Transient HA-100 exposure improves aggregate uniformity and cell-cell contact stability in suspension human pluripotent stem cell cultures.

Abstract

Human pluripotent stem cell (hPSC) manufacturing workflows frequently rely on suspension aggregation, yet inter-line and batch-to-batch variability in aggregate formation can compromise process consistency and downstream differentiation performance. We evaluated whether a short exposure to HA-100, a small-molecule inhibitor of protein kinase A and protein kinase C signaling, could be used as an upstream process intervention to improve aggregate uniformity without compromising hPSC identity or developmental competence. Nine hPSC lines, including human embryonic stem cell and induced pluripotent stem cell lines, were examined in suspension culture. HA-100 was applied during the first 24 h of aggregation. Aggregate morphology and size distribution were assessed across lines. To investigate the cellular basis of this effect, we generated an mCherry-TJP1 reporter hESC line, which enabled live visualization of junction dynamics, including responses under calcium-depleted conditions and recovery of transepithelial electrical resistance. HA-100 treatment promoted more compact and spherical aggregates, increased aggregate size into a narrower range across lines, and reduced overall variability relative to medium alone. Across the nine-line panel, HA-100-treated aggregates fell within an empirically definesd size range of 25.37-33.95 x 10^-4 mm^3 after 24 h of suspension culture, providing a practical benchmark for process monitoring. In calcium-depleted conditions, HA-100 delayed disruption of intercellular contacts and accelerated recovery of transepithelial electrical resistance, consistent with improved junctional resilience. Transient exposure to HA-100 did not abolish pluripotency marker expression or tri-lineage differentiation capacity. These data support HA-100 as a practical upstream intervention to reduce aggregate heterogeneity in suspension hPSC cultures and improve reproducibility in manufacturing-oriented workflows requiring consistent aggregation.