Culture substrate-associated YAP inactivation underlies chondrogenic differentiation of human induced pluripotent stem cells

Exosomes of stem cells: a potential frontier in the treatment of osteoarthritis

The aging population has led to a global issue of osteoarthritis (OA), which not only impacts the quality of life for patients but also poses a significant economic burden on society. While biotherapy offers hope for OA treatment, currently available treatments are unable to delay or prevent the onset or progression of OA. Recent studies have shown that as nanoscale bioactive substances that mediate cell communication, exosomes from stem cell sources have led to some breakthroughs in the treatment of OA and have important clinical significance. This paper summarizes the mechanism and function of stem cell exosomes in delaying OA and looks forward to the development prospects and challenges of exosomes.

FAK mediates mechanical signaling to maintain epithelial homeostasis through YAP/TAZ-TEADs

Epithelial homeostasis ensures that the epithelium can perform its normal physiological functions. Mechanical signaling response through integrin-mediated adhesions of the basement membrane (BM) is crucial for maintaining epithelial homeostasis. The essential mechanosensors YAP and the paralog TAZ (YAP/TAZ) have been shown to play a critical role in epithelial homeostasis, but the key regulator that mediates mechanical signaling to YAP/TAZ in maintaining epithelial homeostasis has not been fully understood. In this study, we noticed that mechanical signals correlated with YAP/TAZ activation and basal state maintenance in epithelial stem/progenitor cells through immunohistochemistry. Subsequently, we found that inhibition of focal adhesion kinase (FAK) suppressed YAP/TAZ activation in the human keratinocyte line HaCaT cells. Furthermore, inhibition of the interaction between YAP/TAZ and the transcriptional enhanced associate domains (TEADs) resulted in the differentiation of HaCaT cells. Finally, we used primary mouse epithelial cells to reconstruct the epithelium in vitro and found that FAK inhibition led to both a reduction in YAP/TAZ activity and an increase of differentiation in the basal layer cells. In conclusion, our findings reveal that FAK mediates mechanical signaling to maintain epithelial homeostasis via YAP/TAZ-TEADs.

Pluripotent stem-cell-derived therapies in clinical trial: A 2025 update

Since the first derivation of human pluripotent stem cells (hPSCs) 27 years ago, technologies to control their differentiation and manufacturing have advanced immensely, enabling increasing numbers of clinical trials with hPSC-derived products. Here, we revew the landscape of interventional hPSC trials worldwide, highlighting available data on clinical safety and efficacy. As of December 2024, we identify 116 clinical trials with regulatory approval, testing 83 hPSC products. The majority of trials are targeting eye, central nervous system, and cancer. To date, more than 1,200 patients have been dosed with hPSC products, accumulating to >1011 clinically administered cells, so far showing no generalizable safety concerns.

Biomechanical properties of laminins and their impact on cancer progression

Laminins (LMs) constitute a family of heterotrimeric glycoproteins essential for the formation of basement membranes (BM). They act as molecular bridges between cells and the extracellular matrix (ECM), thereby transmitting signals influencing cell behavior and tissue organization. In the realm of cancer pathobiology, LMs regulate key processes such as migration, differentiation, or fibrosis. This review critically examines the multifaceted impact of LMs on tumor progression, with a particular focus on the isoform-specific structure-function relationships, and how this structural diversity contributes to the biomechanical properties of BMs. LM interactions with integrin and non-integrin cell surface receptors, as well as with other ECM proteins, modify the response of cancer cells to the ECM stiffness, ultimately influencing the capacity of malignant cells to breach the BM, a limiting step in metastatic dissemination. Comprehension of the mechanisms underlying LM-driven tumor biomechanics holds potential for better understand cancer pathobiology and design new targeted therapeutic strategies.

