Intratendon Delivery Of Lp-PRP Improves Healing Compared With Lr-PRP In A Rabbit Achills Tendinopathy Model

Background:Tendinopathy is a commonly occurring clinical problem that affects both athletes and inactive middle-aged patients.Some current studies in vitro have shown that there are differences in cellular components in platelet-rich plasma(PRP)preparations made by different preparation methods:for example,leukocyte,platelet and fibrinogen.These differences in composition,especially the difference in leukocyte content,may be one of the main reasons for the inaccuracy of clinical efficacy of PRP in tendinopathy.However,currently,there is no study in vivo about the effects of leukocytes in PRP in the context of tendinopathy.The specific mechanism by which PRP affects leukocyte components in the treatment of tendinopathy is not yet clear.Methods and Contents:Four weeks after a local injection of collagenase in rabbit Achilles tendon,the animal models of tendinopathy was established,the following treatments were randomly administered on the lesions:injections of(1)200 ?L of Leukocyte-Poor PRP(Lp-PRP)(n = 8),(2)200 ?L of Leukocyte-Rich PRP(Lr-PRP)(n = 8),or(3)200 ?L of saline(n = 8).Healing outcomes were assessed at 4 weeks after injection therapy with magnetic resonance imaging(MRI)scan,Hematoxylin&Eosin(H&E)and Masson staining,histological evaluation and transmission electron microscopy(TEM)scan.Statistically analysis was used to compare the differences in treatment results between the Lp-PRP group,the Lr-PRP group and the control group.Enzyme-Linked Immuno Sorbent Assay(ELISA)was used for the quantitative analysis of IL-1?,TNF-? and IL-6 cytokines in tendon tissue.RT-PCR was used to determine the expression levels of MMP-1,3,9 and TIMP genes in tendon tissue to explore the possible role which leukocyte plays in the treatment of tendinopathy by PRP.Results MRI scan of rabbit Achilles tendon tissue revealed that the Lr-PRP group and control group displayed higher mean signal intensities compared with the Lp-PRP group with T2 mapping.The histological results of H&E and Masson staining showed that the Lp-PRP group displayed significantly better inflammation scores,better cell density scores and better general scores compared with the Lr-PRP group(P = 0.001)and control group(P<0.001).Additionally,the TEM scan showed that the Lp-PRP group had larger collagen fibril diameters than the Lr-PRP group(P<0.001).The Lp-PRP group had lower collagen fibril density than the Lr-PRP group(P<0.001).Enzyme-linked immunosorbent assay showed a significantly lower level of catabolic cytokine IL-6 in the Lp-PRP group compared with the Lr-PRP group(P =0.001)and control group(P = 0.021).The Lp-PRP group displayed significantly higher expression of collagen I compared with the saline group(P = 0.004)but not the Lr-PRP group.Both the Lp-PRP and Lr-PRP groups exhibited significantly lower matrix metalloproteinase-1(MMP-1)and MMP-3 expression levels compared with the control group.However,only the Lp-PRP group displayed significantly higher expression of TIMP-1 than the control group(P = 0.024).Conclusions:Compared with Lr-PRP,Lp-PRP improves tendon healing and is a preferable option for the clinical treatment of tendinopathy.