Lineage-specific Differentiation Research Articles

MMP13 promotes the osteogenic potential of BMP9 by enhancing Wnt/β-catenin signaling via HIF-1α upregulation in mouse embryonic fibroblasts.

Bone morphogenetic protein 9 (BMP9) has been validated as one of the most potent osteoinduction factors, but its underlying mechanism remains unclear. As a member of the matrix metalloproteinase (MMP) family, MMP13 may be involved in regulating the lineage-specific differentiation of mouse embryonic fibroblasts (MEFs). The goal of this study was to determine whether MMP13 regulates the osteoinduction potential of BMP9 in MEFs, which are multipotent progenitor cells widely used for stem cell biology research. In vitro and in vivo experiments showed that BMP9-induced osteogenic markers and/or bone were enhanced by exogenous MMP13 in MEFs, but were reduced by MMP13 knockdown or inhibition. The expression of hypoxia inducible factor 1 alpha (HIF-1α) was induced by BMP9, which was enhanced by MMP13. The protein expression of β-catenin and phosphorylation level of glycogen synthase kinase-3 beta (GSK-3β) were increased by BMP9 in MEFs, as was the translocation of β-catenin from the cytoplasm to the nucleus; all these effects of BMP9 were enhanced by MMP13. Furthermore, the MMP13 effects of increasing BMP9-induced β-catenin protein expression and GSK-3β phosphorylation level were partially reversed by HIF-1α knockdown. These results suggest that MMP13 can enhance the osteoinduction potential of BMP9, which may be mediated, at least in part, through the HIF-1α/β-catenin axis. Our findings demonstrate a novel role of MMP13 in the lineage decision of progenitor cells and provide a promising strategy to speed up bone regeneration.

Current Strategies of Modeling Human Trophoblast Using Human Pluripotent Stem Cells in vitro.

We previously established a trophoblast differentiation protocol from primed human pluripotent stem cells (PSC). To induce this lineage, we use a combination of Bone Morphogenetic Protein-4 (BMP4) and the WNT inhibitor IWP2. This protocol has enabled us to obtain a pure population of trophectoderm (TE)-like cells that could subsequently be terminally differentiated into syncytiotrophoblasts (STB) and extravillous trophoblasts (EVT). However, the resulting TE-like cells could only be terminally differentiated to a variable mixture of STB and EVT, with a bias toward the STB lineage. Recently, methods have been developed for derivation and culture of self-renewing human trophoblast stem cells (TSC) from human embryos and early gestation placental tissues. These primary TSCs were further able to differentiate into either STB or EVT with high efficiency using the lineage specific differentiation protocols. Based partly on these protocols, we have developed methods for establishing self-renewing TSC-like cells from PSC, and for efficient lineage-specific terminal differentiation. Here, we describe in detail the protocols to derive and maintain PSC-TSC, from both embryonic stem cells (ESC) and patient-derived induced pluripotent stem cells (iPSC), and their subsequent terminal differentiation to STB and EVT. © 2023 The Authors. Current Protocols published by Wiley Periodicals LLC. Basic Protocol 1: Trophoblast Differentiation into TE-like Cells Basic Protocol 2: Conversion of PSC-Derived TE-like Cells to TSC Basic Protocol 3: Passaging PSC-Derived TSC in iCTB Complete Medium Basic Protocol 4: STB Differentiation from PSC-derived TSC Basic Protocol 5: EVT Differentiation from PSC-derived TSC Support Protocol 1: Geltrex-coated tissue culture plate preparation Support Protocol 2: Collagen IV-coated tissue culture plate preparation Support Protocol 3: Fibronectin-coated tissue culture plate preparation.

TOBF1 modulates mouse embryonic stem cell fate through regulating alternative splicing of pluripotency genes

Embryonic stem cells (ESCs) can undergo lineage-specific differentiation, giving rise to different cell types that constitute an organism. Although roles of transcription factors and chromatin modifiers in these cells have been described, how the alternative splicing (AS) machinery regulates their expression has not been sufficiently explored. Here, we show that the long non-coding RNA (lncRNA)-associated protein TOBF1 modulates the AS of transcripts necessary for maintaining stem cell identity in mouse ESCs. Among the genes affected is serine/arginine splicing factor 1 (SRSF1), whose AS leads to global changes in splicing and expression of a large number of downstream genes involved in the maintenance of ESC pluripotency. By overlaying information derived from TOBF1 chromatin occupancy, the distribution of its pluripotency-associated OCT-SOX binding motifs, and transcripts undergoing differential expression and AS upon its knockout, we describe local nuclear territories where these distinct events converge. Collectively, these contribute to the maintenance of mouse ESC identity.

