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There is much interest in the applications of pluripotent stem cells for regenerative medicine. In this Perspective, the authors discuss the factors that might contribute to the potential risk of tumorigenicity from pluripotent stem cell therapies. They also outline recent developments in techniques that allow the sorting of tumorigenic species from nontumorigenic cells and offer a viewpoint into the future hurdles for moving pluripotent stem cell–based therapies from bench to bedside. Human pluripotent stem cells (PSCs) are a leading candidate for cell-based therapies because of their capacity for unlimited self renewal and pluripotent differentiation. These advances have recently culminated in the first-in-human PSC clinical trials by Geron, Advanced Cell Technology and the Kobe Center for Developmental Biology for the treatment of spinal cord injury and macular degeneration. Despite their therapeutic promise, a crucial hurdle for the clinical implementation of human PSCs is their potential to form tumors in vivo . In this Perspective, we present an overview of the mechanisms underlying the tumorigenic risk of human PSC–based therapies and discuss current advances in addressing these challenges.

The recent success of mRNA therapeutics against pathogenic infections has increased interest in their use for other human diseases including cancer. However, the precise delivery of the genetic cargo to cells and tissues of interest remains challenging. Here, we show an adaptive strategy that enables the docking of different targeting ligands onto the surface of mRNA-loaded small extracellular vesicles (sEVs). This is achieved by using a microfluidic electroporation approach in which a combination of nano- and milli-second pulses produces large amounts of IFN-γ mRNA-loaded sEVs with CD64 overexpressed on their surface. The CD64 molecule serves as an adaptor to dock targeting ligands, such as anti-CD71 and anti-programmed cell death-ligand 1 (PD-L1) antibodies. The resulting immunogenic sEVs (imsEV) preferentially target glioblastoma cells and generate potent antitumour activities in vivo, including against tumours intrinsically resistant to immunotherapy. Together, these results provide an adaptive approach to engineering mRNA-loaded sEVs with targeting functionality and pave the way for their adoption in cancer immunotherapy applications. There is an emerging interest in the use of mRNA therapeutics in cancer treatment, but their precise in vivo delivery remains a challenge. Here the authors develop IFN-γ mRNA-loaded small extracellular vesicles (sEVs) with CD64 overexpressed on their surface and demonstrate its efficacy in glioblastoma mouse models resistant to immunotherapy.

Tumour cell phagocytosis by antigen presenting cells (APCs) is critical to the generation of antitumour immunity. However, cancer cells can evade phagocytosis by upregulating anti-phagocytosis molecule CD47. Here, we show that CD47 blockade alone is inefficient in stimulating glioma cell phagocytosis. However, combining CD47 blockade with temozolomide results in a significant pro-phagocytosis effect due to the latter’s ability to induce endoplasmic reticulum stress response. Increased tumour cell phagocytosis subsequently enhances antigen cross-presentation and activation of cyclic GMP-AMP synthase–stimulator of interferon genes (cGAS–STING) in APCs, resulting in more efficient T cell priming. This bridging of innate and adaptive responses inhibits glioma growth, but also activates immune checkpoint. Sequential administration of an anti-PD1 antibody overcomes this potential adaptive resistance. Together, these findings reveal a dynamic relationship between innate and adaptive immune regulation in tumours and support further investigation of phagocytosis modulation as a strategy to enhance cancer immunotherapy responses. Professional antigen presenting cells (APCs) are deterred from phagocytosing cancer cells that express CD47. Here, the authors show that in glioblastoma mouse models, temozolomide improves the phagocytosis effect of CD47 blockade in APCs and results in the activation of adaptive anti-tumour responses.

Exosomes are attractive as nucleic-acid carriers because of their favourable pharmacokinetic and immunological properties and their ability to penetrate physiological barriers that are impermeable to synthetic drug-delivery vehicles. However, inserting exogenous nucleic acids, especially large messenger RNAs, into cell-secreted exosomes leads to low yields. Here we report a cellular-nanoporation method for the production of large quantities of exosomes containing therapeutic mRNAs and targeting peptides. We transfected various source cells with plasmid DNAs and stimulated the cells with a focal and transient electrical stimulus that promotes the release of exosomes carrying transcribed mRNAs and targeting peptides. Compared with bulk electroporation and other exosome-production strategies, cellular nanoporation produced up to 50-fold more exosomes and a more than 10 3 -fold increase in exosomal mRNA transcripts, even from cells with low basal levels of exosome secretion. In orthotopic phosphatase and tensin homologue (PTEN)-deficient glioma mouse models, mRNA-containing exosomes restored tumour-suppressor function, enhanced inhibition of tumour growth and increased survival. Cellular nanoporation may enable the use of exosomes as a universal nucleic-acid carrier for applications requiring transcriptional manipulation. A cellular-nanoporation method produces large quantities of exosomes containing therapeutic mRNAs and targeting peptides that restore tumour-suppressor function in mice with orthotopically implanted phosphatase and tensin homologue (PTEN)-deficient brain gliomas.

