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Martha Funderburgh, Fatima Syed-Picard, Charles Sfeir, James Funderburgh; Dental Pulp: a Source of Stem Cells with Keratocyte Potential. Invest. Ophthalmol. Vis. Sci. 2013;54(15):1010.
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Blindness due to corneal stromal opacity can be successfully treated by allografts; however, inflammation or previous graft rejections predict poor outcome for some allogenic tissue in the stroma. These difficult cases may benefit from autologous stem cell therapy or from autologous grafts of bioengineered tissue. Dental pulp contains a potent stem cell population with immune-suppressive properties, cells that could be the autologous stem cells ideal for corneal regeneration. The purpose of this study was to explore the potential for dental pulp stem cells (DPSC) to adopt a keratocyte phenotype.
Dental pulp extracted from human molars was dispersed with collagenase, cultured and used at passage 3. Cells expressing CXCR4 protein were isolated using MACS technology. Expression of stem cell genes was determined using flow cytometry and qPCR. Differentiation to keratocytes was carried out on collagen gels or aligned nanofiber substrata in serum-free medium containing FGF2 and ascorbate-2-phosphate.
Cultured cells from dental pulp expressing the chemokine receptor CXCR4 were isolated by immunoaffinity. CXCR4+ DPSC cells had increased expression of pluripotent genes OCT4, NANOG, and SOX2, neural crest marker p75NTR, and genes expressed by corneal stromal stem cells ABCG2, KIT, SIX2, PAX6, and NOTCH1. When the CXCR4+ cells were cultured on collagen gels in medium that induced keratocyte differentiation, expression of stem cells genes was downregulated and mRNAs for several keratocyte-specific products were upregulated, including keratocan (KERA), ALDH3A1, PTGDS and enzymes involved in keratan sulfate synthesis beta-1,3, glucosaminyltransferase 7 (B3GNT7) and corneal 6-O-glucosaminyl-sulfotransferase 6 (CHST6). The expression levels of these genes were almost identical to those in corneal stromal stem cells, which under the same conditions produce a stroma-like extracellular matrix.
CXCR4 appears to be a key cell-surface marker of stem cells with potential to differentiate in the keratocyte lineage. The availability and potency of stem cells from dental pulp makes these cells an excellent candidate as a source of autologous stromal cells for future bioengineering or cell-based therapies for stromal blindness.
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