Investigating ego modules involved in TGFß3-induced chondrogenesis in mesenchymal stem cells based on ego network.

OBJECTIVE: This paper aimed to investigate ego modules for TGFß3-induced chondrogenesis in mesenchymal stem cells (MSCs) using ego network algorithm. METHODS: The ego network algorithm comprised three parts, extracting differential expression network (DEN) based on gene expression data and protein-protein interaction (PPI) data; exploring ego genes by reweighting DEN; and searching ego modules by ego gene expansions. Subsequently, permutation test was carried out to evaluate the statistical significance of the ego modules. Finally, pathway enrichment analysis was conducted to investigate ego pathways enriched by the ego modules. RESULTS: A total of 15 ego genes were obtained from the DEN, such as PSMA4, HNRNPM and WDR77. Starting with each ego genes, 15 candidate modules were gained. When setting the thresholds of the area under the receiver operating characteristics curve (AUC) ≥0.9 and gene size ≥4, three ego modules (Module 3, Module 8 and Module 14) were identified, and all of them had statistical significances between normal and TGFß3-induced chondrogenesis in MSCs. By mapping module genes to confirmed pathway database, their ego pathways were detected, Cdc20:Phospho-APC/C mediated degradation of Cyclin A for Module 3, Mitotic G1-G1/S phases for Module 8, and mRNA Splicing for Module 14. CONCLUSIONS: We have successfully identified three ego modules, evaluated their statistical significances and investigated their functional enriched ego pathways. The findings might provide potential biomarkers and give great insights to reveal molecular mechanism underlying this process.

[Effects of bone morphogenetic protein-2 gene therapy on the bone-implant interface: an experimental study with dogs].

OBJECTIVE: To investigate the effects of bone morphogenetic protein-2 (BMP-2) gene therapy on the bone-implant interface in the reconstruction of periprosthetic bone defect. METHODS: Transverse defects were caused in the external condylae of both femurs of 14 adult Beagle dogs. Titanium alloy implants were inserted and a bone defect 3 mm wide around the titanium alloy implant was preserved. Then the total 28 defects were divided into 4 groups: 8 bone defects remained untreated (blank control group); 8 bone defects were implanted with heterogeneous freeze-dried bone by impaction grafting technique (non-cell group); 8 bone defects were implanted with heterogeneous freeze-dried bone loaded with autogenous bone marrow stromal cells (BMSCs) from the greater trochanter of the same dog (cell group); and 10 bone defects were implanted with freeze-dried allograft loaded with autogenous BMSCs from the greater trochanter of the same dog which were transfected by Adv-BMP-2 gene (gene group). Three, 6, and 12 weeks after implantation X-ray examination was carried out to observe the place of the implant and the absorption of the implants. Six and 12 weeks after the dogs were killed and their bone defects were taken out to undergo histological, histomorphometric and biomechanical examination to observe the healing and oseeointegration of the bone-implant interface. RESULTS: Histological examination showed that 6 weeks after implantation new bone formation was found on the implant surface and there was point contact between the bone and implant in the gene group with the bone-to-impact contact (BIC) of about 10%; and continuous soft tissue was found at bone-implant interface in all other groups. Twelve weeks after, there was thick soft tissue membrane between the new bone and implant in the blank control group; most of the interface was connective fibrous tissue in the non-cell group and cell group with point contact between the bone and implant and a BIC lower than 10%; and in the gene group the interface consisted mainly of bone tissue and continuous bone-implant contact was found with the BIC of 50%, significantly higher than those of the other 2 groups (both P < 0.01). The mechanical strength of interface increased time-dependently in all groups, that of the gene group being significantly higher than those of the other 2 groups at any time-points (both P < 0.01). CONCLUSION: BMP-2 gene therapy can improve the osseointegration of bone-implant interface.