Macrophages modulate fibrosis during newt lens regeneration

Abstract

Previous studies indicated that macrophages play a role during lens regeneration in newts, but their function has not been tested experimentally. Here we generated a transgenic newt reporter line in which macrophages can be visualized in vivo. Using this new tool, we analyzed the location of macrophages during lens regeneration. We uncovered early gene expression changes using bulk RNAseq in two newt species, Notophthalmus viridescens and Pleurodeles waltl. Next, we used clodronate liposomes to deplete macrophages, which inhibited lens regeneration in both newt species. Macrophage depletion induced the formation of scar-like tissue, an increased and sustained inflammatory response, an early decrease in iris pigment epithelial cell (iPEC) proliferation and a late increase in apoptosis. Some of these phenotypes persisted for at least 100 days and could be rescued by exogenous FGF2. Re-injury alleviated the effects of macrophage depletion and re-started the regeneration process. Together, our findings highlight the importance of macrophages in facilitating a pro-regenerative environment in the newt eye, helping to resolve fibrosis, modulating the overall inflammatory landscape and maintaining the proper balance of early proliferation and late apoptosis.

Cellular and Molecular Triggers of Retinal Regeneration in Amphibians

“…However, a secondary injury alone or the addition of FGF2 restarted the scar resolution and the regeneration processes. The findings in the study indicate the importance and multiple functions of macrophages in facilitating a pro-regenerative environment in the newt eye, helping to resolve fibrosis, modulating the overall inflammatory landscape, and maintaining the proper balance of early proliferation and late apoptosis between scarring and regenerative phenotypes [188].…”

“…Recently, a broad study was conducted on the role of macrophages in the regeneration of the lens that occurs through the conversion of iris cells in the newts N. viridescens and P. waltl [188]. The authors of the study generated a transgenic newt reporter line, in which macrophages can be visualized in vivo.…”

Molecular Signatures Integral to Natural Reprogramming in the Pigment Epithelium Cells after Retinal Detachment in Pleurodeles waltl

“…This is due to the large number of genes from this category (5640) and also to the closeness of the expected and obtained numbers of up-regulated genes in the samples. The binding activity is associated with mRNA binding processes that determine the specificity of the processing, splicing, and translation of mRNA ("early" sample: p-value 1.91 × 10‾ 12 , FDR 9.66 × 10‾ 9 and "late" sample: p-value 9.45 × 10‾ 29 , FDR 4.78 × 10‾ 25 ). The significance of the enrichment of up-regulated genes/proteins of all other classes at the early stage of RPE reprogramming has not been confirmed while taking into account the FDR values.…”

“…Studies on newt tissue regeneration are making progress thanks to incorporating highly efficient technologies and allowing us to use microquantities of tissue for the analysis of transcriptomes, genomes, and proteomes [23,24], as well as for the analysis of gene functions [25][26][27]. The application of these approaches allow us to unravel the cellular and molecular mechanisms of aging and its relations with regeneration [28,29].…”