NFIB–MLL1 complex is required for the stemness and Dlx5-dependent osteogenic differentiation of C3H10T1/2 mesenchymal stem cells

Despite significant progress in our understanding of the molecular mechanisms of mesenchymal stem cell (MSC) differentiation, less is known about the factors maintaining the stemness and plasticity of MSCs. Here we show that the NFIB/MLL1 complex plays key roles in osteogenic differentiation and stemness of C3H10T1/2 MSCs. We find that depletion of either NFIB or MLL1 results in a severely hampered osteogenic potential and failed activation of key osteogenic transcription factors, such as Dlx5, Runx2, and Osx, following osteogenic stimuli. In addition, the NFIB/MLL1 complex binds directly to the promoter of Dlx5, and exogenous expression of Myc-Dlx5, but not the activation of either the BMP- or the Wnt-signaling pathway, is sufficient to restore the osteogenic potential of cells depleted of NFIB or MLL1. Moreover, ChIP and ChIP-seq analysis showed that the NFIB/MLL1 complex mediates the deposition of trimethylated histone H3K4 (H3K4me3) at both Dlx5 and Cebpa, key regulator genes that function at the early stages of osteogenic and adipogenic differentiation, respectively, in uncommitted C3H10T1/2 MSCs. Surprisingly, the depletion of either NFIB or MLL1 leads to decreased H3K4me3 and results in elevated H3K9me3 at those developmental genes. Furthermore, gene expression profiling and ChIP-seq analysis revealed lineage-specific changes in chromatin landscape and gene expression in response to osteogenic stimuli. Taken together, these data provide evidence for the hitherto unknown role of the NFIB/MLL1 complex in the maintenance and lineage-specific differentiation of C3H10T1/2 mesenchymal stem cells and support the epigenetic regulatory mechanism underlying the stemness and plasticity of mesenchymal stem cells.

Progress In Stem Cells Based Replacement Therapy for Retinal Pigment Epithelium: In Vitro Differentiation to In Vivo Delivery.

Retinal pigment epithelium (RPE) is a critical cell monolayer forming the blood-retina-barrier (BRB) and a permeable bridge between the choriocapillaris and the retina. RPE is also crucial in maintaining photoreceptor function and for completing the visual cycle. Loss of the RPE is associated with the development of degenerative diseases like age-related macular degeneration (AMD). To treat diseases like AMD, pluripotent stem cell-derived RPE (pRPE) has been recently explored extensively as a regenerative module. pRPE like other ectodermal tissues requires specific lineage differentiation and long-term in vitro culturing for maturation. Therefore, understanding the differentiation process of RPE could be useful for stem cell based RPE derivation. Developing pRPE-based transplants and delivering them into the subretinal space is another aspect that has garnered interest in the last decade. In this review, we discuss the basic strategies currently employed for stem cell-based RPE derivation, their delivery, and recent clinical studies related to pRPE transplantation in patients. We have also discussed a few limitations with in vitro RPE culture and potential solutions to overcome such problems which can be helpful in developing functional RPE tissue.

Hyperplastic Human Macromass Cartilage for Joint Regeneration.

Cartilage damage affects millions of people worldwide. Tissue engineering strategies hold the promise to provide off-the-shelf cartilage analogs for tissue transplantation in cartilage repair. However, current strategies hardly generate sufficient grafts, as tissues cannot maintain size growth and cartilaginous phenotypes simultaneously. Herein, a step-wise strategy is developed for fabricating expandable human macromass cartilage (macro-cartilage) in a 3D condition by employing human polydactyly chondrocytes and a screen-defined serum-free customized culture (CC). CC-induced chondrocytes demonstrate improved cell plasticity, expressing chondrogenic biomarkers after a 14.59-times expansion. Crucially, CC-chondrocytes form large-size cartilage tissues with average diameters of 3.25 ± 0.05mm, exhibiting abundant homogenous matrix and intact structure without a necrotic core. Compared with typical culture, the cell yield in CC increases 2.57 times, and the expression of cartilage marker collagen type II increases 4.70 times. Transcriptomics reveal that this step-wise culture drives a proliferation-to-differentiation process through an intermediate plastic stage, and CC-chondrocytes undergo a chondral lineage-specific differentiation with an activated metabolism. Animal studies show that CC macro-cartilage maintains a hyaline-like cartilage phenotype in vivo and significantly promotes the healing of large cartilage defects. Overall, an efficient expansion of human macro-cartilage with superior regenerative plasticity is achieved, providing a promising strategy for joint regeneration.

Molecular Beacon Imaging System to Discriminate the Differentiation State of Cells from Energy Metabolic Pathways.

