RecruitingPhase 1Biological interventionDose-Escalation Trial of Mesenchymal Stromal Cells in Patients With Medical XerostomiaThe goal of this clinical trial is to evaluate the safety and tolerability of injecting certain cells produced in bone marrow called mesenchymal stromal cells (MSCs) into salivary glands. The main question it aims to answer is whether injection of MSCs into salivary glands results in any improvement in dry mouth. Participants will: * have bone marrow collected using a needle * undergo a salivary gland ultrasound * complete questionnaires * receive an injection of the bone marrow cells into a salivary gland