Selective Laminin-Directed Differentiation of Human Induced Pluripotent Stem Cells into Distinct Ocular Lineages

Efficient and cost-effective differentiation of induced neural crest cells from induced pluripotent stem cells using laminin 211

Introduction

Neural crest cells (NCCs) are cell populations that originate during the formation of neural crest in developmental stages. They are characterized by their multipotency, self-renewal and migration potential. Given their ability to differentiate into various types of cells such as neurons and Schwann cells, NCCs hold promise for cell therapy applications. The conventional method for obtaining NCCs involves inducing them from stem cells like induced pluripotent stem cells (iPSCs), followed by a long-term passage or purification using fluorescence-activated cell sorting (FACS). Although FACS allows high purity induced neural crest cells (iNCCs) to be obtained quickly, it is complex and costly. Therefore, there is a need for a simpler, cost-effective and less time-consuming method for cell therapy application.

Methods

To select differentiated iNCCs from heterogeneous cell populations quickly without using FACS, we adopted the use of scaffold material full-length laminin 211 (LN211), a recombinant, xeno-free protein suitable for cell therapy. After fist passage on LN211, iNCCs characterization was performed using polymerase chain reaction and flow cytometry. Additionally, proliferation and multipotency to various cells were evaluated.

Result

The iNCCs obtained using our new method expressed cranial NCC- related genes and exhibited stable proliferation ability for at least 57 days, while maintaining high expression level of the NCCs marker CD271. They demonstrated differentiation ability into several cell types: neurons, astrocytes, melanocytes, smooth muscle cells, osteoblasts, adipocytes and chondrocytes. Furthermore, they could be induced to differentiate into induced mesenchymal stem cells (iMSCs) which retain the essential functions of somatic MSCs.

Conclusion

In this study, we have developed novel method for obtaining high purity iNCCs differentiated from iPSCs in a short time using LN211 under xeno-free condition. Compared with traditional methods, like FACS or long-term passage, this approach enables the acquisition of a large amount of cells at a lower cost and labor, and it is expected to contribute to stable supply of large scale iNCCs for future cell therapy applications.

Spatial cell fate manipulation of human pluripotent stem cells by controlling the microenvironment using photocurable hydrogel

Human pluripotent stem cells (hPSCs) dynamically respond to their chemical and physical microenvironment, dictating their behavior. However, conventional in vitro studies predominantly employ plastic culture wares, which offer a simplified representation of the in vivo microenvironment. Emerging evidence underscores the pivotal role of mechanical and topological cues in hPSC differentiation and maintenance. In this study, we cultured hPSCs on hydrogel substrates with spatially controlled stiffness. The use of culture substrates that enable precise manipulation of spatial mechanical properties holds promise for better mimicking in vivo conditions and advancing tissue engineering techniques. We designed a photocurable polyethylene glycol-polyvinyl alcohol (PVA-PEG) hydrogel, allowing the spatial control of surface stiffness and geometry at a micrometer scale. This versatile hydrogel can be functionalized with various extracellular matrix proteins. Laminin 511-functionalized PVA-PEG gel effectively supports the growth and differentiation of hPSCs. Moreover, by spatially modulating the stiffness of the patterned gel, we achieved spatially selective cell differentiation, resulting in the generation of intricate patterned structures.

Corneal Epithelial Development and the Role of Induced Pluripotent Stem Cells for Regeneration

Severe corneal disorders due to infective aetiologies, trauma, chemical injuries, and chronic cicatricial inflammations, are among vision-threatening pathologies leading to permanent corneal scarring. The whole cornea or lamellar corneal transplantation is often used as a last resort to restore vision. However, limited autologous tissue sources and potential adverse post-allotransplantation sequalae urge the need for more robust and strategic alternatives. Contemporary management using cultivated corneal epithelial transplantation has paved the way for utilizing stem cells as a regenerative potential. Humaninduced pluripotent stem cells (hiPSCs) can generate ectodermal progenitors and potentially be used for ocular surface regeneration. This review summarizes the process of corneal morphogenesis and the signaling pathways underlying the development of corneal epithelium, which is key to translating the maturation and differentiation process of hiPSCs in vitro. The current state of knowledge and methodology for driving efficient corneal epithelial cell differentiation from pluripotent stem cells are highlighted.

Corneal epithelium models for safety assessment in drug development: Present and future directions

The human corneal epithelial barrier plays a crucial role in drug testing studies, including drug absorption, distribution, metabolism, and excretion (ADME), as well as toxicity testing during the preclinical stages of drug development. However, despite the valuable insights gained from animal and current in vitro models, there remains a significant discrepancy between preclinical drug predictions and actual clinical outcomes. Additionally, there is a growing emphasis on adhering to the 3R principles (refine, reduce, replace) to minimize the use of animals in testing. To tackle these challenges, there is a rising demand for alternative in vitro models that closely mimic the human corneal epithelium. Recently, remarkable advancements have been made in two key areas: microphysiological systems (MPS) or organs-on-chips (OoCs), and stem cell-derived organoids. These cutting-edge platforms integrate four major disciplines: stem cells, microfluidics, bioprinting, and biosensing technologies. This integration holds great promise in developing powerful and biomimetic models of the human cornea.

Extracellular matrix modulates the spatial hepatic features in hepatocyte-like cells derived from human embryonic stem cells

BACKGROUND

Human pluripotent stem cell (hPSC)-derived hepatocyte-like cells (HLCs) can provide a valuable in vitro model for disease modelling and drug development. However, generating HLCs with characteristics comparable to hepatocytes in vivo is challenging. Extracellular matrix (ECM) plays an important role in supporting liver development and hepatocyte functions, but their impact on hepatocyte differentiation and maturation during hPSC differentiation remains unclear. Here, we investigate the effects of two ECM components-Matrigel and type I collagen on hepatic differentiation of human embryonic stem cells (hESCs).

METHODS

hESC-derived HLCs were generated through multistage differentiation in two-dimensional (2D) and three-dimensional (3D) cultures, incorporating either type I collagen or Matrigel during hepatic specification and maturation. The resulting HLCs was characterized for their gene expression and functionality using various molecular and cellular techniques.

