Acute cell‑death and lysosomal stress responses to nicotine and cigarette smoke extract in human mesenchymal stromal cells

Mesenchymal stromal cells (MSCs) are essential for connective tissue repair, and impaired healing is well documented in tobacco users. MSCs are one plausible target for these adverse effects, but the underlying cellular mechanisms of high localized nicotine exposure remain poorly understood. This study investigated how short-term nicotine and cigarette smoke extract (CSE) exposure affect human MSC function, viability, and inflammatory signaling in vitro. MSCs isolated from bone marrow were exposed to CSE containing 4-40 µM nicotine or to 100 µM-10 mM pure nicotine. CSE produced markedly stronger cytotoxicity than nicotine, reducing proliferation and rapidly inducing necrotic cell death at 20-40 µM nicotine equivalents. Pure nicotine elicited a biphasic response: concentrations below 5 mM slightly increased proliferation, while 5 mM caused apoptotic cell death with prominent lysosomal vacuolization, and 10 mM shifted cell death toward necrosis. Sublethal exposures that generated pre-apoptotic cells were associated with significant IL8 induction and MMP2 activation, whereas IL6 remained largely unchanged. Nicotine induced lysosomal disruption suggests broader impacts on MSC homeostasis beyond viability, potentially influencing lineage commitment. These findings elucidate short-term effects of nicotine and CSE; high-dose nicotine and CSE are toxic to MSCs, while the lower doses perturb the inflammatory signaling and lysosomal function. Such alterations may compromise tissue regeneration, wound healing, and periodontal stability in users of potent localized nicotine delivery products.