Large-scale perturbation atlases have transformed systems biology, yet no equivalent resource exists for the human heart, where contractile function and transcriptomic state must be measured together. Here, we establish Cardiopedia-Ligand, a comprehensive perturbation-function-transcriptome atlas generated by stimulating human cardiac organoids (hCOs) with 87 ligands targeting 98 cell-membrane receptors expressed in the human heart. We developed an automated high-throughput pipeline enabling individualized contractility measurements and single-organoid mRNA sequencing. We use this pipeline to define both recognized and previously unrecognized functional and transcriptional clusters, including inotropes, endothelin peptides, extracellular matrix regulators, and multiple inflammatory clusters. Clustering analysis, machine learning, and the "fingerprinting" of human heart failure biopsies revealed previously underappreciated similarities between ligands and an interferon-γ signaling signature driving heart failure with preserved ejection fraction (HFpEF). Together, this comprehensive Cardiopedia-Ligand dataset provides a valuable and accessible resource for interrogating cardiac biology and human disease.

Myocardial ischemia-reperfusion (MIR) injury drives adverse remodeling and heart failure after ST-elevation myocardial infarction (STEMI), yet no therapy directly targets the fibrotic response. Here, we developed a good manufacturing practice-compatible extracellular vesicle (EV)-enriched secretome from bone marrow mesenchymal stromal cells and identified a laminin-521-based production strategy suitable for clinical translation. The EV-enriched secretome exhibited in vitro immunomodulatory activity, and in murine MIR-injury models, treatment preserved left ventricular ejection fraction, reduced platelet-derived growth factor receptor beta (PDGFRβ)-associated myofibroblast activation quantified by positron emission tomography (PET) imaging, attenuated fibrosis, and promoted reparative macrophage polarization. In a clinically relevant porcine ischemia-reperfusion model, intracoronary administration was cardioprotective. We further developed a clinically approved PDGFRβ-targeted PET-imaging platform for longitudinal assessment of fibrotic activity in STEMI patients, where preliminary observations suggest that myofibroblast activation persists for up to 2 months after STEMI in selected patients. Together, these findings establish a translational therapeutic-diagnostic framework for individualized management of MIR injury.

Fetal tissue transplantation established proof-of-concept for dopamine cell replacement in Parkinson's disease but yielded inconsistent outcomes due to limited tissue availability and cellular heterogeneity. Advances in generating high-purity dopamine progenitors from pluripotent stem cells have enabled standardized products that show safety and motor improvement in clinical trials. However, these trials revealed divergent outcomes arising at three levels: between clinical studies, driven by differences in cell products, baseline patient characteristics, or immunosuppressants; between patients, influenced by alloimmune factors, genetic background, or co-pathology; and within patients, where graft survival varies across transplantation sites due to the local microenvironment or surgical technique.

Using a xenogeneic reconstituted testis transplanted beneath the kidney capsule, Whelan et al. advance human and rhesus macaque pluripotent stem cell-derived germ cells beyond fetal prospermatogonia.[1] Their study highlights developmental time, niche organization, and lineage history as central challenges for reconstructing faithful primate gametogenesis.

The prognosis for heart failure (HF) with preserved ejection fraction (HFpEF) remains poor, with treatment evidence and studies at the human cellular level limited. Here, we aimed to model HFpEF-associated diastolic dysfunction in vitro by generating human engineered heart tissues (hEHTs) using human induced pluripotent stem cells and culturing the tissues under high fatty acid and L-N[G]-nitroarginine methyl ester supplementation. Medium-loaded hEHTs showed a marked reduction in relaxation function while preserving contraction function; secreted high levels of the HF marker, BNP; exhibited abnormal calcium transients; and showed structural and functional features of HF. After treatment with several existing HF drugs, a sodium-glucose cotransporter 2 inhibitor (SGLT2i) improved the decline in relaxation function and contributed to an improvement in the diastolic dysfunction phenotype. This mechanism exhibited an anti-inflammatory effect mediated by the recovery of the eNOS-NO-cGMP-PKG signaling pathway. These findings serve as a basis for elucidating the pathogenesis and mechanisms of improvement in HFpEF.

Bone marrow aging compromises hematopoiesis and immunity, yet whether these processes are modifiable in primates remains unexplored. Here, we map the single-cell transcriptomic landscape of primate bone marrow aging and demonstrate that long-term oral vitamin C (VC) supplementation attenuates selected molecular and progenitor-level decline. Aging drives severe common lymphoid progenitor (CLP) depletion, myeloid-biased hematopoietic stem and progenitor cell (HSPC) output, and anatomical site-specific molecular adaptations. VC administration partially offsets these phenotypes, expanding the CLP pool and rebalancing lineage commitment trajectories. This aligns with a ∼4-year reduction in transcriptomic age estimates, cross-validated by an epigenetic clock. Cell-cell communication analyses revealed that VC remodels intercellular signaling, nominating a VC-responsive, progranulin (GRN)-linked candidate pathway. In parallel, human in vitro assays demonstrate that recombinant progranulin mirrors selected VC-associated molecular actions. Collectively, these findings delineate the molecular architecture of primate bone marrow aging and nominate modifiable pathways for further investigation.

