Neuron-like differentiation of adipose tissue-derived stromal cells and vascular smooth muscle cells

Treatment of stress urinary incontinence with adipose tissue-derived stem cells

BACKGROUND AIMS

Effective treatment for stress urinary incontinence (SUI) is lacking. This study investigated whether transplantation of adipose tissue-derived stem cells (ADSC) can treat SUI in a rat model.

METHODS

Rats were induced to develop SUI by postpartum vaginal balloon dilation and bilateral ovariectomy. ADSC were isolated from the peri-ovary fat, examined for stem cell properties, and labeled with thymidine analog BrdU or EdU. Ten rats received urethral injection of saline as a control. Twelve rats received urethral injection of EdU-labeled ADSC and six rats received intravenous injection of BrdU-labeled ADSC through the tail vein. Four weeks later, urinary voiding function was assessed by conscious cystometry. The rats were then killed and their urethras harvested for tracking of ADSC and quantification of elastin, collagen and smooth muscle contents.

RESULTS

Cystometric analysis showed that eight out 10 rats in the control group had abnormal voiding, whereas four of 12 (33.3%) and two of six (33.3%) rats in the urethra-ADSC and tail vein-ADSC groups, respectively, had abnormal voiding. Histologic analysis showed that the ADSC-treated groups had significantly higher elastin content than the control group and, within the ADSC-treated groups, rats with normal voiding pattern also had significantly higher elastin content than rats with voiding dysfunction. ADSC-treated normal-voiding rats had significantly higher smooth muscle content than control or ADSC-treated rats with voiding dysfunction.

CONCLUSIONS

Transplantation of ADSC via urethral or intravenous injection is effective in the treatment and/or prevention of SUI in a pre-clinical setting.

Comparison of the efficiencies of three neural induction protocols in human adipose stromal cells

The aim of this study was to compare the neural differentiation potential and the expression of neurotrophic factors (NTFs) in differentiated adipose-derived stem cells (ADSCs) using three established induction protocols, serum free (Protocol 1), chemical reagents (Protocol 2), and spontaneous (Protocol 3) protocols. Protocol 1 produced the highest percentage of mature neural-like cells (MAP2ab(+)). Protocol 2 showed the highest percentage of immature neural-like cells (beta-tubulin III(+)), but the neural-like state was transient and reversible. Protocol 3 caused ADSCs to differentiate spontaneously into immature neural-like cells, but not into mature neural cell types. The neural-like cells produced by Protocol 1 lived the longest in culture with little cell death, but Protocol 2 and 3 led to the significant cell death. Therefore, Protocol 1 is the most efficient among these protocols. Additionally, soon after differentiation, the mRNA levels of nerve growth factor (NGF) and brain-derived neurotrophic factor (BDNF) in dADSCs were sharply decreased by Protocol 1 and 2 (acute induction protocol), but not by Protocol 3 (chronic induction protocol). The results indicate that NTFs played an important role in neural differentiation via acute responses to NGF and BDNF, but not chronically during the transdifferentiation process.

MicroRNA regulation of neuron-like differentiation of adipose tissue-derived stem cells

We have reported previously that adipose tissue-derived stem cells (ADSC) could be induced by isobutylmethylxanthine (IBMX) to differentiate into neuron-like cells and such differentiation was mediated by insulin-like growth factor I (IGF-I) signaling. In the present study we show that both IBMX and IGF-I upregulated neural markers beta-III-tubulin and paired-like homeobox transcription factor (Pitx3) in ADSC. Because Pitx3 is important for the maturation and function of dopaminergic neurons and has been shown to be regulated by microRNA miR-133b, we also examined the effects of IBMX and IGF-I on miR-133b expression. The results show that both IBMX and IGF-I upregulated miR-133b expression. When miR-133b was overexpressed in ADSC through transfection of a synthetic microRNA mimic, it caused a downregulation of beta-III-tubulin as evidenced by immunofluorescence staining and western blot analysis. Overexpression of miR-133b also downregulated Pitx3 and IGF-1 receptor (IGF-IR), and all such downregulation occurred at the protein but not the RNA level. The apparent posttranscriptional regulation was subsequently found to be exerted through a potential miR-133b target in the 3'-untranslated region of IGF-IR, as evidenced by luciferase assay. Thus, IGF-I signaling and miR-133b co-regulate potential neural differentiation of ADSC through a feedback mechanism, in which IGF-I upregulates miR-133b while miR-133b in turn downregulates IGF-IR.