Metabolic pathways of energy production play an essential role as a function of cells. It is well recognized that the differentiation state of stem cells is highly associated with their metabolic profile. Therefore, visualization of the energy metabolic pathway makes it possible to discriminate the differentiation state of cells and predict the cell potential for reprogramming and differentiation. However, at present, it is technically difficult to directly assess the metabolic profile of individual living cells. In this study, we developed an imaging system of cationized gelatin nanospheres (cGNS) incorporating molecular beacons (MB) (cGNSMB) to detect intracellular pyruvate dehydrogenase kinase 1 (PDK1) and peroxisome proliferator-activated receptor γ, coactivator-1α (PGC-1α) mRNA of key regulators in the energy metabolism. The prepared cGNSMB was readily internalized into mouse embryonic stem cells, while their pluripotency was maintained. The high level of glycolysis in the undifferentiated state, the increased oxidative phosphorylation over the spontaneous early differentiation, and the lineage-specific neural differentiation were visualized based on the MB fluorescence. The fluorescence intensity corresponded well to the change of extracellular acidification rate and the oxygen consumption rate of representative metabolic indicators. These findings indicate that the cGNSMB imaging system is a promising tool to visually discriminate the differentiation state of cells from energy metabolic pathways.

Electroconductive and mechano-competent PUCL@CNT nanohybrid scaffolds guiding neuronal specification of neural stem/progenitor cells

Diseased or injured nervous systems lead to lifelong disability and even death due to their limited self-repair and regenerative capability. For successful neuronal regeneration and functional recovery, it is critical to selectively guide neural stem/progenitor cells (NSPCs) to differentiate into neurons and oligodendrocytes rather than astrocytes. Biomaterial scaffolds with specific properties such as electroconductivity can boost this event and guide the specific differentiation of NSPCs. Here, we prepared electroconductive and mechano-competent scaffolds made of shape-memory polyurethane‐polycaprolactone (PUCL) nanofibers and carbon nanotubes (CNTs) (namely, PUCL@CNT). The CNT-decorated PUCL platforms provided excellent shape-formable and shape-memorable properties for surgical compatibility as well as electroconductivity (∼ 8 S/m) and nanoscale-topography (tens-of-nm), which could promote the initial cell adhesion via the integrin-mediated focal adhesion signaling pathway, and promote neuron and oligodendrocyte differentiation. The potential mechanism of this lineage-specific differentiation of NSPCs upon the PUCL@CNT was evaluated by transcriptome sequencing analysis and pharmacological intervention tests, revealing the involvement of the intracellular calcium levels and the FAK-AKT-β-catenin pathway. When implanted in a rat corticectomy model, PUCL@CNT could induce a larger number of endogenous neural stem cells (both Nestin+ and β-catenin+) and neurons (Tuj1+) near the injured region (vs. PUCL and PBS), demonstrating the in vivo therapeutic role of PUCL@CNT. Taken together, the CNT surface-decoration was effective in driving NSPCs toward neuronal specification and their maturation, and the PUCL@CNT scaffold is potentially useful for neural tissue regeneration that can benefit via the neuronal activation of endogenous NSPCs.

Bovine Fibroblast-Derived Extracellular Matrix Promotes the Growth and Preserves the Stemness of Bovine Stromal Cells during In Vitro Expansion

Cultivated meat is a fast-growing research field and an industry with great potential to overcome the limitations of traditional meat production. Cultivated meat utilizes cell culture and tissue engineering technologies to culture a vast number of cells in vitro and grow/assemble them into structures mimicking the muscle tissues of livestock animals. Stem cells with self-renewal and lineage-specific differentiation abilities have been considered one of the key cell sources for cultivated meats. However, the extensive in vitro culturing/expansion of stem cells results in a reduction in their abilities to proliferate and differentiate. Extracellular matrix (ECM) has been used as a culturing substrate to support cell expansion for cell-based therapies in regenerative medicine due to its resemblance to the native microenvironment of cells. In this study, the effect of the ECM on the expansion of bovine umbilical cord stromal cells (BUSC) in vitro was evaluated and characterized. BUSCs with multi-lineage differentiation potentials were isolated from bovine placental tissue. Decellularized ECM prepared from a confluent monolayer of bovine fibroblasts (BF) is free of cellular components but contains major ECM proteins such as fibronectin and type I collagen and ECM-associated growth factors. Expansion of BUSC on ECM for three passages (around three weeks) resulted in about 500-fold amplification, while cells were amplified less than 10-fold when cultured on standard tissue culture plates (TCP). Moreover, the presence of ECM reduced the requirement for serum in the culture medium. Importantly, the cells amplified on ECM retained their differentiation abilities better than cells cultured on TCP. The results of our study support the notion that monolayer cell-derived ECM may be a strategy to expand bovine cells in vitro effectively and efficiently.

