The discovery of mesenchymal stem cells (MSCs) in perinatal sources, such as the amniotic fluid (AF) and the umbilical connective tissue, the so-called Wharton’s jelly (WJ), has transformed them into promising stem cell grafts for the application in regenerative medicine. The advantages of AF-MSCs and WJ-MSCs over adult MSCs, such as bone marrow-derived mesenchymal stem cells (BM-MSCs), include their minimally invasive isolation procedure, their more primitive cell character without being tumourigenic, their low immunogenicity and their potential autologous application in congenital disorders and when cryopreserved in adulthood.
This chapter gives an overview of the biology of AF-MSCs and WJ-MSCs, and their regenerative potential based on the results of recent preclinical and clinical studies. In the end, open questions concerning the use of WJ-MSCs and AF-MSCs in regenerative medicine will be emphasized.
Highlights
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Wharton’s jelly (WJ) and amniotic fluid (AF) are more primitive that adult mesenchymal stem cells (MSC), but not tumorigenic.
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Preclinical and clinical studies suggest the safe and efficacious use of WJ-MSCs and AF-MSCs in future stem cell therapies.
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WJ-MSCs and AF-MSCs are regenerative due to their migration, differentiation, secretome and immunomodulatory properties.
The constant progress in understanding the biology of stem cells and their function in tissue regeneration has transformed them into a crucial implement in the research of regenerative medicine. Particularly, because of their multipotent differentiation potential and marginal immunogenicity, mesenchymal stem cells (MSCs) are promising candidates in stem cell therapy . In 1976, Friedenstein and co-workers discovered non-haematopoietic stem cells in the bone marrow of normal and irradiated mice, the so-called bone marrow-derived mesenchymal stem cells (BM-MSCs) . Since then, MSCs from many other adult organs, such as adipose tissue, have been characterized . Lately, a unique, less invasive source of MSCs have been detected, namely the placenta. Amongst others, MSCs can be isolated from the amniotic fluid (AF) and the umbilical cord (UC) tissue, the Wharton’s jelly (WJ) surrounding the umbilical vein and the two arteries .
MSCs derived from the amniotic fluid and wharton’s jelly
In 2003, three independent research groups demonstrated that the AF from second trimester human pregnancies is a rich source of fetal MSCs .
In humans, most of the studies evaluating amniotic fluid mesenchymal stem cells (AF-MSCs) are conducted with cells from the mid-trimester of pregnancy, as the AF can be collected during amniocentesis, which is usually performed between the 16th and 28th weeks of gestation . However, there are publications describing the isolation of AF-MSCs even in the first trimester and after delivery by caesarean section .
AF-MSCs express many markers, which are also characteristic for BM-MSCs, including CD73, CD90, CD105 and major histocompatibility complex (MHC) class I . Furthermore, they do not display MHC class II molecules and the co-stimulatory molecules CD40, CD80 and CD86, suggesting a low immunogenic phenotype . AF-MSCs express markers, which are characteristic for pluripotent cells, such as stage-specific embryonic antigen 3 (SSEA3), SSEA4, NANOG and c-MYC . Despite the similarity to embryonic stem cells, AF-MSCs are not tumuorigenic .
The human UC, whose largest fraction is the WJ, has been characterized as another promising source of MSCs . Wharton’s jelly mesenchymal stem cells (WJ-MSCs) could be isolated from the intervascular, perivascular and subamniotic area of the WJ . These cells are also referred to as MSCs derived from the UC connective tissue or matrix (UC-MSCs).
WJ-MSCs express cell-surface markers, which are known to be associated with an MSC-like phenotype. These molecules include CD73, CD90, CD105, CD146 and CD166 . However, relative to BM-MSCs, WJ-MSCs are a more primitive cell population, with a faster doubling time and more passage numbers to senescence . Human WJ-MSCs express key embryonic stem cell markers, including NANOG, SSEA3, SSEA4 and c-MYC . Furthermore, WJ-MSCs also display progenitor markers of the cardiac, hepatic and neural lineage, as well as mature neuroglial markers, such as fetal liver kinase 1, insulin gene-enhancer protein-1, dipeptidylpeptidase-4, desmoglein-2, nestin, glial fibrillary acidic protein (GFAP), myelin basic protein (MBP) and microtubule-associated protein-2 (MAP-2) .