RESULTS

Our results showed that HLCs cultured with collagen exhibited a significant increase in albumin and alpha-1 anti-trypsin expression with reduced AFP compared to HLCs cultured with Matrigel. They also secreted more urea than Matrigel cultures. However, these HLCs exhibited lower CYP3A4 activity and glycogen storage than those cultured with Matrigel. These functional differences in HLCs between collagen and Matrigel cultures closely resembled the hepatocytes of periportal and pericentral zones, respectively.

CONCLUSION

Our study demonstrates that Matrigel and collagen have differential effects on the differentiation and functionality of HLCs, which resemble, to an extent, hepatic zonation in the liver lobules. Our finding has an important impact on the generation of hPSC-HLCs for biomedical and medical applications.

Cell Behavioral Dynamics as a Cue in Optimizing Culture Stabilization in the Bioprocessing of Pluripotent Stem Cells

Pluripotent stem cells (PSCs) are important for future regenerative medicine therapies. However, in the production of PSCs and derivatives, the control of culture-induced fluctuations in the outcome of cell quality remains challenging. A detailed mechanistic understanding of how PSC behaviors are altered in response to biomechanical microenvironments within a culture is necessary for rational bioprocessing optimization. In this review, we discuss recent insights into the role of cell behavioral and mechanical homeostasis in modulating the states and functions of PSCs during culture processes. We delineate promising ways to manipulate the culture variability through regulating cell behaviors using currently developed tools. Furthermore, we anticipate their potential implementation for designing a culture strategy based on the concept of Waddington's epigenetic landscape that may provide a feasible solution for tuning the culture quality and stability in the bioprocessing space.

Generation of Lens Progenitor Cells and Lentoid Bodies from Pluripotent Stem Cells: Novel Tools for Human Lens Development and Ocular Disease Etiology

In vitro differentiation of human pluripotent stem cells (hPSCs) into specialized tissues and organs represents a powerful approach to gain insight into those cellular and molecular mechanisms regulating human development. Although normal embryonic eye development is a complex process, generation of ocular organoids and specific ocular tissues from pluripotent stem cells has provided invaluable insights into the formation of lineage-committed progenitor cell populations, signal transduction pathways, and self-organization principles. This review provides a comprehensive summary of recent advances in generation of adenohypophyseal, olfactory, and lens placodes, lens progenitor cells and three-dimensional (3D) primitive lenses, "lentoid bodies", and "micro-lenses". These cells are produced alone or "community-grown" with other ocular tissues. Lentoid bodies/micro-lenses generated from human patients carrying mutations in crystallin genes demonstrate proof-of-principle that these cells are suitable for mechanistic studies of cataractogenesis. Taken together, current and emerging advanced in vitro differentiation methods pave the road to understand molecular mechanisms of cataract formation caused by the entire spectrum of mutations in DNA-binding regulatory genes, such as PAX6, SOX2, FOXE3, MAF, PITX3, and HSF4, individual crystallins, and other genes such as BFSP1, BFSP2, EPHA2, GJA3, GJA8, LIM2, MIP, and TDRD7 represented in human cataract patients.

In Vitro Expansion of Corneal Endothelial Cells for Clinical Application: Current Update

ABSTRACT

Endothelial dysfunction is one of the leading causes of corneal blindness and one of the common indications for keratoplasty. At present, the standard of treatment involves the replacement of the dysfunctional endothelium with healthy tissue taken from a donor. Because there is a paucity of healthy donor tissues, research on the corneal endothelium has focused primarily on expanding these cells in the laboratory for transplantation in an attempt to reduce the gap between the demand and supply of donor tissues for transplantation. To expand these cells, which are nonmitotic in vivo, various mitogens, substrates, culture systems, and alternate strategies have been tested with varying success. The biggest challenge has been the limited proliferative capacity of these cells compounded with endothelial to mesenchymal transition that alters the functioning of these cells and renders them unsuitable for human transplantation. This review aims to give a comprehensive overview of the most common and successful techniques used in the culture of the cells, the current available evidence in support of epithelial to mesenchymal transition (EMT), alternate sources for deriving the corneal endothelial cells, and advances made in transplantation of these cells.

Mechanotransduction through adhesion molecules: Emerging roles in regulating the stem cell niche

Stem cells have been shown to play an important role in regenerative medicine due to their proliferative and differentiation potential. The challenge, however, lies in regulating and controlling their potential for this purpose. Stem cells are regulated by growth factors as well as an array of biochemical and mechanical signals. While the role of biochemical signals and growth factors in regulating stem cell homeostasis is well explored, the role of mechanical signals has only just started to be investigated. Stem cells interact with their niche or to other stem cells via adhesion molecules that eventually transduce mechanical cues to maintain their homeostatic function. Here, we present a comprehensive review on our current understanding of the influence of the forces perceived by cell adhesion molecules on the regulation of stem cells. Additionally, we provide insights on how this deeper understanding of mechanobiology of stem cells has translated toward therapeutics.

Genome-Wide Identification of Laminin Family Related to Follicular Pseudoplacenta Development in Black Rockfish (Sebastes schlegelii)

As major elements of the basement membrane, laminins play a significant role in angiogenesis, migration, and adhesion of various cells. Sebastes schlegelii is a marine viviparous teleost of commercial importance. Previous research has reported abundant blood vessels and connective tissue in the ovary during gestation. In this study, 14 laminin genes of the α, β, and γ subfamilies from genomic data were identified based on zebrafish and human laminins, distributed on 9 chromosomes in S. schlegelii. Analysis of structural domains showed that coiled-coil regions and EGF domains existed in all laminin genes. Moreover, via qPCR, we found that the expression of laminin genes, including lama4, lama5, lamb4, lamc1, and lamc3, gradually increased from the phase III ovary stage and peaked in the early stage of gestation, especially lama4 and lama5 which showed dramatically increased expression at the blastula stage. Accordingly, in situ hybridization of lama4 was conducted. The results revealed that signals became stronger following the phase IV ovary stage, and the strongest signals were located on the follicular pseudoplacenta at the blastula stage. These results suggest that the high expression of laminin genes, especially lama4 after fertilization, may drive cell proliferation, migration, and tissue expansion in the S. schlegelii ovary and ultimately promote follicular pseudoplacenta formation.

