Induced pluripotent stem cells (iPSCs) can be generated from a wide range of fully differentiated cells and, under optimal conditions, can potentially be driven to differentiate into virtually any fate. Induced stem-like cells not only provide an alternative to embryonic stem cells, but more importantly represent a powerful tool for drug development and disease modeling.
Methods to induce pluripotency have been developed, including OCT4, SOX2, c-MYC, and KLF4. The expression of these four factors proved sufficient to induce iPSCs from human fibroblasts. In combination, these genes control cell proliferation, inhibit differentiation and regulate epigenetic programs that lead to a pluripotent state. Since the discovery of these key factors, the exact combination of genes and methods used to induce pluripotency has been continuously developed with the goal of improving the efficiency and safety of eventual application in humans.
Traditionally, iPSCs are first generated by viral vector transduction into somatic cells for gene expression. However, for eventual application in patients, this approach presents the caveat of the integration of foreign genetic material into the genome. Therefore, new approaches have focused on the use of plasmid DNA and mRNA to express genes that control pluripotency. Furthermore, protein-based reprogramming methods avoid the introduction of foreign genetic material. Recombinant proteins can be produced and purified using bacterial systems or mammalian cells. However, the protein must be modified to enter the cell and nucleus. Thus, the inclusion of specific sequences from the Human Immunodeficiency Virus Transactivator of Transcription (HIV-TAT), including the TAT protein, allows pluripotency-inducing factors (OCT4, SOX2, c-MYC and KLF4) to reach the nucleus and target key promoters area. Polyarginine-fused pluripotency-inducing factor can also efficiently enter cells and induce iPSCs. Collectively, the discovery of these four key transcription factors continues to drive the development of new strategies focused on the use of iPSCs in regenerative and personalized medicine.
FGF acidity was detected in submerged-fixed paraffin-embedded sections of the human mammary gland using goat anti-human FGF acidic antigen affinity-purified polyclonal antibody at 15 µg/mL overnight at 4 °C. Tissue was stained using the anti-goat HRP-DAB Cell and Tissue Stain Kit and counterstained with hematoxylin (blue). Specific staining is localized to epithelial cells. View our protocol for chromogenic IHC staining of paraffin-embedded tissue sections.
Recently, a new method for differentiating human iPSCs into mammary organoids was developed that incorporates factors necessary for embryonic mammary gland development. For this new two-step approach, the researchers first induced hiPSCs to adopt a predominantly non-neuronal ectoderm model. Using conditioned media for mammary gland differentiation, the researchers developed suspension sphere cultures to generate embryoid bodies (mEBs) enriched in the expression of non-neuronal ectoderm markers, including CK8, CK18, AP-2alpha, Microarray analysis of AP-2gamma and P63. mEBs cultured for 10 days demonstrated the expression of molecular markers supporting the mammary gland differentiation program.
Finally, the researchers confirmed the expression of several mammary gland markers, including α-lactalbumin/LALBA, EpCAM, CK14, and P63, suggesting that organoids grown under specific conditions can differentiate mammary gland fates.
The discovery and development of human induced pluripotent stem cell (iPSC) technology have been revolutionary for biomedical science. iPSCs can be derived from somatic cells of different genetic backgrounds and differentiated into cells of all three germ layers. Similar to embryonic stem cells, iPSCs can be easily grown in the laboratory due to their ability to self-renew indefinitely and serve as starting materials for biomedical applications, including toxicity studies, drug screening, disease modeling, and regenerative medicine. Since this discovery, research groups around the world have generated numerous iPSC lines, including control, disease-associated, and gene-edited lines. However, the high cost of generating and validating iPSC lines is a significant barrier to the development of new iPSC lines. Therefore, there is an urgent need for high-quality, validated iPSC cell banks as a repository to meet the diverse needs of the research and clinical communities.