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U. Vossmerbaeumer, S. Kuehl, S. Kern, H. Kluter, J. B. Jonas, K. Bieback; RPE Transdifferentiated Human Mesenchymal Stem Cells Respond to Melanocyte Stimulating Hormone With Melanin Synthesis. Invest. Ophthalmol. Vis. Sci. 2007;48(13):2509.
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© ARVO (1962-2015); The Authors (2016-present)
Mesenchymal Stem Cells (MSC) from adipose tissue have the potential to differentiate into a variety of cell types of the mesodermal lineage. Under in-vitro conditions they can be induced to take a differentiation pathway beyond their natural lineage as shown for characteristics of RPE cells. This transdifferentiation process, as typed by specific protein markers also involves functional features. We investigate the responsiveness to α-Melanocyte Stimulating Hormone (α-MSH).
Human MSC were isolated from liposuction material and characterized for lineage specific undifferentiation properties. Transdifferentiation to RPE lineage was induced using porcine RPE conditioned medium (CM) and a combination of CM and vasoactive intestinal peptide (VIP), subsequently cells were treated with10-5 mM α-MSH for 3 days. Light microscopic analysis revealed pigmented granula. Immunochemical α-tyrosinase staining served to prove melanin synthesis and was quantified by counting 5 randomly selected, discontiguous fields of vision.
Primary MSC showed no relevant level of pigmentation. Induction of transdifferentiation of the MSC alone did not lead to relevant levels of melanin synthesis (2.4 ± 2.3%) either. 34.9 ± 8.7% of undifferentiated MSC contained pigmented granula after exposure to α-MSH. Following RPE directed stimulation, α-MSH treatment increased pigmentation to 75.7 ± 2.3% (CM) and 80.3 ± 0.4% (CM + VIP), respectively. Tyrosinase staining was used to prove active melanin synthesis within the cells.
MSC are spontaneously devoid of pigment but show a basic responsiveness to α-MSH stimulation. Induction of RPE directed differentiation enhances this susceptibility significantly with melanin being found in up to 80% of the cultured and stimulated cells. Tyrosinase staining demonstrates melanin synthesis within the cells. It remains subject to further research to determine whether these in vitro data correspond to in vivo conditions. Reconstructive therapies of degenerative retinal disease could stem from such implicit differentiational plasticity crossing the natural destination limits of a mesenchymal cell type.
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