α-5 Laminin Synthesized by Human Pluripotent Stem Cells Promotes Self-Renewal

• α-5 laminin is produced by undifferentiated hPSCs under defined culture conditions
• Disruption of endogenous α-5 laminin production causes hPSC apoptosis
• Exogenous α-5 laminin rescues cell survival
• α-5 laminin acts as a critical autocrine and paracrine factor for hPSC self-renewal

SummarySubstrate composition significantly impacts human pluripotent stem cell (hPSC) self-renewal and differentiation, but relatively little is known about the role of endogenously produced extracellular matrix (ECM) components in regulating hPSC fates. Here we identify α-5 laminin as a signature ECM component endogenously synthesized by undifferentiated hPSCs cultured on defined substrates. Inducible shRNA knockdown and Cas9-mediated disruption of the LAMA5 gene dramatically reduced hPSC self-renewal and increased apoptosis without affecting the expression of pluripotency markers. Increased self-renewal and survival was restored to wild-type levels by culturing the LAMA5-deficient cells on exogenous laminin-521. Furthermore, treatment of LAMA5-deficient cells with blebbistatin or a ROCK inhibitor partially restored self-renewal and diminished apoptosis. These results demonstrate that endogenous α-5 laminin promotes hPSC self-renewal in an autocrine and paracrine manner. This finding has implications for understanding how stem cells dynamically regulate their microenvironment to promote self-renewal and provides guidance for efforts to design substrates for stem cell bioprocessing.

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