Human induced pluripotent stem cells (iPSCs) can be genetically engineered to evade host immune recognition, rendering them hypoimmunogenic and suitable as “universal donor” cells for allogeneic transplantation. Such modifications enable the development of off-the-shelf iPSC-derived therapeutics that are immediately available for clinical use without the need for patient-specific derivation or immunosuppression. This review focuses on recent developments in strategies for generating hypoimmunogenic human iPSCs, with particular emphasis on their applications in central nervous system (CNS) cell therapy and repair. We assess immunomodulatory factors based on their immune functions and potential roles in CNS development and disease, with the goal of identifying strategies to use these factors either individually, in combination, or alongside gene editing to reduce immune rejection without compromising neurogenesis or tissue repair.

N-glycanase 1 (NGLY1) is a cytoplasmic glycoenzyme that removes N-linked glycans from misfolded glycoproteins. It plays an important role in the endoplasmic reticulum-associated degradation (ERAD) pathway in mammalian cells. NGLY1 dysfunction in humans causes NGLY1 deficiency as a rare autosomal recessive disorder that is characterized by neurodevelopmental delay, hypotonia, movement disorders, seizures, and multi-system involvement. In this review, we summarize recent advances in understanding the neural functions of NGLY1 and the neuropathological phenotypes associated with its deficiency. We discuss the molecular basis of NGLY1 deficiency in the central nervous system (CNS) and pathophysiological insights from animal and human induced pluripotent stem cell (iPSC)-based models. We also highlight emerging gene therapy approaches aimed at restoring NGLY1 activity and alleviating neurological symptoms.

Repressor element 1-silencing transcription factor (REST) is a transcriptional repressor that recognizes neuron-restrictive silencer elements in the mammalian genomes in a tissue- and cell-specific manner. The identity of REST target genes and molecular details of how REST regulates them are emerging. We performed conditional null deletion of Rest (cKO), mainly restricted to murine hair cells (HCs) and auditory neurons (aka spiral ganglion neurons [SGNs]). Null inactivation of full-length REST did not affect the development of normal HCs and SGNs but manifested as progressive hearing loss in adult mice. We found that the inactivation of REST resulted in an increased abundance of K_v7.4 channels at the transcript, protein, and functional levels. Specifically, we found that SGNs and HCs from Rest cKO mice displayed increased K_v7.4 expression and augmented K_v7 currents; SGN’s excitability was also significantly reduced. Administration of a compound with K_v7.4 channel activator activity, fasudil, recapitulated progressive hearing loss in mice. In contrast, inhibition of the K_v7 channels by XE991 rescued the auditory phenotype of Rest cKO mice. Previous studies identified some loss-of-function mutations within the K_v7.4-coding gene, Kcnq4, as a causative factor for progressive hearing loss in mice and humans. Thus, the findings reveal that a critical homeostatic K_v7.4 channel level is required for proper auditory functions.

Human induced pluripotent stem cells (iPSCs) offer immense potential as a source for cell therapy in spinal cord injury (SCI) and other diseases. The development of hypoimmunogenic, universal cells that could be transplanted to any recipient without requiring a matching donor could significantly enhance their therapeutic potential and accelerate clinical translation. To create off-the-shelf hypoimmunogenic cells, we used CRISPR-Cas9 to delete B2M (HLA class I) and CIITA (master regulator of HLA class II). Double-knockout (DKO) iPSC-derived neural progenitor cells (NPCs) evaded T-cell-mediated immune rejection in vitro and after grafting into the injured spinal cord of athymic rats and humanized mice. However, loss of HLA class I heightened susceptibility to host natural killer (NK) cell attack, limiting graft survival. To counter this negative effect, we engineered DKO NPCs to overexpress macrophage migration inhibitory factor (MIF), an NK cell checkpoint ligand. MIF expression markedly reduced NK cell-mediated cytotoxicity and improved long-term engraftment and integration of NPCs in the animal models for spinal cord injury. These findings demonstrate that MIF overexpression, combined with concurrent B2M and CIITA deletion, generates hiPSC neural derivatives that escape both T- and NK-cell surveillance. This strategy provides a scalable route to universal donor cells for regenerative therapies in SCI and potentially other disorders.