Suppression of YAP Ameliorates Cartilage Degeneration in Ankle Osteoarthritis via Modulation of the Wnt/β-Catenin Signaling Pathway

Ankle osteoarthritis is a relatively understudied condition and the molecular mechanisms involved in its development are not well understood. This investigation aimed to explore the role and underlying molecular mechanisms of Yes-associated protein (YAP) in rat ankle osteoarthritis. The results demonstrated that YAP expression levels were abnormally increased in the ankle osteoarthritis cartilage model. In addition, knockdown of YAP expression was shown to hinder the imbalance in ECM metabolism induced by IL-1β in chondrocytes, as demonstrated by the regulation of matrix metalloproteinase (MMP)-3, MMP-9, and MMP-13, a disintegrin, metalloprotease with thrombospondin motifs, aggrecan, and collagen II expression. Additional studies revealed that downregulation of YAP expression markedly inhibited the overexpression of β-catenin stimulated by IL-1β. Furthermore, inhibition of the Wnt/β-catenin signaling pathway reversed the ECM metabolism imbalance caused by YAP overexpression in chondrocytes. It is important to note that the YAP-specific inhibitor verteporfin (VP) significantly delayed the progression of ankle osteoarthritis. In conclusion, the findings highlighted the crucial role of YAP as a regulator in modulating the progression of ankle osteoarthritis via the Wnt/β-catenin signaling pathway. These findings suggest that pharmacological inhibition of YAP can be an effective and critical therapeutic target for alleviating ankle osteoarthritis.

Biologically Relevant Laminin-511 Moderates the Derivation and Proliferation of Human Lens Epithelial Stem/Progenitor-Like Cells

Purpose

The role of specific extracellular matrix (ECM) molecules in lens cell development and regeneration is poorly understood, as appropriate cellular models are lacking. Here, a laminin-based lens cell in vitro induction system was developed to study the role of laminin in human lens epithelial stem/progenitor cell (LES/PC) development.

Methods

The human embryonic stem cell-based lens induction system followed a three-stage protocol. The expression profile of laminins during lens induction was screened, and laminin-511 (LN511) was tested as a candidate substitute. LN511 induction system cellular and molecular features, including induction efficiency, transcription factor expression related to different lens development stages, ECM alterations, and Hippo/YAP signaling, were evaluated.

Results

LAMA5, LAMB1, and LAMC1 were highly expressed around the time of LES/PC derivation. We chose LN511 (product of LAMA5, LAMB1, and LAMC1) and found that it considerably enhanced lens cell induction efficiency, compared to that in Matrigel-coated culture, as more and larger lentoid bodies were detected. Notably, LES/PC induction efficiency improved by promoting lens specification-related transcription factor expression and cell proliferation. Transcriptome analysis revealed that compared to those with Matrigel, ECM accumulation and cell adhesion were downregulated in the LN511 system. Hippo/YAP signaling was hypoactive during LES/P-like cell generation, and small molecule inhibitors of YAP/TAZ activity upregulated LES/PC marker expression and promoted the efficiency of LES/P-like cell derivation.

Conclusions

The laminin isoform LN511 is a reliable substitute for the LES/P-like cell induction system, and LN511-YAP acted as efficient modulators of LES/PC derivation; this contributes to knowledge of the role of the ECM in human lens development.

Assessment of human embryonic stem cells differentiation into definitive endoderm lineage on the soft substrates

Pluripotent stem cells (PSCs) hold enormous potential for treating multiple diseases owing to their ability to self-renew and differentiate into any cell type. Albeit possessing such promising potential, controlling their differentiation into a desired cell type continues to be a challenge. Recent studies suggest that PSCs respond to different substrate stiffness and, therefore, can differentiate towards some lineages via Hippo pathway. Human PSCs can also differentiate and self-organize into functional cells, such as organoids. Traditionally, human PSCs are differentiated on stiff plastic or glass plates towards definitive endoderm and then into functional pancreatic progenitor cells in the presence of soluble growth factors. Thus, whether stiffness plays any role in differentiation towards definitive endoderm from human pluripotent stem cells (hPSCs) remains unclear. Our study found that the directed differentiation of human embryonic stem cells towards endodermal lineage on the varying stiffness did not differ from the differentiation on stiff plastic dishes. We also observed no statistical difference between the expression of yes-associated protein (YAP) and phosphorylated YAP. Furthermore, we demonstrate that lysophosphatidic acid, a YAP activator, enhanced definitive endoderm formation, whereas verteporfin, a YAP inhibitor, did not have the significant effect on the differentiation. In summary, our results suggest that human embryonic stem cells may not differentiate in response to changes in stiffness, and that such cues may not have as significant impact on the level of YAP. Our findings indicate that more research is needed to understand the direct relationship between biophysical forces and hPSCs differentiation.

