Let-7, Lin28 and Hmga2 Expression in Ciliary Epithelium and Retinal Progenitor Cells

Invest Ophthalmol Vis Sci. 2021 Mar 1;62(3):31. doi: 10.1167/iovs.62.3.31.


Purpose: Ciliary epithelium (CE) of adult mammalian eyes contains quiescent retinal progenitor/stem cells that generate neurospheres in vitro and differentiate into retinal neurons. This ability doesn't evolve efficiently probably because of regulatory mechanisms, such as microRNAs (miRNAs) that control pluripotent, progenitor, and differentiation genes. Here we investigate the presence of Let-7 miRNAs and its regulator and target, Lin28 and Hmga2, in CE cells from neurospheres, newborns, and adult tissues.

Methods: Newborn and adult rats CE cells were dissected into pigmented and nonpigmented epithelium (PE and NPE). Newborn PE cells were cultured with growth factors to form neurospheres and we analyzed Let-7, Lin28a, and Hmga2 expression. During the neurospheres formation, we added chemically modified single-stranded oligonucleotides designed to bind and inhibit or mimic endogenous mature Let-7b and Let-7c. After seven days in culture, we analyzed neurospheres size, number and expression of Let-7, Lin28, and Hmga2.

Results: Let-7 miRNAs were expressed at low rates in newborn CE cells with significant increase in adult tissues, with higher levels on NPE cells, that does not present the stem cells reprogramming ability. The Lin28a and Hmga2 protein and transcripts were more expressed in newborns than adults cells, opposed to Let-7. Neurospheres presented higher Lin28 and Hmga2 expression than newborn and adult, but similar Let-7 than newborns. Let-7b inhibitor upregulated Hmga2 expression, whereas Let-7c mimics upregulated Lin28 and downregulated Hmga2.

Conclusions: This study shows the dynamic of Lin28-Let-7-Hmga regulatory axis in CE cells. These components may develop different roles during neurospheres formation and postnatal CE cells.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Animals, Newborn
  • Blotting, Western
  • Cells, Cultured
  • Ciliary Body / metabolism*
  • Fluorescent Antibody Technique, Indirect
  • Gene Expression Regulation / physiology
  • HMGA2 Protein / genetics*
  • MicroRNAs / genetics*
  • Pigment Epithelium of Eye / metabolism*
  • RNA, Messenger / genetics
  • RNA-Binding Proteins / genetics*
  • Rats
  • Rats, Wistar
  • Retina / metabolism*
  • Stem Cells / metabolism*


  • HMGA2 Protein
  • HMGA2 protein, rat
  • Lin28A protein, rat
  • MIRNLET7 microRNA, rat
  • MicroRNAs
  • RNA, Messenger
  • RNA-Binding Proteins