Spatial and temporal patterns of interstitial cell migration in Hydra vulgaris

Interstitial cell migration was characterized in Hydra vulgaris (formerly H. attenuata) and the effects of axial position and tissue injury on migration were investigated. Migrating cells were labeled with the thymidine analog, bromodeoxyuridine, and grafted into unlabeled host polyps. Alternatively, cells were labeled directly in hosts with the fluorescent, carbocyanine dye, DiI. The results show that cell migration appeared constrained to proximal (toward the basal disk) or distal (toward the tentacles) movements, but were never lateral. Some cells moved bidirectionally. The fastest migrating cells moved an average of 28 microns/hr. Two to six percent of the gastric region interstitial cells migrated in 1 day and accumulated throughout the body column. In grafted polyps, an average of eight cells emigrated from midgastric regions every hour. Tissue injury had no observed effect on the amount of cell migration. Cells emigrating from midgastric regions showed a preference for distal accumulation, and this bias was enhanced when migrating cells originated from more distal positions in the polyp. Proximally derived tissue grafted to a more distal position also showed similar, preferential distal migration, indicating that interstitial cell migration patterns are dependent upon their position in the body column and not upon their origin. Migrating interstitial cells are slower moving and less numerous than migrating nematocytes in H. vulgaris, but since their migration patterns are similar, the migration of both cell types may be influenced by the same directional cues.