Electrical Stimulation of Adipose-Derived Stem Cells in 3D Nanofibrillar Cellulose Increases Their Osteogenic Potential

Evaluation of genetic response of mesenchymal stem cells to nanosecond pulsed electric fields by whole transcriptome sequencing

BACKGROUND

Mesenchymal stem cells (MSCs) modulated by various exogenous signals have been applied extensively in regenerative medicine research. Notably, nanosecond pulsed electric fields (nsPEFs), characterized by short duration and high strength, significantly influence cell phenotypes and regulate MSCs differentiation via multiple pathways. Consequently, we used transcriptomics to study changes in messenger RNA (mRNA), long noncoding RNA (lncRNA), microRNA (miRNA), and circular RNA expression during nsPEFs application.

AIM

To explore gene expression profiles and potential transcriptional regulatory mechanisms in MSCs pretreated with nsPEFs.

METHODS

The impact of nsPEFs on the MSCs transcriptome was investigated through whole transcriptome sequencing. MSCs were pretreated with 5-pulse nsPEFs (100 ns at 10 kV/cm, 1 Hz), followed by total RNA isolation. Each transcript was normalized by fragments per kilobase per million. Fold change and difference significance were applied to screen the differentially expressed genes (DEGs). Gene Ontology and Kyoto Encyclopedia of Genes and Genomes analyses were performed to elucidate gene functions, complemented by quantitative polymerase chain reaction verification.

RESULTS

In total, 263 DEGs were discovered, with 92 upregulated and 171 downregulated. DEGs were predominantly enriched in epithelial cell proliferation, osteoblast differentiation, mesenchymal cell differentiation, nuclear division, and wound healing. Regarding cellular components, DEGs are primarily involved in condensed chromosome, chromosomal region, actin cytoskeleton, and kinetochore. From aspect of molecular functions, DEGs are mainly involved in glycosaminoglycan binding, integrin binding, nuclear steroid receptor activity, cytoskeletal motor activity, and steroid binding. Quantitative real-time polymerase chain reaction confirmed targeted transcript regulation.

CONCLUSION

Our systematic investigation of the wide-ranging transcriptional pattern modulated by nsPEFs revealed the differential expression of 263 mRNAs, 2 miRNAs, and 65 lncRNAs. Our study demonstrates that nsPEFs may affect stem cells through several signaling pathways, which are involved in vesicular transport, calcium ion transport, cytoskeleton, and cell differentiation.

Stimulation strategies for electrical and magnetic modulation of cells and tissues

Electrical phenomena play an important role in numerous biological processes including cellular signaling, early embryogenesis, tissue repair and remodeling, and growth of organisms. Electrical and magnetic effects have been studied on a variety of stimulation strategies and cell types regarding cellular functions and disease treatments. In this review, we discuss recent advances in using three different stimulation strategies, namely electrical stimulation via conductive and piezoelectric materials as well as magnetic stimulation via magnetic materials, to modulate cell and tissue properties. These three strategies offer distinct stimulation routes given specific material characteristics. This review will evaluate material properties and biological response for these stimulation strategies with respect to their potential applications in neural and musculoskeletal research.

Advances in materials-based therapeutic strategies against osteoporosis

Osteoporosis is caused by the disruption in homeostasis between bone formation and bone resorption. Conventional management of osteoporosis involves systematic drug administration and hormonal therapy. These treatment strategies have limited curative efficacy and multiple adverse effects. Biomaterials-based therapeutic strategies have recently emerged as promising alternatives for the treatment of osteoporosis. The present review summarizes the current status of biomaterials designed for managing osteoporosis. The advantages of biomaterials-based strategies over conventional systematic drug treatment are presented. Different anti-osteoporotic delivery systems are concisely addressed. These materials include injectable hydrogels and nanoparticles, as well as anti-osteoporotic bone tissue engineering materials. Fabrication techniques such as 3D printing, electrostatic spinning and artificial intelligence are appraised in the context of how the use of these adjunctive techniques may improve treatment efficacy. The limitations of existing biomaterials are critically analyzed, together with deliberation of the future directions in biomaterials-based therapies. The latter include discussion on the use of combination strategies to enhance therapeutic efficacy in the osteoporosis niche.