Semi-3D cultures using Laminin 221 as a coating material for human induced pluripotent stem cells

It was previously believed that human induced pluripotent stem cells (hiPSCs) did not show adhesion to the coating material Laminin 221, which is known to have specific affinity for cardiomyocytes. In this study, we report that human mononuclear cell-derived hiPSCs, established with Sendai virus vector, form peninsular-like colonies rather than embryonic stem cell-like colonies; these peninsular-like colonies can be passaged more than 10 times after establishment. Additionally, initialization-deficient cells with residual Sendai virus vector adhered to the coating material Laminin 511 but not to Laminin 221. Therefore, the expression of undifferentiated markers tended to be higher in hiPSCs established on Laminin 221 than on Laminin 511. On Laminin 221, hiPSCs15M66 showed a semi-floating colony morphology. The expression of various markers of cell polarity was significantly lower in hiPSCs cultured on Laminin 221 than in hiPSCs cultured on Laminin 511. Furthermore, 201B7 and 15M66 hiPSCs showed 3D cardiomyocyte differentiation on Laminin 221. Thus, the coating material Laminin 221 provides semi-floating culture conditions for the establishment, culture and induced differentiation of hiPSCs.

Limbal BCAM expression identifies a proliferative progenitor population capable of holoclone formation and corneal differentiation

The corneal epithelium is renowned for high regenerative potential, which is dependent on the coordinated function of its diverse progenitor subpopulations. However, the molecular pathways governing corneal epithelial progenitor differentiation are incompletely understood. Here, we identify a highly proliferative limbal epithelial progenitor subpopulation characterized by expression of basal cell adhesion molecule (BCAM) that is capable of holocone formation and corneal epithelial sheet generation. BCAM-positive cells can be found among ABCB5-positive limbal stem cells (LSCs) as well as among ABCB5-negative limbal epithelial cell populations. Mechanistically, we show that BCAM is functionally required for cellular migration and differentiation and that its expression is regulated by the transcription factor p63. In aggregate, our study identifies limbal BCAM expression as a marker of highly proliferative corneal epithelial progenitor cells and defines the role of BCAM as a critical molecular mediator of corneal epithelial differentiation.

Using scRNA sequencing of ABCB5-positive human limbal stem cells, Sasamoto et al. identify a BCAM-positive highly proliferative limbal epithelial progenitor subpopulation that is capable of holocone formation and corneal epithelial sheet generation. BCAM regulated by the stem cell transcription factor p63 is functionally required for corneal cell migration and differentiation.

Laminin 332-functionalized coating to regulate the behavior of keratinocytes and gingival mesenchymal stem cells to enhance implant soft tissue sealing

Peri-implant epithelial sealing is the first line of defense against external pathogens or stimuli; hence, an essential process to prevent peri-implantitis. Laminin 332 (LN332) is the main component of the internal basal lamina and participates in peri-implant epithelial sealing by forming hemidesmosomes (HDs) with integrin α6β4. In this work, poly (D, L-lactide) (PDLLA)-LN332 composite coating was successfully constructed by a method similar to layer-by-layer assembly, displaying staged LN332 release for as long as 28 days. The PDLLA-LN332 composite coating can activate the intracellular PI3K-Akt pathway via binding to cellular integrin α6β4, which can promote adhesion, migration and proliferation of HaCaT cells and further enhance the expression of keratinocyte HD-related molecules, including integrin α6β4, LN332 and plectin. Furthermore, the PDLLA-LN332 composite coating can promote the adhesion, spreading and proliferation of gingival mesenchymal stem cells and accelerate their epithelial differentiation. Therefore, the PDLLA-LN332 composite coating can enhance implant soft tissue sealing, warranting further in vivo study.

Induced Pluripotent Stem Cell-Derived Corneal Cells: Current Status and Application

Deficiency and dysfunction of corneal cells leads to the blindness observed in corneal diseases such as limbal stem cell deficiency (LSCD) and bullous keratopathy. Regenerative cell therapies and engineered corneal tissue are promising treatments for these diseases [1]. However, these treatments are not yet clinically feasible due to inadequate cell sources. The discovery of induced pluripotent stem cells (iPSCs) by Shinya Yamanaka has provided a multitude of opportunities in research because iPSCs can be generated from somatic cells, thus providing an autologous and unlimited source for corneal cells. Compared to other stem cell sources such as mesenchymal and embryonic, iPSCs have advantages in differentiation potential and ethical concerns, respectively. Efforts have been made to use iPSCs to model corneal disorders and diseases, drug testing [2], and regenerative medicine [1]. Autologous treatments based on iPSCs can be exorbitantly expensive and time-consuming, but development of stem cell banks with human leukocyte antigen (HLA)- homozygous cell lines can provide cost- and time-efficient allogeneic alternatives. In this review, we discuss the early development of the cornea because protocols differentiating iPSCs toward corneal lineages rely heavily upon recapitulating this development. Differentiation of iPSCs toward corneal cell phenotypes have been analyzed with an emphasis on feeder-free, xeno-free, and well-defined protocols, which have clinical relevance. The application, challenges, and potential of iPSCs in corneal research are also discussed with a focus on hurdles that prevent clinical translation.

