Polynucleotide-Incorporated Collagen Membrane Enhances Bone Regeneration in Calvarial Defects of Ovariectomized Rats

Guided bone regeneration (GBR) with conventional collagen membranes may yield limited bone formation under estrogen-deficient conditions. This study evaluated whether a collagen membrane incorporating high-molecular-weight polynucleotide (PN) enhances bone regeneration in osteoporotic rats. PN (approximately 5 mg) was loaded onto a porcine collagen membrane and characterized by attenuated total reflectance Fourier-transform infrared spectroscopy, X-ray diffraction, and an in vitro release assay. Bilateral 5-mm calvarial defects were created in 30 ovariectomized female Sprague–Dawley rats and left unfilled (Control) or covered with a collagen membrane alone (Mem) or a PN-incorporated collagen membrane (PN_Mem) (n = 10 defects per group per time point). Regeneration was assessed at 4 and 8 weeks by micro-computed tomography, Masson’s trichrome staining, and immunohistochemistry for runt-related transcription factor 2 (Runx2) and bone morphogenetic protein-2/4 (BMP-2/4). PN was physically incorporated and released biphasically (approximately 50% within 8 h and 77% within 7 days). Bone volume did not differ among the groups at 4 weeks, whereas at 8 weeks it was greater in PN_Mem (5.98 ± 2.20 mm3) than in Control (1.24 ± 0.67 mm3; p < 0.0001) and Mem (2.52 ± 1.79 mm3; p < 0.001), with more Runx2-positive cells than in both groups and stronger BMP-2/4 immunoreactivity than in Control. PN incorporation enhanced the osteogenic performance of collagen membranes in this osteoporotic calvarial model; validation in clinically relevant alveolar defect models is required.