In the renal collecting duct the cells are exposed to high osmolality. The high osmolality also induces the expression of the aquaporin-2-4 (AQP2-4). Beside their role in water reabsorption several AQPs have been shown to be involved in cell migration. Therefore we first wanted to analyze if osmolality affects the migration of primary cultured inner medullary collecting duct (IMCD) cells. Next we wanted to show if the AQP2-4 contribute to the migratory capacity.

We performed wound healing assays at different osmolality (300 or 600 mOsmol/kg) and calculated the covered area over the time (mm²/min). The localization of proteins in migrating cells was analyzed by immunofluorescence.

The cells cultivated at 300 were faster than those cultivated at 600 mOsmol/kg. An acute increase from 300 to 600 mOsmol/kg massively decreased and a drop from 600 to 300 mOsmol/kg increased the migratory speed. Western Blot analysis and immunofluorescence analysis showed that the expression of AQP2-4 is induced by an increase in osmolality. Only a weak signal was detectable for them in migrating cells cultivated at 300 mOsmol/kg. At 600 mOsmol/kg none of the AQPs were enriched at the leading edge of the migrating cells. While AQP2 showed no changes in localization interestingly AQP4 was enriched at the rear end of the leading cells. AQP3 completely disapperared from the first 2–3 rows of cells close to the leading edge.

With this study we were able to show that osmolality affects migration of IMCD cells. The migration also affects the expression and localization of AQP3 and AQP4. If and how these AQPs contribute to the migratory capacity has to be elucidated in further studies.