Correct Option (d):
Statement 3 is correct. Embryonic stem cells, and more recently induced pluripotent stem cells (iPSCs), possess the unique characteristic of self-renewal. This allows them to proliferate extensively or virtually indefinitely in vitro under appropriate culture conditions while maintaining their undifferentiated state and developmental potential. This property is fundamental for their research and therapeutic applications.
Statement 4 is correct. Indian research institutions, including the National Centre for Biological Sciences (NCBS) and the Centre for Cellular and Molecular Biology (CCMB), have successfully established and characterized various human pluripotent stem cell lines. These cell lines demonstrate the capacity to differentiate into multiple cell types and tissues, contributing significantly to advancements in regenerative medicine, disease modeling, and drug discovery within the country.
Incorrect Options:
Statement 1 is incorrect. While embryos at the blastocyst stage are a significant source of human embryonic stem cells (ESCs), they are not the exclusive source of human stem cells. Other crucial sources include adult stem cells (e.g., hematopoietic stem cells from bone marrow, mesenchymal stem cells from adipose tissue), umbilical cord blood stem cells, and induced pluripotent stem cells (iPSCs) which are reprogrammed adult somatic cells.
Statement 2 is incorrect. The conventional method for deriving human embryonic stem cells (ESCs) from blastocysts necessitates the destruction of the embryo. This ethical concern has driven research into alternative, non-destructive methods. However, the general assertion that ESCs can be derived without blastocyst destruction is inaccurate.
Options (a), (b), and (c) are incorrect as they include statement 1 and/or statement 2, both of which are factually inaccurate.