PRP allows an increase in expression of vascular endothelial growth factor, thrombospondin-1, neurotrophin-3, growth-associated protein-43, and nerve growth factor mRNA.
PRP alters the expression of target genes (growth factor-b1, collagen type1A1, collagen type3A1, decorin, biglycan, matrix metalloproteinase-1, matrix metalloproteinase-13, and tissue inhibitor of metalloproteinase-1 during the remodelling process (evaluations performed at 2, 6, and 12 weeks after surgery).
No statistical difference in biomechanical properties (anteroposterior laxity and structural properties). Histological aspects: compared to 3x PRP, 5x PRP group had significantly greater cellular density and number of vessels and better organization of cells and collagen fibres.
Significant improvements in mechanical properties (load at yield, maximum load, and linear stiffness) of repaired ACL compared to sutured only at 4 weeks after surgery.
The application of collagen-PRP scaffold allows significant effects of increasing the wound filling and enhancing the presence of fibronectin, fibrinogen, PDGF-A, TBG-b1, FGF-2, procollagen I, and vWF.
Significantly improvements between PRP group and control group concerning cross-sectional area, failure load, stiffness, and tensile stress after 3, 6, or 12 weeks; however, after 24 weeks this difference is not confirmed and mechanical scores are worse than the intact ACL.
PRP with PBMCs determined an increasing of type I and type III procollagen gene expression, collagen protein expression, and cell proliferation. An increase of IL-6 expression was detected in PBMCs exposed to PRP. No effect of PBMCs without PRP.
Does cell’s age influence the ACL cell response to PRP?
Platelet count: pts/mL Leukocyte count: —
Scaffold’s augmentation (collagen scaffold)
PRP increases cellular metabolic activity and reduced apoptotic rate and stimulation of collagen production on immature and adolescent cells, compared to collagen only scaffold. Lower effects of PRP on adult cells.
The comparison between immature and adolescent cells showed a significantly higher cell migration and proliferation in immature group, whereas no differences were seen in scaffold contraction.
Does PRP components (pts or PPP) independently influence ACL cells behaviour?
Platelet count: pts/mL Leukocyte count: —
Scaffold’s augmentation (collagen scaffold) with PRP, pts, or PPP
The addition of PPP, platelets, or PRP all reduced cell apoptosis and enhanced metabolic activity of fibroblasts. Significantly higher expression of collagen only with PRP.
Analysis of effects of single growth factors (GF) on fibroblasts harvested from medial collateral ligament and ACL of skeletally mature rabbits
Growth factor analysed are as follows: epidermal GF, basic fibroblast GF, platelet derived GF-BB, acid fibroblast GF, TGF-b1, insulin-like GF-1, platelet derived GF-AA, and interleukin-1a
Epidermal GF, basic fibroblast GF, and platelet derived GF-BB determined a significantly higher fibroblast’s proliferation than the untreated cells. No significant difference reported for the others GFs analysed.