WJ-MSCs as well as AF-MSCs allow autologous use. However, a remarkable advantage of WJ-MSCs over AF-MSCs and MSCs derived from other tissue sources is that they are easily available and collectable after spontaneous delivery without any invasive procedure, any risk for mother and child or ethical concerns. Furthermore, it has been lately suggested that AF might not be the ideal source for autologous stem cell treatment, as they are very heterogeneous .
Regenerative capacities of AF-MSCs and WJ-MSCs at the site of injury
Several properties make MSCs strong candidates for cellular therapy in regenerative medicine.
Migration
Transplanted MSCs home to the site of injury. Chemokines, secreted in increased amounts by resident tissue cells and recruited immune cells, are the major molecules responsible for cell homing . Cells expressing the matching receptors migrate against the chemokine gradient towards the injured area. WJ-MSCs display the chemokine receptors CXCR3, CXCR4 and CXCR6, which play a key role in the target-oriented migration of stem cells to the site of tissue damage . The secretion of stromal factor-1α (SDF-1α), the ligand of CXCR4, by the cells of the injured tissue area, also elevates the migration of AF-MSCs .
Differentiation potential
As defined by the International Society of Cellular Therapy (ISCT), one of the three main criteria characterizing MSCs is their in vitro differentiation potential into bone, cartilage and fat . Besides the differentiation into osteocytes, chondrocytes and adipocytes , AF-MSCs and WJ-MSCs could be successfully induced into cardiomyocytes , myocytes , epidermal cells , endothelial cells , retinal progenitor cells , insulin-producing cells and hepatocytes in vitro . However, most studies evaluating the differentiation capacities of WJ-MSCs and AF-MSCs describe their neuroglial commitment .
Secretome
The curative effect of MSCs has been recently suggested to mainly rely on the release of paracrine factors. WJ-MSCs produce several cytokines, chemokines, interleukins and trophic factors predominately involved in neurology, angiogenesis, haematopoiesis, cardiovascular biology and bone development . WJ-MSCs express more trophic factors assigned to neurogenesis, neuroprotection and angiogenesis than BM-MSCs or adipose tissue-derived MSCs .
The secretome of AF-MSCs includes pro-angiogenic cytokines and chemokines, such as monocyte chemoattractant protein-1 (MCP-1), interleukin (IL)-8, IL-6, endothelial growth factor (EGF), SDF-1 and vascular endothelial growth factor (VEGF), being important in wound healing . Furthermore, AF-MSCs produce significantly higher messenger RNA (mRNA) and protein levels of the neurotrophic factors brain-derived neurotrophic factor (BDNF) and nerve growth factor (NGF) relative to BM-MSCs .
Immunomodulatory effects
When MSCs are exposed to an inflammatory environment, pro-inflammatory cytokines including tumour necrosis factor-α (TNF-α) and interleukin (IL)-1β induce the shift from a balanced type to an immunosuppressive type of MSCs . WJ-MSCs and AF-MSCs have been shown to have immunomodulatory characteristics akin to BM-MSCs . The immunogenicity and immunosuppressive capacity of human WJ-MSCs has been verified in vitro by xenogeneic and allogeneic models through cell contact and paracrine mechanisms . Pretreatment with pro-inflammatory cytokines even boosted the immunomodulatory capacity of WJ-MSCs . In addition, human WJ-MSCs did not trigger the proliferation of xenogeneic and allogeneic immune cells . The immunosuppressive character of WJ-MSCs is further supported by the expression of the immunosuppressive human leukocyte antigen (HLA)-G6, IL-6 and VEGF, as well as the absence of the expression of the co-stimulatory molecules CD40, CD80 and CD86 . The in vitro evaluation of the immunomodulatory properties of AF-MSCs showed that neither resting AF-MSCs nor AF-MSCs pretreated with the pro-inflammatory cytokines TNF-α and interferon (IFN)-γ induced the activation and proliferation of immune effector cells . Resting AF-MSCs blocked T-cell replication, which was significantly enhanced upon pretreatment with TNF-α and IFN-γ . Lymphocyte activation is blocked either by direct contact with AF-MSCs or by the cell-free culture supernatant of AF-MSCs previously primed with either peripheral blood monocytes (PBMCs) or the inflammatory cytokine IL-1β . AF-MSCs secrete relevant factors of immunomodulation, such as MCP and IL-6 . Priming with PBMC and IL-1β induced the secretion of additive or increased amounts of cytokines by AF-MSCs, including macrophage inflammatory protein-3α (MIP-3α) and MCP-1, when compared with BM-MSCs .
Regenerative capacities of AF-MSCs and WJ-MSCs at the site of injury
Several properties make MSCs strong candidates for cellular therapy in regenerative medicine.
