Bone Marrow-Derived Mesenchymal Stem Cells-Derived Exosomes Promote Survival of Retinal Ganglion Cells Through miRNA-Dependent Mechanisms

Abstract

The loss of retinal ganglion cells (RGC) and their axons is one of the leading causes of blindness and includes traumatic (optic neuropathy) and degenerative (glaucoma) eye diseases. Although no clinical therapies are in use, mesenchymal stem cells (MSC) have demonstrated significant neuroprotective and axogenic effects on RGC in both of the aforementioned models. Recent evidence has shown that MSC secrete exosomes, membrane enclosed vesicles (30–100nm) containing proteins, mRNA and miRNA which can be delivered to nearby cells. The present study aimed to isolate exosomes from bone marrow-derived MSC (BMSC) and test them in a rat optic nerve crush (ONC) model. Treatment of primary retinal cultures with BMSC-exosomes demonstrated significant neuroprotective and neuritogenic effects. Twenty-one days after ONC and weekly intravitreal exosome injections; optical coherence tomography, electroretinography, and immunohistochemistry was performed. BMSC-derived exosomes promoted statistically significant survival of RGC and regeneration of their axons while partially preventing RGC axonal loss and RGC dysfunction. Exosomes successfully delivered their cargo into inner retinal layers and the effects were reliant on miRNA, demonstrated by the diminished therapeutic effects of exosomes derived from BMSC after knockdown of Argonaute-2, a key miRNA effector molecule. This study supports the use of BMSC-derived exosomes as a cell-free therapy for traumatic and degenerative ocular disease.

MicroRNA‐31a‐5p from aging BMSCs links bone formation and resorption in the aged bone marrow microenvironment

“…The supernatant was then centrifuged at 100,000  g for 70 min twice, removing the contaminating protein, and the pellet was collected each time and resuspended in PBS. Lastly, exosomes in the pellet were resuspended in 100 μl of PBS and stored at −80°C (Mead, & Tomarev, 2017). …”

“…Exosomes are intracellularly secreted by endocytic invagination of mammalian cells. These vesicles may contain proteins as well as mRNAs and miRNAs and have specific cargo (Greenhill, 2017; Mathivanan, Ji, & Simpson, 2010; Mead, & Tomarev, 2017). Upon secretion into the extracellular environment, exosomes have been demonstrated to carry their cargo to target cells, protecting the cargo from degradation during transportation (Sugatani, Hildreth, Toribio, Malluche, & Hruska, 2014; Xu, & Tahara, 2013).…”

Roles of exosomes in the normal and diseased eye

“…In line with this idea, another strategy uses mesenchymal-derived stem cells to secrete neurotrophic factors for neuroprotection or axonal regeneration of retinal cells (Johnson et al, 2010; Johnson et al, 2014; Mead et al, 2013). A recent study demonstrated that intravitreal injections of exosomes from mesenchymal-derived stem cells partially prevents axonal loss and degeneration following mechanical injury (Mead and Tomarev, 2017). Interestingly, the investigators find that RNA exosomal cargo is responsible for these protective effects.…”

“…For example, MiR-133b containing exosomes transferred this microRNA to astrocytes and neurons in rats resulting in changes to gene expression that led to neurite remodeling and recovery from stroke (Xin et al, 2013). These neuroprotective effects of exosomes from mesenchymal cells have recently been shown useful in supporting retinal ganglion cells in a model of glaucoma (Mead and Tomarev, 2017). Finally, exosomes can induce proliferation in a number cell types (Deregibus et al, 2007; Jeong et al, 2014; Raimondo et al, 2015).…”

Newt cells secrete extracellular vesicles with therapeutic bioactivity in mammalian cardiomyocytes

“…Additionally, we used highly-sensitive, single particle flow nanocytometry to quantify the relative proportions of A1-EVs expressing a particular protein surface marker within the entire EV population [29,47]. Sizable fractions of A1-EVs expressed TSP1 (79%), POSTN (60%), FN (52%) and low levels of CD81 (22%) (right panels, Figure 6(a,b)); positive particles highlighted in green).…”