Laminin 511 E8 fragment promotes to form basement membrane-like structure in human skin equivalents

Introduction

Laminin 511 (LM511), a component of the skin basement membrane (BM), is known to enhance the adhesion of some cell types and it has been reported to affect cell behavior. A recombinant fragment consisting of the integrin recognition site; E8 region of LM511 (511E8) has also been studied. 511E8 has been reported by many as a superior culture substrate. However, the effects of 511E8 on human skin cells remain unclear. In this study, we added 511E8 during the culture period of a reconstituted skin equivalent (SE) and investigated its effect on the formation of BM-like structures.

Methods

SEs were formed by air-liquid culture of human foreskin keratinocytes (HFKs) on contracted type I collagen (Col-I) gels containing human fibroblasts. We compared the BM-like structures formed with and without 511E8 during HFKs culture periods. Morphological analysis, gene expression analysis of extracellular matrix components, and localization analysis of 511E8 in order to identify where 511E8 works were performed.

Results

Immunohistochemical observation by light microscopy showed an accumulation of BM components between the gels and cell layers regardless of the addition of 511E8. There was a stronger and more continuous positive staining for LM α3, type IV collagen, and type VII collagen in the 511E8-added group compared to the no-added group. Transmission electron microscopic observation showed that the continuity of BM-like structures was increased with the addition of 511E8. Furthermore, gene expression analysis showed that the 511E8 addition increased some BM component genes expression, with collagen type IV and type VII α1 chains showing significant increases. His-tagged 511E8 was stained around the basal cells of HFK layers, not in basal regions. Co-staining with anti-His-tag and anti-integrin β1 antibodies revealed the co-localization of theses in some intercellular regions among basal cells.

Conclusion

These results suggest that 511E8 effected on HFKs, enhancing the production of BM components and strengthening the anchoring between the Col-I gels and the HFK layers.

Cartilage Tissue Engineering in Practice: Preclinical Trials, Clinical Applications, and Prospects

Articular cartilage defects significantly compromise the quality of life in the global population. Although many strategies are needed to repair articular cartilage, including microfracture, autologous osteochondral transplantation, and osteochondral allograft, the therapeutic effects remain suboptimal. In recent years, with the development of cartilage tissue engineering, scientists have continuously improved the formulations of therapeutic cells, biomaterial-based scaffolds, and biological factors, which have opened new avenues for better therapeutics of cartilage lesions. This review focuses on advances in cartilage tissue engineering, particularly in preclinical trials and clinical applications, prospects, and challenges.

Mesenchymal stromal cells modulate YAP by verteporfin to mimic cartilage development and construct cartilage organoids based on decellularized matrix scaffolds

The mechanical elasticity or stiffness of the ECM modulates YAP activity to regulate the differentiation of stem cells during the development and defect regeneration of cartilage tissue. However, the understanding of the scaffold-associated mechanobiology during the initiation of chondrogenesis and hyaline cartilaginous phenotype maintenance remains unclear. In order to elucidate such mechanisms to promote articular cartilage repair by producing more hyaline cartilage, we identify the relationship between YAP subcellular localization and variation of the cartilage structure and organization during the early postnatal explosive growth in incipient articular cartilage. Next, we prepared a decellularized cartilage scaffold with different stiffness (2-33 kPa) to investigate the effect of scaffold stiffness on the formation of hyaline cartilage by mesenchymal stem cells and the change of YAP activity. Furthermore, we simulated the decrease of cellular YAP activity during postnatal cartilage development by inhibiting YAP activity with verteporfin, and realized that the timing of drug incorporation was critical to regulate the differentiation of MSCs to hyaline chondrocytes and inhibit their hypertrophy and fibrosis. On this basis, we constructed hyaline cartilage organoids by decellularized matrix scaffolds. Collectively, the results herein demonstrate that YAP plays a critical role during in vitro chondrogenic differentiation which is tightly regulated by biochemical and mechanical regulation.

