Why are human eggs a challenge for stem-cell research using somatic cell nuclear transfer?

In the context of somatic cell nuclear transfer (SCNT), human eggs present significant challenges for research due to both technical and ethical factors.12

• Scarcity and Procurement: Human eggs are in short supply, and their procurement for research purposes is subject to complex legal and ethical scrutiny. Ethical principles demand that the acquisition of human biological materials be conducted with strict adherence to informed consent and regulatory standards, which complicates the availability of eggs for scientific study.123
• Technical Inefficiency: The SCNT process is highly inefficient, often requiring more than a dozen human eggs to successfully produce a single embryonic stem cell line. Maintaining the viability of these embryos during development to the blastocyst stage has proven exceptionally difficult, with many failing to develop properly.12
• Biological Complexity: The precise mechanism by which an unfertilized egg reprograms the DNA of a differentiated somatic cell remains not entirely understood, posing risks for potential clinical applications.1

These challenges, combined with the ethical concerns regarding the moral status of human embryos, have led many researchers to favor induced pluripotent stem cells as an alternative source of pluripotent cells.32