Abstract 512: Identification of SS008871, a novel Polθ inhibitor that effectively inhibits tumors with homologous recombination deficiency in vitro and in vivo

Abstract The repair of DNA double strand break (DSB) is crucial for genome stability and cell survival. There are three main DSB repair pathways: homologous recombination (HR), non-homologous end joining (NHEJ) and microhomology-mediated end joining (MMEJ). HR is a high-fidelity, error-free DSB repair pathway, and the dysfunction of HR confers cell genome instability and leads to tumorigenesis. HR deficiency is especially prevalent in gynecologic tumors, sharing about 10% population of all the gynecologic tumor patients. In situation of HR deficiency, MMEJ, in which DNA polymerase theta (Polθ) plays an essential role, is up-regulated to serve as a backup pathway for DSB repair. Several studies have proved that the inhibition of Polθ causes synthetic lethality with HR deficiency. Hence, Polθ emerges as a potential DNA damage repair target for the treatment of HR deficient tumors. Here we report a novel small molecular Polθ inhibitor, SS008871, which inhibits Polθ activity with an IC50 of 22 nM, and strongly inhibits cellular MMEJ pathway with an IC50 of single-digital nanomolar level. SS008871 strongly inhibits proliferation of HR deficient BRCA2-/- DLD-1 cells, and shows a >125× selectivity folds over DLD-1 parent cells as well as non-malignant cells. Besides, SS008871 elicits synergetic anti-proliferation activities in combination of a PARP inhibitor, olaparib on BRCA2-/- DLD-1 and MDA-MB-436 cells. In the BRCA2-/- DLD-1 xenograft model, SS008871 shows tumor growth inhibition as a single agent, and the combination of SS008871 and olaparib further results in tumor regression. Accordingly, the level of γH2AX, a common DSB marker, correlates well to the anti-tumor efficacy. In a human hematopoietic stem cells based in vitro hematotoxicity assay, SS008871 shows no significant inhibition on lineage-specific (myeloid, erythroid and megakaryocytic) cell differentiation and survival, suggesting the low hematotoxicity risk. In comparison, olaparib significantly attenuated hematopoietic stem cells on both differentiation and survival in the parallel assay, which is consistent with the hematological toxicity observed in human. Furthermore, there is no clinical abnormalities observed after a high dose treatment of SS008871 in mice, demonstrating that SS008871 is well-tolerated. Taken together, SS008871 is proved to be an encouraging Polθ inhibitor with good safety. Citation Format: Feng Zhou, Lu Liu, Lei Jiang, Feng Tang, Zhen Li, Wenqing Yang, Liting Xue, L Chen, Renhong Tang. Identification of SS008871, a novel Polθ inhibitor that effectively inhibits tumors with homologous recombination deficiency in vitro and in vivo [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 512.

Abstract 6201: Identification of SP-002, a highly selective USP1 inhibitor effectively inhibits HRD tumor growth and displays low hematotoxicity risk

Abstract Tumors with homologous repair deficiencies (HRD) are sensitive to agents interrupting DNA repair. The deubiquitinase USP1 involves in the DNA damage response by translesion synthesis and Fanconi anemia pathway. And the synthetic lethality of USP1 and HRD is well reported. Moreover, deficiency of USP1 or its downstream pathway leads to hypersensitivity of HRD tumors to PARP inhibition. In addition, target-related hematotoxicity is widely observed in serval DNA Damage Response (DDR) pathway inhibitors, including PARP and ATR inhibitors, which limits the combination therapy. Here, we reported SP-002, a highly selective USP1 inhibitor, displayed monotherapy potential and combination activity with PARP inhibitor in HRD cancers. In the biochemical assay, SP-002 strongly inhibited USP1 enzyme with IC50 of 15.7 nM, and potently inhibited proliferation of BRCA1-mutant MDA-MB-436 breast cell (GI50, 47.4 nM). SP-002 demonstrated synergistic anti-proliferation effects in combination of olaparib, a PARP inhibitor, in MDA-MB-436 cells. And further results revealed that the combination significantly enhances the DNA damage burden and cells apoptosis. Moreover, synergistic activities of SP-002 and olaparib also were observed in a panel of HRD cell lines, such as UWB1.289, Capan-1, MDA-MB-453 and NCI-H292. In a human hematopoietic stem cells based in vitro hematotoxicity assay, SP-002 showed no significant inhibition on lineage-specific (myeloid, erythroid, and megakaryocytic) cell differentiation and survival. In comparison, positive controls, 5-fluorouracil and olaparib significantly attenuated those primary cells both on differentiation and survival, which was consistent with the hematological toxicity observed in human. Oral administration of SP-002 led to completely tumor growth inhibition in MDA-MB-436 xenograft model, and combination of SP-002 and olaparib resulted in tumor regression. In conclusion, SP-002, a selective and potent USP1 inhibitor without significant hematotoxicity, that demonstrated excellent efficacy on treatment of HRD cancers. Citation Format: Feng Zhou, Zhengtao Li, Lei Zhou, Wei Zhu, Jiyan Zhang, Wenqing Yang, Liting Xue, Xiaokang Qin, Ping Chen, Renhong Tang. Identification of SP-002, a highly selective USP1 inhibitor effectively inhibits HRD tumor growth and displays low hematotoxicity risk [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 6201.