Pancreatic ductal adenocarcinoma (PDAC) tumours carry multiple gene mutations and respond poorly to treatments. There is currently an unmet need for drug carriers that can deliver multiple gene cargoes to target high solid tumour burden like PDAC. Here, we report a dual targeted extracellular vesicle (dtEV) carrying high loads of therapeutic RNA that effectively suppresses large PDAC tumours in mice. The EV surface contains a CD64 protein that has a tissue targeting peptide and a humanized monoclonal antibody. Cells sequentially transfected with plasmid DNAs encoding for the RNA and protein of interest by Transwell®-based asymmetric cell electroporation release abundant targeted EVs with high RNA loading. Together with a low dose chemotherapy drug, Gemcitabine, dtEVs suppress large orthotopic PANC-1 and patient derived xenograft tumours and metastasis in mice and extended animal survival. Our work presents a clinically accessible and scalable way to produce abundant EVs for delivering multiple gene cargoes to large solid tumours. KRAS G12D mutations frequently co-occur with mutated TP53 tumour suppressor in patients with pancreatic ductal adenocarcinoma (PDAC). Here the authors report the design of dual targeted therapeutic extracellular vesicles containing high copy numbers of TP53 mRNA and siKRAS G12D , showing anti-tumor activity in PDAC preclinical models.

Regenerative medicine in tissue engineering often relies on stem cells and specific growth factors at a supraphysiological dose. These approaches are costly and may cause severe side effects. Herein, therapeutic small extracellular vesicles (t‐sEVs) endogenously loaded with a cocktail of human vascular endothelial growth factor A (VEGF‐A) and human bone morphogenetic protein 2 (BMP‐2) mRNAs within a customized injectable PEGylated poly (glycerol sebacate) acrylate (PEGS‐A) hydrogel for bone regeneration in rats with challenging femur critical‐size defects are introduced. Abundant t‐sEVs are produced by a facile cellular nanoelectroporation system based on a commercially available track‐etched membrane (TM‐nanoEP) to deliver plasmid DNAs to human adipose‐derived mesenchymal stem cells (hAdMSCs). Upregulated microRNAs associated with the therapeutic mRNAs are enriched in t‐sEVs for enhanced angiogenic–osteogenic regeneration. Localized and controlled release of t‐sEVs within the PEGS‐A hydrogel leads to the retention of therapeutics in the defect site for highly efficient bone regeneration with minimal low accumulation in other organs. This study describes an easily scalable and cost‐effective method to produce abundant therapeutic small extracellular vesicles (t‐sEVs) carrying a cocktail of functional mRNAs (VEGF‐A and BMP‐2) within a customized injectable PEGylated poly (glycerol sebacate) acrylate (PEGS‐A) hydrogel cage for coupling bone regeneration in rats that have challenging femur critical‐size defects.

Human induced pluripotent stem cells (hiPSCs) and human embryonic stem cells (hESCs) are promising candidate cell sources for regenerative medicine. However, despite the common ability of hiPSCs and hESCs to differentiate into all 3 germ layers, their functional equivalence at the single cell level remains to be demonstrated. Moreover, single cell heterogeneity amongst stem cell populations may underlie important cell fate decisions. Here, we used single cell analysis to resolve the gene expression profiles of 362 hiPSCs and hESCs for an array of 42 genes that characterize the pluripotent and differentiated states. Comparison between single hESCs and single hiPSCs revealed markedly more heterogeneity in gene expression levels in the hiPSCs, suggesting that hiPSCs occupy an alternate, less stable pluripotent state. hiPSCs also displayed slower growth kinetics and impaired directed differentiation as compared with hESCs. Our results suggest that caution should be exercised before assuming that hiPSCs occupy a pluripotent state equivalent to that of hESCs, particularly when producing differentiated cells for regenerative medicine aims.

