The effects of electromagnetic fields on osteogenesis during co-culture of bone marrow mesenchymal stem cells with osteoblasts

Objective To explore the effects of electromagnetic fields (EMFs) on osteogenesis during co-culture of bone mesenchymal stem cells (BMSCs) with osteoblasts in rats.Methods BMSCs and osteoblasts were isolated from Sprague-Dawley rats and cultured.Sub-cultured osteoblasts and BMSCs were seeded in transwell cell-culture-chamber polyester inserts to establish the co-culture system.The co-cultures were then randomly divided into a normal co-culture group and a group exposed to an EMF.Single-cultured BMSCs and osteoblasts were set as a single culture group.The EMF group was exposed to an EMF for 4 hours per day.On the 14th day,cell culture plates or inserts were randomly selected for total RNA extraction and measurement of the mRNA expression levels of Runt-related transcription factor 2,transcription factor 7,alkaline phosphatase,collagen type Ⅰ,bone morphogenetic protein 2 (BMP-2) and bone gamma-carboxyglutamate protein (Osteocalcin gene,OC gene) using real-time PCR assays.Cell culture dishes or inserts were also randomly chosen for Alizarin red staining to detect mineralized nodules.Results The level of osteogenic gene expression in single-cultured BMSCs and osteoblasts was low,while it was much higher in the co-culture group.The level of gene expression in the EMF-exposed and co-cultured group was even higher.Alizarin red staining also showed that calcium mineralized modules had increased in the stimulated,co-cultured system compared with the unstimulated,co-cultured cells.Conclusion EMF exposure can promote osteogenic differentiation of BMSCs and osteoblasts when they are co-cultured.BMP2-mediated cellular interaction might play an important role in osteogenic differentiation induced by EMF exposure. Key words: Electromagnetic fields;  Osteoblasts;  Bone marrow;  Mesenchymal stem cells;  Coculturing