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Published on: February 20, 2019
The systemic effects of sclerostin overexpression using ΦC31 integrase in mice
Dongdong Zhang1, Bo Mi Park2, Myengmo Kang3
1Brain Korea 21 PLUS Project for Medical Science, Yonsei University, Seoul, Republic of Korea; Division of Endocrinology & Metabolism, Department of Internal Medicine, Affiliated Yantai Hospital of Binzhou Medical University, Yantai, PR China.
Abstract:
Sclerostin, encoded by the Sost gene, is mainly produced by osteocytes in bone and antagonizes the Wnt/β-catenin signaling pathway, which is a requisite for bone formation. Currently, human anti-sclerostin antibodies are being tested in phase III clinical trials. In addition, serum sclerostin levels are reported to be associated with bone mineral density and fracture risk in normal individuals; however, the correlation between serum sclerostin and bone mass remains controversial. To study the effects of the continuous exposure of exogenous sclerostin on bone, a ΦC31 integrase system, which has the characteristics of site-specificity and efficiency, was applied for the delivery of the Sost gene in this study. We injected Sost-attB plasmid with or without ΦC31 integrase plasmid into the mouse tail vein using a hydrodynamic-based method. The site-specific integration of the Sost gene into the mouse genome was confirmed by examining a pseudo-attP site on the hepatic genomic DNA. Sclerostin was expressed in the hepatocytes, secreted into the blood flow, and maintained at high concentrations in the mice with both Sost-attB plasmid and ΦC31 integrase plasmid injections, which was observed by serial measurement. Moreover, the mice with long-term high levels of serum sclerostin showed trabecular bone loss on micro-CT analysis. Peripheral B cell populations were not affected. Our results suggested that sclerostin could be expressed in the liver and sustained successfully at high levels in the blood by using the ΦC31 integrase system, leading to trabecular bone loss. These findings may help to further ascertain the effects of sclerostin introduced exogenously on the skeleton.
Insights
Researchers used a gene delivery system to increase sclerostin levels in mice, leading to significant trabecular bone loss. This study clarifies sclerostin's impact on bone density.
Area of Science:
- Bone Biology
- Molecular Genetics
- Endocrinology
Background:
- Sclerostin (encoded by Sost gene) inhibits Wnt/β-catenin signaling, crucial for bone formation.
- Anti-sclerostin antibodies are in clinical trials, but serum sclerostin's role in bone mass is debated.
- Understanding exogenous sclerostin effects is vital for bone metabolism research.
Purpose of the Study:
- To investigate the skeletal effects of continuous exogenous sclerostin exposure.
- To establish a method for sustained sclerostin expression in vivo.
- To analyze bone mass changes under high sclerostin conditions.
Main Methods:
- Utilized the ΦC31 integrase system for site-specific Sost gene delivery via hydrodynamic injection.
- Confirmed Sost gene integration in mouse hepatic genomic DNA.
- Quantified serum sclerostin levels and analyzed bone microarchitecture using micro-CT.
Main Results:
- Successful site-specific integration and sustained high serum sclerostin levels were achieved.
- Long-term high sclerostin exposure resulted in significant trabecular bone loss.
- Peripheral B cell populations remained unaffected.
Conclusions:
- The ΦC31 integrase system enables efficient liver expression and sustained high blood levels of sclerostin.
- Sustained high sclerostin leads to trabecular bone loss, confirming its catabolic role.
- Findings provide insights into exogenous sclerostin's skeletal impact.
