Cho, S. G. | Search bioRxiv

bioRxiv2026

Microfluidic Mechanical Reactivation of Aged Stem Cells

Stem cell aging significantly impairs therapeutic efficacy, requiring innovative strategies to restore potency. We present a microfluidic cell-compressing platform for reactivation (-CPR) designed to apply controlled hydrodynamic deformation to late-passage stem cells. This mechanical stimulation facilitates functional reactivation without external chemical cues. Within a defined window, -CPR effectively reduces oxidative stress, SA-{beta}-Gal activity, and {gamma}H2AX foci, while simultaneously restoring proliferation and canonical stemness markers (OCT4, SOX2, and KLF4). Mechanical stimulation via -CPR induces coordinated structural remodeling: nuclei become more compact, actin cortex organization is restored, -actinin redistributes to focal adhesions, and microtubule networks are restructured, suggesting a rebalanced intracellular tension. Transcriptomic and proteomic analyses reveal that this process reprograms extracellular matrix remodeling and DNA repair pathways while attenuating pro-fibrotic and senescence-associated secretory phenotype (SASP)-associated pathways. Crucially, this reactivation occurs without compromising fundamental MSC hallmarks, preserving intrinsic immunophenotypes and multilineage differentiation potential. Functionally, -CPR-processed stem cells demonstrate restored in vitro wound closure and enhanced tissue repair in vivo, with efficacy appearing dependent on mechanical dosage. This platform establishes a non-genetic, mechanobiological approach to restoring stem cell function, offering a scalable strategy for functional reactivation and potentially paving the way toward comprehensive cellular rejuvenation.

bioengineering↗

bioRxiv2026

Periaqueductal gray neurotensin neurons drive simultaneousthreat response and reinforcement

The periaqueductal gray (PAG) is a midbrain structure known to influence responses to both threat and reward. The PAG sends projections to the ventral tegmental area (VTA), a region critical for regulating motivated behavior via dopamine release. We previously identified a population of VTA-projecting PAG neurons that express the peptide neurotensin (Nts), a potent dopamine neuron activator. Here we find that PAG-Nts neurons co-release glutamate and Nts in the VTA to drive dopamine neuron activation. These neurons are activated by threats and threat-predictive cues and are inhibited by entry into a shelter and during reward consumption. Optogenetic stimulation elicits a robust threat response, including freezing and tail rattle, but remarkably can also drive intracranial self-stimulation. This operant reinforcement behavior is dopamine dependent while the threat response is not. Together, these results identify a dual-output circuit that engages the dopamine system, likely to increase the salience of environmental stimuli, while simultaneously driving specific threat response behaviors.

neuroscience↗