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Quantum Dot Tracking of Mesenchymal Stem Cell Markers

(Developmental Collaborator-Driven Research Project)

UCLA: G Iyer, S Weiss;

UC Davis: S Olson, F Chuang, J Nolta

It has been shown that the phenotype of mesenchymal stem cells (MSCs) varies, depending on culture conditions.  For purposes of developing stem cells for clinical treatment of disease (such as the repair of damaged heart tissue) – this issue must absolutely be resolved for further development to continue.  We hypothesize that, even under the most strict adherence to laboratory culture standards, the majority of the most primitive cells are lost during the process of expanding the original MSC population – thus greatly diminishing the therapeutic value of these cells.  Aim (1) will be the evaluation of chemokine receptor (and stem cell marker) CXCR-4 interaction with its natural ligand (and chemoattractant), stromal cell-derived factor-1 (SDF-1).  Aim (2) would be the similar evaluation of the c-met (mesenchymal epithelial transition factor) surface marker and its natural ligand, hepatocyte growth factor or HGF.  Using these two systems to characterize MSC phenotype, together with advanced biophotonic technology to perform longitudinal high-resolution video microscopic studies – we hope to discover information that will lead to greatly improved laboratory culture standards for developing stem cells certified for clinical therapy.

Prof Jan Nolta, Director of the Stem Cell Program at UC Davis, has extensive research experience in this area and has built a Good Manufacturing Practice (GMP) facility for the purpose of developing stem cells for clinical therapy, specifically to repair damaged heart tissue.   She has also developed and refined methods to isolate and extract candidate pluripotent MSC populations from human marrow and adipose tissue – as well as to selectively differentiate them into muscle, bone, cartilage, fat and fibroblast lineages in vitro, to demonstrate their multipotency.  Dr. Gopal Iyer, PhD, postdoctoral researcher working with Prof. Shimon Weiss at UCLA, has developed an aldehyde-hydrazone chemistry to conjugate antibodies to peptide-coated visible quantum dots (see figure).  This chemistry is amenable to heterobifunctionalization of QDots and should greatly increase the range of applications for these labels.  We have used these quantum dot formulations to confirm the expression of EGFR in control Chinese hamster ovary (CHO) and breast cancer epithelial cell (MCF-7) line and to demonstrate the use of these quantum dot probes.  Dr. Jack Li and Dr. Gopal Iyer have also developed superior near infrared-emitting quantum dots and has been working with research collaborators at Stanford University to perform in vivo imaging with these probes in mice.