Effects of lactate on the transcriptome of human pluripotent stem cells

Human pluripotent stem cells (hPSCs) rely heavily on glycolysis and consequently generate substantial lactate, yet the functional role of lactate in hPSC expansion and fate control remains incompletely defined. Here, we tested whether extracellular lactate acts solely as a growth-inhibitory byproduct or instead functions as a regulatory metabolite that modulates hPSC physiology, transcriptional state, and differentiation potential. H9 human embryonic stem cells and IMR90 induced pluripotent stem cells were cultured with exogenous sodium L-lactate (2.5 or 5 g/L; isomolar NaCl controls) and evaluated for proliferation, viability, and pluripotency, followed by tri-lineage differentiation, mitochondrial and lipid staining, histone lactylation analysis, and RNA sequencing after one (P1) or four passages (P4) of exposure. RNA-seq revealed a robust but selective response characterized by checkpoint-centered proliferation restraint, dampened morphogen/lineage-priming signaling pathways, reconfigured monocarboxylate transport and LDH isoform balance, induction of acylation-associated chromatin regulators, and persistent remodeling of lipid/membrane programs.