Potential of adipose-derived stem cells for treatment of erectile dysfunction

INTRODUCTION

Adipose-derived stem cells (ADSCs) are a somatic stem cell population contained in fat tissue that possess the ability for self-renewal, differentiation into one or more phenotypes, and functional regeneration of damaged tissue, which may benefit the recovery of erectile function by using a stem cell-based therapy.

AIM

To review available evidence concerning ADSCs availability, differentiation into functional cells, and the potential of these cells for the treatment of erectile dysfunction (ED).

METHODS

We examined the current data (from 1964 to 2008) associated with the definition, characterization, differentiation, and application of ADSCs, as well as other kinds of stem cells for the cell-based therapies of ED.

MAIN OUTCOME MEASURES

There is strong evidence supporting the concept that ADSCs may be a potential stem cell therapy source in treating ED.

RESULTS

The ADSCs are paravascularly localized in the adipose tissue. Under specific induction medium conditions, these cells differentiated into neuron-like cells, smooth muscle cells, and endothelium in vitro. The insulin-like growth factor/insulin-like growth factor receptor (IGF/IGFR) pathway participates in neuronal differentiation while the fibroblast growth factor 2 (FGF2) pathway is involved in endothelium differentiation. In a preliminary in vivo experiment, the ADSCs functionally recovered the damaged erectile function. However, the underlying mechanism needs to be further examined.

CONCLUSION

The ADSCs are a potential source for stem cell-based therapies, which imply the possibility of an effective clinical therapy for ED in the near future.

IFATS collection: The conditioned media of adipose stromal cells protect against hypoxia-ischemia-induced brain damage in neonatal rats

Adipose tissue stroma contains a population of mesenchymal stem cells, which support repair when administered to damaged tissues, in large part through secreted trophic factors. We directly tested the ability of media collected from cultured adipose-derived stem cells (ASCs) to protect neurons in a rat model of brain hypoxic-ischemic (HI) injury. Concentrated conditioned medium from cultured rat ASCs (ASC-CM) or control medium was infused through the jugular vein of neonatal Sprague-Dawley rats subjected to HI injury. The ASC-CM was administered either 1 hour before or 24 hours after induction of injury. Analysis at 1 week indicated that administration at both time points significantly protected against hippocampal and cortical volume loss. Analysis of parallel groups for behavioral and learning changes at 2 months postischemia demonstrated that both treated groups performed significantly better than the controls in Morris water maze functional tests. Subsequent post-mortem evaluation of brain damage at the 2-month time point confirmed neuronal loss to be similar to that observed at 1 week for all groups. We have identified several neurotrophic factors in ASC-CM, particularly insulin-like growth factor-1 and brain-derived neurotrophic factor, which are important factors that could contribute to the protective effects of ASCs observed in studies with both in vitro and in vivo neuronal injury models. These data suggest that delivery of the milieu of factors secreted by ASCs may be a viable therapeutic option for treatment of HI, as well as other brain injuries.

Defining stem and progenitor cells within adipose tissue

Adipose tissue-derived stem cells (ADSC) are routinely isolated from the stromal vascular fraction (SVF) of homogenized adipose tissue. Freshly isolated ADSC display surface markers that differ from those of cultured ADSC, but both cell preparations are capable of multipotential differentiation. Recent studies have inferred that these progenitors may reside in a perivascular location where they appeared to coexpress CD34 and smooth muscle actin (alpha-SMA) but not CD31. However, these studies provided only limited histological evidence to support such assertions. In the present study, we employed immunohistochemistry and immunofluorescence to define more precisely the location of ADSC within human adipose tissue. Our results show that alpha-SMA and CD31 localized within smooth muscle and endothelial cells, respectively, in all blood vessels examined. CD34 localized to both the intima (endothelium) and adventitia neither of which expressed alpha-SMA. The niche marker Wnt5a was confined exclusively to the vascular wall within mural smooth muscle cells. Surprisingly, the widely accepted mesenchymal stem cell marker STRO-1 was expressed exclusively in the endothelium of capillaries and arterioles but not in the endothelium of arteries. The embryonic stem cell marker SSEA1 localized to a pericytic location in capillaries and in certain smooth muscle cells of arterioles. Cells expressing the embryonic stem cell markers telomerase and OCT4 were rare and observed only in capillaries. Based on these findings and evidence gathered from the existing literature, we propose that ADSC are vascular precursor (stem) cells at various stages of differentiation. In their native tissue, ADSC at early stages of differentiation can differentiate into tissue-specific cells such as adipocytes. Isolated, ADSC can be induced to differentiate into additional cell types such as osteoblasts and chondrocytes.

