Mah, J. | bioRxiv Science

bioRxiv2025

Extracellular matrix remodeling supports Hydra vulgaris head regeneration and stem cell invasion

The small freshwater cnidarian Hydra vulgaris is a classic model for investigating the genetic regulation of whole-body regeneration, but the underlying cell biology is comparatively underexplored. Hydra has a simple body plan consisting of two epithelial monolayers separated by an extracellular matrix (ECM). This ECM contains conserved components such as collagen and laminin, making Hydra well suited for dissecting ECM function during regeneration. Following head amputation and wound closure, we observe a retraction of ECM proteins from the wound site, creating a region of low ECM protein accumulation that persists for several days during head regeneration. Several matrix metalloproteinase (MMP) genes are expressed during this process, and MMP inhibition reduces the size of the ECM gap and results in a regenerative outcome with gross morphological defects. We further find that interstitial stem cells (ISCs), which originate in the ectoderm, localize in the regenerating head endoderm near regions of reduced ECM. This suggests that the ECM gap facilitates stem cell invasion to populate the new head with neurons and gland cells. However, inhibition of collagen cross-linking reveals that collagen synthesis is also required for regeneration, indicating that Hydra must balance ECM degradation and synthesis to complete regeneration. Together, these findings highlight ECM remodeling as a critical and conserved feature of regeneration. Summary statementThis study uses Hydra vulgaris, a highly regenerative freshwater cnidarian, to study remodeling of extracellular matrix proteins and stem cell invasion during tissue regeneration.

developmental biology↗

bioRxiv2025

Examination of germline and somatic intercellular bridges in Hydra vulgaris reveals insights into the evolutionarily conserved mechanism of intercellular bridge formation

Incomplete cytokinesis results in the formation of stable intercellular bridges that have been extensively studied in bilaterians, where they play essential roles in cell-cell communication and coordination of differentiation. However, little is known about their structure and molecular composition in non-bilaterian animals. This study characterizes germline and somatic intercellular bridges in the cnidarian Hydra vulgaris, providing insights into their evolutionary origins and functional significance. We identified key conserved components, including KIF23, F-actin, and phosphotyrosine. Notably, we observed microtubule localization within Hydra ring canals, suggesting previously unrecognized functions for this cytoskeletal component in intercellular bridge formation. Bioinformatic analyses confirmed the conserved expression of Kif23 and suggested its role as a molecular marker for identifying ring canal-associated components. EdU incorporation during DNA replication demonstrated that cells connected by ring canals exhibit synchronized cell cycles, which may be critical for the coordination of division and differentiation. Our findings reveal that the molecular and structural features of intercellular bridges in Hydra are conserved across evolutionary lineages, highlighting their ancient origins and functional significance in cellular connectivity. The presence of synchronized cell cycles in ring canal-connected cells underscores their role in promoting coordinated cellular behaviors, processes fundamental to multicellular organization. This study provides new perspectives on the evolution of incomplete cytokinesis and establishes a framework for comparative investigations into the diversity and conservation of intercellular bridge mechanisms across metazoans.

cell biology↗