Osteogenic Effect of Local Administration of Fluvastatin using a Fluvastatin-gelatin Complex in Senile Osteoporosis Model Rat

Abstract

Statins, inhibitors of 3-hydroxy-2-methyl-glutaryl coenzyme A reductase, were recently reported to promote the differentiation of osteoblasts produced by the stimulation of bone morphogenetic protein-2 (BMP-2). The aim of this study was to investigate the osteogenic effect of a local administration of fluvastatin in senile osteoporosis model rats using a fluvastatin-gelatin complex. The gelatin-hydrogel was put into cylindrical titanium tubes 1.5 mm in diameter and 2.2 mm high. It was then crosslinked by ultraviolet irradiation, after which it was lyophilized. Subsequently, the carriers were placed in the fluvastatin solution (300 μM) for one day to bind the alkaline gelatin and acidic statin electrostatically (fluvastatin-gelatin complex; statin group). A control group consisted of the carriers immersed in sterilized water. Specimens of both the statin group and the control group were implanted into the femur of 15-week-old male senile osteoporosis model rats (SHRSP). Radiographic analysis, histologic examination, and immunohistochemical staining (BMP-2 and Runx2) were then performed. At 14 and 21 days, the bone volumes of the newly formed bone in the statin group was significantly higher compared to those of the control group (P<0.05). Histological observation showed that a high level of new bone formation was present in the statin group compared to that of the control group during all time periods. At 7 days, positive immune reactions with BMP-2 and Runx2 were seen in the statin group. The local administration of the fluvastatin-gelatin complex facilitated bone formation in senile osteoporosis model rats.

Effect of Locally Applied Fluvastatin in Low-turnover Osteoporosis Model Mouse with Femur Bone Defect

“…The results showed that improved bone healing was recognized in the low-turnover osteoporosis model. Similar results were reported in our previous study showing that the osteogenic effect of fluvastatin was extended by using a fluvastatin-gelatin complex in senile osteoporosis model rats 13) .…”

“…Previous experiments by our group have shown that local administration of fluvastatin, one of the statins, promotes osteogenesis in normal rat bone defect models using a fluvastatin-gelatin complex 11,12) . In our previous study, influence of the local administration of fluvastatin on bone healing was evaluated in a senile osteoporosis model rat 13) .…”

Release properties of atelocollagen-gelatin complexes as carriers for local administration of fluvastatin

“…In our earlier studies, we used a Gel sponge carrying Flu via electrostatic interactions [18][19][20] . The dissolution rate of this Gel sponge is controllable for up to 3 days by thermal crosslinking 20) .…”

“…Crosslinking is accomplished using chemicals such as formaldehyde 24) and glutaraldehyde 25) or physical methods such as UV irradiation 26) and heating [18][19][20] . However, it has been reported that with chemical crosslinking, cytotoxicity of residual reactants from the chemical treatment causes issues 24,25,27) .…”

“…In our earlier studies, we have investigated fluvastatin sodium, an amphiphilic statin that has both membrane permeability and water solubility 17) , which have the properties that are advantageous for local administration. We conjugated fluvastatin sodium to a nontoxic, thermally crosslinked gelatin sponge and showed that the resulting sponge-form conjugates promoted bone formation in vivo [18][19][20] . However, gelatin is water-soluble, and the thermal crosslinking treatment could prolong dissolution time by only approximately 3 days 20) .…”