Abstract
Human bone marrow-derived mesenchymal stem cells (hBM-MSCs) are considered a great promise in the repair and regeneration of bone. Considerable efforts have been oriented towards uncovering the best strategy to promote stem cells osteogenic differentiation. In previous studies, hBM-MSCs exposed to physical stimuli such as pulsed electromagnetic fields (PEMFs) or directly seeded on nanostructured titanium surfaces (TiO2) were shown to improve their differentiation to osteoblasts in osteogenic condition. In the present study, the effect of a daily PEMF-exposure on osteogenic differentiation of hBM-MSCs seeded onto nanostructured TiO2 (with clusters under 100 nm of dimension) was investigated. TiO2-seeded cells were exposed to PEMF (magnetic field intensity: 2 mT; intensity of induced electric field: 5 mV; frequency: 75 Hz) and examined in terms of cell physiology modifications and osteogenic differentiation. Results showed that PEMF exposure affected TiO2-seeded cells osteogenesis by interfering with selective calcium-related osteogenic pathways, and greatly enhanced hBM-MSCs osteogenic features such as the expression of early/late osteogenic genes and protein production (e.g., ALP, COL-I, osteocalcin and osteopontin) and ALP activity. Finally, PEMF-treated cells resulted to secrete into conditioned media higher amounts of BMP-2, DCN and COL-I than untreated cell cultures. These findings confirm once more the osteoinductive potential of PEMF, suggesting that its combination with TiO2 nanostructured surface might be a great option in bone tissue engineering applications.
Highlights
The research on human mesenchymal stem cells from bone marrow has been an active field of investigation since 1970
We found that at least two Ca-pathways involved in the process of osteogenesis - namely the expression of L-type voltage gated Ca channels (VGCC) and the modulation of the concentration of cytosolic free Ca2+ - were positively conditioned from repetitive exposure to low-frequency pulsed electromagnetic fields (PEMFs) and can be proposed as reliable hallmarks of the osteogenic developmental stage
The relative current-voltage relationships depicted in Fig 1B show that nifedipine, a specific blocker of L-type Ca channels, reduces the peak value of the maximal current by about 40-50%; this effect is always detectable during osteogenesis and it is independent from PEMF exposure or growth substrate
Summary
The research on human mesenchymal stem cells from bone marrow (hBM-MSCs) has been an active field of investigation since 1970. Many studies assessed hBM-MSCs stability in culturing conditions and provided evidence of their immunomodulatory and tissue reparatory properties, selecting them as suitable candidates for many therapeutic applications, including improved healing of large bone defects, cell therapy and tissue regeneration. This great interest has emerged because of the multipotent ability of hBM-MSCs to naturally differentiate in several cell lineages, such as chondrocytes, adipocytes and osteoblasts. It is generally accepted that the surface topography (roughness, shape, and texture) of a biomaterial has an important effect on cellular attachment, adherence, proliferation and migration, as well as on the differentiation and survival of different cell types [3,4,5]
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