Laminin-511 activates the human induced pluripotent stem cell survival via α6β1 integrin-Fyn-RhoA-ROCK signaling

In human induced pluripotent stem cells (hiPSCs), laminin-511/α6β1 integrin interacts with E-cadherin, an intercellular adhesion molecule, to induce the activation of the PI3K-dependent signaling pathway. The interaction between laminin-511/α6β1 integrin and E-cadherin, an intercellular adhesion molecule, results in protection against apoptosis via the proto-oncogene tyrosine-protein kinase Fyn(Fyn)-RhoA-ROCK signaling pathway and the Ras homolog gene family member A (RhoA)/Rho kinase (ROCK) signaling pathway (the major pathway for cell death). In this paper, the impact of laminin-511 on hiPSC on α6β1 integrin-Fyn-RhoA-ROCK signaling is discussed and explored along with validation experiments. PIK3CA mRNA (mean [standard deviation {SD}]: iMatrix-511, 1.00 [0. 61]; collagen+MFGE8, 0.023 [0.02]; **P<0.01; n=6) and PIK3R1 mRNA (mean [SD]: iMatrix-511, 1.00 [0. 79]; collagen+MFGE8, 0.040 [0.06]; *P<0.05; n=6) were upregulated by iMatrix-511 resulting from an increased expression of Integrin α6 mRNA (mean [SD]: iMatrix-511, 1.00 [0. 42]; collagen+MFGE8, 0.23 [0.05]; **P<0.01; n=6). iMatrix-511 increased the expression of p120-Catenin mRNA (mean [SD]: iMatrix-511, 1.00 [0. 71]; collagen+MFGE8, 0.025 [0.03]; **P<0.01; n=6) and RAC1 mRNA (mean [SD]: iMatrix-511, 1.00 [0. 28]; collagen+MFGE8, 0.39 [0.15]; **P<0.01; n=6) by increasing the expression of E-cadherin mRNA (mean [SD]: iMatrix-511, 1.00 [0. 38]; collagen+MFGE8, 0.16 [0.11]; **P<0.01; n=6). As a result, iMatrix-511 increased the expression of P190 RhoGAP (GTPase-activating proteins) mRNA, such as ARHGAP1 mRNA (mean [SD]: iMatrix-511, 1.00 [0. 57]; collagen+MFGE8, 0.032 [0.03]; **P<0.01; n=6), ARHGAP4 mRNA (mean [SD]: iMatrix-511, 1.00 [0. 56]; collagen+MFGE8, 0.039 [0.049]; **P<0.01; n=6), and ARHGAP5 mRNA (mean [SD]: iMatrix-511, 1.00 [0. 39]; collagen+MFGE8, 0.063 [0.043]; **P<0.01; n=6). Western blotting showed that phospho-Rac1 remained in the cytoplasm and phospho-Fyn showed nuclear transition in iPSCs cultured on iMatrix-511. Proteome analysis showed that PI3K signaling was enhanced and cytoskeletal actin was activated in iPSCs cultured on iMatrix-511. In conclusion, laminin-511 strongly activated the cell survival by promoting α6β1 integrin-Fyn-RhoA-ROCK signaling in hiPSCs.

Generation of 3D lacrimal gland organoids from human pluripotent stem cells

Lacrimal glands are the main exocrine glands of the eyes. Situated within the orbit, behind the upper eyelid and towards the temporal side of each eye, they secrete lacrimal fluid as a major component of the tear film. Here we identify cells with characteristics of lacrimal gland primordia that emerge in two-dimensional eye-like organoids cultured from human pluripotent stem cells¹. When isolated by cell sorting and grown under defined conditions, the cells form a three-dimensional lacrimal-gland-like tissue organoid with ducts and acini, enabled by budding and branching. Clonal colony analyses indicate that the organoids originate from multipotent ocular surface epithelial stem cells. The organoids exhibit notable similarities to native lacrimal glands on the basis of their morphology, immunolabelling characteristics and gene expression patterns, and undergo functional maturation when transplanted adjacent to the eyes of recipient rats, developing lumina and producing tear-film proteins.

Laminin 511-E8 Fragment Offers Superior Adhesion Properties for Gastric Cancer Cells Compared with Full-Length Laminin 511

Simple Summary

Numerous studies over the past few decades have revealed that the interactions of gastric cancer cells with laminins through integrins play important roles in tumor cell proliferation, infiltration, and metastasis. However, the association between gastric cancer cells and the laminin E8 fragment, which is the smallest integrin-binding component, has not been investigated. In this study, we revealed that the laminin 511-E8 fragment had a greater impact on the adhesion, morphology, and proliferation of gastric cancer cells than full-length laminin 511. Thus, the laminin 511-E8 fragment is considered to be suitable for investigating the interaction between gastric cancer cells and extracellular matrices in tumor invasion and metastasis. Further, the involvement of Cdc42 in the laminin 511-E8 fragment-induced enhanced adhesion of gastric cancer cells was suggested.

Abstract

Background: The interaction between cancer cells and laminin (Ln) is a key event in tumor invasion and metastasis. Previously, we determined the effect of full-length Ln511 on gastric cancer cells. However, the interactions between the Ln511-E8 fragment, a truncated protein of Ln511, and gastric cancer cells have not been investigated. Methods: We investigated the adhesion properties of gastric cancer cells to full-length Ln511 and Ln511-E8 fragments. Results: The proliferation of four gastric cancer cell lines (SH-10-TC, MKN74, SC-6-JCK, and MKN45) was highest on the Ln511-E8 fragment. Further, a larger cytoplasm was observed in SH-10-TC and MKN74 cells cultured on full-length Ln511 or Ln511-E8 fragments. The percentage of adhesive cells was highest on the Ln511-E8 fragment in all four cell lines. Moreover, adhesion of the gastric cancer cells to Ln511-E8 fragment-coated plates was reduced by the Cdc42 GTPase inhibitor in a dose-dependent manner, suggesting the involvement of Cdc42 in the Ln511-E8 fragment-induced enhanced adhesion of gastric cancer cells. Conclusions: The Ln511-E8 fragment had a greater impact on the adhesion, morphology, and proliferation of gastric cancer cells than full-length laminin. Thus, the Ln511-E8 fragment is suitable for investigating the interaction between gastric cancer cells and extracellular matrices in tumor invasion and metastasis.

