Co-Culture with Human Osteoblasts and Exposure to Extremely Low Frequency Pulsed Electromagnetic Fields Improve Osteogenic Differentiation of Human Adipose-Derived Mesenchymal Stem Cells.

Marina Unger,Anne-Kristin Fentz,Hanna Scheffler,Sabrina Ehnert,Karsten Falldorf,Martijn Van Griensven,Elizabeth Balmayor,Andreas Nussler,Steffen Schröter,Claudine Seeliger

doi:10.3390/ijms19040994

Abstract

Human adipose-derived mesenchymal stem cells (Ad-MSCs) have been proposed as suitable option for cell-based therapies to support bone regeneration. In the bone environment, Ad-MSCs will receive stimuli from resident cells that may favor their osteogenic differentiation. There is recent evidence that this process can be further improved by extremely low frequency pulsed electromagnetic fields (ELF-PEMFs). Thus, the project aimed at (i) investigating whether co-culture conditions of human osteoblasts (OBs) and Ad-MSCs have an impact on their proliferation and osteogenic differentiation; (ii) whether this effect can be further improved by repetitive exposure to two specific ELF-PEMFs (16 and 26 Hz); (iii) and the effect of these ELF-PEMFs on human osteoclasts (OCs). Osteogenic differentiation was improved by co-culturing OBs and Ad-MSCs when compared to the individual mono-cultures. An OB to Ad-MSC ratio of 3:1 had best effects on total protein content, alkaline phosphatase (AP) activity, and matrix mineralization. Osteogenic differentiation was further improved by both ELF-PEMFs investigated. Interestingly, only repetitive exposure to 26 Hz ELF-PEMF increased Trap5B activity in OCs. Considering this result, a treatment with gradually increasing frequency might be of interest, as the lower frequency (16 Hz) could enhance bone formation, while the higher frequency (26 Hz) could enhance bone remodeling.

Highlights

Extensive bone loss after trauma or diseases often results in delayed or impaired bone healing [1]
We investigated whether co-culture of OBs and adipose-derived mesenchymal stem cells (Ad-mesenchymal stem cells (MSCs)), with different ratios, improves their proliferation and osteogenic differentiation potential compared to the individual mono-cultures
All co-culture conditions showed increased total protein content and mitochondrial activity as compared to the respective mono-cultures, which refers to increased proliferation. This is in line with the work of Heino and colleagues, which showed that conditioned medium from an osteocytic cell line (MLO-Y4), but not an osteoblastic cell line (MC3T3-E1), was able to improve proliferation and osteogenic differentiation of mouse B-MSCs [28], suggesting that the observed effect is triggered by factors released from the osteocytes

Summary

Introduction

Extensive bone loss after trauma or diseases often results in delayed or impaired bone healing [1]. In addition to surgical stabilization, such critical-sized bone defects often require additional intervention to achieve union. Present surgical procedures, such as the Masquelet technique and Ilizarov technique, may reconstruct large bone defects, but require a large volume of bone to fill the defect [2]. The following process of bone regeneration requires recruitment, expansion, and differentiation of mesenchymal stem cells (MSCs) [3], known as multipotent or mesenchymal stromal cells. Bone tissue engineering with MSCs has great potential to provide the means for inducing osteogenesis and ossification, and thereby consolidation of large bone defects in a timely manner [2]. There are over 350 registered clinical trials worldwide, which in different phases, aim at evaluating the cell therapeutic potential of MSCs [4]

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