Contrary to the minimal criteria proposed by the International Society for Cell and Gene Therapy for defining multipotent mesenchymal stromal cells (MSC), human leukocyte antigen (HLA)-DR expression is largely unpredictable in ex vivo-expanded clinical-grade cultures. Although activation of MSC in culture does not appear to affect their functionality, a large study investigating the impact of HLA-DR expression on cell identity and potency is still missing in the literature. A retrospective analysis of HLA-DR expression in 130 clinical batches of bone marrow (BM)-MSC from two independent Good Manufacturing Practice-compliant production facilities was performed in order to identify the consequences on critical quality attributes as well as potential activation cues and dynamics of MSC activation in culture. HLA-DR+ cells in culture were confirmed to maintain fibroblastic morphology, mesenchymal phenotype identity, multipotency in vitro, and immunomodulatory capacity. Interestingly, the use of either human sera or platelet lysate supplements resulted in similar results. HLA-DR expression should be considered informative rather than as a criterion to define MSC. Further work is still required to understand the impact of HLA-DR expression in the context of product specifications on BM-MSC qualities for clinical use in specific indications.

The capacity of organoids to generate complex 3D structures resembling organs is revolutionizing the fields of developmental and stem cell biology. We are currently establishing the foundations for translational applications of organoids such as drug screening, personalized medicine and launching the future of cell therapy using organoids. However, clinical translation of organoids into cell replacement therapies is halted due to (A) a few preclinical studies demonstrating their efficacy and (B) the lack of robust, reproducible, and scalable methods of production in compliance with current pharmaceutical standards. In this issue of Stem Cell Research & Therapy [ref], Dossena and collaborators present a validated bioprocess design for large-scale production of human pancreatic organoids from cadaveric tissue in accordance with current good manufacturing practice. The authors also propose a set of specifications of starting materials and critical quality attributes of final products that are of interest to other developments provided that this type of medicines are different than any other medicinal product due to their complex composition and living nature of the active ingredient. Although large-scale production of functional cells secreting insulin is still a challenge, the development of methods such as the one presented by Dossena and collaborators contributes to move toward clinical use of organoids in the treatment of type 1 diabetes and opens avenues for future clinical use of organoids in degenerative pathologies.