Abstract
BackgroundMammary stem cells have been extensively studied as a system to delineate the pathogenesis and treatment of breast cancer. However, research on mammary stem cells requires tissue biopsies which limit the quantity of samples available. We have previously identified putative mammary stem cells in human breast milk, and here, we further characterised the cellular component of human breast milk.Methodology/Principal FindingsWe identified markers associated with haemopoietic, mesenchymal and neuro-epithelial lineages in the cellular component of human breast milk. We found 2.6±0.8% (mean±SEM) and 0.7±0.2% of the whole cell population (WCP) were found to be CD133+ and CD34+ respectively, 27.8±9.1% of the WCP to be positive for Stro-1 through flow-cytometry. Expressions of neuro-ectodermal stem cell markers such as nestin and cytokeratin 5 were found through reverse-transcription polymerase chain reaction (RT-PCR), and in 4.17±0.2% and 0.9±0.2% of the WCP on flow-cytometry. We also established the presence of a side-population (SP) (1.8±0.4% of WCP) as well as CD133+ cells (1.7±0.5% of the WCP). Characterisation of the sorted SP and non-SP, CD133+ and CD133- cells carried out showed enrichment of CD326 (EPCAM) in the SP cells (50.6±8.6 vs 18.1±6.0, P-value = 0.02). However, culture in a wide range of in vitro conditions revealed the atypical behaviour of stem/progenitor cells in human breast milk; in that if they are present, they do not respond to established culture protocols of stem/progenitor cells.Conclusions/SignificanceThe identification of primitive cell types within human breast milk may provide a non-invasive source of relevant mammary cells for a wide-range of applications; even the possibility of banking one's own stem cell for every breastfeeding woman.
Highlights
The mammary gland is metabolically active, and has the capacity to undergo cycles of extensive proliferation and hypertrophy in order to meet the needs of pregnancy, lactation and involution
In order to further characterise this heterogeneous cellular population of human breast milk (HBM), we looked for lineage specific markers in this mixed cell population at the mRNA and protein level in freshly isolated, uncultured whole cell population (WCP) from HBM
We looked for the presence of haemopoietic stem/ progenitor cell types through the presence of CD34, a well known haemopoietic stem cell marker [23], and CD133, which is associated with haemopoietic as well as neural stem/progenitor cells [24], [25]
Summary
The mammary gland is metabolically active, and has the capacity to undergo cycles of extensive proliferation and hypertrophy in order to meet the needs of pregnancy, lactation and involution. Gudjonsson et al, using well characterised immortalized cell lines from human breast tissues, demonstrated that these mammary stem cells are derived from the suprabasal compartment of the ductal epithelium in human breast [2]. This was followed closely by the description of a serum-free spheroid culture system which enriches for MaSC that demonstrated selfrenewal and the capacity to differentiate into terminal ductal lobular units (TDLU) when placed into matrigel-coated plates, allowing their culture and in vitro behavior to be studied [3]. We have previously identified putative mammary stem cells in human breast milk, and here, we further characterised the cellular component of human breast milk
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