1497.3.3 Experimental Animal Models
In order to reach the long-term aim of clinical translation of cell-based therapy,
preclinical safety and efficacy need to be demonstrated in animal models.
Transplantation of in vitro expanded ASCs in the appropriate experimental animal
model is therefore an important step in the development of cell therapy products.
Sensitive cell-tracking techniques are needed in order to determine the most optimal
route of administration as well as the homing ability of the transplanted ASCs.
Transduced ASCs containing GFP lentiviral vectors could offer a feasible in vivo
tracking system as it has been shown that transduction of ASCs with a GFP-
expressing lentiviral vector does not affect their phenotypic expression or their dif-
ferentiation potential (van Vollenstee et al. 2016 ).
7.4 Conclusion
Although manual isolation procedures are less costly than closed automated sys-
tems, the risk of contamination associated with manual procedures makes them a
less attractive option for clinical applications. GMP isolation and expansion proce-
dures require the minimal use of xenogeneic components, and only cell therapy
products that are free of animal-derived products will lead to successful translation
into the clinic. ASCs are regarded as non-minimally manipulated cells and are clas-
sified as a drug by the Food and Drug Administration (FDA). However, it is cur-
rently unclear whether in vitro expanded ASCs hold any significant benefit over
AD-SVF, particularly in the clinical setting.
One of the major pitfalls in the rapidly expanding field of ASCs is that no inclu-
sive panel of either cellular or molecular markers exists that specifically character-
ize these cells. The ISCT and IFATS regularly publish updated guidelines for the
classification of ASCs. However, the current guidelines are still not specific and are
based on the ability of the cells to adhere to plastic, to express a set of non-specific
cellular markers and to differentiate into adipogenic, osteogenic, chondrogenic and
myogenic lineages.
For example, although classical stains (Oil Red O, Alizarin Red S and Toluidine
Blue) confirm lineage differentiation in vitro, it is unclear if all induced ASCs have
differentiated into the respective lineage. The translation of in vitro assays to the
patient is also unclear, and well-characterized in vivo experimental models are
needed to validate the engrafting, homing and differentiation potential of the cell
therapy in question. The availability of reliable and reproducible in vivo experimen-
tal models will therefore contribute to a more confident and potentially more rapid
translation of ASC research to the clinical setting.
7 Isolation and Characterization of Adipose-Derived Stromal Cells