Expression of OCT4 isoforms is reduced in primary colorectal cancer

Introduction

Colorectal cancer (CRC) is one of the most common types of cancer worldwide. The carcinogenesis of CRC is indeed complex, and there are many different mechanisms and pathways that contribute to the development of malignancy and the progression from primary to metastatic tumors. The OCT4A, encoded by the POU5F1 gene, is a transcription factor responsible for the phenotype of stem cells, maintaining pluripotency and regulation of differentiation. The POU5F1 gene is made up of five exons that can create numerous isoforms through alternative promoter or alternative splicing. In addition to OCT4A, other isoforms called OCT4B are also translated into protein; however, their role in cells has been unclear. The aim of our work was to investigate the expression patterns of OCT4 isoforms in primary and metastatic CRC, providing us with useful information about their role in the development and progression of CRC.

Methods

Surgical specimens from a total of 78 patients were collected and isolated from primary tumors (n = 47) and metastases (n = 31). The relative gene expression of OCT4 isoforms was investigated using the RT-qPCR method together with the TaqMan probes for particular OCT4 isoforms.

Results

Our results suggest significantly downregulated expression of the OCT4A and OCT4Bs isoforms in both primary (p = 0.0002 and p < 0.0001, respectively) and metastatic tumors (p = 0.0006 and p = 0.00051, respectively) when compared with the control samples. We also observed a correlation between reduced expression of all OCT4 isoforms and both primary and left-sided tumors (p = 0.001 and p = 0.030, respectively). On the other hand, the expression of all OCT4 isoforms was significantly upregulated in metastases compared with primary tumors (p < 0.0001).

Discussion

Unlike previous reports, we found out that the expression of OCT4A, OCT4Bs, and all OCT4 isoforms was significantly reduced in primary tumors and metastases compared with control samples. On the other hand, we supposed that the expression rate of all OCT4 isoforms may be related to the cancer type and side, as well as to liver metastases. However, further studies are required to investigate the detailed expression patterns and significance of individual OCT4 isoforms in carcinogenesis.

Engraftment of allogeneic iPS cell-derived cartilage organoid in a primate model of articular cartilage defect

Induced pluripotent stem cells (iPSCs) are a promising resource for allogeneic cartilage transplantation to treat articular cartilage defects that do not heal spontaneously and often progress to debilitating conditions, such as osteoarthritis. However, to the best of our knowledge, allogeneic cartilage transplantation into primate models has never been assessed. Here, we show that allogeneic iPSC-derived cartilage organoids survive and integrate as well as are remodeled as articular cartilage in a primate model of chondral defects in the knee joints. Histological analysis revealed that allogeneic iPSC-derived cartilage organoids in chondral defects elicited no immune reaction and directly contributed to tissue repair for at least four months. iPSC-derived cartilage organoids integrated with the host native articular cartilage and prevented degeneration of the surrounding cartilage. Single-cell RNA-sequence analysis indicated that iPSC-derived cartilage organoids differentiated after transplantation, acquiring expression of PRG4 crucial for joint lubrication. Pathway analysis suggested the involvement of SIK3 inactivation. Our study outcomes suggest that allogeneic transplantation of iPSC-derived cartilage organoids may be clinically applicable for the treatment of patients with chondral defects of the articular cartilage; however further assessment of functional recovery long term after load bearing injuries is required.

A clinical-grade HLA haplobank of human induced pluripotent stem cells matching approximately 40% of the Japanese population

BACKGROUND

Human induced pluripotent stem cells (iPSCs) are expected to be useful for regenerative medicine for many diseases. Many researchers have focused on and enabled the generation of differentiated cells or tissue-like structures, including organoids, which help to ameliorate target diseases. To promote such cell therapies, we established a clinically applicable iPSC haplobank matching as many people as possible in Japan.

METHODS

Through cooperation with several organizations, we recruited donors whose human leukocyte antigens (HLAs) involved in immunorejection were homozygous. The peripheral or umbilical cord blood collected from the donors was used for iPSC production by electroporation of episomal vectors. These iPSC lines were then subjected to testing, including genome analyses and sterility, to maximize safety.

FINDINGS

We constructed a clinical-grade haplobank of 27 iPSC lines from 7 donors according to good manufacturing practice regulations. However, reasons to avoid using iPSC lines include the presence of residual episomal vectors or genetic mutations in cancer-related genes.