Harnessing electromagnetic fields to assist bone tissue engineering

Bone tissue engineering (BTE) emerged as one of the exceptional means for bone defects owing to it providing mechanical supports to guide bone tissue regeneration. Great advances have been made to facilitate the success of BTE in regenerating bone within defects. The use of externally applied fields has been regarded as an alternative strategy for BTE. Electromagnetic fields (EMFs), known as a simple and non-invasive therapy, can remotely provide electric and magnetic stimulation to cells and biomaterials, thus applying EMFs to assist BTE would be a promising strategy for bone regeneration. When combined with BTE, EMFs improve cell adhesion to the material surface by promoting protein adsorption. Additionally, EMFs have positive effects on mesenchymal stem cells and show capabilities of pro-angiogenesis and macrophage polarization manipulation. These advantages of EMFs indicate that it is perfectly suitable for representing the adjuvant treatment of BTE. We also summarize studies concerning combinations of EMFs and diverse biomaterial types. The strategy of combining EMFs and BTE receives encouraging outcomes and holds a promising future for effectively treating bone defects.

Organoids and Their Research Progress in Plastic and Reconstructive Surgery

Organoids are 3D structures generated from stem cells. Their functions and physiological characteristics are similar to those of normal organs. They are used in disease mechanism research, new drug development, organ transplantation and other fields. In recent years, the application of 3D materials in plastic surgery for repairing injuries, filling, tissue reconstruction and regeneration has also been investigated. The PubMed/MEDLINE database was queried to search for animal and human studies published through July of 2022 with search terms related to Organoids, Plastic Surgery, Pluripotent Stem Cells, Bioscaffold, Skin Reconstruction, Bone and Cartilage Regeneration. This review presents stem cells, scaffold materials and methods for the construction of organoids for plastic surgery, and it summarizes their research progress in plastic surgery in recent years.Level of Evidence III This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

A quick pipeline for the isolation of 3D cell culture-derived extracellular vesicles

Recent advances in cell biology research regarding extracellular vesicles have highlighted an increasing demand to obtain 3D cell culture-derived EVs, because they are considered to more accurately represent EVs obtained in vivo. However, there is still a grave need for efficient and tunable methodologies to isolate EVs from 3D cell cultures. Using nanofibrillar cellulose (NFC) scaffold as a 3D cell culture matrix, we developed a pipeline of two different approaches for EV isolation from cancer spheroids. A batch method was created for delivering high EV yield at the end of the culture period, and a harvesting method was created to enable time-dependent collection of EVs to combine EV profiling with spheroid development. Both these methods were easy to set up, quick to perform, and they provided a high EV yield. When compared to scaffold-free 3D spheroid cultures on ultra-low affinity plates, the NFC method resulted in similar EV production/cell, but the NFC method was scalable and easier to perform resulting in high EV yields. In summary, we introduce here an NFC-based, innovative pipeline for acquiring EVs from 3D cancer spheroids, which can be tailored to support the needs of variable EV research objectives.

Low-intensity pulsed ultrasound/nanomechanical force generators enhance osteogenesis of BMSCs through microfilaments and TRPM7

BACKGROUND

Low-intensity pulsed ultrasound (LIPUS) has been reported to accelerate fracture healing, but the mechanism is unclear and its efficacy needs to be further optimized. Ultrasound in combination with functionalized microbubbles has been shown to induce local shear forces and controllable mechanical stress in cells, amplifying the mechanical effects of LIPUS. Nanoscale lipid bubbles (nanobubbles) have high stability and good biosafety. However, the effect of LIPUS combined with functionalized nanobubbles on osteogenesis has rarely been studied.

