Decellularized matrix hydrogel optimized MSC secretome alleviates radiation sialadenitis by apoptosis restoration to induce Senolysis

Abstract

Introduction: Radiation sialadenitis is a debilitating complication of head and neck cancer radiotherapy for which no effective therapy exists. Conventional MSC-based strategies face translational barriers, and crude MSC-conditioned medium (MSC-CM) provides only limited efficacy, underscoring the need for cell-free alternatives. Materials and methods: Rat salivary gland MSCs were characterized and cultured on porcine decellularized matrix hydrogel to generate optimized concentrated conditioned medium (CC-CM). CC-CM was tested in irradiated SGMSCs and in a rat submandibular gland irradiation model; senescence, apoptosis, and transcriptomic changes were assessed. Apoptosis dependence was examined using the pan-caspase inhibitor Z-VAD-FMK, and senescent cell clearance was evaluated by flow cytometry, live-cell imaging, and co-staining for senescence and apoptosis markers. Results and discussion: CC-CM demonstrated markedly superior therapeutic effects against radiation sialadenitis compared with conventional MSC-CM. Mechanistically, irradiation induces an early apoptosis-resistant state in SGMSCs that precedes the senescence phenotype, and the accumulated senescent cells are refractory to apoptosis. CC-CM eliminates these pathogenic senescent cells, exhibiting senolytic activity. Dynamic live cell imaging revealed that CC-CM restores the impaired apoptotic process in irradiated SGMSCs. CC-CM increased the number of dead cells in a caspase-dependent manner, and co-staining for senescence markers and cleaved caspase-3 confirmed that CC-CM directs senescent cells into apoptosis. This senolytic activity was further validated in vivo in irradiated submandibular gland tissues. Pharmacological blockade of apoptosis attenuated the therapeutic effects of CC-CM, establishing the functional necessity of apoptosis restoration. Conclusion: Tissue-specific decellularized matrix priming endows the MSC secretome with the capacity to eliminate radiation-induced senescent cells through restoration of the apoptotic program. This mechanism-based, cell-free platform represents a promising strategy for treating radiation-induced salivary gland injury.

Keywords

Radiation sialadenitis / Mesenchymal stem cells / Decellularized matrix hydrogel / Cell senescence / Cell apoptosis

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