Update of application of olfactory ensheathing cells and stem cells/exosomes in the treatment of retinal disorders

Age-related macular degeneration, diabetic retinopathy, retinitis pigmentosa and other retinal disorders are the main causes of visual impairment worldwide. In the past, these retinal diseases, especially dry age-related macular degeneration, proliferative diabetic retinopathy and retinitis pigmentosa, were treated with traditional surgery and drugs. However, the effect was moderate. In recent years, researchers have used embryonic stem cells, induced pluripotent stem cells, mesenchymal stem cells, olfactory ensheathing cells and other stem cells to conduct experiments and found that stem cells can inhibit inflammation, regulate immune response, secrete neurotrophic factors, and differentiate into retinal cells to replace and promote restoration of the damaged parts. These stem cells have the potential to treat retinal diseases. Whether it is in animal experiments or clinical trials, the increase in the number of retinal cells, maintenance of function and improvement of visual function all reflect the advanced of stem cells to treat retinal diseases, but its risk preserves the donor’s hidden pathogenic genes, immune rejection and tumorigenicity. With the development of exosomes study, researchers have discovered that exosomes come from a wide range of sources and can be secreted by almost all types of cells. Using exosomes with stem cell to treat retinal diseases is more effective than using stem cells alone. This review article summarizes the recent advances in the application of olfactory ensheathing cells and stem cells/exosomes in the treatment of retinal disorders.

The Promoting Effects of Activated Olfactory Ensheathing Cells on Angiogenesis after Spinal Cord Injury Through the PI3K/Akt Pathway

ObjectiveThe aim of this study was to investigate the pro-angiogenic potential of olfactory ensheathing cells (OECs) activated by curcumin (CCM) and lipopolysaccharide (LPS) and the possible underlying mechanisms. MethodsVascular endothelial cells or tissues were cultured and treated with conditioned medium (CM) extracted from the activated through the addition of LPS and CCM or unactivated OECs. Concomitantly, the pro-angiogenic potential of OECs was assessed in vitro by aortic ring sprouting assay, endothelial wound healing assay, CCK-8 assay and tube formation assay. Subsequently, the OECs were co-cultured with endothelial cells to evaluate their promoting effect on the proliferation and migration of endothelial cells following undergoing a mechanical scratch. Moreover, the spinal cord injury (SCI) model in rats was established, and the number of endothelial cells and vascular structure in the injured area after SCI was observed with OECs transplantation. Finally, the underlying mechanism was investigated by western blot analysis of phosphorylated kinase expression with or without the MK-2206 (Akt-inhibitor). ResultThe present results showed that the activated OECs can effectively promote the proliferation, migration and vessel-like structure formation of vascular endothelial cells. Strikingly, several pro-angiogenic growth factors such as VEGF-A and PDGF-AA, which facilitate vessel formation, were found to be significantly elevated in CM. In addition, the PI3K/Akt signaling pathway involved in pro-angiogenic event caused by activated OEC CM, displaying higher phosphorylation levels in cells. On contrary, the delivery of MK2206 can effectively abrogate all the positive effects. ConclusionsOECs activated by LPS and CCM, have a strong pro-angiogenesis effect, and can effectively promote angiogenesis and improve the injury microenvironment when transplanted in injured spinal cord. This potentiated ability of OECs to pro-angiogenesis is likely mediated through the PI3K/Akt pathway.

miR-6780-5p-Enriched Exosomes Derived From Butylidenephthalide-Pre-Conditioned Human Olfactory Ensheathing Cells Via Autophagy Improve Motor Coordination and Balance in a SCA3/MJD Mouse Model

