Platelet autologous growth factors decrease the osteochondral regeneration capability of a collagen-hydroxyapatite scaffold in a sheep model

Abstract

Background: Current research aims to develop innovative approaches to improve chondral and osteochondral regeneration. The objective of this study was to investigate the regenerative potential of platelet-rich plasma (PRP) to enhance the repair process of a collagen-hydroxyapatite scaffold in osteochondral defects in a sheep model.

Methods: PRP was added to a new, multi-layer gradient, nanocomposite scaffold that was obtained by nucleating collagen fibrils with hydroxyapatite nanoparticles. Twenty-four osteochondral lesions were created in sheep femoral condyles. The animals were randomised to three treatment groups: scaffold, scaffold loaded with autologous PRP, and empty defect (control). The animals were sacrificed and evaluated six months after surgery.

Results: Gross evaluation and histology of the specimens showed good integration of the chondral surface in both treatment groups. Significantly better bone regeneration and cartilage surface reconstruction were observed in the group treated with the scaffold alone. Incomplete bone regeneration and irregular cartilage surface integration were observed in the group treated with the scaffold where PRP was added. In the control group, no bone and cartilage defect healing occurred; defects were filled with fibrous tissue. Quantitative macroscopic and histological score evaluations confirmed the qualitative trends observed.

Conclusions: The hydroxyapatite-collagen scaffold enhanced osteochondral lesion repair, but the combination with platelet growth factors did not have an additive effect; on the contrary, PRP administration had a negative effect on the results obtained by disturbing the regenerative process. In the scaffold + PRP group, highly amorphous cartilaginous repair tissue and poorly spatially organised underlying bone tissue were found.

Figure 1

Three-gradient, multi-layer scaffold that mimics the articular osteochondral compartment, reproducing both molecularly and morphologically cartilage and the subchondral bone layer.

Figure 2

Macroscopic, micro X-ray and histological evaluations at 6 months of the C-Group (A), S-PRP Group (B), S-Group (C).

Figure 3

Comparison of scores obtained with the modified Fortier evaluation of gross appearance (max 0-min 15).

Figure 4

Comparison of scores obtained with the Niederauer evaluation of gross appearance (max 8-min 0).

Figure 5

Comparison of scores obtained with the Niederauer histologic scoring scale for osteochondral defects (max 28-min 0).

Figure 6

Histological evaluation at 6 months of undecalcified samples of the C-Group (A), S-PRP Group (B), S-Group (C). Staining with fuchsin acid/fast green/toluidine blue, 10× magnification.

Figure 7

Representative fields of immunohistochemical staining for type II (A, B, C) and type I (D, E, F) collagen of decalcified samples of the C-Group (A, D), S-PRP Group (B, E) and S-Group (C, F) at 6 months. Bar = 100 microns.