Neural differentiation of adipose-derived stem cells by indirect co-culture with Schwann cells

To investigate whether adipose-derived stem cells (ADSCs) could be subject to neural differentiation induced only by Schwann cell (SC) factors, we co-cultured ADSCs and SCs in transwell culture dishes. Immunoassaying, Western blot analysis, and RT-PCR were performed (1, 3, 7, 14 d) and the co-cultured ADSCs showed gene and protein expression of S-100, Nestin, and GFAP. Further, qRT-PCR disclosed relative quantitative differences in the above three gene expressions. We think ADSCs can undergo induced neural differentiation by being co-cultured with SCs, and such differentia?tions begin 1 day after co-culture, become apparent after 7 days, and thereafter remain stable till the 14th day.

Neuronal differentiation potential of human adipose-derived mesenchymal stem cells

Adult mesenchymal stem cells derived from adipose tissue (A-MSC) have the capacity to differentiate in vitro into mesenchymal as well as endodermal and ectodermal cell lineages. We investigated the neuronal differentiation potential of human A-MSC with a protocol which included sphere formation and sequential culture in brain-derived neurotrophic factor (BDNF) and retinoic acid (RA). After 30 days, about 57% A-MSC showed morphological, immunocytochemical and electrophysiological evidence of initial neuronal differentiation. In fact, A-MSC displayed elongated shape with protrusion of two or three cellular processes, selectively expressed nestin and neuronal molecules (including GABA receptor and tyroxine hydroxilase) in the absence of glial phenotypic markers. Differentiated cells showed negative membrane potential (-60 mV), delayed rectifier potassium currents and TTX-sensitive sodium currents. Such changes were stable for at least 7 days after removal of differentiation medium. In view of these results and the easy availability of adipose tissue, A-MSC may be a ready source of adult MSC with neuronal differentiation potential, an useful tool to treat neurodegenerative diseases.

Neural differentiation and potential use of stem cells from the human umbilical cord for central nervous system transplantation therapy

The human umbilical cord is a rich source of autologous stem and progenitor cells. Interestingly, subpopulations of these, particularly mesenchymal-like cells from both cord blood and the cord stroma, exhibited a potential to be differentiated into neuron-like cells in culture. Umbilical cord blood stem cells have demonstrated efficacy in reducing lesion sizes and enhancing behavioral recovery in animal models of ischemic and traumatic central nervous system (CNS) injury. Recent findings also suggest that neurons derived from cord stroma mesenchymal cells could alleviate movement disorders in hemiparkinsonian animal models. We review here the neurogenic potential of umbilical cord stem cells and discuss possibilities of their exploitation as an alternative to human embryonic stem cells or neural stem cells for transplantation therapy of traumatic CNS injury and neurodegenerative diseases.

Identification of an aberrant cell line among human adipose tissue-derived stem cell isolates