CONCLUSIONS

This haplobank provides HLA-matched iPSC lines for approximately 40% of the Japanese population. Since the haplobank's release in 2015, these iPSC lines have been used in more than 10 clinical trials. The establishment of this haplobank is an important step toward the clinical application of iPSCs in cell therapies.

FUNDING

This study was supported by a research center network for the realization of regenerative medicine of the Japan Agency for Medical Research and Development (AMED) under grant number JP20bm0104001h0108.

Aspirin reverses inflammatory suppression of chondrogenesis by stabilizing YAP

Bone marrow mesenchymal stem cells (BMMSCs) transplantation methods are promising candidates for osteoarthritis (OA) treatment. However, inflammatory factors (such as TNF-α) that occur at cell transplantation sites are critical factors that impair the effectiveness of the treatment. Previous studies have shown that aspirin (AS) had a regulatory role in stem cell differentiation. However, little is known about the role of AS on the chondrogenesis of BMMSCs. The purpose of this study is to explore the protective role of AS against the negative effects of TNF-α on BMMSC chondrogenesis. In this study, we investigated the effects of AS and TNF-α on BMMSCs chondrogenesis by performing the Alcian Blue staining, safranin O-fast green staining, haematoxylin and eosin staining, and immunohistochemical staining, as well as real-time RT-PCR and western blot assays. Our results demonstrated that TNF-α inhibited chondrogenic differentiation of BMMSCs by disrupting the balance of cartilage metabolism and promoting oxidative stress in BMMSCs, while AS treatment attenuated these effects. Furthermore, a detailed molecular mechanistic analysis indicated that Yes-associated protein (YAP) played a critical regulatory role in this process. In addition, AS treatment mitigated the progression of cartilage degeneration in a mouse destabilization of the medial meniscus (DMM) model. AS alleviated the inhibitory effect of TNF-α on chondrogenesis of BMMSCs by stabilizing YAP, which may provide new therapeutic strategies for OA treatment.

Role of YAP as a Mechanosensing Molecule in Stem Cells and Stem Cell-Derived Hematopoietic Cells

Yes-associated protein (YAP) and WW domain-containing transcription regulator protein 1 (WWTR1, also known as TAZ) are transcriptional coactivators in the Hippo signaling pathway. Both are well-known regulators of cell proliferation and organ size control, and they have significant roles in promoting cell proliferation and differentiation. The roles of YAP and TAZ in stem cell pluripotency and differentiation have been extensively studied. However, the upstream mediators of YAP and TAZ are not well understood. Recently, a novel role of YAP in mechanosensing and mechanotransduction has been reported. The present review updates information on the regulation of YAP by mechanical cues such as extracellular matrix stiffness, fluid shear stress, and actin cytoskeleton tension in stem cell behaviors and differentiation. The review explores mesenchymal stem cell fate decisions, pluripotent stem cells (PSCs), self-renewal, pluripotency, and differentiation to blood products. Understanding how cells sense their microenvironment or niche and mimic those microenvironments in vitro could improve the efficiency of producing stem cell products and the efficacy of the products.

Laminin-511 and recombinant vitronectin supplementation enables human pluripotent stem cell culture and differentiation on conventional tissue culture polystyrene surfaces in xeno-free conditions

Human pluripotent stem cells (hPSCs) are typically cultivated on extracellular matrix (ECM) protein-coated dishes in xeno-free culture conditions. We supplemented mixed ECM proteins (laminin-511 and recombinant vitronectin, rVT) in culture medium for hPSC culture on conventional polystyrene dishes. Three hPSC cell lines were successfully cultivated on uncoated polystyrene dishes in medium supplemented with optimal conditions of laminin-511 and rVT. Excellent colony shape and colony size as well as high expansion fold of hPSCs were found under these conditions, whereas the colony size was small and poor expansion fold was found solely on L-511-coated dishes. A small portion of L-511 in the culture medium supported hPSC adhesion and prevented the adhesion from being too strong on the uncoated dishes, and rVT in the culture medium further supported adhesion of hPSCs on the dishes by maintaining their pluripotency. Having the optimal composition of L-511 and rVT in the culture medium was important for generating good hPSC colony shapes and sizes as well as a high expansion fold. After long-term culture of hPSCs on uncoated dishes supplemented with the mixed proteins, the hPSCs successfully showed pluripotent markers and could differentiate into a specific lineage of cells, cardiomyocytes, with high efficiency.

