Quantitative Bioimage Analysis of Passaging Effect on the Migratory Behavior of Human Mesenchymal Stem Cells During Spheroid Formation

Effects of high glucose and severe hypoxia on the biological behavior of mesenchymal stem cells at various passages

BACKGROUND

Mesenchymal stem cells (MSCs) have been extensively studied for therapeutic potential, due to their regenerative and immunomodulatory properties. Serial passage and stress factors may affect the biological characteristics of MSCs, but the details of these effects have not been recognized yet.

AIM

To investigate the effects of stress factors (high glucose and severe hypoxia) on the biological characteristics of MSCs at different passages, in order to optimize the therapeutic applications of MSCs.

METHODS

In this study, we investigated the impact of two stress conditions; severe hypoxia and high glucose on human adipose-tissue derived MSCs (hAD-MSCs) at passages 6 (P6), P8, and P10. Proliferation, senescence and apoptosis were evaluated measuring WST-1, senescence-associated beta-galactosidase, and annexin V, respectively.

RESULTS

Cells at P6 showed decreased proliferation and increased apoptosis under conditions of high glucose and hypoxia compared to control, while the extent of senescence did not change significantly under stress conditions. At P8 hAD-MSCs cultured in stress conditions had a significant decrease in proliferation and apoptosis and a significant increase in senescence compared to counterpart cells at P6. Cells cultured in high glucose at P10 had lower proliferation and higher senescence than their counterparts in the previous passage, while no change in apoptosis was observed. On the other hand, MSCs cultured under hypoxia showed decreased senescence, increased apoptosis and no significant change in proliferation when compared to the same conditions at P8.

CONCLUSION

These results indicate that stress factors had distinct effects on the biological processes of MSCs at different passages, and suggest that senescence may be a protective mechanism for MSCs to survive under stress conditions at higher passage numbers.

Bioinspired Collagen/Hyaluronic Acid/Fibrin-Based Hydrogels for Soft Tissue Engineering: Design, Synthesis, and In Vitro Characterization

A major challenge for future drug development comprises finding alternative models for drug screening. The use of animal models in research is highly controversial, with an ongoing debate on their ethical acceptability. Also, animal models are often poorly predictive of therapeutic outcomes due to the differences between animal and human physiological environments. In this study, we aimed to develop a biomimetic hydrogel that replicates the composition of skin for potential use in in vitro modeling within tissue engineering. The hydrogel was fabricated through the crosslinking of collagen type I, hyaluronic acid, four-arm PEG succinimidyl glutarate (4S-StarPEG), and fibrinogen. Various ratios of these components were systematically optimized to achieve a well-interconnected porosity and desirable rheological properties. To evaluate the hydrogel's cytocompatibility, fibroblasts were embedded within the matrix. The resulting hydrogel exhibited promising properties as a scaffold, also facilitating the growth of and proliferation of the cells. This biomimetic hydrogel holds great potential for tissue engineering applications, particularly in skin regeneration and cancer research. The study used melanoma spheroids fabricated using the 96-round bottom well plate method as a potential application. The results demonstrate that the developed hydrogels allowed the maintenance of spheroid integrity and viability, meaning it has a promising use as a three-dimensional in vitro model of melanoma for both tissue engineering and drug screening applications.

Nonspectroscopic Migratory Cell Monitoring Method Using Retroreflective Janus Microparticles

This study aims to suggest a simple migratory cell monitoring method in the Transwell system by utilizing retroreflective Janus microparticles (RJPs) as an optical probe. The RJP could be internalized on cells without compromising the cell viability and can be registered as bright spots within the cell body by inducing retroreflection from nonspectroscopic light sources. Conventional optical probes (e.g., fluorophores, chromogens, and nanoparticles) have been extensively studied and applied across diverse platforms (e.g., Boyden chamber, wound closing, and microfluidic chips) for understanding in vitro kinetic cell behavior. However, the complexities of running such platforms and setting up analytical instruments are limiting. In this regard, we aimed to demonstrate a modified Transwell migration assay by introducing the retroreflection principle to the cell quantification procedures that ensure a simplified optical setup, assure easy signal acquisition, and are compatible with conventional platforms. To demonstrate retroreflection as a signaling principle, a half-metal-coated silica particle that can induce interior retroreflection was synthesized. Because the RJPs can concentrate incident light and reflect it back to the light source, retroreflection was distinctively recognizable and enabled sensitive visualization. To verify the applicability of the developed migration assay, cell quantification during the incremental progress of macrophage migration, and cell quantification under gradients of chemoattractant monocyte protein-1, was accomplished by obtaining phagocytosed RJP-mediated retroreflection signals. Considering that conventional assays are designed as endpoint measurements, we anticipate the proposed retroreflection-based cell quantification technique to be a promising solution, bypassing current limitations.