Compromised Neurotrophic and Angiogenic Regenerative Capability during Tendon Healing in a Rat Model of Type-II Diabetes

PLoS One. 2017 Jan 25;12(1):e0170748. doi: 10.1371/journal.pone.0170748. eCollection 2017.

Abstract

Metabolic diseases such as diabetes mellitus type-II (DM-II) may increase the risk of suffering painful connective tissue disorders and tendon ruptures. The pathomechanisms, however, by which diabetes adversely affects connective tissue matrix metabolism and regeneration, still need better definition. Our aim was to study the effect of DM-II on expressional changes of neuro- and angiotrophic mediators and receptors in intact and healing Achilles tendon. The right Achilles tendon was transected in 5 male DM-II Goto-Kakizaki (GK) and 4 age-matched Wistar control rats. The left Achilles tendons were left intact. At week 2 post-injury, NGF, BDNF, TSP, and receptors TrkA, TrkB and Nk1 gene expression was studied by quantitative RT-PCR (qRT-PCR) and their protein distribution by immunohistochemistry in intact and injured tendons. The expression of tendon-related markers, Scleraxis (SCX) and Tenomodulin (TNMD), was evaluated by qRT-PCR in intact and injured tendons. Injured tendons of diabetic GK rats exhibited significantly down-regulated Ngf and Tsp1 mRNA and corresponding protein levels, and down-regulated Trka gene expression compared to injured Wistar controls. Intact tendons of DM-II GK rats displayed reduced mRNA levels for Ngf, Tsp1 and Trkb compared to corresponding intact non-diabetic tendons. Up-regulated Scx and Tnmd gene expression was observed in injured tendons of normal and diabetic GK rats compared to intact Wistar controls. However, these molecules were not up-regulated in injured DM-II GK rats compared to their corresponding controls. Our results suggest that DM-II has detrimental effects on neuro- and angiotrophic pathways, and such effects may reflect the compromised repair seen in diabetic Achilles tendon. Thus, novel approaches for regeneration of injured, including tendinopathic, and surgically repaired diabetic tendons may include therapeutic molecular modulation of neurotrophic pathways such as NGF and its receptors.

MeSH terms

  • Achilles Tendon / injuries*
  • Achilles Tendon / metabolism
  • Achilles Tendon / physiopathology
  • Animals
  • Brain-Derived Neurotrophic Factor / genetics
  • Brain-Derived Neurotrophic Factor / metabolism
  • Diabetes Mellitus, Type 2 / metabolism
  • Diabetes Mellitus, Type 2 / physiopathology*
  • Disease Models, Animal
  • Gene Expression
  • Male
  • Neovascularization, Physiologic / physiology*
  • Nerve Growth Factor / genetics
  • Nerve Growth Factor / metabolism
  • Rats
  • Rats, Wistar
  • Receptor, trkA / genetics
  • Receptor, trkA / metabolism
  • Receptor, trkB / genetics
  • Receptor, trkB / metabolism
  • Receptors, Neurokinin-1 / genetics
  • Receptors, Neurokinin-1 / metabolism
  • Substance P / genetics
  • Substance P / metabolism
  • Tendon Injuries / metabolism
  • Tendon Injuries / physiopathology*
  • Wound Healing / physiology*

Substances

  • Brain-Derived Neurotrophic Factor
  • Receptors, Neurokinin-1
  • Substance P
  • Nerve Growth Factor
  • Receptor, trkA
  • Receptor, trkB

Grants and funding

This work was supported by Stockholm County Council (ALF),project no. SLL20100168, PA; the Swedish National Centre for Sports Research, a COREF-Sweden grant, PA, PA; Alberta Innovates Health Solutions OA Team Grant, DAH and CH. The Swedish Research Council grant, project no. 2012-3510, PA.