Reparative osteogenesis markers during bone defects substitution with germanium-doped ceramics under experimental osteoporosis

Osteoporosis, as a systemic skeletal disease, is characterized by the loss of bone mass, decreased mineral density, and microarchitecture changes. In cases of traumatic fractures and critical-size bone defects osteoporosis can lead to spontaneous fractures, impair regeneration and complication when using bone substituting materials. Ceramic implants, doped with germanium to impart osteoinductive properties, are among promising bone substituting materials. In this study we aimed to assess biochemical markers of reparative osteogenesis at bone defects substitution with germanium-doped ceramics in rabbits under osteoporosis. The study was conducted on California White rabbits with osteoporosis, induced by administration of 0.4% dexamethasone solution. The model defects were created in trabecular and cortical bones, following the exposure of the periosteum with drills of 3 and 4.2 mm diameters, respectively, in compliance with the anesthetic regimen and antiseptic rules. Calcium phosphate ceramic granules with a size of 700 μm, synthesized from hydroxyapatite and β-tricalcium phosphate and doped with 0.8 mass.% germanium (CPC-Ge) were used for healing. In the control group of animals (n = 9) bone defects were healed under a blood clot. In the experimental group (n = 9), the defects were replaced with CPC-Ge granules. Blood samples for biochemical studies were collected before modeling the bone defect and on the 7th, 14th, 30th, and 60th days of reparative osteogenesis­. The activity of tartrate-resistant acid phosphatase, alkaline phosphatase and its bone isoenzyme, as well as circulating immune complexes, protein C and NO serum levels were determined. It was shown that substitution of both trabecular and cortical bones defects with CPC-Ge, as compared to healing under a blood clot, leads to reduced inflammatory and immune responses, prevented the depletion of protein C and promotes a more dynamic course of reparative osteogenesis in animals with glucocorticoid-induced osteoporosis. Keywords: calcium phosphate ceramic granules, germanium, immune complexes, nitric oxide, osteoporosis, osteosubstitution, phosphatases, protein C, reparative osteogenesis­ Download full text as a pdf-file