PDGF-AB and 5-Azacytidine induce conversion of somatic cells into tissue-regenerative multipotent stem cells

Sall4 and Gata4 induce cardiac fibroblast transition towards a partially multipotent state with cardiogenic potential

Cardiac cellular fate transition holds remarkable promise for the treatment of ischemic heart disease. We report that overexpressing two transcription factors, Sall4 and Gata4, which play distinct and overlapping roles in both pluripotent stem cell reprogramming and embryonic heart development, induces a fraction of stem-like cells in rodent cardiac fibroblasts that exhibit unlimited ex vivo expandability with clonogenicity. Transcriptomic and phenotypic analyses reveal that around 32 ± 6.4% of the expanding cells express Nkx2.5, while 13 ± 3.6% express Oct4. Activated signaling pathways like PI3K/Akt, Hippo, Wnt, and multiple epigenetic modification enzymes are also detected. Under suitable conditions, these cells demonstrate a high susceptibility to differentiating into cardiomyocyte, endothelial cell, and extracardiac neuron-like cells. The presence of partially pluripotent-like cells is characterized by alkaline phosphatase staining, germ layer marker expression, and tumor formation in injected mice (n = 5). Additionally, significant stem-like fate transitions and cardiogenic abilities are induced in human cardiac fibroblasts, but not in rat or human skin fibroblasts. Molecularly, we identify that SALL4 and GATA4 physically interact and synergistically stimulate the promoters of pluripotency genes but repress fibrogenic gene, which correlates with a primitive transition process. Together, this study uncovers a new cardiac regenerative mechanism that could potentially advance therapeutic endeavors and tissue engineering.

Bioengineering-tissue strategies to model mammalian implantation in vitro

During mammalian implantation, complex and well-orchestrated interactions between the trophectoderm of implanting blastocysts and the maternal endometrium lead to a successful pregnancy. On the other hand, alteration in endometrium-blastocyst crosstalk often causes implantation failure, pregnancy loss, and complications that result in overall infertility. In domestic animals, this represents one of the major causes of economic losses and the understanding of the processes taking place during the early phases of implantation, in both healthy and pathological conditions, is of great importance, to enhance livestock system efficiency. Here we develop highly predictive and reproducible functional tridimensional (3D) in vitro models able to mimic the two main actors that play a key role at this developmental stage: the blastocyst and the endometrium. In particular, we generate a 3D endometrial model by co-culturing primary epithelial and stromal cells, isolated from sow uteri, onto highly porous polystyrene scaffolds. In parallel, we chemically reprogram porcine adult dermal fibroblasts and encapsulate them into micro-bioreactors to create trophoblast (TR) spheroids. Finally, we combine the generated artificial endometrium with the TR spheroids to model mammalian implantation in vitro and mimic the embryo-maternal interactions. The protocols here described allow the generation of reproducible and functional 3D models of both the maternal compartment as well as the implanting embryo, able to recreate in vitro the architecture and physiology of the two tissues in vivo. We suggest that these models can find useful applications to further elucidate early implantation mechanisms and to study the complex interactions between the maternal tissue and the developing embryos.

Use of Epigenetic Cues and Mechanical Stimuli to Generate Blastocyst-Like Structures from Mammalian Skin Dermal Fibroblasts

Mammalian embryogenesis is characterized by complex interactions between embryonic and extra-embryonic tissues that coordinate morphogenesis, coupling bio-mechanical and bio-chemical cues, to regulate gene expression and influence cell fate. Deciphering such mechanisms is essential to understand early embryogenesis, as well as to harness differentiation disorders. Currently, several early developmental events remain unclear, mainly due to ethical and technical limitations related to the use of natural embryos.Here, we describe a three-step approach to generate 3D spherical structures, arbitrarily defined "epiBlastoids," whose phenotype is remarkably similar to natural embryos. In the first step, adult dermal fibroblasts are converted into trophoblast-like cells, combining the use of 5-azacytidine, to erase the original cell phenotype, with an ad hoc induction protocol, to drive erased cells into the trophoblast lineage. In the second step, once again epigenetic erasing is applied, in combination with mechanosensing-related cues, to generate inner cell mass (ICM)-like spheroids. More specifically, erased cells are encapsulated in micro-bioreactors to promote 3D cell rearrangement and boost pluripotency. In the third step, chemically induced trophoblast-like cells and ICM-like spheroids are co-cultured in the same micro-bioreactors. The newly generated embryoids are then transferred to microwells, to encourage further differentiation and favor epiBlastoid formation. The procedure here described is a novel strategy for in vitro generation of 3D spherical structures, phenotypically similar to natural embryos. The use of easily accessible dermal fibroblasts and the lack of retroviral gene transfection make this protocol a promising strategy to study early embryogenesis as well as embryo disorders.

