Table 1.

Stem cell sources in pre-clinical trials.

Stem cell source	References	Advantages and disadvantages
Embryonic stem cells	90	Advantages: Ability to differentiate into any cell line Disadvantages: Controversial harvesting, potentially tumorigenic
Induced pluripotent fibroblasts	91, 93, 95	Advantages: No ethical problem with harvesting, immunogenicity. Disadvantages: Induction of pluripotency may take longer and not as efficient.
Induced pluripotent keratinocytes	92, 94	Advantages: No ethical problems with harvesting, improved production of IPSCs compared to fibroblasts. Disadvantages: May be difficult to harvest and isolate from samples, slower growth and replication.
Hematopoeitic stem cells	96, 97, 98	Advantages: CD44 allows homing to sites of inflammation, potentially allowing injection rather than topical application. Disadvantages: Have only shown ability to differentiate into blood cells, hepatocytes, and fibroblasts
Bone marrow mesenchymal stem cells	99, 100, 101	Advantages: Rapid proliferation, wide differentiation capacity, anti-inflammatory effects. Disadvantages: More difficult to harvest than AMSCs.
Adipocyte mesenchymal stem cells	99, 100, 102	Advantages: Ease of harvest, rapid proliferation, wide differentiation capacity, angiogenic properties. Disadvantages: Decreased proliferation and density compared to BMMSCs. May have poorer anti-inflammatory effects.
Urine derived stem cells	104, 105, 106, 107, 108	Advantages: Extreme ease of harvest, ability to form urothelial, endothelial, smooth muscle, or even neural lineages. Disadvantages: Varying isolation efficiency, increased heterogeneity of cell lines, lack of data on long term effectiveness of USC grafts