Optogenetic manipulation of BMP signalling to drive chondrogenic differentiation of hPSCs

Optogenetics is a rapidly advancing technology that combines photochemical, optical and synthetic biology techniques to control cellular behaviour and physiology. Combining sensitive light responsive optogenetic intervention tools with human pluripotent stem cell differentiation models has the potential to refine differentiation and unpick the processes by which morphogenetic signals direct tissue patterning, organisation and cell specification. Here, we utilised an optogenetic bone morphogenetic protein (BMP) signalling system (optoBMP) to drive chondrogenic differentiation of human embryonic stem cells (hESCs). We initially engineered light-sensitive hESCs through CRISPR/Cas9-mediated integration of the optoBMP system into the AAVS1 locus. Activation of optoBMP with blue light in lieu of BMP family growth factors during differentiation resulted in activation of BMP signalling pathway mechanisms and upregulation of a chondrogenic phenotype, with significant transcriptional differences compared to cells left in the dark. Furthermore, cells differentiated with light were capable of forming chondrogenic pellets consisting of a hyaline-like cartilaginous matrix.