Rat Plantar Fascia Stem/Progenitor Cells Showed Lower Expression of Ligament Markers and Higher Pro-Inflammatory Cytokines after Intensive Mechanical Loading or Interleukin-1β Treatment In Vitro

The pathogenesis of plantar fasciitis is unclear, which hampers the development of an effective treatment. The altered fate of plantar fascia stem/progenitor cells (PFSCs) under overuse-induced inflammation might contribute to the pathogenesis. This study aimed to isolate rat PFSCs and compared their stem cell-related properties with bone marrow stromal cells (BMSCs). The effects of inflammation and intensive mechanical loading on PFSCs' functions were also examined. We showed that plantar fascia-derived cells (PFCs) expressed common MSC surface markers and embryonic stemness markers. They expressed lower Nanog but higher Oct4 and Sox2, proliferated faster and formed more colonies compared to BMSCs. Although PFCs showed higher chondrogenic differentiation potential, they showed low osteogenic and adipogenic differentiation potential upon induction compared to BMSCs. The expression of ligament markers was higher in PFCs than in BMSCs. The isolated PFCs were hence PFSCs. Both IL-1β and intensive mechanical loading suppressed the mRNA expression of ligament markers but increased the expression of inflammatory cytokines and matrix-degrading enzymes in PFSCs. In summary, rat PFSCs were successfully isolated. They had poor multi-lineage differentiation potential compared to BMSCs. Inflammation after overuse altered the fate and inflammatory status of PFSCs, which might lead to poor ligament differentiation of PFSCs and extracellular matrix degeneration. Rat PFSCs can be used as an in vitro model for studying the effects of intensive mechanical loading-induced inflammation on matrix degeneration and erroneous stem/progenitor cell differentiation in plantar fasciitis.

Combination of epigenetic erasing and mechanical cues to generate human epiBlastoids from adult dermal fibroblasts

PURPOSE

This study is to develop a new protocol that combines the use of epigenetic cues and mechanical stimuli to assemble 3D spherical structures, arbitrarily defined "epiBlastoids," whose phenotype is remarkably similar to natural embryos.

METHODS

A 3-step approach is used to generate epiBlastoids. In the first step, adult dermal fibroblasts are converted into trophoblast (TR)-like cells, combining the use of 5-azacytidine, to erase the original phenotype, with an ad hoc induction protocol, to drive cells towards TR lineage. In the second step, epigenetic erasing is applied once again, in combination with mechanosensing-related cues, to generate inner cell mass (ICM)-like organoids. Specifically, erased cells are encapsulated into micro-bioreactors to promote 3D cell rearrangement and boost pluripotency. In the third step, TR-like cells are co-cultured with ICM-like spheroids in the same micro-bioreactors. Subsequently, the newly generated embryoids are transferred to microwells to favor epiBlastoid formation.

RESULTS

Adult dermal fibroblasts are successfully readdressed towards TR lineage. Cells subjected to epigenetic erasing and encapsulated into micro-bioreactors rearrange in 3D ICM-like structures. Co-culture of TR-like cells and ICM-like spheroids into micro-bioreactors and microwells induces the formation of single structures with uniform shape reminiscent in vivo embryos. CDX2+ cells localized in the out layer of the spheroids, while OCT4+ cells in the inner of the structures. TROP2+ cells display YAP nuclear accumulation and actively transcribed for mature TR markers, while TROP2- cells showed YAP cytoplasmic compartmentalization and expressed pluripotency-related genes.

CONCLUSION

We describe the generation of epiBlastoids that may find useful application in the assisted reproduction field.

Synergistic Effect of miR-200 and Young Extracellular Matrix-based Bio-scaffolds to Reduce Signs of Aging in Senescent Fibroblasts

Aging is defined as a complex, multifaceted degenerative process that causes a gradual decline of physiological functions and a rising mortality risk with time. Stopping senescence or even rejuvenating the body represent one of the long-standing human dreams. Somatic cell nuclear transfer as well as cell reprogramming have suggested the possibility to slow or even reverse signs of aging. We exploited miR-200 family ability to induce a transient high plasticity state in human skin fibroblasts isolated from old individuals and we investigated whether this ameliorates cellular and physiological hallmarks of senescence. In addition, based on the assumption that extracellular matrix (ECM) provides biomechanical stimuli directly influencing cell behavior, we examine whether ECM-based bio-scaffolds, obtained from decellularized ovaries of young swine, stably maintain the rejuvenated phenotype acquired by cells after miR-200 exposure. The results show the existence of multiple factors that cooperate to control a unique program, driving the cell clock. In particular, miR-200 family directly regulates the molecular mechanisms erasing cell senescence. However, this effect is transient, reversible, and quickly lost. On the other hand, the use of an adequate young microenvironment stabilizes the miR-200-mediated rejuvenating effects, suggesting that synergistic interactions occur among molecular effectors and ECM-derived biomechanical stimuli. The model here described is a useful tool to better characterize these complex regulations and to finely dissect the multiple and concurring biochemical and biomechanical cues driving the cell biological clock.

