Several studies were published describing the use of some more exotic cell types. Multipotent mesenchymal stem cells (MSCs) can be relatively easy isolated from mononuclear cells from bone marrow, although a surgical intervention is needed [76]. Approximately one week after bone marrow aspiration, MSCs can be observed and enriched in cell culture. These cells share several properties with fibroblasts, namely, adherent growth and a fibroblast-like morphology [51]. The reprogramming efficiency was indicated at about 0.01%. With respect to the invasive acquisition, the use of MSC is not a broadly applicable choice but represents an option under special circumstances. For example, MSCs can be gathered during planned bone marrow biopsies.
