Biology subjects

Kandoi, S.

Publications and source records attributed to Kandoi, S..

5 recordsLinked to original sources

bioRxiv2026

Transplantation of human iPSC-derived retinal cells in the cone-dominant Northern tree shrew

Abstract: Purpose: To characterize the transplantation and survival of photoreceptors generated from human induced pluripotent stem cell (hiPSC)-derived retinal organoids in the Northern tree shrew (Tupaia belangeri, TS). Methods: TS eyes were injected with retinal cells dissociated from GFP-expressing hiPSC-derived retinal organoids (12 animals; n=22 eyes). 15 eyes had prior damage induced by either experimental retinal detachment (n=11) or ATP-induced retinal damage (n=4), and seven eyes were undamaged. Retinal organoids were treated with Notch pathway inhibitor 2 days before transplant. TS retinal structure and cellular details were assessed post-transplantation for up to 8 weeks using scanning laser ophthalmoscopy (SLO), optical coherence tomography (OCT), and adaptive optics SLO (AOSLO). Histological analysis was done at the end of the experiment. Results: Cell transplants in eyes treated with a simple immunosuppression treatment failed to survive for more than 2 weeks (n=10 eyes). Robust cell survival was observed in the eyes treated with a complex immunosuppression cocktail for up to 8 weeks (n=12 eyes). The transplanted cells were confirmed to be subretinally located using OCT imaging and the cell fate was confirmed to be human photoreceptors by histology. Finally, AOSLO imaging captured structures resembling photoreceptor inner segments. Conclusions: Our results demonstrate survival of transplanted cells using a species-specific immunosuppression treatment. Future studies should aim to explore the long-term survival and function of the transplanted cells.

neuroscience↗

bioRxiv2025

Heterochronic transcription factor expression drives cone-dominant retina development in 13-lined ground squirrels.

Evolutionary adaptation to diurnal vision in ground squirrels has led to the development of a cone-dominant retina, in stark contrast to the rod-dominant retinas of most mammals. The molecular mechanisms driving this shift remain largely unexplored. Here, we perform single-cell RNA sequencing (scRNA-Seq) and chromatin accessibility profiling (scATAC-Seq) across developmental retinal neurogenesis in the 13-lined ground squirrel (13LGS) to uncover the regulatory basis of this adaptation. We find that 13LGS cone photoreceptors arise not only from early-stage neurogenic progenitors, as seen in rod-dominant species like mice, but also from late-stage neurogenic progenitors. This extended period of cone generation is driven by a heterochronic shift in transcription factor expression, with cone-promoting factors such as Onecut2, Pou2f1, and Zic3 remaining active in late-stage progenitors, and factors that promote cone differentiation such as Thrb, Rxrg, and Mef2c expressed precociously in late-stage neurogenic progenitors. Functional analyses reveal that Zic3 and Mef2c are sufficient to promote cone and repress rod photoreceptor-specific gene expression, and act through species-specific regulatory elements that drive their expression in late-stage progenitors. These results demonstrate that modifications to gene regulatory networks underlie the development of cone-dominant retinas, and provide insight into mechanisms of sensory adaptation and potential strategies for cone photoreceptor regeneration in vision disorders.

neuroscience↗

bioRxiv2022

Timed Notch Inhibition drives Photoreceptor fate specification in Human Retinal Organoids

