I recently attended a fascinating lecture by Cambridge neuroscientist Robin Franklin on progenitor cells ("neural stem cells") and their treatment potential in neurodegenerative diseases, such as multiple sclerosis (MS). The progressive form of MS, which follows from the relapsing-remitting version, stems from a decreasing ability of oligodendrocyte cells and their crucial myelin sheaths to be regenerated after they are destroyed through the course of the disease. Dr. Franklin's lab studies cell remyelination, specifically focusing on oligodendrocyte precursor cells (OPCs), which are a form of progenitor that can evolve into oligodendrocytes to replace the damaged cells and sheaths. However, as an individual ages, these cells have a greater difficulty differentiating and do not regenerate as efficiently, which is most likely the cause in the transition to the progressive form of the disease. Dr. Franklin's lab has used parabiosis to study the effects of aging on progenitor cell differentiation, the amazing science fiction-esque research method of fusing two mice together (in this case young and old), enabling them to share blood flow. From this research, Dr. Franklin has provided the most compelling evidence to date that decreases in crucial blood proteins as an individual ages are behind the increasing disability in remyelination and disease progression.