OBJECTIVES: To quantify the intratendinous levels of substance P (SP) at different stages of overload in an established model for Achilles tendinopathy (rabbit). Also, to study the distribution of the SP-receptor, the NK-1R, and the source of SP, in the tendon. METHODS: Animals were subjected to the overuse protocol for 1, 3 or 6 weeks. One additional group served as unexercised controls. Immunoassay (EIA), immunohistochemistry (IHC), and in situ hybridisation (ISH) were performed. RESULTS: EIA revealed increased SP-levels in the Achilles tendon of the exercised limb in all the experimental groups as compared to in the controls (statistically significant; p=0.01). A similar trend in the unexercised Achilles tendon was observed but was not statistically significant (p=0.14). IHC and in ISH illustrated reactions of both SP and NK-1R mainly in blood vessel walls, but the receptor was also found on tenocytes. CONCLUSIONS: Achilles tendon SP-levels are elevated already after 1 week of loading. This shows that increased SP-production precedes tendinosis, as tendinosis-like changes occur only after a minimum of 3 weeks of exercise, as shown in a recent study using this model. We propose that central neuronal mechanism may be involved as similar trends were observed in the contralateral Achilles tendon.
OBJECTIVES: To quantify the intratendinous levels of substance P (SP) at different stages of overload in an established model for Achilles tendinopathy (rabbit). Also, to study the distribution of the SP-receptor, the NK-1R, and the source of SP, in the tendon. METHODS: Animals were subjected to the overuse protocol for 1, 3 or 6 weeks. One additional group served as unexercised controls. Immunoassay (EIA), immunohistochemistry (IHC), and in situ hybridisation (ISH) were performed. RESULTS: EIA revealed increased SP-levels in the Achilles tendon of the exercised limb in all the experimental groups as compared to in the controls (statistically significant; p=0.01). A similar trend in the unexercised Achilles tendon was observed but was not statistically significant (p=0.14). IHC and in ISH illustrated reactions of both SP and NK-1R mainly in blood vessel walls, but the receptor was also found on tenocytes. CONCLUSIONS: Achilles tendon SP-levels are elevated already after 1 week of loading. This shows that increased SP-production precedes tendinosis, as tendinosis-like changes occur only after a minimum of 3 weeks of exercise, as shown in a recent study using this model. We propose that central neuronal mechanism may be involved as similar trends were observed in the contralateral Achilles tendon.
Authors: M F Barbe; B A Hilliard; P W Fisher; A R White; S P Delany; V J Iannarone; M Y Harris; M Amin; G E Cruz; S N Popoff Journal: Connect Tissue Res Date: 2019-08-23 Impact factor: 3.417
Authors: Etienne J O O'Brien; Cyril B Frank; Nigel G Shrive; Benedikt Hallgrímsson; David A Hart Journal: Int J Exp Pathol Date: 2012-10 Impact factor: 1.925
Authors: Paul W Fisher; Yingjie Zhao; Mario C Rico; Vicky S Massicotte; Christine K Wade; Judith Litvin; Geoffrey M Bove; Steven N Popoff; Mary F Barbe Journal: J Cell Commun Signal Date: 2015-01-24 Impact factor: 5.782
Authors: Nagat Frara; Paul W Fisher; Yingjie Zhao; Joseph T Tarr; Mamta Amin; Steven N Popoff; Mary F Barbe Journal: Connect Tissue Res Date: 2017-04-12 Impact factor: 3.417