Inhibition of the TGFβ Pathway Enhances Retinal Regeneration in Adult Zebrafish

Abstract

In contrast to the mammalian retina, the zebrafish retina exhibits the potential for lifelong retinal neurogenesis and regeneration even after severe damage. Previous studies have shown that the transforming growth factor beta (TGFβ) signaling pathway is activated during the regeneration of different tissues in the zebrafish and is needed for regeneration in the heart and the fin. In this study, we have investigated the role of the TGFβ pathway in the N-methyl-N-nitrosourea (MNU)-induced chemical model of rod photoreceptor de- and regeneration in adult zebrafish. Immunohistochemical staining for phosphorylated Smad3 was elevated during retinal regeneration, and phosphorylated Smad3 co-localized with proliferating cell nuclear antigen and glutamine synthetase, indicating TGFβ pathway activation in proliferating Müller glia. Inhibiting the TGFβ signaling pathway using a small molecule inhibitor (SB431542) resulted in accelerated recovery from retinal degeneration. Accordingly, we observed increased cell proliferation in the outer nuclear layer at days 3 to 8 after MNU treatment. In contrast to the observations in the heart and the fin, the inhibition of the TGFβ signaling pathway resulted in increased proliferation after the induction of retinal degeneration. A better understanding of the underlying pathways with the possibility to boost retinal regeneration in adult zebrafish may potentially help to stimulate such proliferation also in other species.

Biphasic Role of Tgf-β Signaling during Müller Glia Reprogramming and Retinal Regeneration in Zebrafish

“…Temporal evaluation of various genes' expression regulated by Tgf-b signaling gave us important clues about its involvement during zebrafish retinal regeneration, after a mechanical injury damaging all retinal layers equally. Furthermore, the blockade of Tgf-b signaling causing a significant decline in MGPCs formation at 4 dpi, unlike reported in exclusive photoreceptor injury (Lenkowski et al, 2013;Tappeiner et al, 2016), substantiated our hypothesis that Tgf-b signaling is pro-proliferative during retinal regeneration. Apart from this, blockade of Tgf-b signaling caused a substantial decline in various regeneration-associated factors, which confirmed its importance in MGPCs formation.…”

Polygonatum sibiricum polysaccharide potentially attenuates diabetic retinal injury in a diabetic rat model

“…TGF-b works on cell differentiation and proliferation, and inhibits the DNA synthesis of vascular endothelial cells 29 . Also, the inhibition of the TGF-b signaling pathway promotes retinal regeneration in a zebrafish model 30 . In the present study, the mRNA and protein expression levels of VEGF, EGF and TGF-b in the retina were significantly increased with the aggravation lesions of DR, but PSP intervention can significantly reduce VEGF, EGF and TGFb expression.…”

microRNA expression in the neural retina: Focus on Müller glia

“…Several studies have addressed this issue, providing in vivo and in vitro evidence of the molecular mechanisms involved in neuronal differentiation of Müller glia–derived cells. Wnt and TGFβ have been postulated as some of the instructive clues required for the acquisition of neuronal phenotypes in human Müller cell lines (MIO‐M1, MIO‐M7, and MIO‐M8) (Angbohang et al, ) and in zebrafish (Tappeiner et al, ). In addition, expression of the gene encoding the proneural TF Ascl1 provides Müller glia with the potential to respond to retinal injury in zebrafish (Fausett, Gumerson, & Goldman, ) and mice (Jorstad et al, ; Pollak et al, ; Ueki et al, ).…”

“…After M€ uller cell de-differentiation and expansion of MGDP, the cells must undergo differentiation into all the lost retinal cell types (Powell, Cornblath, Elsaeidi, Wan, & Goldman, 2016;. In fact, in situ replacement of neurons might serve as a potential (Angbohang et al, 2016) and in zebrafish (Tappeiner et al, 2016). In addition, expression of the gene encoding the proneural TF Ascl1 provides M€ uller glia with the potential to respond to retinal injury in zebrafish (Fausett, Gumerson, & Goldman, 2008) and mice (Jorstad et al, 2017;Pollak et al, 2013;Ueki et al, 2015).…”

“…Recent research has revealed substantive functions for microRNAs (miRNAs) in the retina (Lumayag et al, ; Fulzele et al, ; Krol et al, ; Sundermeier & Palczewski, ; ). These short noncoding RNAs have the ability to regulate target proteins by interfering with mRNA translation, affecting almost all cellular processes (Huntzinger & Izaurralde, ; Valencia‐Sanchez, Liu, Hannon, & Parker, ).…”