A small synthetic cripto blocking Peptide improves neural induction, dopaminergic differentiation, and functional integration of mouse embryonic stem cells in a rat model of Parkinson's disease.

Cripto is a glycosylphosphatidylinositol-anchored coreceptor that binds Nodal and the activin type I (ALK)-4 receptor, and is involved in cardiac differentiation of mouse embryonic stem cells (mESCs). Interestingly, genetic ablation of cripto results in increased neuralization and midbrain dopaminergic (DA) differentiation of mESCs, as well as improved DA cell replacement therapy (CRT) in a model of Parkinson's disease (PD). In this study, we developed a Cripto specific blocking tool that would mimic the deletion of cripto, but could be easily applied to embryonic stem cell (ESC) lines without the need of genetic manipulation. We thus screened a combinatorial peptide library and identified a tetrameric tripeptide, Cripto blocking peptide (BP), which prevents Cripto/ALK-4 receptor interaction and interferes with Cripto signaling. Cripto BP treatment favored neuroectoderm formation and promoted midbrain DA neuron differentiation of mESCs in vitro and in vivo. Remarkably, Cripto BP-treated ESCs, when transplanted into the striatum of PD rats, enhanced functional recovery and reduced tumor formation, mimicking the effect of genetic ablation of cripto. We therefore suggest that specific blockers such as Cripto BP may be used to improve the differentiation of ESC-derived DA neurons in vitro and their engraftment in vivo, bringing us closer towards an application of ESCs in CRT.