Scientists recently announced that they have optimized a way of assembling mobile clusters of cells to organize other cells into micro clusters that, under the right condition, could be mobile on themselves. Scientist call this process “kinematic self-replication,” although that’s not entirely right—the copies need help from humans to start moving on their own, are smaller than the originals, and the copying this process grinds to a halt after just a couple of cycles.
“This is profound,” added Michael Levin, co-leader of the research. “These cells have the genome of a frog, but, freed from becoming tadpoles, they use their collective intelligence, a plasticity, to do something astounding.”
The research team stated that the new research may be beneficial for advancements in human regenerative medicine.
“If we knew how to tell collections of cells to do what we wanted them to do, ultimately, that’s regenerative medicine — that’s the solution to traumatic injury, birth defects, cancer, and aging,” Levin said.
“All of these different problems are here because we don’t know how to predict and control what groups of cells are going to build. Xenobots are a new platform for teaching us.”
Mobile orbs of cells
The entire process begins by isolating the embryonic cells from a single frog’s egg. With the cells’ many very interesting properties, two are relevant for this work. The first is that these cells adhere to each other. If you leave a cluster of them in a culture dish, they’ll pull together into a ball. You can even dissociate them entirely and leave a collection of them in culture, and they’ll s cling back together and form a ball of cells that way.
The living cells’ second relevant feature is that they will intelligently self-organize, such that the external cells have thread-like projections called cilia. These spin around in circles, pushing against the surrounding fluid of the culture medium. Over time, neighboring cells coordinate their cilia such that, eventually, the entire ball of cells will end up spinning its cilia in synchrony.
The issue with this process is that it’s is thus inefficient. The second generation of MBCs was smaller than the first and traced a smaller circle. At most, you could go two generations of progeny MBCs before the whole process stalled out. So, these are not especially accurate or efficient replicators.
The new research looked at ways to optimize this by altering the shape of the original MBCs. But surgically modifying an MBC is challenging work, and then it needs a few weeks in contamination-prone culture dishes to see how it behaves. Being inherently lazy, the researchers decided to model their behavior using computers, implementing an evolutionary algorithm that created variations of shapes that were then tested for their ability to herd cells using a physics simulator.
A researcher who is involved in the work who is in the Department of Computer Science told CNN that this combination of algorithm and modeling is an AI. If scientists want the public to understand what they’re doing better, it would help if they actually gave the public accurate information.)
Since the most effective Xenobot replication starts by piling up a large amount of cells, the algorithm essentially found forms of MBCs that did so most effectively. The solution the model came up with turned out to be a half-toroid.
Creating these Xenobots required the researchers to perform surgery on MBCs, cutting out a notch on one side of the ball after it was squashed flat into a disk, and then unflattening it. But the results were impressive: some of the crescent-shaped MBCs could produce progeny that could go for an additional three generations before the process failed. But again, this wasn’t exactly self-replication, since the ensuing future that generations wouldn’t assume a crescent shape without surgical intervention.