DNA methylation reprogramming provides insights into light-induced anthocyanin biosynthesis in red pear

DNA methylation, an epigenetic mark, is proposed to regulate plant anthocyanin biosynthesis. It well known that light induces anthocyanin accumulation, with bagging treatments commonly used to investigate light-controlled anthocyanin biosynthesis. We studied the DNA methylome landscape during pear skin coloration under various conditions (fruits re-exposed to sunlight after bag removal). The DNA methylation level in gene body/TE and its flanking sequence was generally similar between debagged and bagged treatments, however differentially methylated regions (DMRs) were re-modelled after light-exposure. Both DNA demethylase homologs and the RNA-directed DNA methylation (RdDM) pathways contributed to this re-distribution. A total of 310 DEGs were DMR-associated during light-induced anthocyanin biosynthesis between debagged and bagged treatments. The hypomethylated mCHH context was seen within the promoter of PyUFGT, together with other anthocyanin biosynthesis genes (PyPAL, PyDFR and PyANS). This enhanced transcriptional activation and promoted anthocyanin accumulation after light re-exposure. Unlike previous reports on bud sports, we did not detect DMRs within the MYB10 promoter. Instead, we observed the genome-wide re-distribution of methylation patterns, suggesting different mechanisms underlying methylation patterns of differentially accumulated anthocyanins caused by either bud mutation or environment change. We investigate the dynamic landscape of genome-scale DNA methylation, which is the combined effect of DNA demethylation and RdDM pathway, in the process of light-induced fruit colour formation in pear. This process is regulated by methylation changes on promoter regions of several DEGs. These results provide a DMR-associated DEGs set and new insight into the mechanism of DNA methylation involved in light-induced anthocyanin biosynthesis.

Mesoderm-derived PDGFRA+ cells regulate the emergence of hematopoietic stem cells in the dorsal aorta

Mouse haematopoietic stem cells (HSCs) first emerge at embryonic day 10.5 (E10.5), on the ventral surface of the dorsal aorta, by endothelial-to-haematopoietic transition. We investigated whether mesenchymal stem cells, which provide an essential niche for long-term HSCs (LT-HSCs) in the bone marrow, reside in the aorta-gonad-mesonephros and contribute to the development of the dorsal aorta and endothelial-to-haematopoietic transition. Here we show that mesoderm-derived PDGFRA⁺ stromal cells (Mesp1^der PSCs) contribute to the haemogenic endothelium of the dorsal aorta and populate the E10.5-E11.5 aorta-gonad-mesonephros but by E13.5 were replaced by neural-crest-derived PSCs (Wnt1^der PSCs). Co-aggregating non-haemogenic endothelial cells with Mesp1^der PSCs but not Wnt1^der PSCs resulted in activation of a haematopoietic transcriptional programme in endothelial cells and generation of LT-HSCs. Dose-dependent inhibition of PDGFRA or BMP, WNT and NOTCH signalling interrupted this reprogramming event. Together, aorta-gonad-mesonephros Mesp1^der PSCs could potentially be harnessed to manufacture LT-HSCs from endothelium.

Ovarian Decellularized Bioscaffolds Provide an Optimal Microenvironment for Cell Growth and Differentiation In Vitro

Ovarian failure is the most common cause of infertility. Although numerous strategies have been proposed, a definitive solution for recovering ovarian functions and restoring fertility is currently unavailable. One innovative alternative may be represented by the development of an “artificial ovary” that could be transplanted in patients for re-establishing reproductive activities. Here, we describe a novel approach for successful repopulation of decellularized ovarian bioscaffolds in vitro. Porcine whole ovaries were subjected to a decellularization protocol that removed the cell compartment, while maintaining the macrostructure and microstructure of the original tissue. The obtained bioscaffolds were then repopulated with porcine ovarian cells or with epigenetically erased porcine and human dermal fibroblasts. The results obtained demonstrated that the decellularized extracellular matrix (ECM)-based scaffold may constitute a suitable niche for ex vivo culture of ovarian cells. Furthermore, it was able to properly drive epigenetically erased cell differentiation, fate, and viability. Overall, the method described represents a powerful tool for the in vitro creation of a bioengineered ovary that may constitute a promising solution for hormone and fertility restoration. In addition, it allows for the creation of a suitable 3D platform with useful applications both in toxicological and transplantation studies.

Generation of Trophoblast-Like Cells From Hypomethylated Porcine Adult Dermal Fibroblasts

The first differentiation event in mammalian embryos is the formation of the trophectoderm, which is the progenitor of the outer epithelial components of the placenta, and which supports the fetus during the intrauterine life. However, the epigenetic and paracrine controls at work in trophectoderm differentiation are still to be fully elucidated and the creation of dedicated in vitro models is desirable to increase our understanding. Here we propose a novel approach based on the epigenetic conversion of adult dermal fibroblasts into trophoblast-like cells. The method combines the use of epigenetic erasing with an ad hoc differentiation protocol. Dermal fibroblasts are erased with 5-azacytidine (5-aza-CR) that confers cells a transient high plasticity state. They are then readdressed toward the trophoblast (TR) phenotype, using MEF conditioned medium, supplemented with bone morphogenetic protein 4 (BMP4) and inhibitors of the Activin/Nodal and FGF2 signaling pathways in low O₂ conditions. The method here described allows the generation of TR-like cells from easily accessible material, such as dermal fibroblasts, that are very simply propagated in vitro. Furthermore, the strategy proposed is free of genetic modifications that make cells prone to instability and transformation. The TR model obtained may also find useful application in order to better characterize embryo implantation mechanisms and developmental disorders based on TR defects.

