Differences in the Activity of Endogenous Bone Morphogenetic Protein Signaling Impact on the Ability of Induced Pluripotent Stem Cells to Differentiate to Corneal Epithelial-Like Cells

Abstract

Cornea is a clear outermost layer of the eye which enables transmission of light onto the retina. The transparent corneal epithelium is regenerated by limbal stem cells (LSCs), whose loss/dysfunction results in LSCs deficiency (LSCD). Ex vivo expansion of autologous LSCs obtained from patient's healthy eye followed by transplantation onto the LSCs damaged/deficient eye, has provided a successful treatment for unilateral LSCD. However, this is not applicable to patient with total bilateral LSCD, where LSCs are lost/damaged from both eyes. We investigated the potential of human induced pluripotent stem cell (hiPSC) to differentiate into corneal epithelial‐like cells as a source of autologous stem cell treatment for patients with total bilateral LSCD. Our study showed that combined addition of bone morphogenetic protein 4 (BMP4), all trans‐retinoic acid and epidermal growth factor for the first 9 days of differentiation followed by cell‐replating on collagen‐IV‐coated surfaces with a corneal‐specific‐epithelial cell media for an additional 11 days, resulted in step wise differentiation of human embryonic stem cells (hESC) to corneal epithelial progenitors and mature corneal epithelial‐like cells. We observed differences in the ability of hiPSC lines to undergo differentiation to corneal epithelial‐like cells which were dependent on the level of endogenous BMP signaling and could be restored via the activation of this signaling pathway by a specific transforming growth factor β inhibitor (SB431542). Together our data reveal a differential ability of hiPSC lines to generate corneal epithelial cells which is underlined by the activity of endogenous BMP signaling pathway. Stem Cells 2018;36:337–348

Cyp1b1 directs Srebp-mediated cholesterol and retinoid synthesis in perinatal liver; Association with retinoic acid activity during fetal development

“…These liver progenitor cells (hepatoblasts), which are controlled by Hnf4a [11,42,64,71], are jointly activated by Fgf forms from cardiac mesoderm and by BMP4 from the STM [25]. RA can intervene by stimulating the Hoxb1 effects on Fgf forms [35,41,42] or by enhancing Bmp4 effects [72]. Potential RA contributions are again spatially and metabolically separated.…”

Human iPSC differentiation to retinal organoids in response to IGF1 and BMP4 activation is line- and method-dependent

“…In this study, we used three human iPSC lines and differentiated them to retinal organoids using differentiation protocols activating either BMP4 (Method I) or IGF1 (Method II) signaling pathways; our data indicate that all cell lines were able to generate retinal cell types and the response to IGF1 and BMP4 was line‐ and method‐dependent. Variability in the propensity of iPSCs to differentiate is widely reported in the literature and is thought to be a result of some factors including gene expression heterogeneity among stem cell populations, DNA methylation and histone modifications, and differences in endogenous signaling activities, such as BMP4 . This is unsurprising, since BMP4 has been shown to be involved in the differentiation of the anterior portion of the neural plate toward retinal neurones; in addition, IGF1 promotes induction of retinal fate .…”

“…Variability in the propensity of iPSCs to differentiate is widely reported in the literature and is thought to be a result of some factors including gene expression heterogeneity among stem cell populations, DNA methylation and histone modifications, and differences in endogenous signaling activities, such as BMP4. [20][21][22][23] This is unsurprising, since BMP4 has been shown to be involved in the differentiation of the anterior portion of the neural plate toward retinal neurones; in addition, IGF1 promotes induction of retinal fate. 14,24 Interestingly, it has also been reported that using IGF1 in combination with a BMP4 antagonist results in efficient generation of cone photoreceptors.…”

Corneal cell therapy: with iPSCs, it is no more a far-sight

“…Differentiation of CECs from hPSCs has proven to be rather challenging, with most of the previously published studies relying on the use of undefined factors, such as conditioned medium [ 42 ], PA6 feeder cells, and Bowman’s or amniotic membrane [ 24 , 40 ]. Protocol to derive corneal epithelial cells from iPSCs [ 43 – 46 ] has provided critical insights into the role of each of the exogenous factors incorporated in the culture process. For example, BMP4 has been shown to be critical in the directed differentiation process of PSCs to corneal epithelial progenitors (CEPs) [ 44 , 47 ] while Hayashi et al [ 24 ] demonstrated BMP4 treatment suppressed CE differentiation from iPSCs.…”