Migration
Transplanted MSCs home to the site of injury. Chemokines, secreted in increased amounts by resident tissue cells and recruited immune cells, are the major molecules responsible for cell homing . Cells expressing the matching receptors migrate against the chemokine gradient towards the injured area. WJ-MSCs display the chemokine receptors CXCR3, CXCR4 and CXCR6, which play a key role in the target-oriented migration of stem cells to the site of tissue damage . The secretion of stromal factor-1α (SDF-1α), the ligand of CXCR4, by the cells of the injured tissue area, also elevates the migration of AF-MSCs .
Differentiation potential
As defined by the International Society of Cellular Therapy (ISCT), one of the three main criteria characterizing MSCs is their in vitro differentiation potential into bone, cartilage and fat . Besides the differentiation into osteocytes, chondrocytes and adipocytes , AF-MSCs and WJ-MSCs could be successfully induced into cardiomyocytes , myocytes , epidermal cells , endothelial cells , retinal progenitor cells , insulin-producing cells and hepatocytes in vitro . However, most studies evaluating the differentiation capacities of WJ-MSCs and AF-MSCs describe their neuroglial commitment .
Secretome
The curative effect of MSCs has been recently suggested to mainly rely on the release of paracrine factors. WJ-MSCs produce several cytokines, chemokines, interleukins and trophic factors predominately involved in neurology, angiogenesis, haematopoiesis, cardiovascular biology and bone development . WJ-MSCs express more trophic factors assigned to neurogenesis, neuroprotection and angiogenesis than BM-MSCs or adipose tissue-derived MSCs .
The secretome of AF-MSCs includes pro-angiogenic cytokines and chemokines, such as monocyte chemoattractant protein-1 (MCP-1), interleukin (IL)-8, IL-6, endothelial growth factor (EGF), SDF-1 and vascular endothelial growth factor (VEGF), being important in wound healing . Furthermore, AF-MSCs produce significantly higher messenger RNA (mRNA) and protein levels of the neurotrophic factors brain-derived neurotrophic factor (BDNF) and nerve growth factor (NGF) relative to BM-MSCs .
Immunomodulatory effects
When MSCs are exposed to an inflammatory environment, pro-inflammatory cytokines including tumour necrosis factor-α (TNF-α) and interleukin (IL)-1β induce the shift from a balanced type to an immunosuppressive type of MSCs . WJ-MSCs and AF-MSCs have been shown to have immunomodulatory characteristics akin to BM-MSCs . The immunogenicity and immunosuppressive capacity of human WJ-MSCs has been verified in vitro by xenogeneic and allogeneic models through cell contact and paracrine mechanisms . Pretreatment with pro-inflammatory cytokines even boosted the immunomodulatory capacity of WJ-MSCs . In addition, human WJ-MSCs did not trigger the proliferation of xenogeneic and allogeneic immune cells . The immunosuppressive character of WJ-MSCs is further supported by the expression of the immunosuppressive human leukocyte antigen (HLA)-G6, IL-6 and VEGF, as well as the absence of the expression of the co-stimulatory molecules CD40, CD80 and CD86 . The in vitro evaluation of the immunomodulatory properties of AF-MSCs showed that neither resting AF-MSCs nor AF-MSCs pretreated with the pro-inflammatory cytokines TNF-α and interferon (IFN)-γ induced the activation and proliferation of immune effector cells . Resting AF-MSCs blocked T-cell replication, which was significantly enhanced upon pretreatment with TNF-α and IFN-γ . Lymphocyte activation is blocked either by direct contact with AF-MSCs or by the cell-free culture supernatant of AF-MSCs previously primed with either peripheral blood monocytes (PBMCs) or the inflammatory cytokine IL-1β . AF-MSCs secrete relevant factors of immunomodulation, such as MCP and IL-6 . Priming with PBMC and IL-1β induced the secretion of additive or increased amounts of cytokines by AF-MSCs, including macrophage inflammatory protein-3α (MIP-3α) and MCP-1, when compared with BM-MSCs .
AF-MSCs and WJ-MSCs in regenerative medicine
Preclinical studies with WJ-MSCs and AF-MSCs in adult disorders
In animal disease models, WJ-MSCs and AF-MSCs were successfully engrafted into organs such as the brain, skin, heart, lung and kidney.
Recently, WJ-MSCs and AF-MSCs have been most extensively studied in animal models of ectoderm-related regenerative medicine, such as adult brain disorders.
