Mechanotransduction in Mesenchymal Stem Cells (MSCs) Differentiation: A Review

Manufacturing mesenchymal stromal cells in a microcarrier-microbioreactor platform can enhance cell yield and quality attributes: case study for acute respiratory distress syndrome

Mesenchymal stem and stromal cells (MSCs) hold potential to treat a broad range of clinical indications, but clinical translation has been limited to date due in part to challenges with batch-to-batch reproducibility of potential critical quality attributes (pCQAs) that can predict potency/efficacy. Here, we designed and implemented a microcarrier-microbioreactor approach to cell therapy manufacturing, specific to anchorage-dependent cells such as MSCs. We sought to assess whether increased control of the biochemical and biophysical environment had the potential to create product with consistent presentation and elevated expression of pCQAs relative to established manufacturing approaches in tissue culture polystyrene (TCPS) flasks. First, we evaluated total cell yield harvested from dissolvable, gelatin microcarriers within a microbioreactor cassette (Mobius Breez) or a flask control with matched initial cell seeding density and culture duration. Next, we identified 24 genes implicated in a therapeutic role for a specific motivating indication, acute respiratory distress syndrome (ARDS); expression of these genes served as our pCQAs for initial in vitro evaluation of product potency. We evaluated mRNA expression for three distinct donors to assess inter-donor repeatability, as well as for one donor in three distinct batches to assess within-donor, inter-batch variability. Finally, we assessed gene expression at the protein level for a subset of the panel to confirm successful translation. Our results indicated that MSCs expanded with this microcarrier-microbioreactor approach exhibited reasonable donor-to-donor repeatability and reliable batch-to-batch reproducibility of pCQAs. Interestingly, the baseline conditions of this microcarrier-microbioreactor approach also significantly improved expression of several key pCQAs at the gene and protein expression levels and reduced total media consumption relative to TCPS culture. This proof-of-concept study illustrates key benefits of this approach to therapeutic cell process development for MSCs and other anchorage-dependent cells that are candidates for cell therapies.

Microporous Annealed Particle (MAP) Scaffold Pore Size Influences Mesenchymal Stem Cell Metabolism and Proliferation Without Changing CD73, CD90, and CD105 Expression Over Two Weeks

Scaffold pore architecture is shown to influence stem cell fate through various avenues. It is demonstrated that microporous annealed particle (MAP) microgel diameter can be tuned to control scaffold pore size and, in turn, modulate mesenchymal stem cell (MSC) survivability, proliferation, metabolism, and migration, thereby enhancing bioactivity and guiding future applications of MAP for regenerative medicine.

The bone marrow side of axial spondyloarthritis

Spondyloarthritis (SpA) is characterized by the infiltration of innate and adaptive immune cells into entheses and bone marrow. Molecular, cellular and imaging evidence demonstrates the presence of bone marrow inflammation, a hallmark of SpA. In the spine and the peripheral joints, bone marrow is critically involved in the pathogenesis of SpA. Evidence suggests that bone marrow inflammation is associated with enthesitis and that there are roles for mechano-inflammation and intestinal inflammation in bone marrow involvement in SpA. Specific cell types (including mesenchymal stem cells, innate lymphoid cells and γδ T cells) and mediators (Toll-like receptors and cytokines such as TNF, IL-17A, IL-22, IL-23, GM-CSF and TGFβ) are involved in these processes. Using this evidence to demonstrate a bone marrow rather than an entheseal origin for SpA could change our understanding of the disease pathogenesis and the relevant therapeutic approach.

Tight Regulation of Mechanotransducer Proteins Distinguishes the Response of Adult Multipotent Mesenchymal Cells on PBCE-Derivative Polymer Films with Different Hydrophilicity and Stiffness

Mechanotransduction is a molecular process by which cells translate physical stimuli exerted by the external environment into biochemical pathways to orchestrate the cellular shape and function. Even with the advancements in the field, the molecular events leading to the signal cascade are still unclear. The current biotechnology of tissue engineering offers the opportunity to study in vitro the effect of the physical stimuli exerted by biomaterial on stem cells and the mechanotransduction pathway involved in the process. Here, we cultured multipotent human mesenchymal/stromal cells (hMSCs) isolated from bone marrow (hBM-MSCs) and adipose tissue (hASCs) on films of poly(butylene 1,4-cyclohexane dicarboxylate) (PBCE) and a PBCE-based copolymer containing 50 mol% of butylene diglycolate co-units (BDG50), to intentionally tune the surface hydrophilicity and the stiffness (PBCE = 560 Mpa; BDG50 = 94 MPa). We demonstrated the activated distinctive mechanotransduction pathways, resulting in the acquisition of an elongated shape in hBM-MSCs on the BDG50 film and in maintaining the canonical morphology on the PBCE film. Notably, hASCs acquired a new, elongated morphology on both the PBCE and BDG50 films. We found that these events were mainly due to the differences in the expression of Cofilin1, Vimentin, Filamin A, and Talin, which established highly sensitive machinery by which, rather than hASCs, hBM-MSCs distinguished PBCE from BDG50 films.