RESULTS

In this study, we report cyclic arginine-glycine-aspartic acid-modified nanobubbles (cRGD-NBs), with a particle size of ~ 500 nm, able to actively target bone marrow mesenchymal stem cells (BMSCs) via integrin receptors. cRGD-NBs can act as nanomechanical force generators on the cell membrane, and further enhance the BMSCs osteogenesis and bone formation promoted by LIPUS. The polymerization of actin microfilaments and the mechanosensitive transient receptor potential melastatin 7 (TRPM7) ion channel play important roles in BMSCs osteogenesis promoted by LIPUS/cRGD-NBs. Moreover, the mutual regulation of TRPM7 and actin microfilaments promote the effect of LIPUS/cRGD-NBs. The extracellular Ca^2 + influx, controlled partly by TRPM7, could participated in the effect of LIPUS/cRGD-NBs on BMSCs.

CONCLUSIONS

The nanomechanical force generators cRGD-NBs could promote osteogenesis of BMSCs and bone formation induced by LIPUS, through regulation TRPM7, actin cytoskeleton, and intracellular calcium oscillations. This study provides new directions for optimizing the efficacy of LIPUS for fracture healing, and a theoretical basis for the further application and development of LIPUS in clinical practice.

Adipose-derived cells: building blocks of three-dimensional microphysiological systems

Microphysiological systems (MPS) created with human-derived cells and biomaterial scaffolds offer a potential in vitro alternative to in vivo animal models. The adoption of three-dimensional MPS models has economic, ethical, regulatory, and scientific implications for the fields of regenerative medicine, metabolism/obesity, oncology, and pharmaceutical drug discovery. Key opinion leaders acknowledge that MPS tools are uniquely positioned to aid in the objective to reduce, refine, and eventually replace animal experimentation while improving the accuracy of the finding's clinical translation. Adipose tissue has proven to be an accessible and available source of human-derived stromal vascular fraction (SVF) cells, a heterogeneous population available at point of care, and adipose-derived stromal/stem cells, a relatively homogeneous population requiring plastic adherence and culture expansion of the SVF cells. The adipose-derived stromal/stem cells or SVF cells, in combination with human tissue or synthetic biomaterial scaffolds, can be maintained for extended culture periods as three-dimensional MPS models under angiogenic, stromal, adipogenic, or osteogenic conditions. This review highlights recent literature relating to the versatile use of adipose-derived cells as fundamental components of three-dimensional MPS models for discovery research and development. In this context, it compares the merits and limitations of the adipose-derived stromal/stem cells relative to SVF cell models and considers the likely directions that this emerging field of scientific discovery will take in the near future.

Organic Bioelectronics for In Vitro Systems

Bioelectronics have made strides in improving clinical diagnostics and precision medicine. The potential of bioelectronics for bidirectional interfacing with biology through continuous, label-free monitoring on one side and precise control of biological activity on the other has extended their application scope to in vitro systems. The advent of microfluidics and the considerable advances in reliability and complexity of in vitro models promise to eventually significantly reduce or replace animal studies, currently the gold standard in drug discovery and toxicology testing. Bioelectronics are anticipated to play a major role in this transition offering a much needed technology to push forward the drug discovery paradigm. Organic electronic materials, notably conjugated polymers, having demonstrated technological maturity in fields such as solar cells and light emitting diodes given their outstanding characteristics and versatility in processing, are the obvious route forward for bioelectronics due to their biomimetic nature, among other merits. This review highlights the advances in conjugated polymers for interfacing with biological tissue in vitro, aiming ultimately to develop next generation in vitro systems. We showcase in vitro interfacing across multiple length scales, involving biological models of varying complexity, from cell components to complex 3D cell cultures. The state of the art, the possibilities, and the challenges of conjugated polymers toward clinical translation of in vitro systems are also discussed throughout.

