Experiment tests senescence thresholds

This proposed experiment asks whether senescent cells, cells locked in lasting growth arrest, make nearby human lung connective-tissue cells senescent only once a critical density is reached. Researchers will mix 5–80% senescent IMR-90 donors, human lung fibroblasts, with naïve recipient fibroblasts at a constant starting cell count and 3% oxygen. At 96 hours, they will measure recipient p16INK4a, a marker of cell-cycle arrest, and Lucifer Yellow dye transfer, a readout of cell-to-cell channels. At eight densities, five replicates will compare vehicle and 100 μM carbenoxolone, a channel blocker. A blockade-shifted sigmoidal curve would support connectivity-dependent spread; a linear rise would favor gradual signaling by secreted factors. Because carbenoxolone also blocks hemichannels, it cannot isolate gap-junction effects.