LAUSR

Porous membranes used in co‐culture enable the in vitro partitioning of cellular microenvironments, while still permitting physical and biochemical crosstalk between cells. Thus, features of the co‐culture membrane are crucial for recapitulating the physiological functions of co‐cultured cells. This study presents elastic, porous, and ultrathin membranes (EPUMs), which enhance cell–cell interactions and control cell alignment with surface topology created by stretching the membranes. The EPUM is fabricated using poly(lactide‐co‐caprolactone) as the base material, and the porous feature is endowed by a vapor‐induced phase separation process induced by the presence of hygroscopic salt. Owing to its elastic property, the membrane can be stretched, and the deformed porous structures on the membrane surfaces act as nanostructured topographical cues, resulting in cell alignment. By co‐culturing human mesenchymal stem cells (hMSCs) and human umbilical vein endothelial cells (HUVECs) on the opposite sides of the membrane, rapid endothelialization occurs through the membranes, as compared to the commercial membranes. Furthermore, the stretched membranes induce the alignment of hMSCs and HUVECs and ultimately exhibit enhanced endothelial barrier function. The co‐culture membrane developed in this study may provide an effective tool for recapitulating endothelial basement membranes with a controllable endothelial barrier function.