Failures in germline development drive male infertility, but the lack of model systems that recapitulate human spermatogenesis hampers therapeutic development. Here, we develop a system to differentiate human-induced pluripotent stem cells (iPSCs) into primordial germ cell-like cells that self-organize with mouse fetal testicular cells into seminiferous tubule-like structures within a xenogeneic reconstituted testis (xrTestis). Subsequent transplantation of xrTestes into immunodeficient mice results in efficient generation of male germ cells up to meiotic onset, including spermatogonia with evidence of prepachytene PIWI-interacting RNA (piRNA) biogenesis, as well as differentiating spermatogonia and rare preleptotene spermatocytes exhibiting transcriptomic and phenotypic similarities to their in vivo counterparts. As future clinical applications will require testing in non-human primates, we apply a similar strategy to differentiate rhesus iPSCs through fetal germ cell stages into spermatogonia and differentiating spermatogonia. Together, these platforms provide a foundation for studying primate germ cell lineages and represent a step toward in vitro gametogenesis.

Chimeric antigen receptor (CAR) T cell therapy faces challenges, such as tumor relapse due to antigen loss and poor CAR T cell expansion in vivo. Optimal tonic signaling (spontaneous CAR signaling) is crucial for CAR T cell fitness and antitumor function, requiring precise calibration to avoid dysfunction or exhaustion. Although CAR phase separation can enhance CAR clustering and tonic signaling to improve cytotoxicity and antigen sensitivity, constitutively high signaling could lead to potential side effects, including cytokine storm and neuronal toxicity. To overcome this limitation, we developed a drug-inducible phase-separation CAR (iPhase-CAR) system utilizing FDA-approved fulvestrant and an engineered estrogen receptor α (ERα) mutant as the drug-inducible phase-separation (DiPS) module. Incorporating the DiPS module into CARs enables drug-inducible clustering of CARs on T cell membranes. iPhase-CAR T cells demonstrate superior antitumor function. This system provides quantitative, reversible promotion of CAR T effector functions, enabling precise control over therapeutic efficacy only upon administration of the FDA-approved drug.

Chronic stress influences hematopoietic stem cells (HSCs). However, how psychological stress regulates HSC function remains incompletely understood. Here, we show that psychological stress impairs HSC self-renewal and lymphoid differentiation, inducing aging-like phenotypes. Stress suppresses neuronal activity in the medial prefrontal cortex (mPFC) and periaqueductal gray (PAG), leading to HSC dysfunction, whereas chemogenetic activation of these regions restores HSC function. Psychological stress or chemogenetic inhibition of the mPFC and PAG reduces the abundance of L. reuteri in the gut microbiota and lowers spermidine levels. Mechanistically, spermidine depletion suppresses mitochondrial autophagy, promotes mitochondrial peroxidative stress, and increases ferroptotic stress in HSCs. We further demonstrate that mPFC and PAG activity regulate the intestinal environment through a sympathetic pathway, reducing intestinal mucin levels, L. reuteri abundance, and spermidine levels. These findings identify a brain-gut-bone marrow axis linking psychological stress to aging-like HSC dysfunction through sympathetic regulation of intestinal microbiota and spermidine metabolism.

Despite rapid advances in human stem cell-based embryo model (SCBEM) research, national regulatory frameworks remain limited. On April 1, 2026, Japan implemented revised guidelines extending their scope to encompass human SCBEM research. We examine the revisions, differences from ISSCR guidelines, and practical challenges arising during the international regulatory transition period.

Wang et al. engineer mammary organoids as anticancer drug-secreting depots that inhibit post-surgical tumor recurrence and regenerate functional mammary gland tissue.[1] This work extends the therapeutic utility of organoids beyond tissue reconstruction into living therapeutic depots, establishing a strategy to exploit intrinsic physiological processes of the organoids for therapeutic intervention.

In a long-term follow-up of a phase 1/2 clinical trial, Stuart Forbes and colleagues demonstrate that autologous macrophage therapy improves transplantation-free survival in patients with liver cirrhosis. These findings show the translational value of autologous macrophage-based regenerative therapy for advanced liver diseases.

Two studies[1][,][2] published in the last issue of Cell Stem Cell reveal that leukemic stem cell (LSC) identity in acute myeloid leukemia (AML) encodes both anti-apoptotic dependencies and metabolic survival programs. They reframe LSC-directed therapy: eradication may require combinatorial targeting of BCL-2 family proteins and ferroptosis-suppressive ketogenesis in a cell-state-specific manner.

Hematopoietic stem cells integrate local and systemic cues to sustain blood homeostasis. In this issue of Cell Stem Cell, Tian et al.1 uncover a stress-responsive brain-gut-bone marrow axis that drives aging-like dysfunction of hematopoietic stem cells.

Understanding the cellular diversity of the human hypothalamus has been limited by the lack of accessible models. In this issue of Cell Stem Cell, Abay-Nørgaard et al.[1] demonstrate that temporal control of BMP signaling during human pluripotent stem cell differentiation generates diverse hypothalamic populations, providing a platform to study human hypothalamic development and function.