Preferential Hematopoietic Differentiation in Induced Pluripotent Stem Cells Derived From Human Umbilical Cord Arterial Endothelial Cells.

The major obstacle for applications of human induced pluripotent stem cells (hiPSCs) is efficient and controlled lineage-specific differentiation. Hence, a deeper understanding of the initial populations of hiPSCs is required to instruct proficient lineage commitment. hiPSCs were generated from somatic cells by transduction of 4 human transcription factors (OCT4, SOX2, KLF4, and C-MYC) using Sendai virus vectors. Genome-wide DNA methylation analysis and transcriptional analysis were performed to evaluate the pluripotent capacity and somatic memory state of hiPSCs. Flow cytometric analysis and colony assays were performed to assess the hematopoietic differentiation capacity of hiPSCs. Here, we reveal human umbilical arterial endothelial cell-derived induced pluripotent stem cells (HuA-iPSCs) exhibit indistinguishable pluripotency in comparison with human embryonic stem cells and hiPSCs derived from other tissues of origin (umbilical vein endothelial cells, cord blood, foreskin fibroblasts, and fetal skin fibroblasts). However, HuA-iPSCs retain a transcriptional memory typical of the parental human umbilical cord arterial endothelial cells, together with a strikingly similar DNA methylation signature to umbilical cord blood-derived induced pluripotent stem cells that distinguishes them from other human pluripotent stem cells. Ultimately, HuA-iPSCs are most efficient in targeted differentiation toward hematopoietic lineage among all human pluripotent stem cells based on the functional and quantitative evaluation of both flow cytometric analysis and colony assays. Application of the Rho-kinase activator significantly reduces the effects of preferential hematopoietic differentiation in HuA-iPSCs, reflected in CD34+ cell percentage of day 7, hematopoietic/endothelial-associated gene expression, and even colony-forming unit numbers. Collectively, our data suggest that somatic cell memory may predispose HuA-iPSCs to differentiate more amenably into hematopoietic fate, bringing us closer to generating hematopoietic cell types in vitro from nonhematopoietic tissue for therapeutic applications.

Pluripotent stem cells: Basic biology or else differentiations aimed at translational research and the role of flow cytometry.

Pluripotent stem cell research has revolutionized the modern era for the past 14 years with the advent of induced pluripotent stem cells. Before this time, scientists had access to human and mouse embryonic stem cells primarily for basic research and an attempt towards lineage-specific differentiations for cell therapy applications. Regarding pluripotent stem cells, expression of bonafide marker proteins such as Oct4, Nanog, Sox2, Klf4, c-Myc, and Lin28 have been considered giving a perfect readout for pluripotent stem cells and assessed using an analytical flow cytometer. In addition to the intracellular markers, surface markers such as stage-specific embryonic antigen-1 for mouse cells and SSEA-4 for human cells are needed to sort pure populations of stem cells for further downstream applications for cell therapy. The surface marker SSEA-4 is the most appropriate for obtaining pure populations of human pluripotent stem cells. When differentiated in a controlled manner using growth factors or small molecules, it is mandatory to assess the downregulation of pluripotency markers (Oct4, Nanog, Sox2, and Klf4) with subsequent up-regulation of stage-specific differentiation markers. Such assessments are done using flow cytometry. Pluripotent stem cells have a high teratoma-forming potential in vivo. Small amounts of undifferentiated PSCs might lead to dangerous teratomas upon transplantation if leftover in the pool of differentiated cells. Hence, flow cytometry is essential for sorting out PSC populations with teratoma-forming potential. The pure populations of differentiated progenitors need to be flow-sorted before differentiating them further for cell therapy applications. For example, Glycoprotein 2 is a specific cell-surface marker for pancreatic progenitors that enables one to sort the pancreatic progenitors differentiated from human PSCs. Taken together, analytical flow cytometry, and cell sorting provide indispensable tools in PSC research and cell therapy.

