Our bodies excel at adapting to environmental changes through a process called homeostasis, which keeps our internal temperature steady at 37°C, whether in heat or cold. Maintaining stable internal conditions is crucial for survival, even as external conditions fluctuate.
A new study from the Ikmi Group at EMBL Heidelberg sheds new light on the fundamental importance of maintaining body shape in animals. It enhances our understanding of the molecular pathways involved in regeneration.
Recent research from the Ikmi Group at EMBL Heidelberg reveals that homeostasis goes beyond internal regulation and can actively reshape an organism’s body. The starlet sea anemone (Nematostella vectensis) is a prime example, demonstrating remarkable regenerative abilities.
When injured, it can grow a new head or foot or even split in half to form two complete anemones. Unlike other regenerating animals like salamanders, which restore lost parts proportionally, the sea anemone reshapes its entire body to maintain its overall form, even adjusting unaffected areas. This whole-body regeneration is also observed in flatworms and other similar species.
Aissam Ikmi, EMBL Group Leader and senior author of a new study in the journal Developmental Cell, said, “Regeneration is about restoring function after tissue loss or damage. Most research studies consider patterns and sizes in regeneration, but our findings show that maintaining shape is also crucial – and the organism actively controls it.”
The discovery began when doctoral researcher Stephanie Cheung noticed something unusual: after a sea anemone’s foot was injured, cell division occurred not only at the wound site but also at the opposite end, near the mouth. This suggested that the injury triggered signals across the entire body.
To investigate, the research team used spatial transcriptomics and advanced imaging to track gene activity during regeneration. They found that the injury caused molecular changes throughout the anemone’s body, leading to cell movement and tissue reorganization that reshaped the entire organism.
The degree of reshaping varied with the severity of the injury. A minor injury, like losing a foot, caused mild changes, while a more severe injury, like being cut in half, led to significant remodelling.
The team identified metalloproteases—enzymes that became more active as tissue loss increased. These enzymes weren’t limited to the wound site; they played a crucial role in realigning tissues.
Petrus Steenbergen, one of the study’s lead authors and an Ikmi Group Senior Research Technician said, “Metalloprotease activity has never been shown before in animals like this. I had to design and optimise experimental conditions for Nematostella based on the sparse literature available from other species. This took some time, but the final results were very rewarding.”
The breakthrough came when the researchers realized that all the molecular and cellular changes aimed to restore the anemone’s original shape. By measuring the aspect ratio—length to width—they found that the anemone returned to its pre-injury proportions despite any size reduction after an injury. This meant that the sea anemone maintained its overall body shape, even as it underwent significant remodelling during regeneration.
Ikmi explained, “We were able to witness the body-wide coordination that drives this remodelling. This proportional response allows the anemone to restore its shape, highlighting how organisms like Nematostella interpret and respond to tissue loss in a way that’s scaled to the damage incurred.”
Tobias Gerber, another of the study’s lead authors said, “It was a pleasure to puzzle out the findings of the study together by uniting the team’s expertise in data analysis and cell biology. This work was a truly collaborative journey, and I am glad I was part of it.”
Journal Reference:
- Stephanie Cheung, Danila Bredikhin et al. Systemic coordination of whole-body tissue remodeling during local regeneration in sea anemones. Developmental Cell. DOI: 10.1016/j.devcel.2024.11.001