Label-Free Isolation and Single Cell Biophysical Phenotyping Analysis of Primary Cardiomyocytes Using Inertial Microfluidics

To advance the understanding of cardiomyocyte (CM) identity and function, appropriate tools to isolate pure primary CMs are needed. A label-free method to purify viable CMs from mouse neonatal hearts is developed using a simple particle size-based inertial microfluidics biochip achieving purities of over 90%. Purified CMs are viable and retained their identity and function as depicted by the expression of cardiac-specific markers and contractility. The physico-mechanical properties of sorted cells are evaluated using downstream real-time deformability cytometry. CMs exhibited different physico-mechanical properties when compared with non-CMs. Taken together, this CM isolation and phenotyping method could serve as a valuable tool to progress the understanding of CM identity and function, and ultimately benefit cell therapy and diagnostic applications.

Induction of muscle-regenerative multipotent stem cells from human adipocytes by PDGF-AB and 5-azacytidine

Terminally differentiated murine osteocytes and adipocytes can be reprogrammed using platelet-derived growth factor-AB and 5-azacytidine into multipotent stem cells with stromal cell characteristics. We have now optimized culture conditions to reprogram human adipocytes into induced multipotent stem (iMS) cells and characterized their molecular and functional properties. Although the basal transcriptomes of adipocyte-derived iMS cells and adipose tissue-derived mesenchymal stem cells were similar, there were changes in histone modifications and CpG methylation at cis-regulatory regions consistent with an epigenetic landscape that was primed for tissue development and differentiation. In a non-specific tissue injury xenograft model, iMS cells contributed directly to muscle, bone, cartilage, and blood vessels, with no evidence of teratogenic potential. In a cardiotoxin muscle injury model, iMS cells contributed specifically to satellite cells and myofibers without ectopic tissue formation. Together, human adipocyte-derived iMS cells regenerate tissues in a context-dependent manner without ectopic or neoplastic growth.

Use of a PTFE Micro-Bioreactor to Promote 3D Cell Rearrangement and Maintain High Plasticity in Epigenetically Erased Fibroblasts

Phenotype definition is driven by epigenetic mechanisms as well as directly influenced by the cell microenvironment and by biophysical signals deriving from the extracellular matrix. The possibility to interact with the epigenetic signature of an adult mature cell, reversing its differentiated state and inducing a short transient high plasticity window, was previously demonstrated. In parallel, in vitro studies have shown that 3D culture systems, mimicking cell native tissue, exert significant effects on cell behavior and functions. Here we report the production of "PTFE micro-bioreactors" for long-term culture of epigenetically derived high plasticity cells. The system promotes 3D cell rearrangement, global DNA demethylation and elevated transcription of pluripotency markers, that is dependent on WW domain containing transcription regulator 1 (TAZ) nuclear accumulation and SMAD family member 2 (SMAD2) co-shuttling. Our findings demonstrate that the use of 3D culture strategies greatly improves the induction and maintenance of a high plasticity state.

Adding a dimension to cell fate

Cell fate specification, gene expression and spatial restriction are process finely tuned by epigenetic regulatory mechanisms. At the same time, mechanical forces have been shown to be crucial to drive cell plasticity and boost differentiation. Indeed, several studies have demonstrated that transitions along different specification states are strongly influenced by 3D rearrangement and mechanical properties of the surrounding microenvironment, that can modulate both cell potency and differentiation, through the activation of specific mechanosensing-related pathways. An overview of small molecule ability to modulate cell plasticity and define cell fate is here presented and results, showing the possibility to erase the epigenetic signature of adult dermal fibroblasts and convert them into insulin-producing cells (EpiCC) are described. The beneficial effects exerted on such processes, when cells are homed on an adequate substrate, that shows “in vivo” tissue-like stiffness are also discussed and the contribution of the Hippo signalling mechano-transduction pathway as one of the mechanisms involved is examined. In addition, results obtained using a genetically modified fibroblast cell line, expressing the enhanced green fluorescent protein (eGFP) under the control of the porcine insulin gene (INS) promoter (INS-eGFP transgenic pigs), are reported. This model offers the advantage to monitor the progression of cell conversion in real time mode. All these observations have a main role in order to allow a swift scale-up culture procedure, essential for cell therapy and tissue engineering applied to human regenerative medicine, and fundamental to ensure an efficient translation process from the results obtained at the laboratory bench to the patient bedside. Moreover, the creation of reliable in vitro model represents a key point to ensure the development of more physiological models that, in turn, may reduce the number of animals used, implementing non-invasive investigations and animal welfare and protection.

