In vivo chemical reprogramming of astrocytes into neurons

In mammals, many organs lack robust regenerative abilities. Lost cells in impaired tissue could potentially be compensated by converting nearby cells in situ through in vivo reprogramming. Small molecule-induced cell reprogramming offers a temporally flexible and non-integrative strategy for altering cell fate, which is, in principle, favorable for in vivo reprogramming in organs with notoriously poor regenerative abilities, such as the brain. Here, we demonstrate that in the adult mouse brain, small molecules can reprogram astrocytes into neurons. The in situ chemically induced neurons resemble endogenous neurons in terms of neuron-specific marker expression, electrophysiological properties, and synaptic connectivity. Our study demonstrates the feasibility of in vivo chemical reprogramming in the adult mouse brain and provides a potential approach for developing neuronal replacement therapies.

Chemicals orchestrate reprogramming with hierarchical activation of master transcription factors primed by endogenous Sox17 activation

Mouse somatic cells can be chemically reprogrammed into pluripotent stem cells (CiPSCs) through an intermediate extraembryonic endoderm (XEN)-like state. However, it is elusive how the chemicals orchestrate the cell fate alteration. In this study, we analyze molecular dynamics in chemical reprogramming from fibroblasts to a XEN-like state. We find that Sox17 is initially activated by the chemical cocktails, and XEN cell fate specialization is subsequently mediated by Sox17 activated expression of other XEN master genes, such as Sall4 and Gata4. Furthermore, this stepwise process is differentially regulated. The core reprogramming chemicals CHIR99021, 616452 and Forskolin are all necessary for Sox17 activation, while differently required for Gata4 and Sall4 expression. The addition of chemical boosters in different phases further improves the generation efficiency of XEN-like cells. Taken together, our work demonstrates that chemical reprogramming is regulated in 3 distinct “prime–specify–transit” phases initiated with endogenous Sox17 activation, providing a new framework to understand cell fate determination.

In vivo Chemical Reprogramming of Astrocytes into Functional Neurons

Mammals lack robust regenerative abilities. Lost cells in impaired tissue could potentially be compensated by converting nearby cells in situ through in vivo reprogramming. Small molecule-induced reprogramming is a spatiotemporally flexible and non-integrative strategy for altering cell fate, which is, in principle, favorable for the in vivo reprogramming in organs with poor regenerative abilities, such as the brain. Here, we demonstrate that in the adult mouse brain, small molecules can reprogram resident astrocytes into functional neurons. The in situ chemically induced neurons (CiNs) resemble endogenous neurons in terms of neuron-specific marker expression and electrophysiological properties. Importantly, these CiNs can integrate into the mouse brain. Our study, for the first time, demonstrates in vivo chemical reprogramming in the adult brain, which could be a novel path for generating desired cells in situ for regenerative medicine.