Posted: Tuesday, February 22, 2022
Human mammary tissue remodeling that occurs during pregnancy and lactation is poorly understood due to the challenge of acquiring samples. Recently, a study published in Nature Communications identified transcriptional changes in mammary gland cells by single-cell RNA sequencing of live mammary epithelial cells isolated from human milk. Researchers proposed that the molecular and cellular changes that occur in the mammary gland in response to systemic reproductive hormones may offer insight into the relationships among pregnancy, lactation, and breast cancer.
“The first time [Alecia-Jane Twigger, PhD, of the Cambridge Stem Cell Institute] told me that she found live cells in milk, I was surprised and excited about the possibilities,” explained Walid T. Khaled, PhD, of the University of Cambridge, England, in an institutional press release. “We hope this finding will enable future studies into the early steps of breast cancer.”
The single-cell transcriptomic analysis included 110,744 viable breast cells from human milk or nonlactating breast tissue, isolated from nine and seven donors, respectively. The human milk largely contained epithelial cells that transcriptionally resembled luminal progenitor cells and a collection of immune cells.
The researchers identified two transcriptionally distinct secretory luminal epithelial cell clusters—LC1 and LC2—in the milk samples. The LC2 cells appeared to express high levels of immunomodulatory and antigen-presenting genes not previously associated with mammary luminal cells. A comparison between breast cells isolated from human milk versus those from nonlactating breast tissues also identified shared immune cell clusters from myeloid and lymphocytic lineages.
“Taken together, our data offer a reference map and a window into the cellular dynamics that occur during human lactation and may provide further insights on the interplay between pregnancy, lactation, and breast cancer,” concluded the study authors.
Disclosure: The study authors reported no conflicts of interest.