Stem cells are multipotential progenitors that are capable of self-renewal and multilineage differentiation, and are therefore are of great medical interest because of their therapeutic potential. A major limitation in identifying a pancreatic stem cell has been the complete lack of cell surface markers which are essential in the isolation and characterization of these cells prospectively in vivo. Furthermore, development of a quantitative, clonogenic assay, similar to what exists for studying hematopoietic and neural stem cells, is necessary to prove that a pancreatic stem cell exists.
Prospective identification and isolation of multipotent stem cells or progenitor cells from the pancreas:
Development of antibodies to cell surface markers on stem cells or progenitor cells of the pancreas.
1. Generating antibodies from tissue or cells:
Potential sources of tissue:
- For early markers: dissected mouse embryos or human fetuses (early epithelium, foregut, dorsal pancreatic bud)
- Develop transgenic lines (GFP) from mouse. Take advantage of characterized promoters of developmentally regulated genes of the pancreas anlage (eg. PDX-1 promoter-GFP, isolate GFP-expressing cells from mouse embryos at different stages of development by cell-sorting and then use these sorted "GFP-expressing cells" as a source for generating antibodies.
- Dissected ducts from regenerating pancreas.
2. Generating antibodies to candidate cell surface markers by mining databases.
Sources of data:
Recommendation 2. Development of a clonogenic assay both in vitro and in vivo.
- Functional Genomics of the Developing Pancreas
- Numerous subtraction libraries derived from cell lines or animal models that may contain genes encoding appropriate cell surface markers expressed in early pancreatic progenitor cells
- Microarray of a human islet library, 13,000 genes (Developed by Metabolix/Affymetrix)
In an in vivo clonogenic assay, pancreatic stem cells should give rise to cells that could be transferred or transplanted to a diabetic host, and have to ability to reconstitute all pancreatic cell lineages. Although there are several existing diabetic animal models which might be used in a clonogenic assay, research to develop a transgenic mouse model in which the destruction of pancreatic beta cells is inducible in young animals or adults is needed. The isolation of appropriate lineage-specific markers at all stages of pancreatic development would be critical for establishing a clonogenic assay in vitro. Clonogenic assays have been used to characterize hematopoietic and neural stem cells.Recommendation 3. Establish alliances (centers) of established investigators from the stem cell biology field, developmental biology, and diabetes.
Recommendation 4. Incentives to attract and train young clinical investigators in the fields of endocrinology, and stem cell biology.
Recommendation 5. NIDDK should play a leadership role in the implementation of guidelines to allow research using human embryonic stem cells.
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