Adjunctive Allogeneic Mesenchymal Stem Cells for Treatment-resistant Bipolar Depression

This trial is testing whether a single infusion of donated mesenchymal stem cells (a type of healing cell) can help people with treatment-resistant bipolar depression — meaning depression that has not improved with multiple standard medications. **You may be eligible if...** - You are between 18 and 65 years old - You have been diagnosed with Bipolar I or Bipolar II disorder - You are currently in a depressive episode with a moderate-to-severe score on a depression rating scale (MADRS score of 25 or above) - You have tried at least two mood stabilizers or antidepressants without meaningful improvement - Your blood inflammation marker (CRP) is above 5 mg/L - You are not pregnant, not breastfeeding, and using a reliable contraceptive method - You are fluent enough in English to complete the study questionnaires **You may NOT be eligible if...** - You have received a stem cell transplant in the last 6 months - You cannot attend study visits or comply with study requirements - You have a condition that would make the procedure unsafe Talk to your doctor to see if this trial is right for you.