Can pretreating stem cells with electrical stimulation prior to their use in bone tissue engineering improve outcomes?
Cell Biology
Final Report Abstract
The aim of this project was to determine whether pretreatment of bone marrow-derived mesenchymal stem cells (MSCs) (in conjunction with or without bone graft substitute) with direct current electrical stimulation (DC EStim) could improve bone healing outcomes, and if so, to identify the likely underlying mechanisms by which DC EStim influences cell behaviour. Estim alone or in combination with bone tissue engineering (BTE) approaches was shown to promote bone healing. In previous in vitro studies, MSC were exposed to EStim and a sustained long-lasting increase in osteogenic activity was observed. Based on these findings, we hypothesized that pretreating MSC in 2D- or 3D-culture with EStim before their use to treat large bone defects can improve bone healing. Femur critical size defects were created in 120 Sprague-Dawley rats and treated with BTE constructs, whose cells were in vitro pre-exposed or not (control group) to EStim 1h/day for 7 days in 2D- (MSC alone) or 3D-culture (MSC + scaffold). Bone healing was assessed at 1-, 4-, and 8-weeks post-surgery. Percentage of new bone increased over time in all groups but these and other healing features like mineral density, bending stiffness, amount of new bone and cartilage, and gene expression of osteogenic markers were not significantly different between EStim and control groups. We discuss that the bone healing early environment could counteract the EStim long-lasting proosteogenic effect on MSC. As the proposed in vitro experiments led to inconclusive results alternative experiments which are related to the research question were developed and carried out in order to justify the funding. In previous projects, it was observed that under EStim in vivo in the rat femoral defect model, the ratio of pro-inflammatory M1 macrophages to anti-inflammatory and more pro-regenerative M2 macrophages shifted towards M2 macrophages. These observations led us to hypothesise that EStim regulates macrophage polarisation towards the M2 phenotype. THP-1 cells were differentiated into macrophages using PMA. Once primed, the M0 macrophages were polarized into M1 or M2 phenotype in the presence (or absence, control group) of 100 mV/mm of DC EStim, 1h/day for three days. EStim produced in M0 cells an increase of metabolic activity and induced gene expression of M2 polarization markers IL10, CD163 and PPARG. In M1 cells, EStim upregulated the M2 markers IL10 and TGM2, and downregulated the M1 marker CD86. These transcriptional changes were accompanied by lower surface expression of CD86 protein and a reduced secretion of pro-inflammatory cytokines IL-1β and IL-6. Our results suggest that EStim has differential effects on M0 and M1 macrophages; it upregulates M2 genes in M0 cells while it inhibits in M1 cells some of their features at the protein level (surface markers and cytokines) and induces transcription of M2 markers. Once differentiated, the M2 cells seem to be less responsive to the EStim treatment employed here.
Publications
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Can pretreating stem cells with electrical stimulation prior to their use in bone tissue engineering improve outcomes? Deutscher Kongress für Orthopädie und Unfallchirurgie (DKOU 2023). Berlin, 24.-27.10.2023. Düsseldorf: German Medical Science GMS Publishing House
Leppik L., Klein K.L., Wolf J., Schaible A., Bianconi S., Costa Oliveira K.M., Barker J.H., Marzi I. & Henrich D.
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Electrical stimulation can modulate the regenerative environment in bone by regulating macrophage metabolic activity and polarization. Deutscher Kongress für Orthopädie und Unfallchirurgie (DKOU 2023). Berlin, 24.-27.10.2023. Düsseldorf: German Medical Science GMS Publishing House
Bianconi S., Leppik L., Marzi I. & Henrich D.
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Pretreatment of Mesenchymal Stem Cells with Electrical Stimulation as a Strategy to Improve Bone Tissue Engineering Outcomes. Cells, 12(17), 2151.
Bianconi, Santiago; Oliveira, Karla M. C.; Klein, Kari-Leticia; Wolf, Jakob; Schaible, Alexander; Schröder, Katrin; Barker, John; Marzi, Ingo; Leppik, Liudmila & Henrich, Dirk
