Multiple stimulation with spheroids comprising salivary gland and adipose-derived stem cells enhances regeneration of radiation-damaged salivary glands

•Spheroids are more effective than monolayer cultures in salivary gland regeneration.•Salivary gland stem cells (SGSCs) and adipose-derived stem cells (ASCs) were used.•SGSCs combined with ASCs induced greater regeneration than SGSCs alone.•Signaling pathways related to angiogenesis and anti-apoptosis are likely involved in the effect.