WJ-MSCs and AF-MSCs in adult brain disease models
The regenerative function of WJ-MSCs and oligodendrocyte progenitor cells differentiated from WJ-MSCs in multiple sclerosis has been evaluated in a mouse model of experimental autoimmune encephalomyelitis (EAE) . The treatment with WJ-MSCs decreased the perivascular infiltration of immune cells, demyelination and axonal injury. In addition, WJ-MSCs shifted the T cells from a pro-inflammatory T-helper cell (Th)1 type to an anti-inflammatory Th2 type . WJ-MSC-derived oligodendrocyte progenitor cells significantly increased remyelination . The observed improvements were associated with a functional recovery from EAE symptoms.
Cheng et al. evaluated the therapeutic effect in a rat model of traumatic brain injury (TBI) . Human WJ tissue was placed in the bone window 24 h after TBI, resulting in a reduction of the brain oedema. The lesion volume was diminished, the neurologic functions were increased and memory and cognitive recovery were stimulated . Cheng et al. suggest that the therapeutic effect of WJ tissue might act – at least partly– via the up-regulation of BDNF.
In the transgenic R6/2 mouse model of Huntington’s disease, WJ-MSCs isolated from wild-type mice pups at gestation day 15 were transplanted into the striatum resulting in better spatial memory and the reduced loss of metabolic activity .
Yang and co-workers transplanted human WJ-MSC-derived neuron-like cells into the hippocampus of transgenic AβPP/PS1 mice, an Alzheimer’s disease model . Spatial learning and memory were enhanced, synapsin 1 expression was elevated and the deposition of β-amyloid was reduced.
In an immune-competent rat model of Parkinson’s disease, human WJ-MSCs were injected into the substantia nigra . Performance in behavioural examinations and the amount of dopaminergic neurons in the substantia nigra were elevated relative to non-treated rats . The regenerative potential of AF-MSCs was evaluated in a rat model of Parkinson’s disease . Human AF-MSCs were stereotactically injected into the brain. Soler and co-workers suggested that transplanted AF-MSCs might rather act via cell signalling on neighbouring cells . Furthermore, AF-MSCs ameliorated injury-induced bladder dysfunction. Chang et al. demonstrated that viable AF-MSCs were engrafted into the brain tissue, and they even expressed markers of dopaminergic neurons .
In a rat stroke model, human WJ-MSCs were injected into the infarcted cortex 24 h post focal cerebral ischaemia . Less cortical atrophy, increased neuronal metabolic activity and better motor function were observed in WJ-MSC-treated animals. WJ-MSCs survived at least 36 days in the damaged cortex, and they released BDNF and bFGF, suggesting that the beneficial effects of WJ-MSCs rely on their production of these growth-promoting factors .
Most recently, the therapeutic benefits of human WJ-MSCs previously primed into neuron-like cells with a Rho kinase inhibitor were evaluated in a rat model of intracerebral haemorrhage (ICH) . ICH was induced by the infusion of collagenase type IV into the striatum. Rats were treated with either non-primed or Rho kinase inhibitor-primed WJ-MSCs. Priming ameliorated functional performance, thus increasing the expression of glial cell line-derived neurotrophic factor (GDNF) and the amounts of grafted cells displaying MAP-2 and neurofilament-H.
Recent publications of preclinical studies evaluating the regenerative capacities of WJ-MSCs and AF-MSCs in adult disease models are summarized in Tables 1 and 2 .