Background The development of acellular products is a new trend for regeneration medicine. To provide an acellular product exhibiting characteristics of cells and usefulness as a therapeutic agent, exosomes were employed in the current studies. Method and Result The therapeutic agent hsa-miRNA-6780-5p was enriched up to 98 folds in exosomes derived from butylidenephthalide (bdph)-pre-conditioned human olfactory ensheathing cells (hOECs) compared to naïve hOECs exosomes. The particle size of exosomes derived hOECs and exosomes derived hOECs pre-conditioned bdph were around 124.17 nm and 117.47 nm, respectively. The role of hsa-miRNA-6780-5p was first demonstrated in our studies using a liposome system, showing that it enhances autophagy and inhibits spinocerebellar ataxia type 3 (SCA3) disease proteins of polyglutamine (polyQ) tract expression. At the same time, the exosomes with enriched hsa-miRNA-6780-5p were further applied to HEK-293-84Q, thus resulting in decreased expressions of polyQ and increased autophagy in the cells. In contrast, the results were reversed when the autophagy inhibitor, 3MA, was added to the cells treated with hsa-miRNA-6780-5p enriched exosomes, indicating that the decreased polyQ expression was modulated via autophagy. The SCA3 mice showed improved motor coordination behavior when they received intracranially injected exosomes enriched with hsa-miRNA-6780-5p. The SCA3 mouse cerebellum tissue having received hsa-miRNA6780-5p enriched exosomes also showed a decreased expression of polyQ and increased expression of autophagy marker. Conclusions Together, our findings provide an alternative therapeutic strategy for SCA3 disease treatment, using miRNA enriched exosomes derived from chemically pre-conditioned cells.

High-Yield Mucosal Olfactory Ensheathing Cells Restore Loss of Function in Rat Dorsal Root Injury

In a previous study, we reported that no axons were crossing from the severed dorsal roots to the spinal cord using the rat dorsal rhizotomy paradigm. The injury caused ipsilateral deficits of forepaw function. An attempt to restore the function by transplanting cells containing 5% olfactory ensheathing cells (OECs) cultured from the olfactory mucosa did not succeed. However, obtaining OECs from the olfactory mucosa has an advantage for clinical application. In the present study, we used the same rhizotomy paradigm, but rats with an injury received cells from a modified mucosal culture containing around 20% OECs mixed in collagen. The forelimb proprioception assessment showed that 80% of the rats receiving the transplants had functional improvement over six weeks of the study. The adhesive removal test showed that the time taken for the rats to notice the adhesive label and remove it almost returned to the normal level after receiving the transplants. Transplanted cells were identified with the expression of green fluorescent protein (ZsGreen). Some regeneration fibres immunostained for neurofilament (NF) or traced by biotinylated dextran amine (BDA) in the injury area were associated with the transplanted cells. The evidence in this study improves the prospect of clinical application using OECs from the olfactory mucosa to treat CNS injuries.

Amyloid-Beta Induces Different Expression Pattern of Tissue Transglutaminase and Its Isoforms on Olfactory Ensheathing Cells: Modulatory Effect of Indicaxanthin

Herein, we assessed the effect of full native peptide of amyloid-beta (Aβ) (1-42) and its fragments (25-35 and 35-25) on tissue transglutaminase (TG2) and its isoforms (TG2-Long and TG2-Short) expression levels on olfactory ensheathing cells (OECs). Vimentin and glial fibrillary acid protein (GFAP) were also studied. The effect of the pre-treatment with indicaxanthin from Opuntia ficus-indica fruit on TG2 expression levels and its isoforms, cell viability, total reactive oxygen species (ROS), superoxide anion (O2−), and apoptotic pathway activation was assessed. The levels of Nestin and cyclin D1 were also evaluated. Our findings highlight that OECs exposure to Aβ(1-42) and its fragments induced an increase in TG2 expression levels and a different expression pattern of its isoforms. Indicaxanthin pre-treatment reduced TG2 overexpression, modulating the expression of TG2 isoforms. It reduced total ROS and O2− production, GFAP and Vimentin levels, inhibiting apoptotic pathway activation. It also induced an increase in the Nestin and cyclin D1 expression levels. Our data demonstrated that indicaxanthin pre-treatment stimulated OECs self-renewal through the reparative activity played by TG2. They also suggest that Aβ might modify TG2 conformation in OECs and that indicaxanthin pre-treatment might modulate TG2 conformation, stimulating neural regeneration in Alzheimer’s disease.