Green fluorescent protein bone marrow cells express hematopoietic and neural antigens in culture and migrate within the neonatal rat brain

Human umbilical cord blood-derived mesenchymal stem cells do not differentiate into neural cell types or integrate into the retina after intravitreal grafting in neonatal rats

This study investigated the ability of mesenchymal stem cells (MSCs) derived from full-term human umbilical cord blood to survive, integrate and differentiate after intravitreal grafting to the degenerating neonatal rat retina following intracranial optic tract lesion. MSCs survived for 1 week in the absence of immunosuppression. When host animals were treated with cyclosporin A and dexamethasone to suppress inflammatory and immune responses, donor cells survived for at least 3 weeks, and were able to spread and cover the entire vitreal surface of the host retina. However, MSCs did not significantly integrate into or migrate through the retina. They also maintained their human antigenicity, and no indication of neural differentiation was observed in retinas where retinal ganglion cells either underwent severe degeneration or were lost. These results have provided the first in vivo evidence that MSCs derived from human umbilical cord blood can survive for a significant period of time when the host rat response is suppressed even for a short period. These results, together with the observation of a lack of neuronal differentiation and integration of MSCs after intravitreal grafting, has raised an important question as to the potential use of MSCs for neural repair through the replacement of lost neurons in the mammalian retina and central nervous system.

An overview of stem cell-based clinical trials in China

Adult human stem cells are capable of maintaining, generating, and replacing terminally differentiated cells within their own specific tissue. Data suggest that adult stem cells (ASCs) generate differentiated cells beyond their own tissue boundaries, a process termed "developmental plasticity." Since early reports of developmental plasticity in animal models, researchers have made enormous advances in moving toward clinically applicable treatment options with stem cells from both bone marrow and peripheral blood. It seems China is entering this new therapeutic era more rapidly than other countries around the world. In this review, we focus on therapeutic applications of ASCs derived from bone marrow and peripheral blood. Furthermore, we also discuss concerns related to regulations monitoring stem cell-based clinical trials.

TSP-1 secreted by bone marrow stromal cells contributes to retinal ganglion cell neurite outgrowth and survival

Background

Bone marrow stromal cells (BMSCs) are pluripotent and thereby a potential candidate for cell replacement therapy for central nervous system degenerative disorders and traumatic injury. However, the mechanism of their differentiation and effect on neural tissues has not been fully elucidated. This study evaluates the effect of BMSCs on neural cell growth and survival in a retinal ganglion cell (RGCs) model by assessing the effect of changes in the expression of a BMSC-secreted protein, thrombospondin-1 (TSP-1), as a putative mechanistic agent acting on RGCs.

Methods and Findings

The effect of co-culturing BMSCs and RGCs in vitro was evaluated by measuring the following parameters: neurite outgrowth, RGC survival, BMSC neural-like differentiation, and the effect of TSP-1 on both cell lines under basal secretion conditions and when TSP-1 expression was inhibited. Our data show that BMSCs improved RGC survival and neurite outgrowth. Synaptophysin, MAP-2, and TGF-β expression are up-regulated in RGCs co-cultured with BMSCs. Interestingly, the BMSCs progressively displayed neural-like morphology over the seven-day study period. Restriction display polymerase chain reaction (RD-PCR) was performed to screen for differentially expressed genes in BMSCs cultured alone or co-cultured with RGCs. TSP-1, a multifactorial extracellular matrix protein, is critically important in the formation of neural connections during development, so its function in our co-culture model was investigated by small interfering RNA (siRNA) transfection. When TSP-1 expression was decreased with siRNA silencing, BMSCs had no impact on RGC survival, but reduced neurite outgrowth and decreased expression of synaptophysin, MAP-2 and TGF-β in RGCs. Furthermore, the number of BMSCs with neural-like characteristics was significantly decreased by more than two-fold using siRNA silencing.

Conclusions

Our data suggest that the TSP-1 signaling pathway might have an important role in neural-like differentiation in BMSCs and neurite outgrowth in RGCs. This study provides new insights into the potential reparative mechanisms of neural cell repair.