DNA dioxygenases Tet2/3 regulate gene promoter accessibility and chromatin topology in lineage-specific loci to control epithelial differentiation.

Execution of lineage-specific differentiation programs requires tight coordination between many regulators including Ten-eleven translocation (TET) family enzymes, catalyzing 5-methylcytosine oxidation in DNA. Here, by using Keratin 14-Cre-driven ablation of Tet genes in skin epithelial cells, we demonstrate that ablation of Tet2/Tet3 results in marked alterations of hair shape and length followed by hair loss. We show that, through DNA demethylation, Tet2/Tet3 control chromatin accessibility and Dlx3 binding and promoter activity of the Krt25 and Krt28 genes regulating hair shape, as well as regulate interactions between the Krt28 gene promoter and distal enhancer. Moreover, Tet2/Tet3 also control three-dimensional chromatin topology in Keratin type I/II gene loci via DNA methylation-independent mechanisms. These data demonstrate the essential roles for Tet2/3 in establishment of lineage-specific gene expression program and control of Dlx3/Krt25/Krt28 axis in hair follicle epithelial cells and implicate modulation of DNA methylation as a novel approach for hair growth control.

Exosome-Based Cell Homing and Angiogenic Differentiation for Dental Pulp Regeneration.

Exosomes have attracted attention due to their ability to promote intercellular communication leading to enhanced cell recruitment, lineage-specific differentiation, and tissue regeneration. The object of this study was to determine the effect of exosomes on cell homing and angiogenic differentiation for pulp regeneration. Exosomes (DPSC-Exos) were isolated from rabbit dental pulp stem cells cultured under a growth (Exo-G) or angiogenic differentiation (Exo-A) condition. The characterization of exosomes was confirmed by nanoparticle tracking analysis and an antibody array. DPSC-Exos significantly promoted cell proliferation and migration when treated with 5 × 108/mL exosomes. In gene expression analysis, DPSC-Exos enhanced the expression of angiogenic markers including vascular endothelial growth factor A (VEGFA), Fms-related tyrosine kinase 1 (FLT1), and platelet and endothelial cell adhesion molecule 1 (PECAM1). Moreover, we identified key exosomal microRNAs in Exo-A for cell homing and angiogenesis. In conclusion, the exosome-based cell homing and angiogenic differentiation strategy has significant therapeutic potential for pulp regeneration.

Genome-wide 5-hydroxymethylcytosine (5hmC) reassigned in Pten-depleted mESCs along neural differentiation.

DNA methylation and hydroxymethylation have been implicated in the regulatory dynamics of gene expression in normal development and differentiation. 5-Hydroxymethylcytosine (5hmC), created by the ten-eleven translocation (TET) protein-catalyzed oxidation of 5-methylcytosine (5mC), is abundant in the brain, but the genome-wide distribution and impact of 5hmC during diverse neuronal differentiation remain unknown. Here, we used an in vitro model to differentiate mouse embryonic stem cells (mESCs) into ventral midbrain and hindbrain neural progenitors, followed by characterizing global 5hmC distribution using a nano-5hmC-seal approach. The 5hmC pattern was dynamic in promoter, exon, and enhancer regions, associated with gene activation and repression. For example, ventral midbrain markers (Lmx1a, Otx2, and Th) and hindbrain markers (Hoxa1, Zic1, and Tph1) acquire 5hmC and are upregulated during differentiation. Among the differentially expressed genes involved in both midbrain and hindbrain lineage commitment, phosphatase and tensin homolog (Pten) was identified as a key regulator for neuronal development. We confirmed that Pten knockout disrupted the normal differentiation of midbrain/hindbrain neural progenitors, resulting in immature neurons. In addition, 5421 and 4624 differentially hydroxymethylated regions (DhMRs) were identified in the differentiation of Pten-/- mESC into ventral midbrain and hindbrain progenitors, respectively. Gene ontology analysis showed that the majority of these DhMRs were associated with neurogenesis, ectoderm development, and signal transduction. Moreover, further combinational analysis of the 5hmC pattern and transcriptomic profile in the midbrain progenitor cells demonstrated Pten as a toggle to modulate mitochondrial associated pathways. Therefore, our findings elucidated the molecular mechanisms underlying lineage-specific differentiation of pluripotent stem cells to the midbrain/hindbrain progenitors, where Pten participates as one key regulator.

Identification of DOT1L inhibitor in a screen for factors that promote dopaminergic neuron survival.

