Generation of inner ear hair cells by direct lineage conversion of primary somatic cells

Abstract

The mechanoreceptive sensory hair cells in the inner ear are selectively vulnerable to numerous genetic and environmental insults. In mammals, hair cells lack regenerative capacity, and their death leads to permanent hearing loss and vestibular dysfunction. Their paucity and inaccessibility has limited the search for otoprotective and regenerative strategies. Growing hair cells in vitro would provide a route to overcome this experimental bottleneck. We report a combination of four transcription factors (Six1, Atoh1, Pou4f3, and Gfi1) that can convert mouse embryonic fibroblasts, adult tail-tip fibroblasts and postnatal supporting cells into induced hair cell-like cells (iHCs). iHCs exhibit hair cell-like morphology, transcriptomic and epigenetic profiles, electrophysiological properties, mechanosensory channel expression, and vulnerability to ototoxin in a high-content phenotypic screening system. Thus, direct reprogramming provides a platform to identify causes and treatments for hair cell loss, and may help identify future gene therapy approaches for restoring hearing.

Application of Mesenchymal Stem Cell Therapy and Inner Ear Regeneration for Hearing Loss: A Review

“…Although the mechanism of regeneration of hair cells remains unknown, the transcription factor Atoh1 [14], POU domain factor Pou4f3 [15], and Zinc finger Gfi1 [16], which are required to differentiate progenitor cells into hair cells, have been discovered. A recent study showed that Six1, Atoh1, Pou4f3, and Gfi1 can convert fibroblasts into hair cells similar to those in the ear [17].…”

Multifaceted Actions of GFI1 and GFI1B in Hematopoietic Stem Cell Self-Renewal and Lineage Commitment

“…and has been shown to physically interact with the former three to target many hair cell regulators (Li et al, 2020). Either with or without SIX1, primary mouse embryonic and even adult human fibroblasts could be successfully converted into cells that exhibited most of the physiological traits of inner ear hair cells opening new avenues in potential treatment of deafness caused by the loss of these sensory cells (Figure 4; Duran Alonso et al, 2018;Menendez et al, 2020).…”

“…Strategies to generate induced hair cell-like cells through trans-differentiation of non-hair cells in vitro by forced expression of GFI1 in combination with other factors. The efficiency to produce cells that harbor hair cell characteristics in vitro is indicated along the starting cell type used to achieve trans-differentiation Duran Alonso et al, 2018;Menendez et al, 2020).…”

Combinatorial Atoh1 and Gfi1 induction enhances hair cell regeneration in the adult cochlea

“…Gfi1 was shown to be a down-stream target of Atoh1 and also of Pou4f3, another Atoh1-regulated gene important for HC survival and maturation [35][36][37] . More recently, simultaneous over-expression of Gfi1, Pou4f3 and Atoh1 in mouse embryonic stem cells markedly induced efficient differentiation of HC-like cells (HCLCs) in vitro 38,39 .…”