Summary: Training neural circuits during early development produces stronger, longer-lasting improvements than training mature cells.
Source: University of Illinois
Train neural circuits early for best results in tissue engineering and biomedical applications, a new study from the University of Illinois suggests.
Current approaches to programming engineered neural networks often apply stimulation after cells reach full maturity. Researchers at the University of Illinois, Urbana-Champaign, used optogenetic techniques with light-sensitive neurons derived from mouse embryonic stem cells and found that applying stimulation throughout early development and network formation produced durable improvements in connectivity, responsiveness and gene expression. The team reported these findings in the journal Scientific Reports.
“It’s like an old dog learning new tricks versus a young puppy,” said Gelson Pagan-Diaz, a graduate student and first author of the study. “Stimulating a network while it’s still developing yields a stronger, more lasting response than stimulating a network after it has fully matured.”
These improvements have practical implications for bioengineering and regenerative medicine. The Illinois team envisions using optimally trained neural circuits to control movements and behaviors in miniature bio-hybrid machines. Training during early stages could increase the functionality of those circuits and provide finer control over engineered behaviors.
“As we advance the field of integrating living cells into machines, the ability to stimulate and program neuronal cells with light early in their development could become an essential engineering tool,” said study leader Rashid Bashir, professor of bioengineering and dean of the Grainger College of Engineering at Illinois. “This approach also has potential relevance for developmental biology, regenerative therapies and brain research.”
The research team applied timed pulses of light to stimulate neurons, beginning while the cells were still clusters of stem cells, known as embryoid bodies, that were primed to become motor neurons. They continued stimulation through differentiation into mature neurons and after transferring the cells onto plates where they formed connected networks. These “early-trained” networks were then compared with circuits that were cultured first and stimulated later, following the more common protocol.
The differences were clear. Neurons trained during development exhibited more neurite outgrowth—extensions that form connections between cells—an increase in packages of neurotransmitter release, and more organized patterns of electrical activity, indicating greater network stability. Importantly, the benefits of early training were long-lasting, while networks trained only after maturation tended to show transient effects.
“You can think of the neurons as athletes,” Pagan-Diaz explained. “Regular light stimulation during development acted like a consistent training program: the neurons became stronger, more coordinated, and better at executing their functions.”
To understand the molecular basis for these functional changes, the team analyzed gene expression. They observed elevated expression of genes associated with network maturity and neural function, suggesting that early optogenetic stimulation can induce lasting shifts in genetic programs as neurons develop.
Researchers are now investigating which specific functions can be enhanced or programmed by stimulation during the embryoid body phase. Embryoid bodies offer a promising modular component for building biological machines, and they may also improve outcomes in regenerative medicine applications.
“Previous work has shown that embryoid bodies containing motor neurons can aid tissue regeneration when implanted into injured animal models,” Pagan-Diaz noted. “If we can enhance the functionality of these structures before implantation by training them earlier, it could potentially improve recovery beyond what is achieved by introducing untrained cells and stimulating them afterward.”
Funding: This work was supported by the National Science Foundation through the Emergent Behaviors of Integrated Cellular Systems Science and Technology Center and the Miniature Brain Machinery Research Traineeship. Co-authors included research staffer Jenny Drnevich, graduate students Karla Ramos-Cruz and Richard Sam, and Parijat Sengupta, a bioengineering professor at the University of Illinois, Chicago.
About this neuroscience research article
Source:
University of Illinois
Contacts:
Liz Ahlberg Touchstone – University of Illinois
Image Source:
The image is in the public domain.
Original Research: Open access
“Modulating electrophysiology of motor neural networks via optogenetic stimulation during neurogenesis and synaptogenesis” by Gelson J. Pagan-Diaz, Jenny Drnevich, Karla P. Ramos-Cruz, Richard Sam, Parijat Sengupta & Rashid Bashir. Scientific Reports. DOI: 10.1038/s41598-020-68988-y
Abstract
Modulating electrophysiology of motor neural networks via optogenetic stimulation during neurogenesis and synaptogenesis
Controlling electrical activity in neural circuits through targeted training is a major challenge for both biomedical research and engineering. Previous work has not systematically explored whether applying training regimens at specific stages of neural development can produce long-term changes in firing patterns of in vitro networks. In this study, Channelrhodopsin-2 (ChR2) transfected mouse embryonic stem cell–derived motor neurons were stimulated optically during neurogenesis and synaptogenesis to examine both short- and long-term programming effects. The authors observed increased neurite extension and synaptophysin clustering, and electrophysiological recordings with microelectrode arrays (MEAs) revealed shifts in frequency spectra, enhanced network synchrony, coordinated action potential firing, and stronger evoked responses during network formation. RNA sequencing showed corresponding changes in gene expression linked to network maturity and function. These results indicate that optogenetic stimulation during neural differentiation can induce persistent functional and genetic changes, providing a new strategy for training neural circuits in vitro with potential applications in neurodegenerative disease research and the engineering of multicellular living systems.