Neuroprotective effect of adult hematopoietic stem cells in a mouse model of motoneuron degeneration

Degenerative spinal motor diseases, like amyotrophic lateral sclerosis, are produced by progressive degeneration of motoneurons. Their clinical manifestations include a progressive muscular weakness and atrophy, which lead to paralysis and premature death. Current pharmacological therapies fail to stop the progression of motor deficits or to restore motor function. The purpose of our study was to explore the possible beneficial effect of mouse adult hematopoietic stem cells (hSCs) transplanted into the spinal cord of a mouse model of motoneuron degeneration. Our results show that grafted hSCs survive in the spinal cord. In addition, the number of motoneurons in the transplanted spinal cord is larger than in non-transplanted mdf mice at the same spinal cord segments and importantly, motor function significantly improves. These effects can be explained by the increased levels of glial cell line derived neurotrophic factor (GDNF) around host motoneurons produced by the grafted cells. Thus, these experiments demonstrate the neuroprotective effect of adult hSCs in the model employed and indicate that this cell type may contribute to ameliorating motor function in degenerative spinal motor diseases.

Transplantation of bone marrow stromal cells for peripheral nerve repair

Cell transplantation using bone marrow stromal cells (BMSCs) to alleviate neurological deficits has recently become the focus of research in regenerative medicine. Evidence suggests that secretion of various growth-promoting substances likely plays an important role in functional recovery against neurological diseases. In an attempt to identify a possible mechanism underlying the regenerative potential of BMSCs, this study investigated the production and possible contribution of neurotrophic factors by transected sciatic nerve defect in a rat model with a 15 mm gap. Cultured BMSCs became morphologically homogeneous with fibroblast-like shape after ex vivo expansion. We provided several pieces of evidence for the beneficial effects of implanted fibroblast-like BMSCs on sciatic nerve regeneration. When compared to silicone tube control animals, this treatment led to (i) improved walking behavior as measured by footprint analysis, (ii) reduced loss of gastrocnemius muscle weight and EMG magnitude, and (iii) greater number of regenerating axons within the tube. Cultured fibroblast-like BMSCs constitutively expressed trophic factors and supporting substances, including nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), glial cell line-derived neurotrophic factor (GDNF), ciliary neurotrophic factor (CNTF), collagen, fibronectin, and laminin. The progression of the regenerative process after BMSC implantation was accompanied by elevated expression of neurotrophic factors at both early and later phases. These results taken together, in addition to documented Schwann cell-like differentiation, provide evidence indicating the strong association of neurotrophic factor production and the regenerative potential of implanted BMSCs.

Neurogenic potential of human umbilical cord blood: neural-like stem cells depend on previous long-term culture conditions

In vitro studies conducted by our research group documented that neural progenitor cells can be selected from human umbilical cord blood (HUCB-NPs). Due to further expansion of these cells we have established the first human umbilical cord blood-derived neural-like stem cell line (HUCB-NSC) growing in serum-free (SF) or low-serum (LS) medium for over 3 years. The purpose of the study was to evaluate the neurogenic potential of HUCB-NSCs cultured in SF and LS condition in different in vitro settings before transplantation. We have shown that the number of cells attaining neuronal features was significantly higher for cultures expanded in LS than in SF condition. Moreover, the presence of neuromorphogens, cultured rat astrocytes or hippocampal slices promoted further differentiation of HUCB-NSCs into neural lineage much more effectively when the cells had derived from LS cultures. The highest response was observed in the case of co-cultures with rat primary astrocytes as well as hippocampal organotypic slices. However, the LS cells co-cultured with hippocampal slices expressed exclusively a set of early and late neuronal markers whereas no detection of cells with glial-specific markers was possible. In conclusion, certain level of stem/progenitor cell commitment is important for optimal response of HUCB-NSC on the neurogenic signals provided by surrounding environment in vitro.

Somatic stem cell research for neural repair: current evidence and emerging perspectives

Recent evidence supports the existence of adult mammalian stem cell subpopulations, particularly within the bone marrow, that may be able to "transdifferentiate" across tissue lineage boundaries, thus offering an accessible source for therapeutic applications even for neural tissue repair. However, the difficulties in reproducing some experimental data, the rarity of the transdifferentiation events and observations that cell fusion may be an alternative explanation argue against the idea of stem cell plasticity. Investigations going beyond descriptive experiments and more mechanicistic approaches may provide a more solid foundation to adult stem cell therapeutic potential.

