Abstract
IntroductionPlatelet-rich plasma (PRP) is widely used to treat tendon injuries in clinics. These PRP preparations often contain white blood cells or leukocytes, and the precise cellular effects of leukocyte-rich PRP (L-PRP) on tendons are not well defined. Therefore, in this study, we determined the effects of L-PRP on tendon stem/progenitor cells (TSCs), which play a key role in tendon homeostasis and repair.MethodsTSCs isolated from the patellar tendons of rabbits were treated with L-PRP or P-PRP (pure PRP without leukocytes) in vitro, followed by measuring cell proliferation, stem cell marker expression, inflammatory gene expression, and anabolic and catabolic protein expression by using immunostaining, quantitative real-time polymerase chain reaction, Western blot, and enzyme-linked immunosorbent assay, respectively.ResultsCell proliferation was induced by both L-PRP and P-PRP in a dose-dependent manner with maximum proliferation at a 10 % PRP dose. Both PRP treatments also induced differentiation of TSCs into active tenocytes. Nevertheless, the two types of PRP largely differed in several effects exerted on TSCs. L-PRP induced predominantly catabolic and inflammatory changes in differentiated tenocytes; its treatment increased the expression of catabolic marker genes, matrix metalloproteinase-1 (MMP-1), MMP-13, interleukin-1beta (IL-1β), IL-6 and tumor necrosis factor-alpha (TNF-α), and their respective protein expression and prostaglandin E2 (PGE2) production. In contrast, P-PRP mainly induced anabolic changes; that is, P-PRP increased the gene expression of anabolic genes, alpha-smooth muscle actin (α-SMA), collagen types I and III.ConclusionsThese findings indicate that, while both L-PRP and P-PRP appear to be “safe” in inducing TSC differentiation into active tenocytes, L-PRP may be detrimental to the healing of injured tendons because it induces catabolic and inflammatory effects on tendon cells and may prolong the effects in healing tendons. On the other hand, when P-PRP is used to treat acutely injured tendons, it may result in the formation of excessive scar tissue due to the strong potential of P-PRP to induce inordinate cellular anabolic effects.
Highlights
Platelet-rich plasma (PRP) is widely used to treat tendon injuries in clinics
The two preparations differed largely in the amounts of white blood cells (WBCs) present in them; WBC concentration in leukocyte-rich PRP (L-PRP) preparations ranged between 7.1 and 10.5 × 103/μl, which is higher than the mean WBC concentration in whole rabbit blood 4.87 × 103/μl
Our findings demonstrated that both L-PRP and P-PRP preparations induced tendon stem/progenitor cells (TSCs) differentiation into active tenocytes, which were proliferating in culture in a PRP-dose-dependent manner (Figs. 1–5)
Summary
Platelet-rich plasma (PRP) is widely used to treat tendon injuries in clinics. These PRP preparations often contain white blood cells or leukocytes, and the precise cellular effects of leukocyte-rich PRP (L-PRP) on tendons are not well defined. PRP has several distinct advantages: it is autologous and biocompatible, making it inherently safe; it contains high levels of growth factors that promote healing of injured tissues; and when injected in vivo, it forms a fibrin scaffold, which is conducive for cell migration and new matrix formation [2, 8]. Because of these advantages, PRP has been used widely to promote bone formation [9], skin rejuvenation [10], and colon anastomosis [11] among other things. PRP treatment has been successful in healing injured anterior cruciate ligament, which is known to lack spontaneous healing ability [15,16,17]
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