Calcium Spike Patterns Reveal Linkage of Electrical Stimulus and MSC Osteogenic Differentiation

Physical modulation of mesenchymal stem cell exosomes: A new perspective for regenerative medicine

Mesenchymal stem cell-derived exosomes (MSC-Exo) offer promising therapeutic potential for various refractory diseases, presenting a novel therapeutic strategy. However, their clinical application encounters several obstacles, including low natural secretion, uncontrolled biological functions and inherent heterogeneity. On the one hand, physical stimuli can mimic the microenvironment dynamics where MSC-Exo reside. These factors influence not only their secretion but also, significantly, their biological efficacy. Moreover, physical factors can also serve as techniques for engineering exosomes. Therefore, the realm of physical factors assumes a crucial role in modifying MSC-Exo, ultimately facilitating their clinical translation. This review focuses on the research progress in applying physical factors to MSC-Exo, encompassing ultrasound, electrical stimulation, light irradiation, intrinsic physical properties, ionizing radiation, magnetic field, mechanical forces and temperature. We also discuss the current status and potential of physical stimuli-affected MSC-Exo in clinical applications. Furthermore, we address the limitations of recent studies in this field. Based on this, this review provides novel insights to advance the refinement of MSC-Exo as a therapeutic approach in regenerative medicine.

Signalling pathways underlying pulsed electromagnetic fields in bone repair

Pulsed electromagnetic field (PEMF) stimulation is a prospective non-invasive and safe physical therapy strategy for accelerating bone repair. PEMFs can activate signalling pathways, modulate ion channels, and regulate the expression of bone-related genes to enhance osteoblast activity and promote the regeneration of neural and vascular tissues, thereby accelerating bone formation during bone repair. Although their mechanisms of action remain unclear, recent studies provide ample evidence of the effects of PEMF on bone repair. In this review, we present the progress of research exploring the effects of PEMF on bone repair and systematically elucidate the mechanisms involved in PEMF-induced bone repair. Additionally, the potential clinical significance of PEMF therapy in fracture healing is underscored. Thus, this review seeks to provide a sufficient theoretical basis for the application of PEMFs in bone repair.

Recent Advances in Enhancement Strategies for Osteogenic Differentiation of Mesenchymal Stem Cells in Bone Tissue Engineering

Although bone is an organ that displays potential for self-healing after damage, bone regeneration does not occur properly in some cases, and it is still a challenge to treat large bone defects. The development of bone tissue engineering provides a new approach to the treatment of bone defects. Among various cell types, mesenchymal stem cells (MSCs) represent one of the most promising seed cells in bone tissue engineering due to their functions of osteogenic differentiation, immunomodulation, and secretion of cytokines. Regulation of osteogenic differentiation of MSCs has become an area of extensive research over the past few years. This review provides an overview of recent research progress on enhancement strategies for MSC osteogenesis, including improvement in methods of cell origin selection, culture conditions, biophysical stimulation, crosstalk with macrophages and endothelial cells, and scaffolds. This is favorable for further understanding MSC osteogenesis and the development of MSC-based bone tissue engineering.

Experimental-numerical analysis of cell adhesion-mediated electromechanical stimulation on piezoelectric nanofiber scaffolds

Electrospun nanofibers exhibiting piezoelectricity are a specific class of smart materials which could provide electric stimulation to cells in a noninvasive way and contribute to tissue regeneration. During cell-material interaction, the materials display electromechanical behavior by transforming cell adhesion force into surface charge. In the process, how the cell adhesion states and the electromechanical properties of scaffolds determine the actual piezoelectric potential implemented on a cell is still unclear. Herein, we fabricated piezoelectric poly(vinylidene fluoride) (PVDF) nanofiber scaffolds with different topographies, and investigated their influences on cell morphology and cell adhesion-mediated electromechanical stimulation of mesenchymal stem cell (MSC). Our results demonstrated that MSC seeded on aligned piezoelectric nanofibers exhibited elongated morphology combined with higher intracellular calcium activity than those adhered on random nanofibers with rounded shape. The underlying mechanism was further quantitatively analyzed using a three-dimensional (3D) finite element method with respect to cell adhesion states and architecture parameters of nanofiber scaffolds. The results suggested that cell morphology and cell adhesion force influenced the piezoelectric output through modulating the location and magnification of force implemented on the scaffolds. In addition, the change of alignment, pore size and diameter of the nanofiber network could alter the mechanical property of the scaffolds, and then bias the actual piezoelectric output experienced by a cell. These findings provide new insights for probing the mechanism of cell self-stimulation on piezoelectric scaffolds, and pave the way for rational design of piezoelectric scaffolds for cell regulation and tissue regeneration.