October 2017 | Volume 4 | Article 168 1 CASE REPORT published: 10 October 2017 doi: 10.3389/fvets.2017.00168 Frontiers in Veterinary Science | www.frontiersin.org Edited by: Jan H. Spaas, ANACURA Group, Belgium Reviewed by: Karin Wuertz-Kozak, ETH Zurich, Switzerland Ruchi Sharma, Stemnovate Ltd., United Kingdom *Correspondence: Milomir Kovac kovacmilomir@gmail.com; Albert A. Rizvanov albert.rizvanov@kpfu.ru Specialty section: This article was submitted to Veterinary Regenerative Medicine, a section of the journal Frontiers in Veterinary Science Received: 06 July 2017 Accepted: 25 September 2017 Published: 10 October 2017 Citation: Kovac M, Litvin YA, Aliev RO, Zakirova EY, Rutland CS, Kiyasov AP and Rizvanov AA (2017) Gene Therapy Using Plasmid DNA Encoding Vascular Endothelial Growth Factor 164 and Fibroblast Growth Factor 2 Genes for the Treatment of Horse Tendinitis and Desmitis: Case Reports. Front. Vet. Sci. 4:168. doi: 10.3389/fvets.2017.00168 Gene Therapy Using Plasmid DNA Encoding Vascular Endothelial Growth Factor 164 and Fibroblast Growth Factor 2 Genes for the Treatment of Horse Tendinitis and Desmitis: Case Reports Milomir Kovac 1 *, Yaroslav A. Litvin 2 , Ruslan O. Aliev 1 , Elena Yu Zakirova 2 , Catrin S. Rutland 3 , Andrey P. Kiyasov 2 and Albert A. Rizvanov 2 * 1 Moscow State Academy of Veterinary Medicine and Biotechnology, Moscow, Russia, 2 Kazan Federal University, Kazan, Russia, 3 Faculty of Medicine, School of Veterinary Medicine and Science, University of Nottingham, Nottingham, United Kingdom In this clinical study, for the frst time we used the direct gene therapy to restore severe injuries of the suspensory ligament branch and superfcial digital fexor tendon in horses (Equus caballus). We injected the plasmid DNA encoding two therapeutic species-specifc growth factors: vascular endothelial growth factor 164 and fbroblast growth factor 2 at the site of injury in the suspensory ligament branch and tendon. Treatment effects were evaluated with the use of clinical observation and ultrasound imaging during a period of a few months. We showed that gene therapy used within a period of 2–3 months after the injury resulted in the complete recovery of functions and full restoration of the severely damaged suspensory ligament and superfcial digital fexor tendon. Keywords: gene therapy, tendon, suspensory ligament, horse, vascular endothelial growth factor, fbroblast growth factor INTRODUCTION Tendon or ligament injuries are one of the most common causes of orthopedic disorders in horses (Equus caballus) of any age and breed. Injuries of the digital fexor tendons (superfcial and deep digital fexors) and the suspensory ligament are of utmost clinical importance in the horse resulting in more than 98% of all cases observed in practice (1). In terms of pathogenesis, a course of equine tendinitis (desmitis) can follow three phases: the infammatory response, the fbroblastic phase and the remodeling phase, which lasts for several months and can extend up to 15 months in severe injuries (2). Te main problem observed in ligament healing at the site of tendon fbril damage is the formation of granulation fbrous connective tissue (a scar) with a lot of type III collagen content—up to 30%, whereas in normal healthy tendon it is less than 5% (3). Type III collagen difers from main tendon type I collagen due to smaller sized fbers and reduced strength and elasticity. A selection of treatment modalities are available for equine injured ligaments and tendons and their use depends upon injury type, location and extent as well as the time elapsed since the