H1FOO-DD promotes efficiency and uniformity in reprogramming to naive pluripotency.

Heterogeneity among both primed and naive pluripotent stem cell lines remains a major unresolved problem. Here we show that expressing the maternal-specific linker histone H1FOO fused to a destabilizing domain (H1FOO-DD), together with OCT4, SOX2, KLF4, and LMYC, in human somatic cells improves the quality of reprogramming to both primed and naive pluripotency. H1FOO-DD expression was associated with altered chromatin accessibility around pluripotency genes and with suppression of the innate immune response. Notably, H1FOO-DD generates naive induced pluripotent stem cells with lower variation in transcriptome and methylome among clones and a more uniform and superior differentiation potency. Furthermore, we elucidated that upregulation of FKBP1A, driven by these five factors, plays a key role in H1FOO-DD-mediated reprogramming.

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

BACKGROUND: Human induced pluripotent stem cells (iPSCs) are expected to be useful for regenerative medicine for many diseases. Many researchers have focused on and enabled the generation of differentiated cells or tissue-like structures, including organoids, which help to ameliorate target diseases. To promote such cell therapies, we established a clinically applicable iPSC haplobank matching as many people as possible in Japan. METHODS: Through cooperation with several organizations, we recruited donors whose human leukocyte antigens (HLAs) involved in immunorejection were homozygous. The peripheral or umbilical cord blood collected from the donors was used for iPSC production by electroporation of episomal vectors. These iPSC lines were then subjected to testing, including genome analyses and sterility, to maximize safety. FINDINGS: We constructed a clinical-grade haplobank of 27 iPSC lines from 7 donors according to good manufacturing practice regulations. However, reasons to avoid using iPSC lines include the presence of residual episomal vectors or genetic mutations in cancer-related genes. CONCLUSIONS: This haplobank provides HLA-matched iPSC lines for approximately 40% of the Japanese population. Since the haplobank's release in 2015, these iPSC lines have been used in more than 10 clinical trials. The establishment of this haplobank is an important step toward the clinical application of iPSCs in cell therapies. FUNDING: This study was supported by a research center network for the realization of regenerative medicine of the Japan Agency for Medical Research and Development (AMED) under grant number JP20bm0104001h0108.

Improved Sendai viral system for reprogramming to naive pluripotency.

Naive human induced pluripotent stem cells (iPSCs) can be generated by reprogramming somatic cells with Sendai virus (SeV) vectors. However, only dermal fibroblasts have been successfully reprogrammed this way, and the process requires culture on feeder cells. Moreover, SeV vectors are highly persistent and inhibit subsequent differentiation of iPSCs. Here, we report a modified SeV vector system to generate transgene-free naive human iPSCs with superior differentiation potential. The modified method can be applied not only to fibroblasts but also to other somatic cell types. SeV vectors disappear quickly at early passages, and this approach enables the generation of naive iPSCs in a feeder-free culture. The naive iPSCs generated by this method show better differentiation to trilineage and extra-embryonic trophectoderm than those derived by conventional methods. This method can expand the application of iPSCs to research on early human development and regenerative medicine.

Generation of hypoimmunogenic induced pluripotent stem cells by CRISPR-Cas9 system and detailed evaluation for clinical application.

In order to expand the promise of regenerative medicine using allogeneic induced pluripotent stem cells (iPSCs), precise and efficient genome editing of human leukocyte antigen (HLA) genes would be advantageous to minimize the immune rejection caused by mismatches of HLA type. However, clinical-grade genome editing of multiple HLA genes in human iPSC lines remains unexplored. Here, we optimized the protocol for good manufacturing practice (GMP)-compatible CRISPR-Cas9 genome editing to deplete the three gene locus (HLA-A, HLA-B, and CIITA genes) simultaneously in HLA homozygous iPSCs. The use of HLA homozygous iPSCs has one main advantage over heterozygous iPSCs for inducing biallelic knockout by a single gRNA. RNA-seq and flow cytometry analyses confirmed the successful depletion of HLAs, and lineage-specific differentiation into cardiomyocytes was verified. We also confirmed that the pluripotency of genome-edited iPSCs was successfully maintained by the three germ layers of differentiation. Moreover, whole-genome sequencing, karyotyping, and optical genome mapping analyses revealed no evident genomic abnormalities detected in some clones, whereas unexpected copy number losses, chromosomal translocations, and complex genomic rearrangements were observed in other clones. Our results indicate the importance of multidimensional analyses to ensure the safety and quality of the genome-edited cells. The manufacturing and assessment pipelines presented here will be the basis for clinical-grade genome editing of iPSCs.