Studies in mice have shown that thymic-derived CD4+ CD25+ regulatory T cells (T reg; FOXP3 + lymphocytes) inhibit an antitumour immune response. Additional studies have also reported that the T reg population increases in peripheral blood and tumour tissues from patients with cancer. However, the relationship between the T reg population and the patient prognosis remains controversial. Our aim was to determine the prognostic value of T reg cell density in breast cancer using immunohistochemical assessment of FOXP3, which has been shown to be the optimal marker for T regs. Tissue microarrays were used, and the density of FOXP3 + cells was determined in a series of 1445 cases of well-characterised primary invasive breast carcinoma cases with long-term follow up. FOXP3 + cell numbers were counted in tumour nests, in tumour-adjacent stroma, and in distant stroma. The total number of FOXP3 + cells significantly correlated with higher tumour grade ( r s  = 0.37, P  < 0.001) and ER negativity (Mann–Whitney U test, P  < 0.001). In addition, FOXP3 infiltration positively correlated with HER2 expression and basal phenotype subclass. On univariate analysis, FOXP3 + cells were associated with a worse prognosis ( P  = 0.012, log rank = 6.36). This association was found for intratumoural FOXP3 + and for tumour-adjacent stromal FOXP3 + -cells (tumour-cell associated FOXP3, P  = 0.001 and log rank 10.35). However, the number of FOXP3 + cells was not found to be an independent prognostic factor in multivariate analysis. We therefore conclude that FOXP3 + infiltrating cells do not have a dominant role in breast cancer prognosis and suggest that other inflammatory cell subsets may be more critical variables.

The capacity of the brain to compensate for insults during development depends on the type of cell loss, whereas the consequences of genetic mutations in the same neurons are difficult to predict. We reveal powerful compensation from outside the mouse cerebellum when the excitatory cerebellar output neurons are ablated embryonically and demonstrate that the main requirement for these neurons is for motor coordination and not basic learning and social behaviors. In contrast, loss of the homeobox transcription factors Engrailed1/2 (EN1/2) in the cerebellar excitatory lineage leads to additional deficits in adult learning and spatial working memory, despite half of the excitatory output neurons being intact. Diffusion MRI indicates increased thalamo-cortico-striatal connectivity in En1/2 mutants, showing that the remaining excitatory neurons lacking En1/2 exert adverse effects on extracerebellar circuits regulating motor learning and select non-motor behaviors. Thus, an absence of cerebellar output neurons is less disruptive than having cerebellar genetic mutations. The capacity of the brain to compensate for insults during development depends on the type of cell loss. Here authors reveal that embryonic ablation of cerebellar output neurons leads to powerful compensation by extra-cerebellar circuits, whereas mutations ( En1/2 ) disrupt extra-cerebellar circuits regulating non-motor behaviors.

Background Acute lung injury (ALI) is a life-threatening respiratory condition characterized by severe inflammation and lung tissue damage, frequently causing rapid respiratory failure and long-term complications. The microRNA let-7a-5p is involved in the progression of lung injury, inflammation, and fibrosis by regulating immune cell activation and cytokine production. This study aims to use an innovative cellular electroporation platform to generate extracellular vesicles (EVs) carring let-7a-5p (EV- let-7a-5p ) derived from transfected Wharton’s jelly-mesenchymal stem cells (WJ-MSCs) as a potential gene therapy for ALI. Methods A cellular nanoporation (CNP) method was used to induce the production and release of EV- let-7a-5p from WJ-MSCs transfected with the relevant plasmid DNA. EV- let-7a-5p in the conditioned medium were isolated using a tangential flow filtration (TFF) system. EV characterization followed the minimal consensus guidelines outlined by the International Society for Extracellular Vesicles. We conducted a thorough set of therapeutic assessments, including the antifibrotic effects using a transforming growth factor beta (TGF-β)-induced cell model, the modulation effects on macrophage polarization, and the influence of EV- let-7a-5p in a rat model of hyperoxia-induced ALI. Results The CNP platform significantly increased EV secretion from transfected WJ-MSCs, and the encapsulated let-7a-5p in engineered EVs was markedly higher than that in untreated WJ-MSCs. These EV- let-7a-5p did not influence cell proliferation and effectively mitigated the TGF-β-induced fibrotic phenotype by downregulating SMAD2/3 phosphorylation in LL29 cells. Furthermore, EV- let-7a-5p regulated M2-like macrophage activation in an inflammatory microenvironment and significantly induced interleukin (IL)-10 secretion, demonstrating their modulatory effect on inflammation. Administering EVs from untreated WJ-MSCs slightly improved lung function and increased let-7a-5p expression in plasma in the hyperoxia-induced ALI rat model. In comparison, EV- let-7a-5p significantly reduced macrophage infiltration and collagen deposition while increasing IL-10 expression, causing a substantial improvement in lung function. Conclusion This study reveals that the use of the CNP platform to stimulate and transfect WJ-MSCs could generate an abundance of let-7a-5p -enriched EVs, which underscores the therapeutic potential in countering inflammatory responses, fibrotic activation, and hyperoxia-induced lung injury. These results provide potential avenues for developing innovative therapeutic approaches for more effective interventions in ALI.