Generation of Monkey Induced Pluripotent Stem Cell-Derived Cartilage Lacking Major Histocompatibility Complex Class I Molecules on the Cell Surface

Due to the poor capacity for articular cartilage to regenerate, its damage tends to result in progressively degenerating conditions such as osteoarthritis. To repair the damage, the transplantation of allogeneic human induced pluripotent stem cell (iPSC)-derived cartilage is being considered. However, although allogeneic cartilage transplantation is effective, immunological reactions can occur. One hypothetical solution is to delete the expression of major histocompatibility complex (MHC) class I molecules to reduce the immunological reactions. For this purpose, we deleted the β2 microglobulin (B2M) gene in a cynomolgus monkey (crab-eating monkey [Macaca fascicularis]) iPS cells (cyiPSCs) to obtain B2M^-/- cyiPSCs using the CRISPR/Cas9 system. Western blot analysis confirmed B2M^-/- cyiPSCs lacked B2M protein, which is necessary for MHC class I molecules to be transported to and expressed on the cell surface by forming multimers with B2M. Flow cytometry analysis revealed no B2M^-/- cyiPSCs expressed MHC class I molecules on their surface. The transplantation of B2M^-/- cyiPSCs in immunodeficient mice resulted in teratoma that contained cartilage, indicating that the lack of MHC class I molecules on the cell surface affects neither the pluripotency nor the chondrogenic differentiation capacity of cyiPSCs. By modifying the chondrogenic differentiation protocol for human iPSCs, we succeeded at differentiating B2M^+/+ and B2M^-/- cyiPSCs toward chondrocytes followed by cartilage formation in vitro, as indicated by histological analysis showing that B2M^+/+ and B2M^-/- cyiPSC-derived cartilage were positively stained with safranin O and expressed type II collagen. Flow cytometry analysis confirmed that MHC class I molecules were not expressed on the cell surface of B2M^-/- chondrocytes isolated from B2M^-/- cyiPSC-derived cartilage. An in vitro mixed lymphocyte reaction assay showed that neither B2M^+/+ nor B2M^-/- cyiPSC-derived cartilage cells stimulated the proliferation of allogeneic peripheral blood mononuclear cells. On the contrary, osteochondral defects in monkey knee joints that received allogeneic transplantations of cyiPSC-derived cartilage showed an accumulation of leukocytes with more natural killer cells around B2M^-/- cyiPSC-derived cartilage than B2M^+/+ cartilage, suggesting complex mechanisms in the immune reaction of allogeneic cartilage transplanted in osteochondral defects in vivo.

Culture substrate-associated YAP inactivation underlies chondrogenic differentiation of human induced pluripotent stem cells

Human induced pluripotent stem cells (hiPSCs) are a promising cell source for the creation of cartilage to treat articular cartilage damage. The molecular mechanisms that translate culture conditions to the chondrogenic differentiation of hiPSCs remain to be analyzed. To analyze the effects of culture substrates, we chondrogenically differentiated hiPSCs on Matrigel or laminin 511‐E8 while holding the composition of the chondrogenic medium constant. Cartilage was formed from hiPSCs on Matrigel, but not on laminin 511‐E8. On Matrigel, the hiPSCs were round and yes‐associated protein (YAP) was inactive. In contrast, on laminin 511‐E8, the hiPSCs were flat and YAP was active. Treating the laminin 511‐E8 hiPSCs in a bioreactor caused cell aggregates, in which the cells were round and YAP was inactive. Subsequent culture of the aggregates in chondrogenic medium resulted in cartilage formation. Transient knockdown of YAP in hiPSCs around the start of chondrogenic differentiation successfully formed cartilage on laminin 511‐E8, suggesting that the activation of YAP is responsible for the failure of cartilage formation from hiPSCs on laminin 511‐E8. Consistently, the addition of YAP inhibitors to laminin 511‐E8 hiPSCs caused partial cartilage formation. This study contributes to identifying the molecules that mediate the effects of culture substrates on the chondrogenic differentiation of hiPSCs as well as to developing clinically applicable chondrogenic differentiation methods.