Novel strategy to improve hepatocyte differentiation stability through synchronized behavior-driven mechanical memory of iPSCs

Effects of PDMS culture on stem cell differentiation towards definitive endoderm and hepatocytes

The generation of human induced pluripotent stem cell (hiPSC) derivatives for regenerative medicine applications holds tremendous promise in treating various disorders. One critical target includes liver disease, in which the primary curative treatment is a cellular transplant aimed to restore the lost function of hepatocytes. In an effort to improve the differentiation of hiPSC-derived liver tissue, we manipulated the mechanical conditions of endoderm specification through directed perturbation of the cytoskeleton and through 2D substrate culture on viscoelastic materials. Through a combination of qRT-PCR, immunofluorescence staining, and functional assays, we found that mechanical cues can bias endoderm specification in an actomyosin and Yes-associated protein (YAP) dependent manner, unveiling new insights into mechanotransduction in germ layer specification and downstream maturation toward parenchymal cells. STATEMENT OF SIGNIFICANCE: The translational potential of using human induced pluripotent stem cell (hiPSC) derived hepatocytes to therapeutically improve impaired liver function holds great clinical promise. However, challenges remain in efficiently differentiating functional hepatocytes with mature marker expression. In an effort to improve the differentiation efficiency of hepatocytes, the role of early mechanosensing mechanisms was investigated in the specification of hiPSCs to definitive endoderm progenitor populations. Through a combination of cytoskeletal modulation, control of mechanoresponsive, yes-associated protein expression, and culture on physiologically compliant PDMS substrates, we found that soft environments not only improve progenitor specification but also impact the downstream functionality of differentiated hepatocytes. These results contribute to the collective appreciation that mechanical cues are critical in developmental processes.

Cellular mechanical memory: a potential tool for mesenchymal stem cell-based therapy

Recent studies have shown that mechanical properties such as extracellular matrix stiffness, fluid flow, weight loading, compression, and stretching can affect cellular functions. Some examples of cell responses to mechanical properties could be the migration of cancer cells from rigid to soft surfaces or the differentiation of fibroblasts into myofibroblasts. Cellular responses to mechanical changes can modify the insertion of proteins in the extracellular matrix (ECM), causing an increase in tissue stiffness with functional consequences. In general, mechanical and physical factors can affect any kind of cell phenotype in culture conditions and in vivo tissues. Cells sense mechanical stimuli by applying force and restructuring their shape and functions in response to the resistance of the stimuli. Furthermore, mechanical triggers can develop a "memory" for altering cellular plasticity and adaptation. This phenomenon is called cellular mechanical memory (CMM), a singular feature of mesenchymal stem cells (MSCs). Controlled targeting of CMM may resolve the scarcity of viable cells needed for cell based therapy (CBT) and implement studies concerning cancer research, fibrosis, and senescence. This review focusses on cells from the mesodermal lineage, such as MSCs, fibroblasts and chondrocytes, and the role of CMM as a potential target for CBT.

Stable and efficient generation of functional iPSC-derived neural progenitor cell rosettes through regulation of collective cell-cell behavior

Although the potential of stem cells to differentiate into several cell types has shown promise in regenerative medicine, low differentiation efficiency and poor reproducibility significantly limit their practical application. We developed an effective and robust differentiation strategy for the efficient and robust generation of neural progenitor cell rosettes from induced pluripotent stem cells (iPSCs) incorporating botulinum hemagglutinin (HA). Treatment with HA suppressed the spontaneous differentiation of iPSCs cultured under undirected differentiation conditions, resulting in the preservation of their pluripotency. Moreover, treatment with HA during neural progenitor differentiation combined with dual SMAD inhibition generated a highly homogeneous population of PAX6-and SOX1-expressing neural progenitor cells with 8.4-fold higher yields of neural progenitor cells than untreated control cultures. These neural progenitor cells formed radially organized rosettes surrounding the central lumen. This differentiation method enhanced the generation of functional iPSC-derived neural progenitor cell rosettes throughout the culture vessel, suggesting that the regulation of collective cell-cell behavior using HA plays a morphogenetically important role in rosette formation and maturation. These findings show the significance of HA in the suppression of spontaneous differentiation through spatial homogeneity. The study proposes a novel methodology for the efficient derivation of functional iPSC-derived neural progenitor cell rosettes.

A simple tool for the synchronous differentiation of human induced pluripotent stem cells into pancreatic progenitors

Efficient differentiation of human induced pluripotent stem cells (hiPSCs) into functional pancreatic cells holds great promise for diabetes research and treatment. However, a robust culture strategy for producing pancreatic progenitors with high homogeneity is lacking. Here, we established a simple differentiation strategy for generating synchronous iPSC-derived pancreatic progenitors via a two-step method of sequential cell synchronization using botulinum hemagglutinin (HA), an E-cadherin function-blocking agent. Of the various methods tested, the first-step synchronization method with HA exposure induces a synchronous switch from E- to N-cadherin and N- to E-cadherin expression by spatially controlling heterogeneous cell distribution, subsequently improving their competency for directed differentiation into definitive endodermal cells from iPSCs. The iPSC-derived definitive endodermal cells can efficiently generate PDX1+ and NKX6.1+ pancreatic progenitor cells in high yields. The PDX1+ and PDX1+ /NKX6.1+ cell densities showed 1.6- and 2.2-fold increases, respectively, compared with those from unsynchronized cultures. The intra-run and inter-run coefficient of variation were below 10%, indicating stable and robust differentiation across different cultures and runs. Our approach is a simple and efficient strategy to produce large quantities of differentiated cells with the highest homogeneity during multistage pancreatic progenitor differentiation, providing a potential tool for guided differentiation of iPSCs to functional insulin-producing cells.