PurposeTransplanting photoreceptors from human pluripotent stem cell derived retinal organoids have the potential to reverse vision loss in affected individuals. However, transplantable photoreceptors are only a subset of all cells in the organoids. Hence the goal of our current study was to accelerate and synchronize photoreceptor differentiation in retinal organoids by inhibiting the Notch signaling pathway at different developmental time-points using a small molecule, PF-03084014 (PF). MethodsHuman induced pluripotent stem cell (hiPSC)- and embryonic stem cells (hESC)-derived retinal organoids were treated with 10M PF for three days at day 45 (D45), D60, D90 and D120 of differentiation. Organoids collected at 14-, 28-, and 42-days post-PF treatment were analyzed for progenitor and photoreceptor markers and Notch pathway inhibition by immunohistochemistry (IHC), quantitative PCR (qPCR) and bulk RNA-seq (n=3-5 organoids from 3 independent experiments). ResultsRetinal organoids collected at 14-days post-PF treatment showed a decrease in progenitor markers (KI67, VSX2, PAX6, and LHX2) and an increase in differentiated pan-photoreceptor markers (OTX2, CRX, and RCVRN) at all organoid stages except D120. PF-treated organoids at D45 and D60 exhibited an increase in cone photoreceptor markers (RXRG and ARR3). PF-treatment at D90 revealed an increase in cone and rod photoreceptors markers (ARR3, NRL, and NR2E3). Bulk RNA-seq analysis mirrored the IHC data and qPCR confirmed Notch effector inhibition. ConclusionsTiming the Notch pathway inhibition in human retinal organoids to align with progenitor competency stages can yield an enriched population of early cone or rod photoreceptors.

developmental biology↗

bioRxiv2022

Biophysical, Molecular and Proteomic profiling of Human Retinal Organoids derived Exosomes

Extracellular vesicles (EVs) are phospholipid bilayer-bound particles released by cells that play a role in cell-cell communication, signal transduction, and extracellular matrix remodeling. There is a growing interest in EVs for ocular applications as therapeutics, biomarkers, and drug delivery vehicles. EVs secreted from mesenchymal stem cells (MSCs) have shown to provide therapeutic benefits in ocular conditions. However, very little is known about the properties of bioreactors cultured-3D human retinal organoids secreted EVs. This study provides a comprehensive morphological, nanomechanical, molecular, and proteomic characterization of retinal organoid EVs and compares it with human umbilical cord (hUC) MSCs. Nanoparticle tracking analysis indicated the average size of EV as 100-250 nm. Atomic force microscopy showed that retinal organoid EVs are softer and rougher than the hUCMSC EVs. Gene expression analysis by qPCR showed a high expression of exosome biogenesis genes in late retinal organoids derived EVs (>120 days). Immunoblot analysis showed highly expressed exosomal markers Alix, CD63, Flotillin-2, HRS and Hsp70 in late retinal organoids compared to early retinal organoids EVs (<120 days). Protein profiling of retinal organoid EVs displayed a higher differential expression of retinal function-related proteins and EV biogenesis/marker proteins than hUCMSC EVs, implicating that the use of retinal organoid EVs may have a superior therapeutic effect on retinal disorders. This study adds supplementary knowledge on the properties of EVs secreted by retinal organoids and suggests their potential use in the diagnostic and therapeutic treatments for ocular diseases.

bioengineering↗

bioRxiv2021

Characterization of retinal development in 13-lined ground squirrels

PurposeThe cone-dominant, 13-lined ground squirrel (13-LGS) retina mimics the human foveal region but retinal development in this useful rodent species has not been reported. Here, the embryonic and postnatal development of the 13-LGS retina was studied to further characterize the species as a practical alternative animal model for investigating cone-based vision in health and disease. MethodsThe spatiotemporal expression of key progenitor and cell type markers was examined in retinas from defined embryonic and postnatal stages using immunohistochemistry. Changes in the postnatal gene expression were also assessed by qPCR. ResultsThe 13-LGS neuroblastic layer expressed key progenitor markers (Sox2, Vsx2, Pax6, and Lhx2) at E18. Sequential cell fate determination evidenced by the first appearance of cell type-specific marker labeling was: at E18, ganglion cells (Brn-3A, HuC/D) and microglia (Iba1); at E24-25.5 shortly before birth, photoreceptor progenitor (Otx2, Recoverin), horizontal and amacrine cells (Lhx1, Oc1); and at P15, bipolar cells (Vsx1, CaBP5) and Muller glia cells (GS, Rlbp1). Photoreceptor maturation indicated by opsin+ outer segments and PNA labeling of cone sheaths was completed at the time of eye opening, P21-24. ConclusionsThe timeline and order of retinal cell development in the 13-LGS generally matches that recorded from other mammalian models but with a stark variation in the proportion of various cell types due to cone-dense photoreceptors. This provides a baseline for future examinations of developmental, disease model, and stem cell approach studies employing this emerging rodent model of human vision.

developmental biology↗