Adipose-Derived Stem Cells Respond to Increased Osmolarities

Powdered Cross-Linked Gelatin Methacryloyl as an Injectable Hydrogel for Adipose Tissue Engineering

The tissue engineering field is currently advancing towards minimally invasive procedures to reconstruct soft tissue defects. In this regard, injectable hydrogels are viewed as excellent scaffold candidates to support and promote the growth of encapsulated cells. Cross-linked gelatin methacryloyl (GelMA) gels have received substantial attention due to their extracellular matrix-mimicking properties. In particular, GelMA microgels were recently identified as interesting scaffold materials since the pores in between the microgel particles allow good cell movement and nutrient diffusion. The current work reports on a novel microgel preparation procedure in which a bulk GelMA hydrogel is ground into powder particles. These particles can be easily transformed into a microgel by swelling them in a suitable solvent. The rheological properties of the microgel are independent of the particle size and remain stable at body temperature, with only a minor reversible reduction in elastic modulus correlated to the unfolding of physical cross-links at elevated temperatures. Salts reduce the elastic modulus of the microgel network due to a deswelling of the particles, in addition to triple helix denaturation. The microgels are suited for clinical use, as proven by their excellent cytocompatibility. The latter is confirmed by the superior proliferation of encapsulated adipose tissue-derived stem cells in the microgel compared to the bulk hydrogel. Moreover, microgels made from the smallest particles are easily injected through a 20G needle, allowing a minimally invasive delivery. Hence, the current work reveals that powdered cross-linked GelMA is an excellent candidate to serve as an injectable hydrogel for adipose tissue engineering.

A Review: Methodologies to Promote the Differentiation of Mesenchymal Stem Cells for the Regeneration of Intervertebral Disc Cells Following Intervertebral Disc Degeneration

Intervertebral disc (IVD) degeneration (IDD), a highly prevalent pathological condition worldwide, is widely associated with back pain. Treatments available compensate for the impaired function of the degenerated IVD but typically have incomplete resolutions because of their adverse complications. Therefore, fundamental regenerative treatments need exploration. Mesenchymal stem cell (MSC) therapy has been recognized as a mainstream research objective by the World Health Organization and was consequently studied by various research groups. Implanted MSCs exert anti-inflammatory, anti-apoptotic, and anti-pyroptotic effects and promote extracellular component production, as well as differentiation into IVD cells themselves. Hence, the ultimate goal of MSC therapy is to recover IVD cells and consequently regenerate the extracellular matrix of degenerated IVDs. Notably, in addition to MSC implantation, healthy nucleus pulposus (NP) cells (NPCs) have been implanted to regenerate NP, which is currently undergoing clinical trials. NPC-derived exosomes have been investigated for their ability to differentiate MSCs from NPC-like phenotypes. A stable and economical source of IVD cells may include allogeneic MSCs from the cell bank for differentiation into IVD cells. Therefore, multiple alternative therapeutic options should be considered if a refined protocol for the differentiation of MSCs into IVD cells is established. In this study, we comprehensively reviewed the molecules, scaffolds, and environmental factors that facilitate the differentiation of MSCs into IVD cells for regenerative therapies for IDD.

Control of hydrostatic pressure and osmotic stress in 3D cell culture for mechanobiological studies

Hydrostatic pressure (HP) and osmotic stress (OS) play an important role in various biological processes, such as cell proliferation and differentiation. In contrast to canonical mechanical signals transmitted through the anchoring points of the cells with the extracellular matrix, the physical and molecular mechanisms that transduce HP and OS into cellular functions remain elusive. Three-dimensional cell cultures show great promise to replicate physiologically relevant signals in well-defined host bioreactors with the goal of shedding light on hidden aspects of the mechanobiology of HP and OS. This review starts by introducing prevalent mechanisms for the generation of HP and OS signals in biological tissues that are subject to pathophysiological mechanical loading. We then revisit various mechanisms in the mechanotransduction of HP and OS, and describe the current state of the art in bioreactors and biomaterials for the control of the corresponding physical signals.

