Table 1 The main characteristics of ESC, iPSCs, and ASCs are compared from five aspects

Embryonic stem cells (ESCs)

Blastocyst

Pluripotent (differentiation ability to any cell type of three germ layers)

1. Unlimited proliferation capacity

2. Strong differentiation potential

1. Immunogenicity

2. Tumorigenicity

3. Ethical dilemmas and regulatory issues

4. Invasive harvesting method

Potential of forming an entire organism

Induced pluripotent stem cells (iPSCs)

Adult somatic cells

Pluripotent (differentiation ability to any adult cell type)

1. Rich and easily accessible source

2. High differentiation capacity

3. Negligible immune responses (syngeneic iPSCs)

4. No ethical controversy

1. Possibilities of tumor formation

2. Possible genetic and epigenetic abnormalities during reprogramming

3. Immunogenicity (allogeneic iPSCs)

Possible genetic defects that can be modified during reprogramming

Adult stem cells (ASCs), mainly mesenchymal stem cells (MSCs)

Differentiated tissues and organs

Multipotent (directed differentiation of multiple cell types)

1. Strong self-renewal ability

2. Limited immunoreactivity and certain immunoregulatory property

3. Controllable security and low tumorigenicity

4. Readily available, non-invasive, and less polluted acquisition of fetal tissue-derived MSCs

1. Invasive obtainment of BM-MSCs and AT-MSCs

2. The most suitable cell source has not been determined

3. Limited cell efficacy and underutilized therapeutic potential

1. The clinical application of MSCs, especially BM-MSCs, is more successful and extensive

2. Fetal tissue-derived MSCs have displayed promising outcomes

3. The application of exosomes presents a cell-free therapy