Unravelling the Impact of Cyclic Mechanical Stretch in Keratoconus-A Transcriptomic Profiling Study

Biomechanical and molecular stresses may contribute to the pathogenesis of keratoconus (KC). We aimed to profile the transcriptomic changes in healthy primary human corneal (HCF) and KC-derived cells (HKC) combined with TGFβ1 treatment and cyclic mechanical stretch (CMS), mimicking the pathophysiological condition in KC. HCFs (n = 4) and HKCs (n = 4) were cultured in flexible-bottom collagen-coated 6-well plates treated with 0, 5, and 10 ng/mL of TGFβ1 with or without 15% CMS (1 cycle/s, 24 h) using a computer-controlled Flexcell FX-6000T Tension system. We used stranded total RNA-Seq to profile expression changes in 48 HCF/HKC samples (100 bp PE, 70-90 million reads per sample), followed by bioinformatics analysis using an established pipeline with Partek Flow software. A multi-factor ANOVA model, including KC, TGFβ1 treatment, and CMS, was used to identify differentially expressed genes (DEGs, |fold change| ≥ 1.5, FDR ≤ 0.1, CPM ≥ 10 in ≥1 sample) in HKCs (n = 24) vs. HCFs (n = 24) and those responsive to TGFβ1 and/or CMS. PANTHER classification system and the DAVID bioinformatics resources were used to identify significantly enriched pathways (FDR ≤ 0.05). Using multi-factorial ANOVA analyses, 479 DEGs were identified in HKCs vs. HCFs including TGFβ1 treatment and CMS as cofactors. Among these DEGs, 199 KC-altered genes were responsive to TGFβ1, thirteen were responsive to CMS, and six were responsive to TGFβ1 and CMS. Pathway analyses using PANTHER and DAVID indicated the enrichment of genes involved in numerous KC-relevant functions, including but not limited to degradation of extracellular matrix, inflammatory response, apoptotic processes, WNT signaling, collagen fibril organization, and cytoskeletal structure organization. TGFβ1-responsive KC DEGs were also enriched in these. CMS-responsive KC-altered genes such as OBSCN, CLU, HDAC5, AK4, ITGA10, and F2RL1 were identified. Some KC-altered genes, such as CLU and F2RL1, were identified to be responsive to both TGFβ1 and CMS. For the first time, our multi-factorial RNA-Seq study has identified many KC-relevant genes and pathways in HKCs with TGFβ1 treatment under CMS, suggesting a potential role of TGFβ1 and biomechanical stretch in KC development.

Functional enhancement strategies to potentiate the therapeutic properties of mesenchymal stromal cells for respiratory diseases

Respiratory diseases remain a major health concern worldwide because they subject patients to considerable financial and psychosocial burdens and result in a high rate of morbidity and mortality. Although significant progress has been made in understanding the underlying pathologic mechanisms of severe respiratory diseases, most therapies are supportive, aiming to mitigate symptoms and slow down their progressive course but cannot improve lung function or reverse tissue remodeling. Mesenchymal stromal cells (MSCs) are at the forefront of the regenerative medicine field due to their unique biomedical potential in promoting immunomodulation, anti-inflammatory, anti-apoptotic and antimicrobial activities, and tissue repair in various experimental models. However, despite several years of preclinical research on MSCs, therapeutic outcomes have fallen far short in early-stage clinical trials for respiratory diseases. This limited efficacy has been associated with several factors, such as reduced MSC homing, survival, and infusion in the late course of lung disease. Accordingly, genetic engineering and preconditioning methods have emerged as functional enhancement strategies to potentiate the therapeutic actions of MSCs and thus achieve better clinical outcomes. This narrative review describes various strategies that have been investigated in the experimental setting to functionally potentiate the therapeutic properties of MSCs for respiratory diseases. These include changes in culture conditions, exposure of MSCs to inflammatory environments, pharmacological agents or other substances, and genetic manipulation for enhanced and sustained expression of genes of interest. Future directions and challenges in efficiently translating MSC research into clinical practice are discussed.

Mechanotransduction of mesenchymal stem cells and hemodynamic implications

Mesenchymal stem cells (MSCs) possess the capacity for self-renewal and multipotency. The traditional approach to manipulating MSC's fate choice predominantly relies on biochemical stimulation. Accumulating evidence also suggests the role of physical input in MSCs differentiation. Therefore, investigating mechanotransduction at the molecular level and related to tissue-specific cell functions sheds light on the responses secondary to mechanical forces. In this review, a new frontier aiming to optimize the cultural parameters was illustrated, i.e. spatial boundary condition, which recapitulates in vivo physiology and facilitates the investigations of cellular behavior. The concept of mechanical memory was additionally addressed to appreciate how MSCs store imprints from previous culture niches. Besides, different types of forces as physical stimuli were of interest based on the association with the respective signaling pathways and the differentiation outcome. The downstream mechanoreceptors and their corresponding effects were further pinpointed. The cardiovascular system or immune system may share similar mechanisms of mechanosensing and mechanotransduction; for example, resident stem cells in a vascular wall and recruited MSCs in the bloodstream experience mechanical forces such as stretch and fluid shear stress. In addition, baroreceptors or mechanosensors of endothelial cells detect changes in blood flow, pass over signals induced by mechanical stimuli and eventually maintain arterial pressure at the physiological level. These mechanosensitive receptors transduce pressure variation and regulate endothelial barrier functions. The exact signal transduction is considered context dependent but still elusive. In this review, we summarized the current evidence of how mechanical stimuli impact MSCs commitment and the underlying mechanisms. Future perspectives are anticipated to focus on the application of cardiovascular bioengineering and regenerative medicine.

Therapeutic angiogenesis and tissue revascularization in ischemic vascular disease

Ischemic vascular disease is a major healthcare problem. The keys to treatment lie in vascular regeneration and restoration of perfusion. However, current treatments cannot satisfy the need for vascular regeneration to restore blood circulation. As biomedical research has evolved rapidly, a variety of potential alternative therapeutics has been explored widely, such as growth factor-based therapy, cell-based therapy, and material-based therapy including nanomedicine and biomaterials. This review will comprehensively describe the main pathogenesis of vascular injury in ischemic vascular disease, the therapeutic function of the above three treatment strategies, the corresponding potential challenges, and future research directions.