Table 1.

Stem cell sources

Name	Sources	Advantages	Disadvantages
Embryonic SCs	Inner cell mass of the mammalian blastocyst	Pluripotent — enabling them to form derivatives of all three germ layers	Results in destruction of the embryo, making them an ethically controversial source Form teratomas when transplanted in vivo, limiting their current clinical value
Haematopoietic SCs	Bone marrow, umbilical cord blood and peripheral blood Embryonic SCs Induced pluripotent SCs	Multipotent — can form lymphoid and myeloid blood cells Extracted in high yields Readily cryopreserved Intrinsic tumour-tropic properties	Limited differentiation potential
Mesenchymal SCs	Fetal origins (Wharton’s jelly and cord blood) Developing tooth bud of the mandibular third molar Adult tissues such as bone marrow and adipose tissue Embryonic SCs Induced pluripotent SCs	Differentiate into mesenchymal lineages that make up bone, cartilage, fat and muscle Readily cryopreserved Many types are tumour-tropic Readily genetically manipulated	Limited differentiation potential Limited yield depending on source
Neural SCs	Brain, spinal cord and retina Embryonic SCs Induced pluripotent SCs	Multipotent — can give rise to neurons, astrocytes and oligodendrocytes Tumour-tropic properties Readily genetically manipulated	Limited differentiation potential Difficult to source
Endothelial SCs	Bone marrow Embryonic SCs Induced pluripotent SCs	Multipotent — give rise to endothelial precursor cells, which form blood and lymphatic vessels Readily cryopreserved Readily genetically manipulated	Limited differentiation potential
Induced SCs	Derived from somatic cells using reprogramming technologies	Can be driven into many different cell types Creation of patient-specific cell types Can be made using various viral and non-viral methods	Tumorigenicity poses a considerable clinical hurdle Heterogeneity in final induced SC population Technically challenging Low efficiency of conversion

SC, stem cell.