Mammary Gland Stem Cells Development and Regeneration Jayanti Tokas 1, Puneet Tokas 2, Rubina Begum 1, Shailini Jain 3 and Hariom Yadav 3 1 Department of Biotechnology, JMIT, Radaur, Haryana, India 2 KITM, Kurukshetra, Haryana, India 3 NIDDK, National Institute of Health, Bethesda, MD 20892, USA

Mammary Gland  Secretory tissue  Ductular system  Connective tissue

Ductular System Starts at the alveoli & ends at the teat canal Ductule Mammary duct Gland cistern Teat cistern Streak canal

The Secretory Tissue

Role of stem cells in Mammary gland Mammary gland regeneration during Pregnancy Lactation Involution MG stem cells control growth and development through self-renewal by Symmetric cell division Asymmetric cell division

Symmetric cell divisionAsymmetric cell division Tissue Growth

Possible lineages of mammary stem cells Pluripotent Progenitor Progenitor Lobule-limited Ductal-limited Fully competent Secretory lobules Mammary ducts Entire mammary epithelium Self-renewing Multipotent

Pluripotent Progenitor Progenitor Fully competent Lobule-limited Ductal-limited Possible lineages of mammary stem cells Secretory lobules Mammary ducts

Mammary Stem Cells (MaSCs) Pale/light-staining cells Located throughout the mature MG ULLC are located between the basal and luminal layer of the MG with large nuclei. SLC - located in the basal layer Large dark cells (LDC) differentiated luminal cells

Mammary Gland Development Birth to Puberty –Gland remains rudimentary –Relatively growth quiescent Puberty MG undergoes rapid growth and differentiation at the tip of the terminal end buds (TEB) TEB is surrounded by Cap cell layer that may enter myoepithelial or luminal epithelial lineage Cap cells are thought to be multipotent stem cells TEBs are temporary niche - disappear as the duct reaches the end of the fat pad

Organization of duct and end bud Nat Rev Cancer, 2004

MG development during pregnancy Growth is controlled by estrogen and progesterone Ductule-lobular growth- first 1/2 of gestation Lobule-alveolar growth-second 1/2 gestation Ductal Lobuloalveolar gland Lobulo-alveolar progenitor cells Alveolar buds Alveoli

MG development during Pregnancy & Lactation Mid pregnancy Alveolar epithelium (I-transition of lactogenesis) Milk proteins (secretion inhibited) Parturition Milk (II-transition of lactogenesis) Cells differentiate rapidly & continues till peak lactation

Involution Degeneration of the secretory cells  Milking stopped  Intramammary pressure  Luminal pressure > blood pressure  Milk biosynthesis ceases  Alveoli degenerate first furthest from the gland cistern  Adipose cells occupy the empty space  Lastly the duct system remains

MG development and involution

Mammary stem cells Different mammary subpopulation havebon their cell surface CD24+ (heat-stable antigen), CD29hi (β1-integrin), CD49hif (α 6-integrin), Sca-1, etc MaSCs express low level of stem cell antigen (Sca-1) A single cell from the CD29hi/CD24+ or CD49hif CD24+ population was found to reconstitute a functional mammary gland