Molecular Insights into the Synergistic Effect of Nano-Hydroxyapatite and L-PRF on Osteoporotic Osseointegration: An In Vivo Gene Expression Study

Poor bone quality in osteoporotic patients remains a major challenge for achieving predictable osseointegration. This study serves as a mechanistic complement to previously reported structural data, aiming to investigate the molecular pathways underlying the synergy between nanostructured surfaces and autologous blood concentrates in compromised bone. Ninety-six Wistar rats were divided into healthy (SHAM) and osteoporotic (OVX) groups. Implants with nanostructured hydroxyapatite (NanoHA) or dual acid-etched (DAE) surfaces were installed in the tibiae, associated or not with leukocyte- and platelet-rich fibrin (L-PRF). Gene expression (RT-qPCR) for Runx2, Alpl, Bglap, Spp1, Tnfrsf11, and Tnfrsf11b was assessed at 7 and 30 days. In compromised systemic conditions (OVX), the NanoHA + L-PRF association promoted a robust “molecular rescue” of bone metabolism. At 30 days, this synergistic group exhibited a significant upregulation of Alpl (mean: 11.69 ± 1.65) and Runx2 (mean: 4.49 ± 0.82) compared to DAE controls (p < 0.05). Crucially, the therapy orchestrated a protective remodeling environment by significantly inducing Tnfrsf11b expression (5.50 ± 0.88), effectively balancing the Tnfrsf11/Tnfrsf11b ratio. Late-stage maturation markers (Bglap and Spp1) were also significantly elevated, effectively mimicking healthy physiological levels observed in the SHAM group. NanoHA biofunctionalization, synergistically with L-PRF, triggers a transcriptional reprogramming of the peri-implant microenvironment, mitigating the catabolic effects of estrogen deficiency. These findings provide a biological foundation for enhanced clinical predictability in high-risk patients, suggesting that local interfacial modifications can overcome systemic bone compromise.