Phenotypical characterization of third trimester human amniotic fluid cells: a new reservoir of stem cells?

The amniotic fluid (AF) is known to contain multiple cell types derived from the developing foetus. AFCs are classified in three main groups: epithelioid cells (from fetal skin and urinary tract), amniotic fluid specific cells (from foetal membranes and trophoblast) and fibroblastic cells (from fibrous connective tissue and dermal fibroblasts) (1). Some of these cells resulted to be multipotent cells that can differentiate along adipogenic, osteogenic, myogenic, endothelial, neurogenic and hepatic pathways (2). The aim of this study was to isolate cells from the third trimester amniotic fluid obtained from caesarean births (instead that cells usually retrieved from amniocentesis) and test their therapeutic potential in a mouse model of spinal cord injury (see Abstract Cigognini et al. SIF 2009). We isolated several different populations of adherent cells from 8 amniotic fluid samples (3); they were then characterized for in vitro proliferation and differentiation potential. The antigenic profile was performed both by immunocytochemistry and cytofluorimetric analysis. The isolated cell populations showed different rates of growth: some cultures presented a very high proliferation capacity; others had an intermediate or low proliferation rate. By immunocytochemistry we found in all of cultures a high expression of four neural-glial markers nestine, GFAP, β-tubulin III and neurofilament H. Some cultures were also positives for the mesenchymal marker vimentin, whereas few of them were strongly positives for the epithelial marker cytokeratin 8-18. Three cultures were more thoroughly investigated by cytofluorimetric analysis, which revealed the presence of adult mesenchymal markers (CD146-, CD73+, CD105+, CD90+) directed to the muscle-neural lineage (CD146-, NG2+, CD56+) (#3.5 and #3.6); one of them also expressed CD117 (#3.6). The third culture (#1.1), instead, showed a mesenchymal phenotype directed to the perivascular lineage (CD146+, CD133+, CD90+, CD73+). Recently, we started to characterize, by cytofluorimetric analysis, fresh amniotic fluid samples in order to verify weather the pattern of expression of the markers highly present in the above mentioned cultures #1.1, #3.5 and #3.6 were already present before an in vitro manipulation. 1. Gosden CM (1983) British Medical Bullettin 39(4):348-354 2. De Coppi P et al. (2007) Nature Biotecnology 25(1):100-105 3. Fauza D (2004) Amniotic fluid and placental stem cells Best practice and research: Clinical Obstretics and Gynaecology 18(6) 877-891