Progranulin enhances the engraftment of transplanted human iPS cell-derived cerebral neurons.

Cerebral organoids (COs) in cell replacement therapy offer a viable approach to reconstructing neural circuits for individuals suffering from stroke or traumatic brain injuries. Successful transplantation relies on effective engraftment and neurite extension from the grafts. Earlier research has validated the effectiveness of delaying the transplantation procedure by 1 week. Here, we hypothesized that brain tissues 1 week following a traumatic brain injury possess a more favorable environment for cell transplantation when compared to immediately after injury. We performed a transcriptomic comparison to differentiate gene expression between these 2 temporal states. In controlled in vitro conditions, recombinant human progranulin (rhPGRN) bolstered the survival rate of dissociated neurons sourced from human induced pluripotent stem cell-derived COs (hiPSC-COs) under conditions of enhanced oxidative stress. This increase in viability was attributable to a reduction in apoptosis via Akt phosphorylation. In addition, rhPGRN pretreatment before in vivo transplantation experiments augmented the engraftment efficiency of hiPSC-COs considerably and facilitated neurite elongation along the host brain's corticospinal tracts. Subsequent histological assessments at 3 months post-transplantation revealed an elevated presence of graft-derived subcerebral projection neurons-crucial elements for reconstituting neural circuits-in the rhPGRN-treated group. These outcomes highlight the potential of PGRN as a neurotrophic factor suitable for incorporation into hiPSC-CO-based cell therapies.

Viral delivery of L1CAM promotes axonal extensions by embryonic cerebral grafts in mouse brain.

Cell replacement therapy is expected as a new and more radical treatment against brain damage. We previously reported that transplanted human cerebral organoids extend their axons along the corticospinal tract in rodent brains. The axons reached the spinal cord but were still sparse. Therefore, this study optimized the host brain environment by the adeno-associated virus (AAV)-mediated expression of axon guidance proteins in mouse brain. Among netrin-1, SEMA3, and L1CAM, only L1CAM significantly promoted the axonal extension of mouse embryonic brain tissue-derived grafts. L1CAM was also expressed by donor neurons, and this promotion was exerted in a haptotactic manner by their homophilic binding. Primary cortical neurons cocultured on L1CAM-expressing HEK-293 cells supported this mechanism. These results suggest that optimizing the host environment by the AAV-mediated expression of axon guidance molecules enhances the effect of cell replacement therapy.

Generation of striatal neurons from human induced pluripotent stem cells by controlling extrinsic signals with small molecules.

Human induced pluripotent stem cells (hiPSCs) are powerful tools for modeling human brain development and treating neurodegenerative diseases. Here we established a robust protocol with high scalability for generating striatal medium spiny neurons (MSNs) from hiPSCs using small molecules under two- and three-dimensional culture conditions. Using this protocol, GSH2+ lateral ganglionic eminence (LGE) progenitors were generated in two-dimensional culture by Sonic hedgehog signaling activation using purmorphamine, WNT signaling inhibition using XAV939, and dual-SMAD inhibition using LDN193189 and A83-01. Quantitative PCR analysis revealed sequential expression of LGE and striatal genes during differentiation. These LGE progenitors subsequently gave rise to DARPP32+ MSNs exhibiting spontaneous and evoked monophasic spiking activity. Applying this protocol in three-dimensional culture, we generated striatal neurospheres with gene expression profiles and cell layer organization resembling that of the developing striatum, including distinct ventricular and subventricular zones and DARPP32+ neurons at the surface. This protocol provides a useful experimental model for studying striatal development and yields cells potentially applicable for regenerative medicine to treat striatum-related disorders such as Huntington's disease.