Induction of Corneal Epithelial Differentiation of Induced Pluripotent and Orbital Fat-Derived Stem Cells Seeded on Decellularized Human Corneas

Up to 40% of donor corneas are deemed unsuitable for transplantation, aggravating the shortage of graft tissue. In most cases, the corneal extracellular matrix is intact. Therefore, their decellularization followed by repopulation with autologous cells may constitute an efficient alternative to reduce the amount of discarded tissue and the risk of immune rejection after transplantation. Although induced pluripotent (hiPSCs) and orbital fat-derived stem cells (OFSCs) hold great promise for corneal epithelial (CE) reconstruction, no study to date has evaluated the capacity of decellularized corneas (DCs) to support the attachment and differentiation of these cells into CE-like cells. Here, we recellularize DCs with hiPSCs and OFSCs and evaluate their differentiation potential into CE-like cells using animal serum-free culture conditions. Cell viability and adhesion on DCs were assessed by calcein-AM staining and scanning electron microscopy. Cell differentiation was evaluated by RT-qPCR and immunofluorescence analyses. DCs successfully supported the adhesion and survival of hiPSCs and OFSCs. The OFSCs cultured under differentiation conditions could not express the CE markers, TP63, KRT3, PAX6, and KRT12, while the hiPSCs gave rise to cells expressing high levels of these markers. RT-qPCR data suggested that the DCs provided an inductive environment for CE differentiation of hiPSCs, supporting the expression of PAX6 and KRT12 without the need for any soluble induction factors. Our results open the avenue for future studies regarding the in vivo effects of DCs as carriers for autologous cell transplantation for ocular surface reconstruction.

Corneal epithelial differentiation of human pluripotent stem cells generates ABCB5+ and ∆Np63α+ cells with limbal cell characteristics and high wound healing capacity

Background

Differentiation of functional limbal stem cells (LSCs) from human pluripotent stem cells (hPSCs) is an important objective which can provide novel treatment solutions for patients suffering from limbal stem cell deficiency (LSCD). Yet, further characterization is needed to better evaluate their immunogenicity and regenerative potential before clinical applications.

Methods

Human PSCs were differentiated towards corneal fate and cryopreserved using a clinically applicable protocol. Resulting hPSC-LSC populations were examined at days 10–11 and 24–25 during differentiation as well as at passage 1 post-thaw. Expression of cornea-associated markers including PAX6, ABCG2, ∆Np63α, CK15, CK14, CK12 and ABCB5 as well as human leukocyte antigens (HLAs) was analyzed using immunofluorescence and flow cytometry. Wound healing properties of the post-thaw hPSC-LSCs were assessed via calcium imaging and scratch assay. Human and porcine tissue-derived cultured LSCs were used as controls for marker expression analysis and scratch assays at passage 1.

Results

The day 24–25 and post-thaw hPSC-LSCs displayed a similar marker profile with the tissue-derived LSCs, showing abundant expression of PAX6, ∆Np63α, CK15, CK14 and ABCB5 and low expression of ABCG2. In contrast, day 10–11 hPSC-LSCs had lower expression of ABCB5 and ∆Np63α, but high expression of ABCG2. A small portion of the day 10–11 cells coexpressed ABCG2 and ABCB5. The expression of class I HLAs increased during hPSC-LSCs differentiation and was uniform in post-thaw hPSC-LSCs, however the intensity was lower in comparison to tissue-derived LSCs. The calcium imaging revealed that the post-thaw hPSC-LSCs generated a robust response towards epithelial wound healing signaling mediator ATP. Further, scratch assay revealed that post-thaw hPSC-LSCs had higher wound healing capacity in comparison to tissue-derived LSCs.

Conclusions

Clinically relevant LSC-like cells can be efficiently differentiated from hPSCs. The post-thaw hPSC-LSCs possess functional potency in calcium responses towards injury associated signals and in wound closure. The developmental trajectory observed during hPSC-LSC differentiation, giving rise to ABCG2⁺ population and further to ABCB5⁺ and ∆Np63α⁺ cells with limbal characteristics, indicates hPSC-derived cells can be utilized as a valuable cell source for the treatment of patients afflicted corneal blindness due to LSCD.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s13287-021-02673-3.

Multiocular organoids from human induced pluripotent stem cells displayed retinal, corneal, and retinal pigment epithelium lineages

BACKGROUND

Recently, great efforts have been made to design protocols for obtaining ocular cells from human stem cells to model diseases or for regenerative purposes. Current protocols generally focus on isolating retinal cells, retinal pigment epithelium (RPE), or corneal cells and fail to recapitulate the complexity of the tissue during eye development. Here, the generation of more advanced in vitro multiocular organoids from human induced pluripotent stem cells (hiPSCs) is demonstrated.

METHODS

A 2-step method was established to first obtain self-organized multizone ocular progenitor cells (mzOPCs) from 2D hiPSC cultures within three weeks. Then, after the cells were manually isolated and grown in suspension, 3D multiocular organoids were generated to model important cellular features of developing eyes.

RESULTS

In the 2D culture, self-formed mzOPCs spanned the neuroectoderm, surface ectoderm, neural crest, and RPE, mimicking early stages of eye development. After lifting, mzOPCs developed into different 3D multiocular organoids composed of multiple cell lineages including RPE, retina, and cornea, and interactions between the different cell types and regions of the eye system were observed. Within these organoids, the retinal regions exhibited correct layering and contained all major retinal cell subtypes as well as retinal morphological cues, whereas the corneal regions closely resembled the transparent ocular-surface epithelium and contained of corneal, limbal, and conjunctival epithelial cells. The arrangement of RPE cells also formed organoids composed of polarized pigmented epithelial cells at the surface that were completely filled with collagen matrix.

CONCLUSIONS

This approach clearly demonstrated the advantages of the combined 2D-3D construction tissue model as it provided a more ocular native-like cellular environment than that of previous models. In this complex preparations, multiocular organoids may be used to model the crosstalk between different cell types in eye development and disease.

