Study on Regenerative Process Identifies TRACS as Secret to Flatworm Regeneration Better Than Earthworms'

Fishing enthusiasts usually recognize their earthworm bait's ability to regenerate in either end when accidentally or even purposely cut for fishing reasons. However, there is an organism that exhibits better performance compared to the astounding regeneration of earthworms. The species is called Schmidtea mediterranea, better known as freshwater planarian flatworm.

Schmidtea mediterranea's Astonishing Regenerative Ability

Schmidtea mediterranea has a more effective regeneration than the standard earthworm we commonly encounter crawling on soils. The flatworm planarian can regrow animals in its mini version that scales 1/279th by using the animal's own tissue fragment.

Stem cells and other regenerative properties comprise the body of the flatworm. In the recent study of the unbelievable regeneration capacity of the species, a team lead by Stowers Institute for Medical Research and the Sanchez Alvarado Lab experts explained the complex tricks behind the fast and near-accurate regrowing method of the flatworms.

Stowers Institute director Blair Benham-Pyle and Howard Hughes Medical Institute expert Alejandro Sanchez Alvarado said in a report by ScienceDaily that the epidermis and wound-induced muscles of the flatworms are responsible for their flawless regeneration.

According to the experts, the research is the first and most comprehensive yet to define the characteristics of the Schmidtea mediterranea species and how they respond to severe amputations. In the study, they also successfully dug the most crucial method for the flatworms to exhibit their regenerative ability.

Among the key factors of the study that pointed out the regeneration process of the Schmidtea mediterranea is its germ layer. The structure consists of three layers, including the muscle, epidermis, and intestine.

Regeneration, in general, is widely known and is studied across every field of biological and medical sciences. Genes, for example, are one of the essential factors needed for a regeneration process to take place. Genes were previously observed to alter both in the event of a muscle amputation and the regenerations that take place after.

However, the experts could not figure out before that various cells throughout the species' body were also contributing to the process. The specified cells are mingling with the regeneration by changing their function and behavior.

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Transient Regeneration-Activating Cell States (TRACS)

The ultimate goal that the experts needed to achieve, and what they actually acquired in the study, was to consolidate the gene expression across animals that can regenerate.

Large-scale RNA sequencing was the initial approach selected by the experts to characterize the single-cells. However, this process did not match the feasibility of the experiment.

Fortunately, a new single-cell sequencing technology called SplitSeq was developed back in 2017, which caught the interest of the authors and collaborated with the project. The recent study was made possible because of the series of development conducted with the same method they came across years ago.

Since then, the SplitSeq-inspired single-cell sequencing was actively used at the Stowers Institute. This method was also used to uncover an unexpected discovery of rare cells states known as the transient regeneration-activating cell states or TRACS.

Further studies will be conducted to answer how the collective cells, including TRACS rare cell states, signal each other to exhibit regeneration and the microscopic process involved.

The study on regeneration was published in the journal Nature Cell Biology, titled "Identification of Rare, Transient Post-Mitotic Cell States That Are Induced by Injury and Required for Whole-Body Regeneration in Schmidtea Mediterranea."