All roads lead to Rome: the many ways to pluripotency

Cell pluripotency, spatial restriction, and development are spatially and temporally controlled by epigenetic regulatory mechanisms that occur without any permanent loss or alteration of genetic material, but rather through modifications "on top of it." These changes modulate the accessibility to transcription factors, either allowing or repressing their activity, thus shaping cell phenotype. Several studies have demonstrated the possibility to interact with these processes, reactivating silenced genes and inducing a high plasticity state, via an active demethylating effect, driven by ten-eleven translocation (TET) enzymes and an overall decrease of global methylation. In agreement with this, TET activities have been shown to be indispensable for mesenchymal to epithelial transition of somatic cells into iPSCs and for small molecule-driven epigenetic erasure. Beside the epigenetic mechanisms, growing evidences highlight the importance of mechanical forces in supporting cell pluripotency, which is strongly influenced by 3D rearrangement and mechanical properties of the surrounding microenvironment, through the activation of specific mechanosensing-related pathways. In this review, we discuss and provide an overview of small molecule ability to modulate cell plasticity and define cell fate through the activation of direct demethylating effects. In addition, we describe the contribution of the Hippo signaling mechanotransduction pathway as one of the mechanisms involved in the maintenance of pluripotency during embryo development and its induction in somatic cells.

The role of DNA demethylation in induction of stem cells

DNA methylation is an epigenetic factor, which plays important roles in embryo and many other diseases development. This factor determines gene expression, and when half of them have CpG islands, DNA methylation and its enzyme effectors have been under the vast studies. Whole genome DNA demethylation is a crucial step of embryogenesis and also cell fate determination in embryos. Therefore, demethylation agents were used as a tool for dedifferentiation and transdifferentiation. Although many of these efforts have been successful, but using this method gave us a vast spectral cell type which is confusing. In this article, we briefly reviewed DNA methylation, and its role in embryogenesis and gene expression. In addition to that, we introduce studies that used this action as a direct method in induction of stem cells and cell fate decision.

New tools for cell reprogramming and conversion: Possible applications to livestock

Somatic cell nuclear transfer and iPS are both forms of radical cell reprogramming able to transform a fully differentiated cell type into a totipotent or pluripotent cell. Both processes, however, are hampered by low efficiency and, in the case of iPS, the application to livestock species is uncertain.

Epigenetic manipulation has recently emerged as an efficient and robust alternative method for cell reprogramming. It is based upon the use of small molecules that are able to modify the levels of DNA methylation with 5-azacitidyne as one of the most widely used. Among a number of advantages, it includes the fact that it can be applied to domestic species including pig, dog and cat.

Treated cells undergo a widespread demethylation which is followed by a renewed methylation pattern induced by specific chemical stimuli that lead to the desired phenotype. A detailed study of the mechanisms of epigenetic manipulation revealed that cell plasticity is achieved through the combined action of a reduced DNA methyl transferase activity with an active demethylation driven by the TET protein family. Surprisingly the same combination of molecular processes leads to the transformation of fibroblasts into iPS and regulate the epigenetic changes that take place during early development and, hence, during reprogramming following SCNT.

Finally, it has recently emerged that mechanic stimuli in the form of a 3D cell rearrangement can significantly enhance the efficiency of epigenetic reprogramming as well as of maintenance of pluripotency. Interestingly these mechanic stimuli act on the same mechanisms both in epigenetic cell conversion with 5-Aza-CR and in iPS.

We suggest that the balanced combination of epigenetic erasing, 3D cell rearrangement and chemical induction can go a long way to obtain ad hoc cell types that can fully exploit the current exiting development brought by gene editing and animal cloning in livestock production.

DNA Methylation-Based Regulation of Human Bone Marrow-Derived Mesenchymal Stem/Progenitor Cell Chondrogenic Differentiation

Stem cells have essential applications in in vitro tissue engineering or regenerative medicine. However, there is still a need to understand more deeply the mechanisms of stem cell differentiation and to optimize the methods to control stem cell function. In this study, we first investigated the activity of DNA methyltransferases (DNMTs) during chondrogenic differentiation of human bone marrow-derived mesenchymal stem/progenitor cells (hBMSCs) and found that DNMT3A and DNMT3B were markedly upregulated during hBMSC chondrogenic differentiation. In an attempt to understand the effect of DNMT3A and DNMT3B on the chondrogenic differentiation of hBMSCs, we transiently transfected the cells with expression vectors for the two enzymes. Interestingly, DNMT3A overexpression strongly enhanced the chondrogenesis of hBMSCs, by increasing the gene expression of the mature chondrocyte marker, collagen type II, more than 200-fold. Analysis of the methylation condition in the cells revealed that DNMT3A and DNMT3B methylated the promoter sequence of early stem cell markers, NANOG and POU5F1(OCT-4). Conversely, the suppression of chondrogenic differentiation and the increase in stem cell markers of hBMSCs were obtained by chemical stimulation with the demethylating agent, 5-azacitidine. Loss-of-function assays with siRNAs targeting DNMT3A also significantly suppressed the chondrogenic differentiation of hBMSCs. Together, these results not only show the critical roles of DNMTs in regulating the chondrogenic differentiation of hBMSCs, but also suggest that manipulation of DNMT activity can be important tools to enhance the differentiation of hBMSCs towards chondrogenesis for potential application in cartilage tissue engineering or cartilage regeneration.