Parkinson's disease (PD) is a common neurodegenerative disorder characterized by the progressive loss of dopaminergic (DA) neurons in the substantia nigra region of the midbrain. Diagnostic criteria for PD require that at least two of three motor signs are observed: tremor, rigidity, and/or bradykinesia. The most common and effective treatment for PD is Levodopa (L-DOPA) which is readily converted to DA and has been the primary treatment since the 1960's. Dopamine agonists have also been developed but are less effective than L-DOPA. Although the lack of a model system to study PD has hampered efforts to identify treatments, diverse screening strategies have been proposed for identification of new pharmaceutical candidates. Here, we describe a pilot screen to identify candidate molecules from a bioactive compound library, that might increase formation, maintenance and/or survival of DA neurons in vitro. The screen used a previously characterized reporter construct consisting of the luciferase gene inserted downstream of the endogenous tyrosine hydroxylase (TH) gene and neurons differentiated from human pluripotent stem cells for 18 days. The reporter mimics expression of TH and includes a secreted luciferase whose activity can be measured non-invasively over multiple timepoints. Screening of the bioactive compound library resulted in the identification of a single molecule, SGC0946, that is an inhibitor of DOT1L (Disruptor Of Telomeric silencing 1-Like) which encodes a widely-conserved histone H3K79 methyltransferase that is able to both activate and repress gene transcription. Our results indicate that SGC0946 increased reporter luciferase activity with a single treatment for 48-h post-plating being equivalent to continuous treatment. Moreover, data suggested that the total number of neurons differentiated in the assays was comparable from experiment to experiment under different SGC0946 treatments over time. In contrast, data suggested that the survival and/or maintenance of DA neurons might be specifically enhanced by SGC0946 treatment. These results document the feasibility of a set of tools for further exploration of small molecules that may impact DA neuron differentiation, maintenance and/or survival. Results provide evidence in support of other reports that indicate inhibition of DOT1L may play an important role in maintenance and survival of neural progenitor cells (NPCs) and their lineage-specific differentiation.

Discreteness of cell–surface contacts affects spatio-temporal dynamics, adhesion, and proliferation of mouse embryonic stem cells

The self-renewal and lineage-specific differentiation of stem cells are regulated by interactions with their microenvironments, called stem cell niche. Stem cells receive both biochemical and biophysical cues from their niche, which leads to the activation of signaling pathways, resulting in the modulation of gene expressions to guide their fate. Most of previous studies are focused on the effect of substrate stiffness using hydrogels with different Young’s moduli, and information is lacking on the effect of the discreteness of cell–substrate contacts on stem cells. Using mouse pluripotent, embryonic stem cells (mESCs) as the model system for early development, we quantitatively investigated the migration, dynamic deformation, and adhesion of mESCs on sparse and dense gelatin nanofibers deposited on glass surfaces, with a continuous layer of gelatin coated on glass substrates as the control. After confirming the maintenance of pluripotency on all the surfaces throughout the experiments, the centroid trajectories were monitored using timelapse imaging. The mean square displacement analysis indicated that both the diffusion coefficient and exponent were largest on sparse nanofibers, while the diffusion coefficient of mESCs on dense nanofibers was comparable to that on the control. Moreover, power spectral analysis of the shape deformation in the Fourier mode indicated that mESCs predominantly underwent elliptic deformation (mode 2), with the largest energy dissipation on sparse nanofibers. These data suggest that mESCs can deform and move on sparse nanofibers owing to the discrete cell–surface contact points. Intriguingly, using a self-developed technique based on laser-induced shock waves, a distinctly larger critical pressure was required to detach cells from nanofibers than from continuous gelatin. This finding suggests that the continuous but weak cell-substrate contacts suppress the deformation-driven mESC migration. As one of the key biological functions of stem cells, the proliferation rate of mESCs on these surfaces was determined. Although the observed difference was not statistically significant, the highest proliferation rate was observed on nanofibers, suggesting that the discreteness of cell–surface contacts can be used to regulate not only spatio-temporal dynamics but also the biological function of pluripotent stem cells.

Stabilization of hESCs in two distinct substates along the continuum of pluripotency.

A detailed understanding of the developmental substates of human pluripotent stem cells (hPSCs) is needed to optimize their use in cell therapy and for modeling early development. Genetic instability and risk of tumorigenicity of primed hPSCs are well documented, but a systematic isogenic comparison between substates has not been performed. We derived four hESC lines in naive human stem cell medium (NHSM) and generated isogenic pairs of NHSM and primed cultures. Through phenotypic, transcriptomic, and methylation profiling, we identified changes that arose during the transition to a primed substate. Although early NHSM cultures displayed naive characteristics, including greater proliferation and clonogenic potential compared with primed cultures, they drifted toward a more primed-like substate over time, including accumulation of genetic abnormalities. Overall, we show that transcriptomic and epigenomic profiling can be used to place human pluripotent cultures along a developmental continuum and may inform their utility for clinical and research applications.