Wound Healing with Electrical Stimulation Technologies: A Review

Electrical stimulation (ES) is an attractive field among clinicians in the topic of wound healing, which is common yet complicated and requires multidisciplinary approaches. The conventional dressing and skin graft showed no promise on complete wound closure. These urge the need for the exploration of electrical stimulation to supplement current wound care management. This review aims to provide an overview of electrical stimulation in wound healing. The mechanism of galvanotaxis related to wound repair will be reviewed at the cellular and molecular levels. Meanwhile, different modalities of externally applied electricity mimicking a physiologic electric field will be discussed and compared in vitro, in vivo, and clinically. With the emerging of tissue engineering and regenerative medicine, the integration of electroconductive biomaterials into modern miniaturised dressing is of interest and has become possible with the advancing understanding of smart biomaterials.

Pulsed Electrical Stimulation Enhances Consistency of Directional Migration of Adipose-Derived Stem Cells

Electrical stimulation is a well-known strategy for regulating cell behavior, both in pathological and physiological processes such as wound healing, tissue regeneration, and embryonic development. Electrotaxis is the directional migration of cells toward the cathode or anode when subjected to electrical stimulation. In this study, we investigated the conditions for enhanced directional migration of electrically stimulated adipose-derived stem cells (ADSCs) during prolonged culture, using a customized agar-salt electrotaxis chamber. Exposure of ADSCs to a 1200 μA electric current for 3 h, followed by cessation of stimulation for 6 h and resumed stimulation for a further 3 h, increased directional cell migration toward the anode without inducing cell death. Moreover, Golgi polarization maintained the direction of polarity parallel to the direction of cell movement. Herein, we demonstrated that a pulsed electric current is sufficient to trigger directional migration of ADSCs in long-term culture while maintaining cell viability.

Time-Dependent Reduction of Calcium Oscillations in Adipose-Derived Stem Cells Differentiating towards Adipogenic and Osteogenic Lineage

Adipose-derived mesenchymal stromal cells (ASCs) are multipotent stem cells which can differentiate into various cell types, including osteocytes and adipocytes. Due to their ease of harvesting, multipotency, and low tumorigenicity, they are a prime candidate for the development of novel interventional approaches in regenerative medicine. ASCs exhibit slow, spontaneous Ca²⁺ oscillations and the manipulation of Ca²⁺ signalling via electrical stimulation was proposed as a potential route for promoting their differentiation in vivo. However, the effects of differentiation-inducing treatments on spontaneous Ca²⁺ oscillations in ASCs are not yet fully characterised. In this study, we used 2-photon live Ca²⁺ imaging to assess the fraction of cells showing spontaneous oscillations and the frequency of the oscillation (measured as interpeak interval—IPI) in ASCs undergoing osteogenic or adipogenic differentiation, using undifferentiated ASCs as controls. The measurements were carried out at 7, 14, and 21 days in vitro (DIV) to assess the effect of time in culture on Ca²⁺ dynamics. We observed that both time and differentiation treatment are important factors associated with a reduced fraction of cells showing Ca²⁺ oscillations, paralleled by increased IPI times, in comparison with untreated ASCs. Both adipogenic and osteogenic differentiation resulted in a reduction in Ca²⁺ dynamics, such as the fraction of cells showing intracellular Ca²⁺ oscillations and their frequency. Adipogenic differentiation was associated with a more pronounced reduction of Ca²⁺ dynamics compared to cells differentiating towards the osteogenic fate. Changes in Ca²⁺ associated oscillations with a specific treatment had already occurred at 7 DIV. Finally, we observed a reduction in Ca²⁺ dynamics over time in untreated ASCs. These data suggest that adipogenic and osteogenic differentiation cell fates are associated with specific changes in spontaneous Ca²⁺ dynamics over time. While this observation is interesting and provides useful information to understand the functional correlates of stem cell differentiation, further studies are required to clarify the molecular and mechanistic correlates of these changes. This will allow us to better understand the causal relationship between Ca²⁺ dynamics and differentiation, potentially leading to the development of novel, more effective interventions for both bone regeneration and control of adipose growth.