A Small-Molecule Wnt Mimic Improves Human Limbal Stem Cell Ex Vivo Expansion

Abstract

HIGHLIGHTS MFH-ND is generated by linking a Frizzled inhibitor and an LRP5/6 inhibitor MFH-ND activates the canonical Wnt pathway by oligomerizing Frizzled and LRP5/6 MFH-ND improves the stem cell phenotype of cultivated limbal epithelial cells MFH-ND has therapeutic potential to improve limbal stem cell deficiency treatment

Wnt signaling activation: targets and therapeutic opportunities for stem cell therapy and regenerative medicine

“…b. Wnt mimics Because Wnt binds to FZD and LRP5/6 and activates canonical Wnt signaling, it was reasoned that inducing the dimerization of FZD and LRP5/6 should also be able to induce Wnt signaling 14,[34][35][36] . Janda et al first described a hydrophilic Wnt surrogate by linking antagonistic FZD and LRP5/LRP6-binding modules into a single polypeptide chain, in a bispecific binding approach 35 .…”

“…They were linked by a Gly-Ser polypeptide linker, forcing receptor heterodimerization that phenocopied Wnt/β-catenin signaling in vitro and in vivo, while blocking endogenous Wnt binding 35 . Using this approach, Zhang et al created a Wnt mimics compound by linking a Wnt inhibitor binding to the CRD of FZD (named MFH) to the N-terminal region of DKK that binds to the first β-propeller domain of LRP6 (named ND) through a MFH free carboxyl group and a pentaethylene glycol spacer 14 . They showed that the consolidated compound MFH-ND enhanced Wnt/β-catenin activation and improved the progenitor cell phenotype of cultured limbal epithelial cells in vitro.…”

“…Theoretically, by activating Wnt, one could promote SC proliferation to restore tissue or organ impaired functions, the ultimate goal of SC therapy and regenerative medicine. Although no therapies affecting the pathway have so far been approved by the Food and Drug Administration, and only a few have entered in clinical trials, small-molecule Wnt regulators have been widely used as chemical biology tools to study Wnt signaling in various biological settings 13,14 .…”

“…High-throughput pipelines are also widely used to target Wnt inhibitors, such as anti-FZD and anti-LRP5/6, or downstream nuclear proteins of the pathway, with the goal of developing new cancer therapies 149,150 . By binding two inhibitors, it possible to engineer Wnt mimics, as did Chen et al 34 , Janda et al 35 , Tao et al 36 , and Zhang et al 14 , when coupling anti-FZD with anti-DKK1 small molecules.…”

“…The local use of Wnt activators could minimize these risks, and have been described in cutaneous injuries and cardiac infarction, where scaffolds loaded with Wnt agonists are placed directly on the site of injury 199 . Wnt agonists can also be successfully used to promote SC expansion in vivo and are perfect applications of ex-vivo limbal stem cell expansion and corneal wound healing 14 .…”