Mesenchymal stromal cells: an update

Purpose of review Mesenchymal stromal cells (MSCs) are widely utilized in preclinical and clinical studies, with over 1500 clinical trials, including applications in Covid-19 treatment. This review consolidates recent advances in understanding MSC biology, mechanisms of action, and clinical utility. Recent findings This review discusses recent progress made in understanding MSC biology, including immunomodulatory mechanisms mediated by microRNAs and long noncoding RNAs. Clinically, MSC therapies have shown promise in treating conditions like Covid-19-associated ARDS and several MSC therapeutic products have been approved. Single-cell analyses have shed light on MSC heterogeneity, revealing tissue-specific and conserved subpopulations influenced by the extracellular matrix. The FDA's updated recommendations on potency assays emphasize a holistic approach to quality control, reinforcing the need for a universal reference standard to improve reproducibility and clinical outcomes. In addition, to better understand their limited success in randomized clinical trials, we highlight the importance of a universal reference standard for MSC potency. Summary MSCs offer significant therapeutic potential, but addressing challenges in heterogeneity and potency standardization is essential. Advances in understanding their immune properties and clinical applications provide opportunities to refine and expand their use in regenerative medicine.