The Influence of Intervertebral Disc Microenvironment on the Biological Behavior of Engrafted Mesenchymal Stem Cells

Intervertebral disc degeneration is the main cause of low back pain. Traditional treatment methods cannot repair degenerated intervertebral disc tissue. The emergence of stem cell therapy makes it possible to regenerate and repair degenerated intervertebral disc tissue. At present, mesenchymal stem cells are the most studied, and different types of mesenchymal stem cells have their own characteristics. However, due to the harsh and complex internal microenvironment of the intervertebral disc, it will affect the biological behaviors of the implanted mesenchymal stem cells, such as viability, proliferation, migration, and chondrogenic differentiation, thereby affecting the therapeutic effect. This review is aimed at summarizing the influence of each intervertebral disc microenvironmental factor on the biological behavior of mesenchymal stem cells, so as to provide new ideas for using tissue engineering technology to assist stem cells to overcome the influence of the microenvironment in the future.

Stem Cell Senescence: the Obstacle of the Treatment of Degenerative Disk Disease

Intervertebral disc (IVD) has a pivotal role in the maintenance of flexible motion. IVD degeneration is one of the primary causes of low back pain and disability, which seriously influences patients' health, and increases the family and social economic burden. Recently, stem cell therapy has been proven to be more effective on IVD degeneration disease. However, stem cell senescence is the limiting factor in the IVD degeneration treatment. Senescent stem cells have a negative effect on the self-repair on IVD degeneration. In this review, we delineate that the factors such as telomerase shortening, DNA damage, oxidative stress, microenvironment and exosomes will induce stem cell aging. Recent studies tried to delay the aging of stem cells by regulating the expression of aging-related genes and proteins, changing the activity of telomerase, improving the survival microenvironment of stem cells and drug treatment. Understanding the mechanism of stem cell aging and exploring new approaches to delay or reverse stem cell aging asks for research on the repair of the degenerated disc.

Mesenchymal stem cell cultivation in electrospun scaffolds: mechanistic modeling for tissue engineering

Tissue engineering is a multidisciplinary field of research in which the cells, biomaterials, and processes can be optimized to develop a tissue substitute. Three-dimensional (3D) architectural features from electrospun scaffolds, such as porosity, tortuosity, fiber diameter, pore size, and interconnectivity have a great impact on cell behavior. Regarding tissue development in vitro, culture conditions such as pH, osmolality, temperature, nutrient, and metabolite concentrations dictate cell viability inside the constructs. The effect of different electrospun scaffold properties, bioreactor designs, mesenchymal stem cell culture parameters, and seeding techniques on cell behavior can be studied individually or combined with phenomenological modeling techniques. This work reviews the main culture and scaffold factors that affect tissue development in vitro regarding the culture of cells inside 3D matrices. The mathematical modeling of the relationship between these factors and cell behavior inside 3D constructs has also been critically reviewed, focusing on mesenchymal stem cell culture in electrospun scaffolds.

The Effects of a Pulsed Electromagnetic Field on the Proliferation and Osteogenic Differentiation of Human Adipose-Derived Stem Cells

Background

A low frequency pulsed electromagnetic field (PEMF) has been confirmed to play an important role in promoting the osteogenic differentiation of human bone marrow stem cells (BMSCs). Adipose-derived stem cells (ASCs) possess some attractive characteristics for clinical application compared to BMSCs, such as abundant stem cells from lipoaspirates, faster growth, less discomfort and morbidity during surgery. ASCs can become adipocytes, osteoblasts, chondrocytes, myocytes, neurocytes, and other cell types. Thus, ASCs might be a good alternative in clinical work involving treatment with PEMF.

Material/Methods

Human ASCs (hASCs)were divided into a control group (without PEMF exposure) and an experimental group (PEMF for two hours per day). We examined the effect of PEMF on promoting cell proliferation and osteogenic differentiation from several aspects: CCK-8 proliferation assay, RNA extraction, qRT-PCR detection, western blotting, and immunofluorescence staining experiments.

Results

PEMF could promote cell proliferation of human ASCs (hASCs) at an early stage as determined by CCK-8 assay. A specific intensity (1 mT) and frequency (50 Hz) of PEMF promoted osteogenic differentiation in hASCs in alkaline phosphatase (ALP) staining experiments. In addition, bone-related gene expression increased after two weeks of PEMF exposure, the protein expression of OPN, OCN, and RUNX-2 also increased after a longer period (three weeks) of PEMF treatment as determined by western blotting and immunofluorescence staining.

Conclusions

We found for the first time that PMEF has a role in stimulating cell proliferation of hASCs at an early period, subsequently promoting bone-related gene expression and inducing the expression of related proteins to stimulate osteogenic differentiation.