Xenogeneic Grafts Combined with Platelet Concentrates: Effects on Bone Microarchitecture and Collagen Maturation

Background: This study assessed the impact of xenogeneic bone grafts (XEN), either utilized alone or combined with autologous platelet concentrates (APCs) prepared using three different centrifugation protocols, on the healing of critical-size defects (CSDs) in rat calvaria. Methods: Forty rats were assigned to five groups (n = 8): Control, XEN, XEN + L-PRF, XEN + A-PRF, and XEN + Bio-PRF. Blood concentrates were prepared by centrifuging blood collected via cardiac puncture: L-PRF (~700 g for 12 min), A-PRF (~208 g for 14 min), and Bio-PRF (~700 g for 8 min). Defects (5 mm diameter) in the right parietal bone of each rat were filled with blood clot, XEN, or XEN combined with L-PRF, A-PRF, or Bio-PRF. Animals were euthanized 60 days post-surgery, and the calvariae were analyzed using histomorphometry and micro-CT. The percentage of mature and immature collagen fibers was analyzed using Picrosirius red staining under polarized light microscopy. Results: Groups XEN-A-PRF, XEN-L-PRF, and XEN-Bio-PRF presented higher bone volume (BV/TV) than the control group (14.35 ± 6.42%, 11.96 ± 4.68%, and 14.92 ± 3.47%, respectively, vs. 4.13 ± 2.25%; p < 0.05). These groups also presented lower bone porosity (BP) than the control group (p < 0.05). The XEN group did not show different values of BV/TV and BP compared to the control group. Only the XEN + A-PRF and XEN + Bio-PRF groups showed a higher percentage of mature collagen fibers (red color) compared to the XEN and control groups (p < 0.05). The control and XEN groups showed a higher amount of immature collagen fibers (green color) compared to the XEN + A-PRF, XEN + L-PRF, and XEN + Bio-PRF groups (p < 0.05). Conclusions: It can be concluded that CSDs treated with XEN combined with APCs presented a more favorable bone microarchitecture than untreated CSDs after a 60-day healing period. Furthermore, CSDs treated with XEN combined with A-PRF or Bio-PRF showed greater collagen maturation than those treated with XEN alone, suggesting that the centrifugation protocol used for preparing APCs may be a decisive factor for the quality of the collagen matrix in newly formed bone tissue.