Table 1.

Comparison of mesenchymal stem cell sources and their characteristics7,9–30

Source	Differentiation potential	Method of procurement	Advantages	Disadvantages	Clinical applications	Proliferation capacity	Other
BM7,9–12,30	Adipocytes Astrocytes Cardiomyocytes Chondrocytes Hepatocytes Mesangial cells Muscle cells Neurons Osteoblasts Stromal cells Embryonic tissue	Isolated from BM aspirate	Stem cells from this source have the potential to differentiate into hepatocytes, much like AT-MSCs. These cells express cytochrome p450. Multiple clinical trials have confirmed the safety and effectiveness of this type of stem cell.	Procurement of cells from this source is often painful and carries the risk of infection. Cell yield and differentiation potential is dependent on donor characteristics (e.g. age).	Generation of pancreatic cells in vitro. Treatment of orthopaedic conditions characterised by large bone defects, including articular cartilage repair and osteoarthritis, rheumatoid arthritis, rotator cuff injuries and tendon, spinal cord and meniscus lesions. BM-MSCs may also be used to treat non-unions, osteonecrosis of the femoral head and to promote growth in osteogenesis imperfecta. Potentially promising treatment for myocardial infarction, as well as GVHD, SLE and MS. In animal models, BM-MSCs have been studied in the context of autoimmune encephalomyelitis, asthma, allergic rhinitis, pulmonary fibrosis and peripheral nerve regeneration.	Mean doubling time of 40 hours. Proliferation capacity increases after passage six. Contact inhibition of proliferation. Senescence by passage seven.	This type of stem cell is the most extensively investigated and is considered to be the gold standard.
AT7,9,10,12,13,30	Adipocytes Chondrocytes Osteocytes Muscle cells	Isolated from liposuction, lipoplasty or lipectomy materials	This source results in the isolation of up to 500 times more stem cells than BM (i.e. 5 × 103 cells from 1 g of AT). AT is accessible and abundant and secretes several angiogenic and antiapoptotic cytokines. The immunosuppressive effects of AT-MSCs are stronger than those of BM-MSCs.	Cells from this source have inferior osteogenic and chondrogenic potential in comparison to BM-MSCs.	Immunosuppressive GVHD therapy. Potential for cell-based therapy for radiculopathy, MI and neuropathic pain. Cosmetic/dermatological applications. Successfully used in the treatment of skeletal muscle injuries, meniscus damage and tendon, rotator cuff and peripheral nerve regeneration.	Mean doubling time of 4 ± 1 days (5 ± 1 days for omental fat). Cells proliferate faster than BM-MSCs. Region-dependent (subcutaneous).	-
Dental pulp14–17	Odontoblasts Osteoblasts Adipocytes Chondrocytes Neurogenic cells Myogenic cells	Isolated from tooth extraction (i.e. wisdom, ectopic or even decayed teeth) or root canal surgery materials	As dental surgeries are fairly common, the source materials for these cells are easily accessible. The frequency of colony-forming cells from dental pulp is high compared to those from BM (22–70 colonies versus 2.4–3.1 colonies/104 cells plated).	The procurement of these cells can be difficult and invasive. Ectomesenchymal and periodontal tissues affect MSC properties.	Orofacial, bone and neural regeneration.	Mean doubling time of 30–40 hours.	These cells have an ectomesenchymal origin (i.e. are derived from neural crest cells). Dental pulp-derived stem cells can differentiate into mesenchymal linages both in vitro and in vivo. PCy-MSCs have recently attracted interest because of their neural and bone differentiation potential. Dental pulp and periodontal ligament stromal cells are the main types of cells.
Birth-derived tissues7,10,11,18,21	UCB-MSCs: Adipocytes Chondrocytes	Isolated from the placenta, amnion and UCB after birth	The benefits of this source includes high availability and the avoidance of invasive procedures and ethical issues. These stem cells demonstrate higher expansion and engraftment capacity than BM-MSCs. UCB-MSCs also possess osteogenic differentiation capabilities. UCB-MSCs produce 2.5-fold more insulin than BM-MSCs.	UCB-MSCs may not have adipogenic potential. In terms of osteogenesis potential, this source is not as useful as BM, blood or the liver.	UCB-MSCs: Pancreatic islet cell generation in vitro. Successful treatment for GVHD and SLE.	Mean doubling time is 30 hours (this remains constant for passages 1–10). Multilayered proliferation. UCB-MSCs do not age over passages (i.e. senescence).	WJ-MSCs have high proliferative potential.
	WJ-MSCs: Dopaminergic neurons • Chondrocytes				WJ-MSCs: Treatment of MI. Peripheral nerve regeneration.