Fetal microchimerism in the maternal mouse brain: a novel population of fetal progenitor or stem cells able to cross the blood-brain barrier?

We investigated whether fetal cells can enter the maternal brain during pregnancy. Female wild-type C57BL/6 mice were crossed with transgenic Green Mice ubiquitously expressing enhanced green fluorescent protein (EGFP). Green Mouse fetal cells were found in the maternal brain. Quantitative real-time polymerase chain reaction (PCR) of genomic DNA for the EGFP gene showed that more fetal cells were present in the maternal brain 4 weeks postpartum than on the day of parturition. After an excitotoxic lesion to the brain, more fetal cells were detected in the injured region. The presence of fetal cells in the maternal brain was also confirmed by quantitative real-time PCR for the sex-determining region of the Y chromosome. Four weeks postpartum, EGFP-positive Green Mouse fetal cells in the maternal brain were found to adopt locations, morphologies, and expression of immunocytochemical markers indicative of perivascular macrophage-, neuron-, astrocyte-, and oligodendrocyte-like cell types. Expression of morphological and immunocytochemical characteristics of neuron- and astrocyte-like cell types was confirmed on identification of fetal cells in maternal brain by Y chromosome fluorescence in situ hybridization. Although further studies are required to determine whether such engraftment of the maternal brain has any physiological or pathophysiological functional significance, fetomaternal microchimerism provides a novel model for the experimental investigation of the properties of fetal progenitor or stem cells in the brain without prior in vitro manipulation. Characterization of the properties of these cells that allow them to cross both the placental and blood-brain barriers and to target injured brain may improve selection procedures for isolation of progenitor or stem cells for brain repair by intravenous infusion.

Generation of bone marrow-derived neural cells in serum-free monolayer culture

Bone marrow-derived cells (BMCs) are reported to trans-differentiate into neural lineages, and are expected to offer a valuable resource for treating severe diseases of the central nervous system. BMCs that show neural differentiation may differ morphologically from typical marrow stromal cells. The present study aimed to obtain efficient generation of cells with neural features from bone marrow. Serum-free culture was applied to BMCs to prevent the growth of differentiated cells. Using basic fibroblast growth factor and extracellular matrix, rodent BMCs capable of proliferation and neural differentiation expanded in monolayer form. Cultured cells were small, round or spindle-shaped, and expressed nestin. Under neural differentiation conditions, cells developed long, thin cellular processes with branches, and expressed neuronal and glial phenotypes. Intracerebrally transplanted BMCs survived and migrated into the subcortex of syngenic animals.

Transplantation of multipotent cells extracted from adult skeletal muscles into the subventricular zone of adult rats

Stem cells isolated from adult tissues may be useful for autologous cell therapy in the nervous system. In the present study we tested the ability of multipotent stem cells isolated from adult muscle to survive and respond to migratory and differentiating cues when transplanted into the adult subventricular zone (SVZ). Prior to transplantation the cells were grown as spheres that expressed doublecortin, nestin, and betaIII-tubulin, as well as the mRNAs for the receptor EphA4 and the ligands ephrin B1, ephrin B2, but not ephrin B3. Four weeks after transplantation into the anterior part of the SVZ in adult rats, surviving cells were observed along the ventricular wall, in the SVZ, and in the posterior rostral migratory stream (RMS). None of these cells stained for betaIII-tubulin or doublecortin, which are molecules expressed by migrating neuroblasts, and none were present in the more rostral regions of the RMS or the olfactory bulb. However, most surviving transplanted cells were integrated into the wall of the lateral ventricle and expressed vimentin, a marker also expressed by ependymocytes. No tumors were observed 4 weeks posttransplantation. Our results suggest that multipotent stem cells isolated from adult muscle, which can be easily and safely isolated from patients and rapidly expanded ex vivo, may provide autologous vectors for the local delivery of secreted factors to the ventricles or nearby regions.