| Organ | Disease model | Graft species | Cell dose | Route of delivery | Time point of cell delivery | Result(s) |
|---|---|---|---|---|---|---|
| Peripheral nervous system | Rat sciatic nerve neurotmesis injury model | Human | Not defined | Infiltration into the lesion site or enwrapping the neurotmesis lesion with WJ-MSCs mixed with a Floseal matrix | After injury induction | ↑ functional and morphologic recovery in the acute and chronic phases of regeneration |
| Rat sciatic nerve neurotmesis injury model | Human | Monolayer of undifferentiated or neuroglial differentiated WJ-MSC/ Vivosorb membrane | enwrapping the neurotmesis lesion with the WJ-MSC–Vivosorb membrane | After injury induction | modestly ameliorated recovery of motor function by undifferentiated WJ-MSCs | |
| Skin | Mouse full-thickness excisional and diabetic wound model | Human | 1 × 10 6 (or WJ-MSC-conditioned medium) | Intradermally at several sites at the borders of the wound | Not defined | ↑ healing rates by differentiation into keratinocytes and release of key molecules |
| Mouse scaffold-based dermal regeneration model | Human | 1 × 10 6 /scaffold | Transplantation onto wounds | After skin defect creation | Improved healing response by inducing angiogenesis | |
| Mouse skin injury model | Human | 1 × 10 6 or 1 × 10 6 /scaffold | Injection into or transplantation onto wounds, respectively | After skin defect creation | WJ-MSCs + scaffold had significantly better healing ability than WJ-MSCs alone | |
| Mouse full-thickness excisional wound model | Human | Mixture of WJ-MSCs + skin microparticles | Smeared on the wound | Not defined | ↑ skin development; | |
| Muscle | Rat myectomy model | Human | 1 × 10 6 (or WJ-MSC-conditioned medium) | Transplantation into defect muscle | After surgical lesion | ↓ scar tissue |
| Pancreas | Rat type 2 diabetes model | Human | 1 × 10 6 (±sitagliptin) | Intravenous injection | At the first and fifth week after diagnosis of diabetes | Combined treatment with WJ-MSCs and sitagliptin improved hyperglycaemia, ↑ regeneration of islet β cell, ↓ generation of islet α cells |
| Mouse type 1 diabetes model | Human | 5 × 10 5 | Intravenous injection | After blood sugar increase to 750–810 mg/dL | Differentiation of injected WJ-MSCs into insulin-producing cells; ↓ blood glucose levels; ↑survival rates; ↓ amounts of autoaggressive T cells; ↑ levels of regulatory T cells; regeneration of destroyed islets |
| Organ | Disease model | Graft species | Cell dose | Route of delivery | Time point of cell delivery | Result(s) |
|---|---|---|---|---|---|---|
| Peripheral nervous system/muscle | Rat sciatic nerve injury model | Human | 5 × 10 6 | Intravenous | Either for 3 days immediately or for 7 days post injury | Recruitment into nerve and muscle by SDF-1α; most cells distributed to the lung; ↑ neurobehaviour, electrophysiological function, myelination, expression of neurotrophic factors in animal transplanted 7 days post injury |
| Skin | Mouse skin injury model | Human | Hypoxic AF-MSC-conditioned medium (CM) | Subcutaneous injection around wound and topical application to the wound bed | After skin defect creation | ↑ proliferation and migration of dermal fibroblast compared with normoxic AF-MSC-CM; mediated by the activation of TGF-β/SMAD2 and PI3K/AKT pathways |
| Liver | Rat fulminant hepatic failure model | Rat | 1 × 10 6 (overexpressing L-1Ra) | Intravenous | 1 day after injury induction | Prevention of liver failure; ↓ mortality; engrafted into livers and generated albumin |
| Bone | Sheep bone regeneration model | Sheep | 10 × 10 6 /scaffold | Placement into injured sinuses | – | ↑ bone deposition; induced a more rapid angiogenic reaction; ↑ expression of VEGF and bigger vascular area 45 days after surgery |
| Lung | Rat emphysema model | Rat | 4 × 10 6 | Intratracheally | After 1 week of conditioning | Relief of lung injury by integrating into the tissue; ↑ levels of surfactant proteins; ↓ apoptosis of alveolar epithelial cells |
| Vascular system | Mouse neovascularization model | Human | 2.5 × 10 5 (combined with 1 × 10 6 umbilical cord blood endothelial colony-forming cells + Matrigel) | Injection into the back | – | Stimulate neovascularization by umbilical cord blood endothelial colony-forming cells |
Preclinical studies with WJ-MSCs and AF-MSCs in congenital disorders
The potential of their autologous applications makes WJ-MSCs and AF-MSCs especially promising stem cell grafts for the treatment of congenital disorders, which result from defective fetal organ development during pregnancy or are due to preterm delivery. Such diseases include periventricular leukomalacia, bronchopulmonary dysplasia, necrotizing enterocolitis and spina bifida.
Periventricular leukomalacia: The recent literature search retrieved three studies examining the influence of WJ-MSCs in rat models of neonatal brain damage . By the ligation of the left common carotid artery followed by exposure to hypoxia, Zhu et al. caused a major lesion in the periventricular white matter of 3-day-old rats . After hypoxia–ischaemia (HI)-induced damage, human WJ-MSCs were applied intraperitoneally. WJ-MSCs migrated to the lesion site in the white matter of the injured animals. In a second approach, WJ-MSCs were injected once daily on days 1, 2 and 3 post HI injury. The treatment with WJ-MSCs enhanced the number of mature oligodendrocytes, reduced reactive astrocytosis and activated microglia counts compared with results in untreated HI-injured animals. Behavioural tests confirmed the therapeutic potential of WJ-MSCs .