Generation and Staging of Human Retinal Organoids Based on Self-Formed Ectodermal Autonomous Multi-Zone System

Methods for stem cell-derived, three-dimensional retinal organoids induction have been established and shown great potential for retinal development modeling and drug screening. Herein, we reported an exogenous-factors-free and robust method to generate retinal organoids based on “self-formed ectodermal autonomous multi-zone” (SEAM) system, a two-dimensional induction scheme that can synchronously generate multiple ocular cell lineages. Characterized by distinct morphological changes, the differentiation of the obtained retinal organoids could be staged into the early and late differentiation phases. During the early differentiation stage, retinal ganglion cells, cone photoreceptor cells (PRs), amacrine cells, and horizontal cells developed; whereas rod PRs, bipolar cells, and Müller glial cells were generated in the late differentiation phase, resembling early-phase and late-phase retinogenesis in vivo. Additionally, we modified the maintenance strategy for the retinal organoids and successfully promoted their long-term survival. Using 3D immunofluorescence image reconstruction and transmission electron microscopy, the substantial mature PRs with outer segment, inner segment and ribbon synapse were demonstrated. Besides, the retinal pigment epithelium (RPE) was induced with distinct boundary and the formation of ciliary margin was observed by co-suspending retina organoids with the zone containing RPE. The obtained RPE could be expanded and displayed similar marker expression, ultrastructural feature and functional phagocytosis to native RPE. Thus, this research described a simple and robust system which enabled generation of retina organoids with substantial mature PRs, RPE and the ciliary margin without the need of exogenous factors, providing a new platform for research of retinogenesis and retinal translational application.

Structural mechanism of laminin recognition by integrin

Recognition of laminin by integrin receptors is central to the epithelial cell adhesion to basement membrane, but the structural background of this molecular interaction remained elusive. Here, we report the structures of the prototypic laminin receptor α6β1 integrin alone and in complex with three-chain laminin-511 fragment determined via crystallography and cryo-electron microscopy, respectively. The laminin-integrin interface is made up of several binding sites located on all five subunits, with the laminin γ1 chain C-terminal portion providing focal interaction using two carboxylate anchor points to bridge metal-ion dependent adhesion site of integrin β1 subunit and Asn189 of integrin α6 subunit. Laminin α5 chain also contributes to the affinity and specificity by making electrostatic interactions with large surface on the β-propeller domain of α6, part of which comprises an alternatively spliced X1 region. The propeller sheet corresponding to this region shows unusually high mobility, suggesting its unique role in ligand capture.

Extracellular laminin regulates hematopoietic potential of pluripotent stem cells through integrin β1-ILK-β-catenin-JUN axis

Recombinant matrices have enabled feeder cell-free maintenance cultures of human pluripotent stem cells (hPSCs), with laminin 511-E8 fragment (LM511-E8) being widely used. However, we herein report that hPSCs maintained on LM511-E8 resist differentiating to multipotent hematopoietic progenitor cells (HPCs), unlike hPSCs maintained on LM421-E8 or LM121-E8. The latter two LM-E8s bound weakly to hPSCs compared with LM511-E8 and activated the canonical Wnt/β-catenin signaling pathway. Moreover, the extracellular LM-E8-dependent preferential hematopoiesis was associated with a higher expression of integrin β1 (ITGB1) and downstream integrin-linked protein kinase (ILK), β-catenin and phosphorylated JUN. Accordingly, the lower coating concentration of LM511-E8 or addition of a Wnt/β-catenin signaling activator, CHIR99021, facilitated higher HPC yield. In contrast, the inhibition of ILK, Wnt or JNK by inhibitors or mRNA knockdown suppressed the HPC yield. These findings suggest that extracellular laminin scaffolds modulate the hematopoietic differentiation potential of hPSCs by activating the ITGB1-ILK-β-catenin-JUN axis at the undifferentiated stage. Finally, the combination of low-concentrated LM511-E8 and a revised hPSC-sac method, which adds bFGF, SB431542 and heparin to the conventional method, enabled a higher yield of HPCs and higher rate for definitive hematopoiesis, suggesting a useful protocol for obtaining differentiated hematopoietic cells from hPSCs in general.

[Generation of Multiple Ocular Lineages from Human Pluripotent Stem Cells and Its Application to Regenerative Medicine]

The eye is a complex organ with highly specialized constituent tissues derived from different primordial cell lineages. The retina develops from neuroectoderm via the optic vesicle, the corneal epithelium is descended from surface ectoderm, while the iris and corneal stroma have a neural crest origin. Recent work with pluripotent stem cells (PSCs) in culture has revealed a previously under-appreciated level of intrinsic cellular self-organization, with a focus on the retina and retinal cells. We recently demonstrated the generation from human induced pluripotent stem cells (iPSCs) of a self-formed ectodermal autonomous multi-zone (SEAM) of ocular cells. The concentric SEAM mimics whole-eye development because cell location within different zones is indicative of ocular cell lineage, spanning the ocular surface ectoderm, lens, neuro-retina, and retinal pigment epithelium. Therefore, SEAM represents a promising resource for new research of ocular morphogenesis and development. Moreover, we successfully isolated corneal epithelial progenitor cells and fabricated corneal epithelial tissue from PSCs. This approach has translational potential for treating severe corneal epithelial disease by transplantation of PSC-derived corneal epithelial tissue. To evaluate the efficacy and safety of the corneal epithelial tissue, we have started a first-in-human clinical study for patients with corneal epithelial stem cell deficiency, which began last year.

Generation of functional conjunctival epithelium, including goblet cells, from human iPSCs

The conjunctival epithelium, which covers the sclera (the white of the eye) and lines the inside of the eyelids, is essential for mucin secretion and the establishment of a healthy tear film. Here, we describe human conjunctival development in a self-formed ectodermal autonomous multi-zone (SEAM) of cells that were derived from human-induced pluripotent stem cells (hiPSCs) and mimic whole-eye development. Our data indicate that epidermal growth factor (EGF) drives the generation of cells with a conjunctival epithelial lineage. We also show that individual conjunctival cells can be sorted and reconstituted by cultivation into a functional conjunctival epithelium that includes mucin-producing goblet cells. Keratinocyte growth factor (KGF), moreover, is necessary for the maturation of hiPSC-derived conjunctival epithelium-particularly the goblet cells-indicating key complementary roles of EGF and KGF in directing the differentiation and maturation, respectively, of the human conjunctival epithelium.

