Characterization of Insulin-Secreting Porcine Bone Marrow Stromal Cells Ex Vivo and Autologous Cell Therapy in Vivo

From Mesenchymal Stromal/Stem Cells to Insulin-Producing Cells: Progress and Challenges

Mesenchymal stromal cells (MSCs) are an attractive option for cell therapy for type 1 diabetes mellitus (DM). These cells can be obtained from many sources, but bone marrow and adipose tissue are the most studied. MSCs have distinct advantages since they are nonteratogenic, nonimmunogenic and have immunomodulatory functions. Insulin-producing cells (IPCs) can be generated from MSCs by gene transfection, gene editing or directed differentiation. For directed differentiation, MSCs are usually cultured in a glucose-rich medium with various growth and activation factors. The resulting IPCs can control chemically-induced diabetes in immune-deficient mice. These findings are comparable to those obtained from pluripotent cells. PD-L₁ and PD-L₂ expression by MSCs is upregulated under inflammatory conditions. Immunomodulation occurs due to the interaction between these ligands and PD-1 receptors on T lymphocytes. If this function is maintained after differentiation, life-long immunosuppression or encapsulation could be avoided. In the clinical setting, two sites can be used for transplantation of IPCs: the subcutaneous tissue and the omentum. A 2-stage procedure is required for the former and a laparoscopic procedure for the latter. For either site, cells should be transplanted within a scaffold, preferably one from fibrin. Several questions remain unanswered. Will the transplanted cells be affected by the antibodies involved in the pathogenesis of type 1 DM? What is the functional longevity of these cells following their transplantation? These issues have to be addressed before clinical translation is attempted.

Graphical Abstract

Current status of stem cell therapy, scaffolds for the treatment of diabetes mellitus

Diabetes mellitus (DM) remains the 7th leading cause of death in the world. Daily insulin injection is one component of a treatment plan for people with Diabetes mellitus type 1 (T1DM) that restores normal or near-normal blood sugar levels. However, Insulin treatment depends upon a variety of individual factors and leads to poor and drastic glycemic control. The need for an effective cell replacement strategy will be the aim of future clinical trials. Therefore, the aim of this systematic review is to outline the latest advances in scaffolding and stem cell therapy as a non-pharmacologic treatment for T1DM. It also emphasizes on some pancreas differentiation protocols and the clinical trials associated with stem cell therapy regarding T1DM in vitro and in vivo.

Durable engraftment of genetically modified FVIII-secreting autologous bone marrow stromal cells in the intramedullary microenvironment

Genetically modified FVIII‐expressing autologous bone marrow‐derived mesenchymal stromal cells (BMSCs) could cure haemophilia A. However, culture‐expanded BMSCs engraft poorly in extramedullary sites. Here, we compared the intramedullary cavity, skeletal muscle, subcutaneous tissue and systemic circulation as tissue microenvironments that could support durable engraftment of FVIII‐secreting BMSC in vivo. A zinc finger nuclease integrated human FVIII transgene into PPP1R12C (intron 1) of culture‐expanded primary canine BMSCs. FVIII‐secretory capacity of implanted BMSCs in each dog was expressed as an individualized therapy index (number of viable BMSCs implanted × FVIII activity secreted/million BMSCs/24 hours). Plasma samples before and after implantation were assayed for transgenic FVIII protein using an anti‐human FVIII antibody having negligible cross‐reactivity with canine FVIII. Plasma transgenic FVIII persisted for at least 48 weeks after implantation in the intramedullary cavity. Transgenic FVIII protein levels were low after intramuscular implantation and undetectable after both intravenous infusion and subcutaneous implantation. All plasma samples were negative for anti‐human FVIII antibodies. Plasma concentrations and durability of transgenic FVIII secretion showed no correlation with the therapy index. Thus, the implantation site microenvironment is crucial. The intramedullary microenvironment, but not extramedullary tissues, supported durable engraftment of genetically modified autologous FVIII‐secreting BMSCs.