Zhang et al. induced HI damage in 7-day-old rats by ligating the right common carotid artery and subsequently exposing them to hypoxia, resulting in primary damage in the frontal cortex . Human WJ-MSCs were administered either via the jugular vein or intraperitoneally 24 h or 72 h from the damage. Rats treated with WJ-MSCs showed significantly better motor function and improved spatial memory compared with non-treated animals. Cell injection 24 h after HI damage evidenced to be the most effective, whereas the route of delivery had no effect on the behavioural outcome. However, more WJ-MSCs migrated to the injured area, and astrogliosis was lower after intravenous application compared with intraperitoneal administration. Twenty-one per cent of transplanted WJ-MSCs differentiated into neuronal cells at the site of injury. The co-administration of the ganglioside GM1 with the cells resulted in an even better behavioural recovery .
In the third study evaluating the efficacy of WJ-MSCs in a neonatal rat model of HI brain damage, human WJ-MSCs were transplanted into the lateral ventricle 24 h after HI injury . The number of apoptotic cells was significantly decreased, whereas the expression of GFAP and neuron-specific enolase was increased following WJ-MSC transplantation .
One case report describes the therapeutic potential of WJ-MSCs on brain injury in a 5-year-old girl suffering from cerebral palsy . The patient received WJ-MSCs from her younger sister. Over a period of 6 months, seven transplantations were performed. Each time, 5–10 × 10 6 cells were applied intravenously and subarachnoidally. After a follow-up of 28 months, the gait was stable, and the patient could stand up by herself, which was impossible before the transplantation. Furthermore, improved immunity, physical strength, speech and comprehension were observed. Besides a transient period of fever, no side effect was observed.
Bronchopulmonary dysplasia (BPD): In a rat model of BPD, pups were exposed to hyperoxia . Human UC perivascular cells (PS) or umbilical cord blood-derived MSCs (UCB-MSCs) were applied into the airways . Stem cells protected and retrieved lung structure and function in parts. The curative potential of PS and UCB-MSCs was ascribed to their secretome, which was proven by applying cell-free conditioned media of PS and UCB-MSCs in the BPD model. In the long term, the stem cell and the cell-free approaches continuously enhance lung structure and function, without any disadvantageous side effects . Previously, in a mouse model of BPD, the appropriate application route of MSCs and the functional outcome were evaluated . High-dose (1 × 10 6 ) intraperitoneal administration led to the restoration of healthy lung structure and function. Soluble factors released by WJ-MSCs are suggested to be responsible for the therapeutic effect .
Necrotizing enterocolitis (NEC): NEC was mediated by gavage-feeding neonatal rats with hyperosmolar formula, hypoxia and lipopolysaccharide . At postnatal days 1 and 2, rats received an intraperitoneal injection of either 2 × 10 6 rat AF-MSCs or rat AF-MSC-conditioned medium. AF-MSCs ameliorated rat survival and clinical status by enhancing enterocyte proliferation and diminishing apoptosis and bowel inflammation .
Spina bifida: In a rat model of spina bifida, fetuses that were previously exposed to retinoic acid to induce neural tube defects received intra-amniotic injections of 5 × 10 5 syngeneic AF-MSCs at embryonic day 17 . The intra-amniotic administration of AF-MSCs resulted in partial or even complete healing of neural tube defects. Thus, transamniotic stem cell therapy has been suggested as a potential therapeutic option in the handling of spina bifida in utero .
Clinical trials with WJ-MSCs in regenerative medicine
The clinical trial registry and results database ClinicalTrial.gov lists three completed studies conducted worldwide using WJ-MSCs ( Table 3 ). The cells were evaluated in the treatment of patients with autism (NCT01343511) , decompensated liver cirrhosis (NCT01342250) and acute myocardial infarction (NCT01291329). All three trials have investigated the safety and efficacy of transplanted cells. To date, the results of the study assessing the potential effects of UC-MSCs and human cord blood mononuclear cells (CBMNCs) in the therapy of autism have been published . The intravenous and intrathecal cell applications were well tolerated with no adverse side effect in the 24 weeks post treatment. The combined treatment with CBMNCs and UC-MSCs indicates a higher therapeutic effect than the administration of CBMNCs only. The mechanisms underlying these improvements might involve the enhanced perfusion of the brain and/or the correction of the immune dysregulation by transplanted stem cells.
