Creation of an Online Game to Simulate Countercurrent Multiplication in the Mammalian Kidney

Prior to the COVID pandemic, we designed and implemented a hands‐on activity to help students understand how countercurrent multiplication (CCM) in the mammalian kidney produces concentrated urine. To supplement the traditional text descriptions, figures, and lecture material we had students play the role of glomerular filtrate, gaining and losing osmolarity while moving through a simulated Loop of Henle. Students were given three poker chips, each representing an osmotic pressure of 100 milliosmolar (m Osm ). Each student took a position at one of six steps on each side of a table. For each round, 1) students on the “ascending” side conducted “active transport” to produce a maximum gradient of 200 m Osm between the lumen of the ascending loop and the interstitial space (difference of 2 chips); 2) after students “pumped” their ions, students on the “descending” side “equilibrated” with the interstitial space by collecting chips from a cup until they had the same quantity as in the interstitial space; 3) students then physically “flowed” through the loop. This learning tool, which was highly effective in a face‐to‐face classroom, did not translate well to a remote environment. Despite spending an entire online class explaining the activity, students remained confused. Unlike in the classroom where everyone participates simultaneously and sees the process “in real‐time,” only one person could participate at any given time virtually, making it hard to visualize flow. To address this shortcoming we collaborated with two undergraduate students to develop a “flipped” version of the CCM activity. In the online version the player 1) actively participates in CCM in “freeplay” mode or 2) watches the process in “simulation” mode. During freeplay, the player drags and drops icons representing solutes or water from the loop of Henle into the interstitial fluid to build the osmotic gradient; a color gradient associated with solute concentrations highlights how the gradient forms. Modeled after the in‐person activity, the loop of Henle is divided into boxes, six on the ascending limb and six on the descending limb, where each box represents the positions of students in the original activity. To maximize engagement by minimizing repetitive dragging and dropping, the player is confined to one box at a time and is only responsible for adjusting the concentration of this “home” box. If the player adjusts the concentration correctly, the player's home box moves one unit over to the adjacent box and thus ‘flows’ through the loop. Along the way, concentration shifts within other boxes are automated by the game engine. The freeplay game ends when the player's home box reaches the top of the ascending limb and exits the loop. In the simulation mode, the icons of solute and water move by themselves, and the osmotic gradient is created automatically. The player can watch the CCM process unimpeded and may pause or speed up the process as desired. We will pilot this interactive, online game in our Spring 2021 course and assess student learning with reflections, homework problems, and exam questions. We predict implementation of this game will enhance student understanding of the CCM mechanism in the mammalian kidney. All protocols were approved by Rice University IRB (Protocol FY2017‐294).