Safety and Efficacy of Epigenetically Converted Human Fibroblasts Into Insulin-Secreting Cells: A Preclinical Study

Type 1 Diabetes Mellitus (T1DM) is a chronic disease that leads to loss of insulin secreting β-cells, causing high levels of blood glucose. Exogenous insulin administration is not sufficient to mimic the normal function of β-cells and, consequently, diabetes mellitus often progresses and can lead to major chronic complications and morbidity. The physiological control of glucose levels can only be restored by replacing the β-cell mass.We recently developed a new strategy that allows for epigenetic conversion of dermal fibroblasts into insulin-secreting cells (EpiCC), using a brief exposure to the demethylating agent 5-aza-cytidine (5-aza-CR), followed by a pancreatic induction protocol. This method has notable advantages compared to the alternative available procedures and may represent a promising tool for clinical translation as a therapy for T1DM. However, a thought evaluation of its therapeutic safety and efficacy is mandatory to support preclinical studies based on EpiCC treatment.We here report the data obtained using human fibroblasts isolated from diabetic and healthy individuals, belonging the two genders. EpiCC were injected into 650 diabetic severe combined immunodeficiency (SCID) mice and demonstrated to be able to restore and maintain glycemic levels within the physiological range. Cells had the ability to self-regulate and not to cause hypoglycemia, when transplanted in healthy animals. Efficacy tests showed that EpiCC successfully re-established normoglycemia in diabetic mice, using a dose range that appeared clinically relevant to the concentration 0.6 × 10⁶ EpiCC. Necropsy and histopathological investigations demonstrated the absence of malignant transformation and cell migration to organs and lymph nodes.The present preclinical study demonstrates safety and efficacy of human EpiCC in diabetic mice and supports the use of epigenetic converted cells for regenerative medicine of diabetes mellitus.

Diversity of dermal fibroblasts as major determinant of variability in cell reprogramming

Induced pluripotent stem cells (iPSCs) are adult somatic cells genetically reprogrammed to an embryonic stem cell-like state. Notwithstanding their autologous origin and their potential to differentiate towards cells of all three germ layers, iPSC reprogramming is still affected by low efficiency. As dermal fibroblast is the most used human cell for reprogramming, we hypothesize that the variability in reprogramming is, at least partially, because of the skin fibroblasts used. Human dermal fibroblasts harvested from five different anatomical sites (neck, breast, arm, abdomen and thigh) were cultured and their morphology, proliferation, apoptotic rate, ability to migrate, expression of mesenchymal or epithelial markers, differentiation potential and production of growth factors were evaluated in vitro. Additionally, gene expression analysis was performed by real-time PCR including genes typically expressed by mesenchymal cells. Finally, fibroblasts isolated from different anatomic sites were reprogrammed to iPSCs by integration-free method. Intriguingly, while the morphology of fibroblasts derived from different anatomic sites differed only slightly, other features, known to affect cell reprogramming, varied greatly and in accordance with anatomic site of origin. Accordingly, difference also emerged in fibroblasts readiness to respond to reprogramming and ability to form colonies. Therefore, as fibroblasts derived from different anatomic sites preserve positional memory, it is of great importance to accurately evaluate and select dermal fibroblast population prior to induce reprogramming.

Cardiotrophic Growth Factor-Driven Induction of Human Muse Cells Into Cardiomyocyte-Like Phenotype

Multilineage-differentiating stress-enduring (Muse) cells are endogenous nontumorigenic stem cells collectable as stage-specific embryonic antigen 3 (SSEA-3) + from various organs including the bone marrow and are pluripotent-like. The potential of human bone marrow-derived Muse cells to commit to cardiac lineage cells was evaluated. We found that (1) initial treatment of Muse cells with 5'-azacytidine in suspension culture successfully accelerated demethylation of cardiac marker Nkx2.5 promoter; (2) then transferring the cells onto adherent culture and treatment with early cardiac differentiation factors including wingless-int (Wnt)-3a, bone morphogenetic proteins (BMP)-2/4, and transforming growth factor (TGF) β1; and (3) further treatment with late cardiac differentiation cytokines including cardiotrophin-1 converted Muse cells into cardiomyocyte-like cells that expressed α-actinin and troponin-I with a striation-like pattern. MLC2a expression in the final step suggested differentiation of the cells into an atrial subtype. MLC2v, a marker for a mature ventricular subtype, was expressed when cells were treated with Dickkopf-related protein 1 (DKK-1) and Noggin, inhibitors of Wnt3a and BMP-4, respectively, between steps (2) and (3). None of the steps included exogenous gene transfection, making induced cells feasible for future clinical application.

