Poly(vinyl alcohol-co-itaconic acid) hydrogels grafted with several designed peptides for human pluripotent stem cell culture and differentiation into cardiomyocytes

Design of dual peptide-conjugated hydrogels for proliferation and differentiation of human pluripotent stem cells

Completely synthetic cell cultivation materials for human pluripotent stem cells (hPSCs) are important for the future clinical use of hPSC-derived cells. Currently, cell culture materials conjugated with extracellular matrix (ECM)-derived peptides are being prepared using only one specific integrin-targeting peptide. We designed dual peptide-conjugated hydrogels, for which each peptide was selected from different ECM sites: the laminin β4 chain and fibronectin or vitronectin, which can target α6β1 and α2β1 or αVβ5. hPSCs cultured on dual peptide-conjugated hydrogels, especially on hydrogels conjugated with peptides obtained from the laminin β4 chain and vitronectin with a low peptide concentration of 200 μg/mL, showed high proliferation ability over the long term and differentiated into cells originating from 3 germ layers in vivo as well as a specific lineage of cardiac cells. The design of grafting peptides was also important, for which a joint segment and positive amino acids were added into the designed peptide. Because of the designed peptides on the hydrogels, only 200 μg/mL peptide solution was sufficient for grafting on the hydrogels, and the hydrogels supported hPSC cultures long-term; in contrast, in previous studies, greater than 1000 μg/mL peptide solution was needed for the grafting of peptides on cell culture materials.

Introduction to stem cells

Stem cells have self-renewal capability and can proliferate and differentiate into a variety of functionally active cells that can serve in various tissues and organs. This review discusses the history, definition, and classification of stem cells. Human pluripotent stem cells (hPSCs) mainly include embryonic stem cells (hESCs) and induced pluripotent stem cells (hiPSCs). Embryonic stem cells are derived from the inner cell mass of the embryo. Induced pluripotent stem cells are derived from reprogramming somatic cells. Pluripotent stem cells have the ability to differentiate into cells derived from all three germ layers (endoderm, mesoderm, and ectoderm). Adult stem cells can be multipotent or unipotent and can produce tissue-specific terminally differentiated cells. Stem cells can be used in cell therapy to replace and regenerate damaged tissues or organs.

Xeno-free culture and proliferation of hPSCs on 2D biomaterials

Human pluripotent stem cells (human embryonic stem cells (hESCs) and induced pluripotent stem cells (hiPSCs)) have unlimited proliferative potential, whereas adult stem cells such as bone marrow-derived stem cells and adipose-derived stem cells have problems with aging. When hPSCs are intended to be cultured on feeder-free or xeno-free conditions without utilizing mouse embryonic fibroblasts or human fibroblasts, they cannot be cultured on conventional tissue culture polystyrene dishes, as adult stem cells can be cultured but should be cultivated on material surfaces grafted or coated with (a) natural or recombinant extracellular matrix (ECM) proteins, (b) ECM protein-derived peptides and specific synthetic polymer surfaces in xeno-free and/or chemically defined conditions. This review describes current developing cell culture biomaterials for the proliferation of hPSCs while maintaining the pluripotency and differentiation potential of the cells into 3 germ layers. Biomaterials for the cultivation of hPSCs without utilizing a feeder layer are essential to decrease the risk of xenogenic molecules, which contributes to the potential clinical usage of hPSCs. ECM proteins such as human recombinant vitronectin, laminin-511 and laminin-521 have been utilized instead of Matrigel for the feeder-free cultivation of hPSCs. The following biomaterials are also discussed for hPSC cultivation: (a) decellularized ECM, (b) peptide-grafted biomaterials derived from ECM proteins, (c) recombinant E-cadherin-coated surface, (d) polysaccharide-immobilized surface, (e) synthetic polymer surfaces with and without bioactive sites, (f) thermoresponsive polymer surfaces with and without bioactive sites, and (g) synthetic microfibrous scaffolds.

Designed peptide-grafted hydrogels for human pluripotent stem cell culture and differentiation

Human pluripotent stem cells (hPSCs) have the ability to differentiate into cells derived from three germ layers and are an attractive cell source for cell therapy in regenerative medicine. However, hPSCs cannot be cultured on conventional tissue culture flasks but can be cultured on biomaterials with specific hPSC integrin interaction sites. We designed hydrogels conjugated with several designed peptides that had laminin-β4 active sites, optimal elasticities and different zeta potentials. A higher expansion fold of hPSCs cultured on the hydrogels was found with the increasing zeta potential of the hydrogels conjugated with designed peptides, where positive amino acid (lysine) insertion into the peptides promoted higher zeta potentials of the hydrogels and higher expansion folds of hPSCs when cultured on the hydrogels using xeno-free protocols. The hPSCs cultured on hydrogels conjugated with the optimal peptides showed a higher expansion fold than those on recombinant vitronectin-coated plates, which are the gold standard of hPSC cultivation dishes. The hPSCs could differentiate into specific cell lineages, such as mesenchymal stem cells (MSCs) and MSC-derived osteoblasts, even after being cultivated on hydrogels conjugated with optimal peptides for long periods of time, such as 10 passages.

