Stretch to See: Lateral Tension Strongly Determines Cell Survival in Long-Term Cultures of Adult Porcine Retina

Abstract

PURPOSE.To explore the effect of lateral tension as a survival factor for retinal explants in vitro. The central nervous system (CNS) resides in a highly mechanical milieu. However, the importance of biomechanical homeostasis for normal CNS function has not been extensively explored. Diseases in which normal mechanical forces are disrupted, such as retinal detachment of the eye, are highly debilitating and the mechanisms underlying disease progression are not fully understood.METHODS. Using a porcine animal model, we developed a novel technique of culturing adult retinal explants under stretch for up to 10 days in vitro (DIV). These were compared with standard (no stretch) and free-floating cultured explants. Cell survival was analyzed using immunohistochemistry, and retinal architecture using hematoxylin and eosin staining.RESULTS. Compared with unstretched specimens, which at 10 DIV degenerated into a gliotic cell mass, stretched retinas displayed a profound preservation of the laminar retinal architecture as well as significantly increased neuronal cell survival, with no signs of impending gliosis. CONCLUSIONS.The results confirm that biomechanical tension is a vital factor in the maintenance of retinal tissue integrity, and suggest that mechanical cues are important components of pathologic responses within the CNS. (Invest Ophthalmol Vis

In vitro biomechanical modulation—retinal detachment in a box

“…The overall morphology and immunohistochemical characteristics of the normal adult porcine retina have been well described previously but will be summarized here [11,12].…”

“…In the retina, the biochemical and biomechanical homeostasis is maintained by Müller cells, which can alter their physical properties through up-or downregulation of intermediary filaments (such as GFAP and vimentin) [11,12,22,23]. This allows Müller cells to control the tissue-wide as well as the cellular biomechanical environment [11,12,22,23].…”

“…This allows Müller cells to control the tissue-wide as well as the cellular biomechanical environment [11,12,22,23]. In this setting, it is interesting to note that the stiff, intermediary filament-rich Müller cell endfeet contain mechanosensory cation channels, such as TRPV4, which are known to respond to changes in cell membrane stretch through Ca2+ influx [11,12,[22][23][24]. Influx of Ca2+ is a known trigger of intermediary filament upregulation in Müller cells [12,25,26].…”

“…Using an in vitro model of adult porcine retina, we were able to show that adult retinal explants maintained in culture with no physical support collapse and display severe signs of neuronal degeneration and gliosis after 2 days in vitro [11]. In contrast, retinas in which tissue collapse is prevented by either stretching the tissue or supporting the inner retina, display excellent survival for at least 10 days [11,12]. These retinas show preservation of ultrastructural elements such as inner and outer segments, the outer limiting membrane, and synapses [12].…”

A new model for in vitro testing of vitreous substitute candidates

“…Additionally, the positive effect on the retina could be due to biomechanical factors via physical interaction from the gel that might prevent retinal folds and keep the explants under tension. This is a factor that previously has been showed to favorably affect retinas in vitro [44].…”