Chondroitin Sulfate as a Potential Modulator of the Stem Cell Niche in Cornea

Chondroitin sulfate (CS) is an important component of the extracellular matrix in multiple biological tissues. In cornea, the CS glycosaminoglycan (GAG) exists in hybrid form, whereby some of the repeating disaccharides are dermatan sulfate (DS). These CS/DS GAGs in cornea, through their presence on the proteoglycans, decorin and biglycan, help control collagen fibrillogenesis and organization. CS also acts as a regulatory ligand for a spectrum of signaling molecules, including morphogens, cytokines, chemokines, and enzymes during corneal growth and development. There is a growing body of evidence that precise expression of CS or CS/DS with specific sulfation motifs helps define the local extracellular compartment that contributes to maintenance of the stem cell phenotype. Indeed, recent evidence shows that CS sulfation motifs recognized by antibodies 4C3, 7D4, and 3B3 identify stem cell populations and their niches, along with activated progenitor cells and transitional areas of tissue development in the fetal human elbow. Various sulfation motifs identified by some CS antibodies are also specifically located in the limbal region at the edge of the mature cornea, which is widely accepted to represent the corneal epithelial stem cell niche. Emerging data also implicate developmental changes in the distribution of CS during corneal morphogenesis. This article will reflect upon the potential roles of CS and CS/DS in maintenance of the stem cell niche in cornea, and will contemplate the possible involvement of CS in the generation of eye-like tissues from human iPS (induced pluripotent stem) cells.

Laminin 511 Precoating Promotes the Functional Recovery of Transplanted Corneal Endothelial Cells

Corneal endothelial dysfunction is a major cause of corneal blindness and is mainly treated by corneal transplantation. However, the global shortage of donor cornea hampers its application. Intracameral injection of cultured primary corneal endothelial cells (CECs) was recently confirmed in clinical trials. However, abnormal adhesion of the grafted CECs affects the application of this strategy. In this study, we explored if laminin 511 (LN511) improves the therapeutic function of the intracameral CEC injection for corneal endothelial dysfunction. To mimic the late stage of corneal endothelial diseases, intense scraping was developed to remove CECs and extracellular matrix of the posterior Descemet's membrane (DM) without DM removal in rabbits. Then, Dulbecco's phosphate-buffered saline (DPBS) and LN511 were intracamerally injected as the control and intervention groups, respectively. We found that the injected LN511 could settle and form a coating on the posterior surface of DM. After CEC transplantation, corneal clarity of rabbits in the LN511 group was rapidly recovered within 7 days, whereas the corneal recovery took 14 days in the DPBS group. Corneal thickness of LN511 group decreased to 413.3 ± 20.8 μm 7 days after operation, which was significantly lower than 1086.3 ± 78.6 μm of DPBS group (p < 0.01). Moreover, for the grafted CECs, LN511 promoted the rapid adhesion, tight junction formation, and expression of Na⁺/K⁺-ATPase and ZO-1. In vitro analysis revealed that the functions of LN511 on the cultured human CECs mechanistically depended on the cell density and the nuclear-cytoplasmic translocation of the Yes-associated protein. Our study demonstrated that LN511 precoating promoted the adhesion of the transplanted CECs and enhanced the functional regeneration of the corneal endothelium. Thus, our data suggested that the strategy of LN511 precoating and CECs' intracameral injection could be a potential method for the therapy of corneal endothelial dysfunction. Impact statement Intracameral injection of cultured corneal endothelial cells (CECs) is a potential alternative therapy for corneal endothelial dysfunction and has been proven to be effective in clinical trials. However, abnormal adhesion of the grafted CECs affects its application. In this study, intense scraping was developed to remove CECs and extracellular matrix of the posterior Descemet's membrane (DM) without DM removal for the therapy of late stage of corneal endothelial diseases. Laminin 511 was intracamerally injected to form a coating, improve the posterior DM, enhance the adhesion of the grafted CECs, and promote the functional regeneration of CEC transplantation through Yes-associated protein signaling.

Ocular surface ectoderm instigated by WNT inhibition and BMP4

We sought to elucidate how and when the ocular surface ectoderm commits to its differentiation into the corneal epithelium in eye development from human induced pluripotent stem cells (hiPSCs) under the influence of WNT signaling and the actions of BMP4. These signals are key drivers ocular surface ectodermal cell fate determination. It was discovered that secreted frizzled related protein-2 (SFRP2) and Dickkopf1 (DKK1), which are expressed in neural ectoderm, are both influential in the differentiation of hiPSCs, where they act as canonical WNT antagonists. BMP4, moreover, was found to simultaneously initiate non-neural ectodermal differentiation into a corneal epithelial lineage. Combined treatment of hiPSCs with exogenous BMP4 aligned to WNT inhibition for the initial four days of differentiation increased the ocular surface ectodermal cell population and induced a corneal epithelial phenotype. Specification of a surface ectodermal lineage and its fate is thus determined by a fine balance of BMP4 exposure and WNT inhibition in the very earliest stages of human eye development.

Two-step induction of trabecular meshwork cells from induced pluripotent stem cells for glaucoma

Glaucoma is a leading cause of irreversible blindness worldwide. Reducing intraocular pressure is currently the only effective treatment. Elevated intraocular pressure is associated with increased resistance of the outflow pathway, mainly the trabecular meshwork (TM). Despite great progress in the field, the development of novel and effective treatment for glaucoma is still challenging. In this study, we reported that human induced pluripotent stem cells (iPSCs) can be cultured as colonies and monolayer cells expressing OCT4, alkaline phosphatase, SSEA4 and SSEA1. After induction to neural crest cells (NCCs) positive to NGFR and HNK1, the iPSCs can differentiate into TM cells. The induced iPSC-TM cells expressed TM cell marker CHI3L1, were responsive to dexamethasone treatment with increased expression of myocilin, ANGPTL7, and formed CLANs, comparable to primary TM cells. To the best of our knowledge, this is the first study that induces iPSCs to TM cells through a middle neural crest stage, which ensures a stable NCC pool and ensures the high output of the same TM cells. This system can be used to develop personalized treatments using patient-derived iPSCs, explore high throughput screening of new drugs focusing on TM response for controlling intraocular pressure, and investigate stem cell-based therapy for TM regeneration.