Epigenetic Erasing and Pancreatic Differentiation of Dermal Fibroblasts into Insulin-Producing Cells are Boosted by the Use of Low-Stiffness Substrate

Several studies have demonstrated the possibility to revert differentiation process, reactivating hypermethylated genes and facilitating cell transition to a different lineage. Beside the epigenetic mechanisms driving cell conversion processes, growing evidences highlight the importance of mechanical forces in supporting cell plasticity and boosting differentiation. Here, we describe epigenetic erasing and conversion of dermal fibroblasts into insulin-producing cells (EpiCC), and demonstrate that the use of a low-stiffness substrate positively influences these processes. Our results show a higher expression of pluripotency genes and a significant bigger decrease of DNA methylation levels in 5-azacytidine (5-aza-CR) treated cells plated on soft matrix, compared to those cultured on plastic dishes. Furthermore, the use of low-stiffness also induces a significant increased up-regulation of ten-eleven translocation 2 (Tet2) and histone acetyltransferase 1 (Hat1) genes, and more decreased histone deacetylase enzyme1 (Hdac1) transcription levels. The soft substrate also encourages morphological changes, actin cytoskeleton re-organization, and the activation of the Hippo signaling pathway, leading to yes-associated protein (YAP) phosphorylation and its cytoplasmic translocation. Altogether, this results in increased epigenetic conversion efficiency and in EpiCC acquisition of a mono-hormonal phenotype. Our findings indicate that mechano-transduction related responsed influence cell plasticity induced by 5-aza-CR and improve fibroblast differentiation toward the pancreatic lineage.

The journey of cells through regeneration

The process of building an organ, appendage, or organism requires the precise coordination of cells in space and time. Regeneration of those same tissues adds an additional element of complexity, emerging from the chaos of disease or injury to build a mass of progenitors from mature tissue. Translating insights from natural examples of tissue regeneration into engineered regenerative therapies requires a deep understanding of the journey of a cell directly following injury to its contribution to functional, scaled replacement tissue. Here we step through the chronological phases of regeneration and highlight emerging work that brings us closer to elucidating the unique intrinsic and extrinsic properties of cells during epimorphic regeneration.

Platelet-derived growth factor receptor beta identifies mesenchymal stem cells with enhanced engraftment to tissue injury and pro-angiogenic property

Mesenchymal stem cells (MSCs) are heterogeneous likely consisting of subpopulations with various therapeutic potentials. Here we attempted to acquire a subset of MSCs with enhanced effect in wound healing. We found that human placental MSCs expressing platelet-derived growth factor (PDGF) receptor (PDGFR)-β exhibited greater proliferation rates and generated more colony-forming unit-fibroblast (CFU-F), compared to PDGFR-β- MSCs. Notably, PDGFR-β+ MSCs expressed higher levels of pro-angiogenic factors such as Ang1, Ang2, VEGF, bFGF and PDGF. When 106 GFP-expressing MSCs were topically applied into excisional wounds in mice, PDGFR-β+ MSCs actively incorporated into the wound tissue, resulting in enhanced engraftment (3.92 ± 0.31 × 105 remained in wound by 7 days) and accelerated wound closure; meanwhile, PDGFR-β- MSCs tended to remain on the top of the wound bed with significantly fewer cells (2.46 ± 0.26 × 105) engrafted into the wound, suggesting enhanced chemotactic migration and engraftment of PDGFR-β+ MSCs into the wound. Real-Time PCR and immunostain analyses revealed that the expression of PDGF-B was upregulated after wounding; transwell migration assay showed that PDGFR-β+ MSCs migrated eightfold more than PDGFR-β- MSCs toward PDGF-BB. Intriguingly, PDGFR-β+ MSC-treated wounds showed significantly enhanced angiogenesis compared to PDGFR-β- MSC- or vehicle-treated wounds. Thus, our results indicate that PDGFR-β identifies a subset of MSCs with enhanced chemotactic migration to wound injury and effect in promoting angiogenesis and wound healing, implying a greater therapeutic potential for certain diseases.

Nanotechnology for Neuroscience: Promising Approaches for Diagnostics, Therapeutics and Brain Activity Mapping

Unlocking the secrets of the brain is a task fraught with complexity and challenge - not least due to the intricacy of the circuits involved. With advancements in the scale and precision of scientific technologies, we are increasingly equipped to explore how these components interact to produce a vast range of outputs that constitute function and disease. Here, an insight is offered into key areas in which the marriage of neuroscience and nanotechnology has revolutionized the industry. The evolution of ever more sophisticated nanomaterials culminates in network-operant functionalized agents. In turn, these materials contribute to novel diagnostic and therapeutic strategies, including drug delivery, neuroprotection, neural regeneration, neuroimaging and neurosurgery. Further, the entrance of nanotechnology into future research arenas including optogenetics, molecular/ion sensing and monitoring, and piezoelectric effects is discussed. Finally, considerations in nanoneurotoxicity, the main barrier to clinical translation, are reviewed, and direction for future perspectives is provided.

Insight into skin cell-based osteogenesis: a review

For decades, researchers have been fascinated by the strategy of using cell therapy for bone defects; some progress in the field has been made. Owing to its ample supply and easy access, skin, the largest organ in the body, has gained attention as a potential source of stem cells. Despite extensive applications in skin and nerve regeneration, an increasing number of reports indicate its potential use in bone tissue engineering and regeneration. Unfortunately, few review articles are available to outline current research efforts in skin-based osteogenesis. This review first summarizes the latest findings on stem cells or progenitors in skin and their niches and then discusses the strategies of skin cell-based osteogenesis. We hope this article elucidates this topic and generates new ideas for future studies.

