gms | German Medical Science

Objectives: The treatment of critical size bone defects needs biologic alternatives to auto- and allografts, due to their scant resources or risks of immunological reaction. For a long time salidroside (SAL), an extract of Rhodiola rosea, has been used as a folk medicine in Traditional Chinese Medicine. SAL is a cytoprotective agent that enhances cellular proliferation and angiogenic differentiation of human bone marrow endothelial progenitor cells. Furthermore, it was shown that SAL stimulates osteoblast differentiation via BMP signaling pathway in vitro and prevents bone loss in vivo. Therefore, we hypothesized that SAL induces regeneration of bone tissue.

Methods: Twenty-six 12-week-old nu/nu nude mice were randomized to two equal groups. All experiments were performed in adherence to the National Institutes of Health Guidelines for the Use of Experimental Animals and were approved by the Local Animal Care Committee. Bone defects of 3 mm length were created at the right femur of each mouse and stabilized by an external fixator. Mineralized collagen scaffolds were inserted at the defect site. Each scaffold was loaded with 10 µl solution with 25 mg/ml fibrinogen and 25 IU/ml thrombin for the control group and additional 2 mg SAL per scaffold for the treatment group.

After 6 weeks the femora of all mice were dissected and µCT-scans were done to analyze regenerated bone volume. The degree of healing of the defect was evaluated after hematoxylin and eosin staining by three independent observers on three representative sections per animal according to Huo et al.. To analyze the number of vessels in the defect area Azan staining according to Geidies has been performed. Vessels were counted in three representative histologic sections per animal using a standard 10 x 10 mm grid. Unpaired t-tests were used for statistical analysis. Differences were considered significant for p<0.05.

Results and Conclusion: Twenty-four animals survived the surgical procedure and observation time. No intergroup differences regarding bone volume were observed (SAL vs. control, 4.8±0.7 mm³ vs. 5.1±0.7 mm³, p=0.77). Histological analysis confirmed an equal degree of defect healing in the SAL group as compared to the control group (4.0±0.3 vs. 4.1±0.2, p=0.81). However, the number of vessels within the defect area was increased 2-fold in the SAL group (4.1±0.5/field vs. 2.1±0.2/field, p<0.001).

SAL did not exert a detectable effect on bone regeneration. However, angiogenesis was significantly increased by SAL. In case of a critical size bone defect a vascular network is essential for tissue regeneration providing both adequate nutrient supply and waste product removal. Thus SAL can have an additional positive impact on bone defect healing when combined with osteoinductive factors.