Epithelial basement membrane of human decellularized cornea as a suitable substrate for differentiation of embryonic stem cells into corneal epithelial-like cells

The ability to decellularize and recellularize the corneas deemed unsuitable for transplantation may increase the number of available grafts. Decellularized corneas (DCs) may provide a natural microenvironment for cell adhesion and differentiation. Despite this, no study to date has evaluated their efficacy as a substrate for the induction of stem cell differentiation into corneal cells. The present study aimed to compare the efficiency of NaCl and NaCl plus nucleases methods to decellularize whole human corneas, and to investigate the effect of epithelial basement membrane (EBM) of whole DCs on the ability of human embryonic stem cells (hESCs) to differentiate into corneal epithelial-like cells when cultured in animal serum-free differentiation medium. As laminin is the major component of EBM, we also investigated its effect on hESCs differentiation. The decellularization efficiency and integrity of the extracellular matrix (ECM) obtained were investigated by histology, electron microscopy, DNA quantification, immunofluorescence, and nuclear staining. The ability of hESCs to differentiate into corneal epithelial-like cells when seeded on the EBM of DCs or laminin-coated wells was evaluated by immunofluorescence and RT-qPCR analyses. NaCl treatment alone, without nucleases, was insufficient to remove cellular components, while NaCl plus nucleases treatment resulted in efficient decellularization and preservation of the ECM. Unlike cells induced to differentiate on laminin, hESCs differentiated on DCs expressed high levels of corneal epithelial-specific markers, keratin 3 and keratin 12. It was demonstrated for the first time that the decellularized matrices had a positive effect on the differentiation of hESCs towards corneal epithelial-like cells. Such a strategy supports the potential applications of human DCs and hESCs in corneal epithelium tissue engineering.

Wnt Activation After Inhibition Restores Trabecular Meshwork Cells Toward a Normal Phenotype

Purpose

Wnt is a spatiotemporally regulated signaling pathway whose inhibition is associated with glaucoma, elevated intraocular pressure (IOP), and cell stiffening. Whether such changes are permanent or may be reversed is unclear. Here, we determine if activation of Wnt pathway after inhibition reverses the pathologic phenotype.

Methods

Primary human trabecular meshwork (hTM) cells from nonglaucomatous donors were cultured for 12 days in the absence or presence of Wnt modulators: (i) LGK974 (Porcn inhibitor, 10 µM); (ii) LY2090314 (pGSK3β inhibitor, 250 nM); or (iii) 9 days of LGK974 followed by 3 days of LY2090314. Wnt modulation were determined by Western blotting and extracellular matrix (ECM) related genes were evaluated by quantitative PCR. Cytoskeletal morphology was determined by immunofluorescence and cell stiffness by atomic force microscopy.

Results

Wnt activation was confirmed by downregulation of pGSK3β (0.3-fold; P < 0.01), overexpression of AXIN2 (6.7-fold; P < 0.001), and LEF1 (3.8-fold; P < 0.001). Wnt inhibition resulted in dramatic changes in F-actin, which were resolved with subsequent Wnt activation. Concurrently, cell stiffness that was elevated with Wnt inhibition (11.86 kPa; P < 0.01) decreased with subsequent Wnt activation (4.195 kPa; P < 0.01) accompanied by significant overexpression of phosphorylated YAP (1.8-fold; P < 0.001) and TAZ (1.4-fold; P < 0.001). Additionally, Wnt activation after inhibition significantly repressed ECM genes (SPARC and CTGF, P < 0.01), cross-linking genes (LOX and TGM2, P < 0.05), inhibitors of matrix metalloproteinases (TIMP1 and PAI1, P < 0.001), and overexpressed MMP 1/9/14 (P < 0.01).

Conclusions

These data strongly demonstrate that, in normal hTM cells, activation of the Wnt pathway reverses the pathological phenotype caused by Wnt inhibition and may thus be a viable therapeutic for lowering IOP.

GDF5 induces TBX3 in a concentration dependent manner - on a gold nanoparticle gradient

Organs and tissues, such as cartilage and limbs, are formed during development through an orchestration of growth factors that function as morphogens. Examples of growth factors include growth differentiation factor 5 (GDF5) and transforming growth factors beta 1 and 3 (TGFβ-1 and TGFβ-3) which can specify creation of more than one cell type after forming a concentration gradient in vivo. Here, we studied the impact of morphogen gradients during differentiation of induced pluripotent stem cells (iPSCs) into the chondrocyte lineage. Cell budding zones, consisting of condensed cell aggregates, were observed only in gradients of GDF5. T-box transcription factor 3 (TBX3) was detected specifically in the budding zones (ranging from 500-1,500 particles/μm2) of nuclei and cell vesicles. A homogenous density of GDF5 of 900 particles/μm2 on a surface induced budding and expression of TBX3 after five days in iPSCs. Therefore, we conclude that a gradient of GDF5, as well as the specific homogenous density of GDF5, support the induction of TBX3 in iPCSs. Moreover, differentiation of iPSCs first on GDF5 gradient or homogenous surfaces for five days and then in a three-dimensional structure for five weeks resulted in pellets that expressed TBX3.

Cell-Type-Specific Adhesiveness and Proliferation Propensity on Laminin Isoforms Enable Purification of iPSC-Derived Corneal Epithelium

A treatment for intractable diseases is expected to be the replacement of damaged tissues with products from human induced pluripotent stem cells (hiPSCs). Target cell purification is a critical step for realizing hiPSC-based therapy. Here, we found that hiPSC-derived ocular cell types exhibited unique adhesion specificities and growth characteristics on distinct E8 fragments of laminin isoforms (LNE8s): hiPSC-derived corneal epithelial cells (iCECs) and other non-CECs rapidly adhered preferentially to LN332/411/511E8 and LN211E8, respectively, through differential expression of laminin-binding integrins. Furthermore, LN332E8 promoted epithelial cell proliferation but not that of the other eye-related cells, leading to non-CEC elimination by cell competition. Combining these features with magnetic sorting, highly pure iCEC sheets were fabricated. Thus, we established a simple method for isolating iCECs from various hiPSC-derived cells without using fluorescence-activated cell sorting. This study will facilitate efficient manufacture of iCEC sheets for corneal disease treatment and provide insights into target cell-specific scaffold selection.