MUSCULOSKELETAL SECTION Dry Needling of a Healthy Rat Achilles Tendon Increases Its Gene Expressions: A Pilot Study Laura Calder  on-D  ıez, PT, PhD,* ,† Jos e Luis S anchez-S anchez, PT, PhD,* Javier Herrero-Turri  on, PhD, ‡,§ Joshua Cleland, PT, PhD, ¶ Jos e L. Arias-Bur  ıa, PT, PhD, k,kk and C esar Fern andez-de-las-Pe ~ nas, PT, PhD k,kk *Department of Physical Therapy, Universidad de Salamanca, Salamanca, Spain; † Physical Therapy Department, Mutua Accidentes Laborales, FREMAP, Salamanca, Spain; ‡ Instituto Investigaci on Biom edica de Salamanca, Universidad de Salamanca, Salamanca, Spain; § Instituto de Neurociencias de Castilla y Le on, Universidad de Salamanca, Salamanca, Spain; ¶ Department of Public Health and Community Medicine, Tufts University School of Medicine, Boston, Massachusetts, USA; k Department of Physical Therapy, Occupational Therapy, Physical Medicine and Rehabilitation, Universidad Rey Juan Carlos, Madrid, Spain; kk C atedra Institucional en Docencia, Cl  ınica e Investigaci on en Fisioterapia: Terapia Manual, Punci on Seca y Ejercicio Terap eutico, Universidad Rey Juan Carlos, Madrid, Spain Correspondence to: C esar Fern andez-de-las-Pe~ nas, PT, PhD, Facultad de Ciencias de la Salud, Universidad Rey Juan Carlos, 57, Avenida de Atenas s/n, 28922 Alcorc on, Madrid, Spain. Tel: þ34 91 488 88 84; Fax: þ34 91 488 89 57; E-mail: cesarfdlp@yahoo.es/cesar.fernandez@urjc.es. Funding sources: No funding was provided for this article. Abstract Background. Tendon dry needling is a potential treatment for tendinopathies. Several hypotheses have been pro- posed to explain its underlying mechanisms. No studies (to the best of our knowledge) have investigated changes in gene expression. Objective. To investigate histological and gene expression changes after the application of dry nee- dling to the healthy Achilles tendons of rats. Methods. Six Sprague-Dawley male rats were randomly divided into two groups: no intervention or dry needling. Dry needling consisted of three sessions (once per week) to the Achilles ten- don. Molecular expression of several genes involved in tendon repair and remodeling (e.g., Cox2, Mmp2, Mmp9, Col1a1, Col3a1, Vefg, and Scx) was assessed 7 days after the last needling session (day 28) or 28 days after for the no-intervention group. Histological tissue changes were determined with hematoxylin-eosin analyses. Results. The hematoxylin-eosin–stained images revealed no substantial differences in collagen structure or the presence of in- flammatory cells between the dry needling and no-intervention groups. A significant increase in the molecular ex- pression of Cox2, Mmp2, Col3a1, and Scx genes was observed in Achilles tendons treated with dry needling when compared with the no-intervention group. Conclusion. This animal pilot study found that the application of dry nee- dling to the healthy Achilles tendons of rats is able to increase the expression of genes associated with collagen re- generation and tissue remodeling of the extracellular matrix with no further histological damage to the tendon. Key Words: Dry Needling; Achilles; Gene Expression; Animal; Histology Introduction Dry needling is defined as a “skilled intervention using a thin filiform needle to penetrate the skin that stimulates myofascial trigger points, muscle or connective tissue for the management of musculoskeletal disorders” [1]. Although dry needling is usually associated with myofas- cial trigger point management [2], its application in the tendon—called “tendon fenestration” (peppering) or “percutaneous needle tenotomy”—has also been proposed [3]. There is evidence supporting a potential clinical effect of dry needling when applied to tendinopathies. Krey et al. [4] concluded that tendon dry needling improved self- reported outcome measures in individuals with tendinop- athy, but due to a lack of uniformity among the trials, firm conclusions were not possible. The meta-analysis per- formed by Tsikopoulos et al. [5] concluded that platelet- rich plasma did not provide significantly greater benefits in pain and function when compared with dry needling for the management of tendinopathy. These latest findings were also replicated by Abate et al. [6], who found similar effects of platelet-rich plasma injections and dry needling on pain and function outcomes in noninsertional Achilles V C The Author(s) 2020. Published by Oxford University Press on behalf of the American Academy of Pain Medicine. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com 112 Pain Medicine, 22(1), 2021, 112–117 doi: 10.1093/pm/pnaa352 Advance Access Publication Date: 6 November 2020 Original Research Article Downloaded from https://academic.oup.com/painmedicine/article/22/1/112/5957436 by guest on 16 February 2023