Grafting of iPS cell-derived tenocytes promotes motor function recovery after Achilles tendon rupture.

Tendon self-renewal is a rare occurrence because of the poor vascularization of this tissue; therefore, reconstructive surgery using autologous tendon is often performed in severe injury cases. However, the post-surgery re-injury rate is relatively high, and the collection of autologous tendons leads to muscle weakness, resulting in prolonged rehabilitation. Here, we introduce an induced pluripotent stem cell (iPSC)-based technology to develop a therapeutic option for tendon injury. First, we derived tenocytes from human iPSCs by recapitulating the normal progression of step-wise narrowing fate decisions in vertebrate embryos. We used single-cell RNA sequencing to analyze the developmental trajectory of iPSC-derived tenocytes. We demonstrated that iPSC-tenocyte grafting contributed to motor function recovery after Achilles tendon injury in rats via engraftment and paracrine effects. The biomechanical strength of regenerated tendons was comparable to that of healthy tendons. We suggest that iPSC-tenocytes will provide a therapeutic option for tendon injury.

Presynaptic dysregulation of the paraventricular thalamic nucleus causes depression-like behavior.

The paraventricular thalamic nucleus (PVT) is a part of epithalamus and sends outputs to emotion-related brain areas such as the medial prefrontal cortex, nucleus accumbens, and amygdala. Various functional roles of the PVT in emotion-related behaviors are drawing attention. Here, we investigated the effect of manipulation of PVT neurons on the firing patterns of medial prefrontal cortical (mPFC) neurons and depression-like behavior. Extracellular single-unit recordings revealed that acute activation of PVT neurons by hM3Dq, an activation type of designer receptors exclusively activated by designer drugs (DREADDs), and administration of clozapine N-oxide (CNO) caused firing rate changes in mPFC neurons. Moreover, chronic presynaptic inhibition in PVT neurons by tetanus toxin (TeTX) increased the proportion of interneurons among firing neurons in mPFC and shortened the immobility time in the forced swimming test, whereas long-term activation of PVT neurons by hM3Dq caused recurrent hypoactivity episodes. These findings suggest that PVT neurons regulate the excitation/inhibition balance in the mPFC and mood stability.

Ant1 mutant mice bridge the mitochondrial and serotonergic dysfunctions in bipolar disorder.

Although mitochondrial and serotonergic dysfunctions have been implicated in the etiology of bipolar disorder (BD), the relationship between these unrelated pathways has not been elucidated. A family of BD and chronic progressive external ophthalmoplegia (CPEO) caused by a mutation of the mitochondrial adenine nucleotide translocator 1 (ANT1, SLC25A4) implicated that ANT1 mutations confer a risk of BD. Here, we sequenced ANT1 in 324 probands of NIMH bipolar disorder pedigrees and identified two BD patients carrying heterozygous loss-of-function mutations. Behavioral analysis of brain specific Ant1 heterozygous conditional knockout (cKO) mice using lntelliCage showed a selective diminution in delay discounting. Delay discounting is the choice of smaller but immediate reward than larger but delayed reward and an index of impulsivity. Diminution of delay discounting suggests an increase in serotonergic activity. This finding was replicated by a 5-choice serial reaction time test. An anatomical screen showed accumulation of COX (cytochrome c oxidase) negative cells in dorsal raphe. Dorsal raphe neurons in the heterozygous cKO showed hyperexcitability, along with enhanced serotonin turnover in the nucleus accumbens and upregulation of Maob in dorsal raphe. These findings altogether suggest that mitochondrial dysfunction as the genetic risk of BD may cause vulnerability to BD by altering serotonergic neurotransmission.

Lunatic fringe potentiates Notch signaling in the developing brain.

Notch signaling is essential for the self-renewal of mammalian neural progenitor cells. A variety of mechanisms modulate Notch signaling to balance the self-renewal and differentiation of progenitor cells. Fringe is a major Notch regulator and promotes or suppresses Notch signaling, depending on the Notch ligands. In the developing brain, Lunatic fringe (Lfng) is expressed in self-renewing progenitors, but its roles are unknown. In this study, in vivo mosaic analyses using in utero electroporation were developed to investigate the roles of Lfng in neural progenitor cells. We found that Lfng potentiates Notch signaling cell-autonomously. Its depletion did not affect the balance between neuronally committed cells and self-renewing progenitors, however, irrespective of the cell density of Lfng-depleted cells, and caused no obvious defects in brain development. In vivo overexpression experiments with Notch ligands suggest that Lfng strongly augments Notch signaling mediated by Delta-like 1 but not Jagged 1.