Enhanced differentiation of mesenchymal stromal cells by three-dimensional culture and azacitidine

BACKGROUND

Mesenchymal stromal cells (MSCs) are useful for cell therapy because of their potential for multilineage differentiation. However, MSCs that are expanded in traditional two-dimensional (2D) culture systems eventually lose their differentiation abilities. Therefore, we investigated whether azacitidine (AZA) supplementation and three-dimensional culture (3D) could improve the differentiation properties of MSCs.

METHODS

2D- or 3D-cultured MSCs which were prepared according to the conventional or hanging-drop culture method respectively, were treated with or without AZA (1 µM for 72 h), and their osteogenic and adipogenic differentiation potential were determined and compared.

RESULTS

AZA treatment did not affect the cell apoptosis or viability in both 2D- and 3D-cultured MSCs. However, compared to conventionally cultured 2D-MSCs, AZA-treated 2D-MSCs showed marginally increased differentiation abilities. In contrast, 3D-MSCs showed significantly increased osteogenic and adipogenic differentiation ability. When 3D culture was performed in the presence of AZA, the osteogenic differentiation ability was further increased, whereas adipogenic differentiation was not affected.

CONCLUSION

3D culture efficiently promoted the multilineage differentiation of MSCs, and in combination with AZA, it could help MSCs to acquire greater osteogenic differentiation ability. This optimized culture method can enhance the therapeutic potential of MSCs.

The quest for an effective and safe personalized cell therapy using epigenetic tools

In the presence of different environmental cues that are able to trigger specific responses, a given genotype has the ability to originate a variety of different phenotypes. This property is defined as plasticity and allows cell fate definition and tissue specialization. Fundamental epigenetic mechanisms drive these modifications in gene expression and include DNA methylation, histone modifications, chromatin remodeling, and microRNAs. Understanding these mechanisms can provide powerful tools to switch cell phenotype and implement cell therapy. Environmentally influenced epigenetic changes have also been associated to many diseases such as cancer and neurodegenerative disorders, with patients that do not respond, or only poorly respond, to conventional therapy. It is clear that disorders based on an individual's personal genomic/epigenomic profile can rarely be successfully treated with standard therapies due to genetic heterogeneity and epigenetic alterations and a personalized medicine approach is far more appropriate to manage these patients. We here discuss the recent advances in small molecule approaches for personalized medicine, drug targeting, and generation of new cells for medical application. We also provide prospective views of the possibility to directly convert one cell type into another, in a safe and robust way, for cell-based clinical trials and regenerative medicine.

Determination and reduction of translocator protein (TSPO) ligand rs6971 discrimination

The 18 kDa translocator protein (TSPO) is a target for development of diagnostic imaging agents for glioblastoma and neuroinflammation.

The 18 kDa translocator protein (TSPO) is a target for development of diagnostic imaging agents for glioblastoma and neuroinflammation. Clinical translation of TSPO imaging agents has been hindered by the presence of a polymorphism, rs6971, which causes a non-conservative substitution of alanine for threonine at amino acid residue 147 (TSPO A147T). Disclosed brain-permeant second-generation TSPO ligands bind TSPO A147T with reduced affinity compared to the wild type protein (TSPO WT). Efforts to develop a TSPO ligand that binds TSPO WT and TSPO A147T with similarly high affinity have been hampered by a lack of knowledge about how ligand structure differentially influences interaction with the two forms of TSPO. To gain insight, we have established human embryonic kidney cell lines stably over-expressing human TSPO WT and TSPO A147T, and tested how modifications of a novel N-alkylated carbazole scaffold influence affinity to both TSPO isoforms. Most of the new analogues developed in this study showed high affinity to TSPO WT and a 5–6-fold lower affinity to TSPO A147T. Addition of electron-withdrawing substituents yielded analogues with highest affinity for TSPO A147T without decreasing affinity for TSPO WT. This knowledge can be used to inform further development of non-discriminating TSPO ligands for use as diagnostic markers for glioblastoma and neuroinflammation irrespective of rs6971.

5-azacytidine affects TET2 and histone transcription and reshapes morphology of human skin fibroblasts

Phenotype definition is controlled by epigenetic regulations that allow cells to acquire their differentiated state. The process is reversible and attractive for therapeutic intervention and for the reactivation of hypermethylated pluripotency genes that facilitate transition to a higher plasticity state. We report the results obtained in human fibroblasts exposed to the epigenetic modifier 5-azacytidine (5-aza-CR), which increases adult cell plasticity and facilitates phenotype change. Although many aspects controlling its demethylating action have been widely investigated, the mechanisms underlying 5-aza-CR effects on cell plasticity are still poorly understood. Our experiments confirm decreased global methylation, but also demonstrate an increase of both Formylcytosine (5fC) and 5-Carboxylcytosine (5caC), indicating 5-aza-CR ability to activate a direct and active demethylating effect, possibly mediated via TET2 protein increased transcription. This was accompanied by transient upregulation of pluripotency markers and incremented histone expression, paralleled by changes in histone acetylating enzymes. Furthermore, adult fibroblasts reshaped into undifferentiated progenitor-like phenotype, with a sparse and open chromatin structure. Our findings indicate that 5-aza-CR induced somatic cell transition to a higher plasticity state is activated by multiple regulations that accompany the demethylating effect exerted by the modifier.