Stromal STAT5-Mediated Trophic Activity Regulates Hematopoietic Multipotent Progenitor Niche Factors

Signal transducer and activator of transcription 5 (STAT5a and STAT5b isoforms) are latent transcription factors that are intrinsically critical for normal hematopoiesis but are also expressed in bone marrow stromal cells. However, despite known STAT5a (prolactin) and STAT5b (growth hormone) functions in breast and liver tissue respectively, hematopoiesis-supporting stromal functions have not been explored. Here, floxed STAT5ab double knockout (KO) was generated with a variety of hematopoietic and stromal Cre-expressing transgenic mouse strains to test whether STAT5a or STAT5b play a role in extrinsic regulation of hematopoiesis. Pan-hematopoietic deletion with Vav1-Cre was the positive control for loss of multipotent hematopoietic function but surprisingly Vav1-Cre also deleted STAT5ab in CD45neg cells, dysregulated stromal niche factor mRNA expression, and altered MSC osteo/chondro-lineage differentiation priming. Single cell transcriptome analysis of bone marrow from wild-type or Vav1-Cre KO mice long-term repopulating hematopoietic stem cells (LT-HSC) showed upregulated oxidative phosphorylation (P<10-10) and protein translation (P<10-39) genes in LT-HSCs and throughout myeloid-primed clusters, while in contrast common lymphoid progenitor-like cells were completely eliminated. Similarly, like Vav1+ cells and based on scRNAseq analysis, Nes+ cells were also detected in both CD45neg and CD45+ cell clusters. Deletion of STAT5ab with Nes-Cre reduced the number of LT-HSCs (30% reduction compared to Nes-Cre control mice, P=0.02, N=4) and caused hematopoietic repopulating defects. To follow up on these promiscuous Cre promoter deletions in CD45+ and CD45neg bone marrow cell populations, additional stroma-specific Cre strains (LepR, Osx, Ocn, Prrx1, Nes-CreERT2) as well as endothelial-specific (Cdh5) strains were generated lacking STAT5ab. Viable mice were assessed for peripheral blood hematology, competitive repopulation, as well as hematopoietic stem/progenitor subsets (LT-HSC, MPP1, MPP2, MPP3, MPP4, KLS) using well-accepted flow cytometry antibody panels. Deletion of STAT5 in stromal cells with LepR-Cre significantly reduced MPP4 (35% reduction, P=0.025, N=4). Overall, extrinsic stromal (but not endothelial) cells were deficient in supporting multipotent and lineage-committed hematopoietic progenitors. However, peripheral blood hematology was rescued through homeostatic production. Gene regulation profiles resembled that of cytokine-starved MPPs. Functional support for niche-supporting activity was also assessed using STAT5ab KO MSCs in vitro. With Lepr-Cre mediated STAT5ab deletion, bone marrow niche factor mRNAs were downregulated (Cxcl12, Angpt1, Igfbp4, Igf1, Il34) and support of multipotent hematopoietic cells was significantly impaired. ELISA assay showed that SDF-1a was reduced 3-fold (P<0.001, N=5) and IGF-1 was reduced 2-fold (P<0.01, N=5) compared to wild type MSCs. Inversely, mRNAs for Kitl and Grem1 were increased in the same stromal cells, consistent with loss of multipotency and mixed HSC vs. MPP stromal support activities. Furthermore, novel scRNAseq analysis on simultaneous bone marrow hematopoietic and stromal cells compared wild-type and KO mice. Differentially expressed gene sets with Maximum Mean Discrepancy (MMD) co-expression revealed a key central role for coordinated STAT5ab/Cish balance as a biomarker of the cellular progenitor activity state (metabolic, protein translation, survival) associated with multipotency, comparing KO to wild-type cells. Importantly, Cish was strongly co-expressed in cells primed for lineage-specific differentiation (MSC - osteo/chondrogenic-primed; HSC - myeloid-primed) with STAT5ab co-expressed genes being associated with multipotent potential. Therefore, novel STAT5ab/Cish-mediated gene regulation programs operate within the bone marrow microenvironment to mediate cytokine production and responsiveness. This work highlights the importance of examining heterotypic cell types within bone marrow to elucidate functional cross-talk underlying hematopoietic homeostasis and defines conserved STAT5ab-mediated gene signatures as potential biomarkers to test in human hematopoietic and immune cell disorders.