic microbes such as Staphylococcus aureus (n = 41). After 6 weeks, all co-housed rats appeared healthy but now carried S aureus. Changes in the gut bacterial flora were tested by API and RapID biochemical tests. All rats (clean and contaminated) underwent Achilles tendon transection under aseptic conditions. Flow cytometry was performed 8 days postoperatively on tendon tissue. Sixty rats received subcutaneous dexamethasone or saline injections on days 5 through 9 after transection. The tendons were tested mechanically on day 12. The predetermined primary outcome was the interaction between contamination and dexamethasone regarding peak stress, tested by 2-way analysis of variance.Results:Dexamethasone increased peak stress in all groups but more in contaminated rats (105%) than in clean rats (53%) (interaction, P = .018). A similar interaction was found for an estimate of elastic modulus (P = .021). Furthermore, dexamethasone treatment reduced transverse area but had small effects on peak force and stiffness. In rats treated with saline only, contamination reduced peak stress by 16% (P = .04) and elastic modulus by 35% (P = .004). Contamination led to changes in the gut bacterial flora and higher levels of T cells (CD3+CD4+) in the healing tendon (P < .05).Conclusion:Changes in the microbiome influence tendon healing and enhance the positive effects of dexamethasone treatment during the early remodeling phase of tendon healing.Clinical Relevance:The positive effect of dexamethasone on early tendon remodeling in rats is strikingly strong. If similar effects could be shown in humans, immune modulation by a few days of systemic corticosteroids, or more specific compounds, could open new approaches to rehabilitation after tendon injury.
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| 2. |
- Hammerman, Malin, et al.
(författare)
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Different mechanisms activated by mild versus strong loading in rat Achilles tendon healing
- 2018
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Ingår i: PLOS ONE. - : PUBLIC LIBRARY SCIENCE. - 1932-6203. ; 13:7
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Tidskriftsartikel (refereegranskat)abstract
- Background Mechanical loading stimulates Achilles tendon healing. However, various degrees of loading appear to have different effects on the mechanical properties of the healing tendon, and strong loading might create microdamage in the tissue. This suggests that different mechanisms might be activated depending on the magnitude of loading. The aim of this study was to investigate these mechanisms further. Methods Female rats had their right Achilles tendon cut transversely and divided into three groups: 1) unloading (calf muscle paralysis by Botox injections, combined with joint fixation by a steel-orthosis), 2) mild loading (Botox only), 3) strong loading (free cage activity). Gene expression was analyzed by PCR, 5 days post-injury, and mechanical testing 8 days post-injury. The occurrence of microdamage was analyzed 3, 5, or 14 days post-injury, by measuring leakage of injected fluorescence-labelled albumin in the healing tendon tissue. Results Peak force, peak stress, and elastic modulus of the healing tendons gradually improved with increased loading as well as the expression of extracellular matrix genes. In contrast, only strong loading increased transverse area and affected inflammation genes. Strong loading led to higher fluorescence (as a sign of microdamage) compared to mild loading at 3 and 5 days post-injury, but not at 14 days. Discussion Our results show that strong loading improves both the quality and quantity of the healing tendon, while mild loading only improves the quality. Strong loading also induces microdamage and alters the inflammatory response. This suggests that mild loading exert its effect via mechanotransduction mechanisms, while strong loading exert its effect both via mechanotransduction and the creation of microdamage. Conclusion In conclusion, mild loading is enough to increase the quality of the healing tendon without inducing microdamage and alter the inflammation in the tissue. This supports the general conception that early mobilization of a ruptured tendon in patients is advantageous.
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