Cell-binding peptides on the material surface guide stem cell fate of adhesion, proliferation and differentiation

Human cells, especially stem cells, need to communicate and interact with extracellular matrix (ECM) proteins, which not only serve as structural components but also guide and support cell fate and properties such as cell adhesion, proliferation, survival and differentiation. The binding of the cells with ECM proteins or ECM-derived peptides via cell adhesion receptors such as integrins activates several signaling pathways that determine the cell fate, morphological change, proliferation and differentiation. The development of synthetic ECM protein-derived peptides that mimic the biological and biochemical functions of natural ECM proteins will benefit academic and clinical application. Peptides derived from or inspired by specific ECM proteins can act as agonists of each ECM protein receptor. Given that most ECM proteins function in cell adhesion via integrin receptors, many peptides have been developed that bind to specific integrin receptors. In this review, we discuss the peptide sequence, immobilization design, reaction method, and functions of several ECM protein-derived peptides. Various peptide sequences derived from mainly ECM proteins, which are used for coating or grafting on dishes, scaffolds, hydrogels, implants or nanofibers, have been developed to improve the adhesion, proliferation or differentiation of stem cells and to culture differentiated cells. This review article will help to inform the optimal choice of ECM protein-derived peptides for the development of scaffolds, implants, hydrogels, nanofibers and 2D cell culture dishes to regulate the proliferation and direct the differentiation of stem cells into specific lineages.

Human embryonic stem cells cultured on hydrogels grafted with extracellular matrix protein-derived peptides with polyethylene glycol joint nanosegments

Human pluripotent stem cells (hPSCs) can be proliferated on completely synthetic materials under xeno-free cultivation conditions using biomaterials grafted with extracellular matrix protein (ECM)-derived peptides. However, cell culture biomaterials grafted with ECM-derived peptides must be prepared using a high concentration of peptide reaction solution (e.g. 1000 μg/ml), whereas the ECM concentration of the ECM-coated surface for hPSC culture is typically 5 μg/ml. We designed a polyethylene glycol (PEG) joint nanosegment (linker) to be used between base cell culture biomaterials and bioactive ECM-derived peptides to enhance the probability of contact between ECM-derived peptides and cell binding receptors of hPSCs. Vitronectin-derived peptides with glycine joint nanosegments (GCGG) were conjugated onto poly (vinyl alcohol-co-itaconic acid) hydrogels via PEG joint nanosegments, and human embryonic stem cells (hESCs) were cultivated on these hydrogels. hESCs could successfully be cultivated on hydrogels while maintaining their pluripotency and differentiation potential to differentiate into cells that are induced from three germ layers in vitro and in vivo, where only a 50 μg/ml ECM-derived peptide concentration was used when the PEG joint nanosegments were introduced into peptides that were grafted onto hydrogel surfaces. The joint nanosegments between bioactive peptides and base cell culture biomaterials were found to contribute to efficient hESC attachment and proliferation.

Neuronal Cell Differentiation of Human Dental Pulp Stem Cells on Synthetic Polymeric Surfaces Coated With ECM Proteins

Stem cells serve as an ideal source of tissue regeneration therapy because of their high stemness properties and regenerative activities. Mesenchymal stem cells (MSCs) are considered an excellent source of stem cell therapy because MSCs can be easily obtained without ethical concern and can differentiate into most types of cells in the human body. We prepared cell culture materials combined with synthetic polymeric materials of poly-N-isopropylacrylamide-co-butyl acrylate (PN) and extracellular matrix proteins to investigate the effect of cell culture biomaterials on the differentiation of dental pulp stem cells (DPSCs) into neuronal cells. The DPSCs cultured on poly-L-ornithine (PLO)-coated (TPS-PLO) plates and PLO and PN-coated (TPS-PLO-PN) plates showed excellent neuronal marker (βIII-tubulin and nestin) expression and the highest expansion rate among the culture plates investigated in this study. This result suggests that the TPS-PLO and TPS-PN-PLO plates maintained stable DPSCs proliferation and had good capabilities of differentiating into neuronal cells. TPS-PLO and TPS-PN-PLO plates may have high potentials as cell culture biomaterials for the differentiation of MSCs into several neural cells, such as cells in the central nervous system, retinal cells, retinal organoids and oligodendrocytes, which will expand the sources of cells for stem cell therapies in the future.

Effect of extracellular matrix proteins on the differentiation of human pluripotent stem cells into mesenchymal stem cells

The transplantation of human mesenchymal stem cells (hMSCs), such as bone marrow stem cells (BMSCs) and adipose-derived stem cells (ADSCs), has shown beneficial effects in protecting transplanted tissues and cells...