A Defective Crosstalk Between Neurons and Müller Glial Cells in the rd1 Retina Impairs the Regenerative Potential of Glial Stem Cells.

Yanel A Volonté,Victoria B Ayala-Peña,Olga L German,Luis E Politi,Marcos J Dibo,Samanta R Zanetti,Axel Turpaud,Harmonie Vallese-Maurizi,Andrés Garelli,Nora P Rotstein,Cheryl Mae Craft

doi:10.3389/fncel.2019.00334

Abstract

Müller glial cells (MGC) are stem cells in the retina. Although their regenerative capacity is very low in mammals, the use of MGC as stem cells to regenerate photoreceptors (PHRs) during retina degenerations, such as in retinitis pigmentosa, is being intensely studied. Changes affecting PHRs in diseased retinas have been thoroughly investigated; however, whether MGC are also affected is still unclear. We here investigated whether MGC in retinal degeneration 1 (rd1) mouse, an animal model of retinitis pigmentosa, have impaired stem cell properties or structure. rd1 MGC showed an altered morphology, both in culture and in the whole retina. Using mixed neuron-glial cultures obtained from newborn mice retinas, we determined that proliferation was significantly lower in rd1 than in wild type (wt) MGC. Levels of stem cell markers, such as Nestin and Sox2, were also markedly reduced in rd1 MGC compared to wt MGC in neuron-glial cultures and in retina cryosections, even before the onset of PHR degeneration. We then investigated whether neuron-glial crosstalk was involved in these changes. Noteworthy, Nestin expression was restored in rd1 MGC in co-culture with wt neurons. Conversely, Nestin expression decreased in wt MGC in co-culture with rd1 neurons, as occurred in rd1 MGC in rd1 neuron-glial mixed cultures. These results imply that MGC proliferation and stem cell markers are reduced in rd1 retinas and might be restored by their interaction with “healthy” PHRs, suggesting that alterations in rd1 PHRs lead to a disruption in neuron-glial crosstalk affecting the regenerative potential of MGC.

Highlights

Retinitis pigmentosa constitutes a group of inherited diseases that have as a common feature the degeneration and loss of rod and cone photoreceptors (PHRs)
The levels of Nestin mRNA were dramatically reduced in wt Müller glial cells (MGC)-rd1 neuron co-cultures relative to pure wt MGC cultures, and significantly increased, up to nearly 3.3 ± 1 times in wt MGC-wt neuron co-cultures (Figure 6Bj). These results suggest that the crosstalk between neurons and MGC is crucial for regulating Nestin expression in MGC, and interactions with wt neurons can restore this expression in rd1 MGC
By day 6, prior to the onset of PHR degeneration, the number of rd1 MGC was about half of that of wt MGC in mixed neuron-glial cultures and their BrdU-uptake was markedly reduced; this uptake was virtually negligible at day 11 in vitro in rd1 MGC, whereas wt MGC still retained their proliferative capacity at this time in culture

Summary

Introduction

Retinitis pigmentosa constitutes a group of inherited diseases that have as a common feature the degeneration and loss of rod and cone photoreceptors (PHRs). The use of stem cells to replace neuronal loss in the injured retina is being actively investigated as a promising. Fischer and Reh (Fischer and Reh, 2003) have shown that MGC are stem cells that effectively regenerate the eye in fish and lower vertebrates. Their regenerative potential is extremely low in vertebrates; generation of a few novel neurons in the murine retina was only possible because of the use of multiple exogenous stimuli (Fischer and Reh, 2003). MGC are inefficient in regenerating the retina in humans, such as in patients suffering from retinitis pigmentosa, and in the rd mice, a frequently used animal model for this disease

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