title: Intratendon Delivery of Leukocyte-Poor Platelet-Rich Plasma Improves Healing Compared With Leukocyte-Rich Platelet-Rich Plasma in a Rabbit Achilles Tendinopathy Model.
abstract: BACKGROUND
  Chronic tendinopathy is a commonly occurring clinical problem that affects both athletes and inactive middle-aged patients. Although some studies have shown that different platelet-rich plasma (PRP) preparations could exert various therapeutic effects in vitro, the role of leukocytes in PRP has not yet been defined under tendinopathy conditions in vivo.
  
  
  OBJECTIVE
  This study compared the effects of the intratendon delivery of leukocyte-poor PRP (Lp-PRP) versus leukocyte-rich PRP (Lr-PRP) in a rabbit chronic tendinopathy model in vivo.
  
  
  METHODS
  Controlled laboratory study.
  
  
  METHODS
  Four weeks after a local injection of collagenase in the Achilles tendon, the following treatments were randomly administered on the lesions: injections of (1) 200 μL of Lp-PRP (n = 8), (2) 200 μL of Lr-PRP (n = 8), or (3) 200 μL of saline (n = 8). Healing outcomes were assessed at 4 weeks after therapy with magnetic resonance imaging (MRI), cytokine quantification, real-time polymerase chain reaction analysis of gene expression, histology, and transmission electron microscopy (TEM).
  
  
  RESULTS
  MRI revealed that the Lr-PRP and saline groups displayed higher signal intensities compared with the Lp-PRP group with T2 mapping. Histologically, the Lp-PRP group displayed significantly better general scores compared with the Lr-PRP ( P = .001) and saline ( P < .001) groups. Additionally, TEM showed that the Lp-PRP group had larger collagen fibril diameters than the Lr-PRP group ( P < .001). Enzyme-linked immunosorbent assay showed a significantly lower level of catabolic cytokine IL-6 in the Lp-PRP group compared with the Lr-PRP ( P = .001) and saline ( P = .021) groups. The Lp-PRP group displayed significantly increased expression of collagen I compared with the saline group ( P = .004) but not the Lr-PRP group. Both the Lp-PRP and Lr-PRP groups exhibited significantly lower matrix metalloproteinase (MMP)-1 and MMP-3 expression levels compared with the saline group. However, only the Lp-PRP group displayed significantly higher expression of TIMP-1 than the saline group ( P = .024).
  
  
  CONCLUSIONS
  Compared with Lr-PRP, Lp-PRP improves tendon healing and is a preferable option for the clinical treatment of tendinopathy.
  
  
  CONCLUSIONS
  PRP is widely used in the clinical management of chronic tendinopathy. However, the clinical results are ambiguous. It is imperative to understand the influence of leukocytes on PRP-mediated tissue healing in vivo, which could facilitate the better clinical management of chronic tendinopathy. Further studies are needed to translate our findings to the clinical setting.
authors.affiliation: Department of Orthopedic Surgery, 2nd Affiliated Hospital, School of Medicine, Zhejiang University, Hangzhou, China.
authors.forename: Ruijian
authors.initials: R
authors.lastname: Yan
authors.affiliation: Department of Orthopedic Surgery, 2nd Affiliated Hospital, School of Medicine, Zhejiang University, Hangzhou, China.
authors.forename: Yanjia
authors.initials: Y
authors.lastname: Gu
authors.affiliation: Department of Orthopedic Surgery, 2nd Affiliated Hospital, School of Medicine, Zhejiang University, Hangzhou, China.
authors.forename: Jisheng
authors.initials: J
authors.lastname: Ran
authors.affiliation: Dr Li Dak Sum & Yip Yio Chin Center for Stem Cell and Regenerative Medicine, School of Medicine, Zhejiang University, Hangzhou, China.
authors.forename: Yejun
authors.initials: Y
authors.lastname: Hu
authors.affiliation: Department of Orthopedic Surgery, 2nd Affiliated Hospital, School of Medicine, Zhejiang University, Hangzhou, China.
authors.forename: Zefeng
authors.initials: Z
authors.lastname: Zheng
authors.affiliation: Zhejiang Xingyue Biotechnology Co Ltd, Hangzhou, China.
authors.forename: Mengfeng
authors.initials: M
authors.lastname: Zeng
authors.affiliation: Faculty of Dentistry, The University of Hong Kong, Pokfulam, Hong Kong.
authors.forename: Boon Chin
authors.initials: BC
authors.lastname: Heng
authors.affiliation: Dr Li Dak Sum & Yip Yio Chin Center for Stem Cell and Regenerative Medicine, School of Medicine, Zhejiang University, Hangzhou, China.|Department of Sports Medicine, School of Medicine, Zhejiang University, Hangzhou, China.|China Orthopaedic Regenerative Medicine Group, Hangzhou, China.
authors.forename: Xiao
authors.initials: X
authors.lastname: Chen
authors.affiliation: Dr Li Dak Sum & Yip Yio Chin Center for Stem Cell and Regenerative Medicine, School of Medicine, Zhejiang University, Hangzhou, China.|Department of Sports Medicine, School of Medicine, Zhejiang University, Hangzhou, China.
authors.forename: Zi
authors.initials: Z
authors.lastname: Yin
authors.affiliation: Department of Orthopedic Surgery, 2nd Affiliated Hospital, School of Medicine, Zhejiang University, Hangzhou, China.
authors.forename: Weishan
authors.initials: W
authors.lastname: Chen
authors.affiliation: Department of Orthopedic Surgery, 2nd Affiliated Hospital, School of Medicine, Zhejiang University, Hangzhou, China.|Dr Li Dak Sum & Yip Yio Chin Center for Stem Cell and Regenerative Medicine, School of Medicine, Zhejiang University, Hangzhou, China.|Department of Sports Medicine, School of Medicine, Zhejiang University, Hangzhou, China.|China Orthopaedic Regenerative Medicine Group, Hangzhou, China.|Orthopaedic Research Institute, Zhejiang University, Hangzhou, China.
authors.forename: Weiliang
authors.initials: W
authors.lastname: Shen
authors.affiliation: Dr Li Dak Sum & Yip Yio Chin Center for Stem Cell and Regenerative Medicine, School of Medicine, Zhejiang University, Hangzhou, China.|Department of Sports Medicine, School of Medicine, Zhejiang University, Hangzhou, China.|China Orthopaedic Regenerative Medicine Group, Hangzhou, China.
authors.forename: Hongwei
authors.initials: H
authors.lastname: Ouyang
mesh_terms: D000125:Achilles Tendon / Q000293:injuries*; D000818:Animals; D017364:Collagenases / Q000008:administration & dosage; D004797:Enzyme-Linked Immunosorbent Assay; D007962:Leukocytes / Q000378:metabolism; D053657:Platelet-Rich Plasma / Q000378:metabolism*; D011817:Rabbits; D052256:Tendinopathy / Q000628:therapy*; D014945:Wound Healing
chemical_list: D017364:Collagenases
keywords: leukocytes; platelet-rich plasma; tendinopathy