AF and placenta19,20	AF-MSCs: Neural stem cells (forming NS) Adipocytes Osteoblasts Chondrocytes Hepatocytes	Obtained following delivery	Both AF-MSCs and P-MSCs can be harvested with minimal invasiveness.	No clinical trials have yet been conducted to assess the safety and effectiveness of these stem cells.	AF-MSCs: Potential treatment for nerve injuries or neuronal degenerative diseases. Bladder regeneration and kidney, lung, heart, heart valve, diaphragm, bone, cartilage and blood vessel formation.	High self-renewal capacity (>300 cell divisions). Doubling time of 36 hours. These cells maintain a normal karyotype, even at late passages.	The phenotype of these cells is similar to that of BM-MSCs. These cells produce immunosuppressive factors and express certain human embryonic stem cell markers.
	P-MSCs: Pancreatic cells				P-MSCs: Treatment for skin and ocular diseases, inflammatory bowel disease, lung injuries, cartilage defects, Duchenne muscular dystrophy, stroke and DM. Peripheral nerve regeneration.
Peripheral blood10,12,21	Adipocytes Fibroblasts Osteoblasts Osteoclasts Chondrocytes	Obtained via density gradient centrifugation	Colony-forming efficiency ranges from 1.2–13 colonies per million mononuclear cells. A large volume of blood and, therefore, a greater quantity of MSCs can be collected compared to BMMSCs (up to 1.91 ± 0.21 mL of mobilised peripheral blood yields 197.8 ± 24.9 × 106 cells/mL versus 21.6 ± 2.7 × 106 cells/mL of BM).	The amount of MSCs obtained from this source varies greatly (0.001–0.01%). Cells from this source have lower osteogenic and chondrogenic potential and higher adipogenic potential than BM-MSCs. No clinical trials have been conducted to assess the safety and effectiveness of this type of stem cell.	Intracoronary infusion in acute or old myocardial infarction. Chondral and meniscus regeneration.	Doubling time of 95 hours.	-
Synovium and synovial fluid22,23	Adipocytes Chondrocytes Osteoblasts	Isolated from the synovium and synovial fluid	These cells have high differentiation and proliferation capacity. Cells from this source are superior to skeletal muscle- and AT-MSCs.	The harvesting of cells from this source requires an invasive procedure.	In animal models, these cells have been used to repair chondral defects and for osteoarthritis and ligament regeneration.	These cells retain their proliferative ability up to passage 10.	Cells from this source have high in vitro expandability, differentiation potential and epitope profile.
Endometrium24,25	Chondrocytes Adipocytes Osteoblasts Smooth muscle cells Myocardial cells Hepatocytes	Isolated from menstrual blood or endometrial biopsies	If isolated from menstrual blood, this source is minimally invasive. Use of these cells may facilitate understanding of gynaecological diseases such as endometrial carcinoma and endometriosis.	The potential clinical applications of these stem cells are limited, as only preclinical studies have been conducted.	Treatment for Duchenne muscular dystrophy, muscle repair, limb ischaemia and myocardial infarction. Other applications include type 1 DM, stroke, ulcerative colitis, endometriosis, endometrial carcinoma, pelvic prolapse and cardiac failure.	High proliferation capacity of 6 × 1011 cells from a single cell. Doubling time of 18–36 hours. These cells can maintain a relatively stable karyotype over 40 passages.	Stem cells from this source demonstrate similar properties to those of AT- and BM-MSCs.
Skin26,27	Chondral cells Bone cells Adipocytes Neural cells Glial cells Pancreatic cells Smooth muscle cells	Can be harvested from human foreskin and skin biopsies	These cells have a high proliferation rate; in particular, neonatal skin-derived MSCs exhibit higher proliferation rates than AT-MSCs.	An invasive procedure is required to obtain these cells. No clinical trials have yet been performed to analyse the safety and effectiveness of this type of stem cell.	Applications include neural tissue, peripheral nerve, haematopoietic lineage and pancreatic cell and skin regeneration after injury. Insulin production. Treatment for alopecia and spinal cord injuries. Bladder reconstruction.	High proliferation rate. Doubling time of 7–8 days.	-
Muscle28,29	Bone cells Adipocytes Chondrocytes Muscle cells Neural cells Hepatocytes Blood cells	Isolated from skeletal muscle tissue	Some subtypes of these stem cells, such as myoendothelial and traumatised muscle-MSCs, are characterised by longterm proliferation and high self-renewal. Muscle-MSCs can be obtained from virtually any muscle in the body.	The procurement of these cells is usually invasive.	Bone, chondral and craniofacial regeneration. Treatment of rotator cuff tears and nerve injuries. Regeneration of skeletal (especially in muscular dystrophy cases and after traumatic injuries) and cardiac muscle. Vascular regeneration, urinary incontinence treatment and repair of vaginal tissue.	High proliferation rate. Doubling time of 40 hours.	-

BM = bone marrow; AT = adipose tissue; MSCs = mesenchymal stem cells; GVHD = graft-versus-host disease; SLE = systemic lupus erythematosus; MS = multiple sclerosis; MI = myocardial infarction; PCy = periapical cyst; UCB = umbilical cord blood; WJ = Wharton’s jelly; AF = amniotic fluid; NS = neurospheres; P = placenta-derived; DM = diabetes mellitus.