Human adult stem cells such as mesenchymal stem cells (hMSCs; derived from bone marrow, fat or circulating blood) have low proliferative capacity and a finite life-span. Many regenerative medicine applications employ hMSCs; however lack of expandability and senescence significantly inhibits their autologous clinical adoption. This is highly significant in diseased (e.g. diabetic) or elderly donors.
Our concept arose from the MASC (Materials that Impose Architecture within Stem Cell Populations) Advanced Grant awarded to Professor Kevin Shakesheff. GET (GAG-binding Enhanced Transduction) technology; which couples a cell-penetrating peptide (CPP) with a membrane docking peptide targeting heparan sulphate glycosaminoglycans (GAGs); was developed using this funding. GET technology allows exceptional intracellular delivery of conjugated cargoes.
The ImmortaSTEM concept originates from the discovery that the GET delivery system can be used to promote cell growth by transiently delivering RNAs encoding immortalisation genes (HPV E6/7 & hTERT). Although this effect was statistically significant the number of serial deliveries of RNA was detrimental to the cells over time. We have achieved a more long lasting and cell compatible effect using pDNA using modified vectors employed for iPSC reprogramming.
We generated cells with doubling times of circa 2 days. This compares with low passage hMSCs which double every 3 to 4 days dependent on health and age of donor. We focused on elderly and diabetic donor hMSCs and aimed to ‘reset the clock’ so they can be efficiently expanded. Continuation of this research will allow transformative patient-specific cell therapy approaches that would not presently be achievable for those donors that are likely to demonstrate problems in stem cell expansion.