Adipose tissue-derived stem cells (ADSC) are isolated from the stromal vascular fraction (SVF) of adipose tissue and considered an excellent cell source for regenerative medicine. During the isolation and propagation of several human ADSC cell lines, we observed the emergence of an unusual cell line designated HADSC-6. Although initially fibroblast-like as typical ADSC are, HADSC-6 cells became homogeneously cuboid in shape, had very little cytoplasm, and formed aggregates with capsule-like boundary. Proliferation assay showed that HADSC-6 grew much faster than typical HADSC cell lines, such as HADSC-20. Immunocytochemistry showed that HADSC-6 did not express endothelial markers CD31 and vWF, and matrigel tube formation assay showed that it was unable to form endothelial-like tube structures. However, LDL uptake, a reliable endothelial marker, was positively identified. Chromosomal analysis showed that HADSC-6 cells were hypertriploid, and soft agar colony formation assay showed that they were able to proliferate and form large colonies in an anchorage-independent manner. However, tumorigenicity test showed that HADSC-6 was unable to form tumors in athymic mice. RT-PCR analysis showed that both HADSC-6 and HADSC-20 expressed VEGF-A, VEGF-B, VEGF-D, and VEGFR1 but not VEGFR2 or VEGFR3. VEGF-C, however, was expressed at a high level in HADSC-20 but undetectable in HADSC-6. In the IGF system, IGF-1 was abundantly expressed in HADSC-20 but marginally detectable in HADSC-6, and IGF-1R was abundantly expressed in HADSC-6 but not detectable in HADSC-20. In the FGF system, bFGF was abundantly expressed in HADSC-20 but marginally detectable in HADSC-6, and FGFR1 was abundantly expressed in both. Taken together, these results suggested that HADSC-6 cells were spontaneously transformed from the endothelium; therefore, they were further compared to previously published data of four naturally occurring human angiosarcoma cell lines. The results showed that the established angiosarcoma cell lines exhibit considerable variations among themselves and HADSC-6 displayed most of these variable characteristics.

Recent progress on tissue-resident adult stem cell biology and their therapeutic implications

Recent progress in the field of the stem cell research has given new hopes to treat and even cure diverse degenerative disorders and incurable diseases in human. Particularly, the identification of a rare population of adult stem cells in the most tissues/organs in human has emerged as an attractive source of multipotent stem/progenitor cells for cell replacement-based therapies and tissue engineering in regenerative medicine. The tissue-resident adult stem/progenitor cells offer the possibility to stimulate their in vivo differentiation or to use their ex vivo expanded progenies for cell replacement-based therapies with multiple applications in human. Among the human diseases that could be treated by the stem cell-based therapies, there are hematopoietic and immune disorders, multiple degenerative disorders, such as Parkinson's and Alzheimer's diseases, type 1 or 2 diabetes mellitus as well as eye, liver, lung, skin and cardiovascular disorders and aggressive and metastatic cancers. In addition, the genetically-modified adult stem/progenitor cells could also be used as delivery system for expressing the therapeutic molecules in specific damaged areas of different tissues. Recent advances in cancer stem/progenitor cell research also offer the possibility to targeting these undifferentiated and malignant cells that provide critical functions in cancer initiation and progression and disease relapse for treating the patients diagnosed with the advanced and metastatic cancers which remain incurable in the clinics with the current therapies.

Recent advances in andrology-related stem cell research

Stem cells hold great promise for regenerative medicine because of their ability to self-renew and to differentiate into various cell types. Although embryonic stem cells (BSC) have greater differentiation potential than adult stem cells, the former is lagging in reaching clinical applications because of ethical concerns and governmental restrictions. Bone marrow stem cells (BMSC) are the best-studied adult stem cells (ASC) and have the potential to treat a wide variety of diseases, including erectile dysfunction (ED) and male infertility. More recently discovered adipose tissue-derived stem cells (ADSC) are virtually identical to bone marrow stem cells in differentiation and therapeutic potential, but are easier and safer to obtain, can be harvested in larger quantities, and have the associated benefit of reducing obesity. Therefore, ADSC appear to be a better choice for future clinical applications. We have previously shown that ESC could restore the erectile function of neurogenic ED in rats, and we now have evidence that ADSC could do so as well. We are also investigating whether ADSC can differentiate into Leydig, Sertoli and male germ cells. The eventual goal is to use ADSC to treat male infertility and testosterone deficiency.

Neural stem cells in the mammalian brain

New fundamental results on stem cell biology have been obtained in the past 15 years. These results allow us to reinterpret the functioning of the cerebral tissue in health and disease. Proliferating stem cells have been found in the adult brain, which can be involved in postinjury repair and can replace dead cells under specific conditions. Numerous genomic mechanisms controlling stem cell proliferation and differentiation have been identified. The involvement of stem cells in the genesis of malignant tumors has been demonstrated. Neural stem cell tropism toward tumors has been shown. These findings suggest new lines of research on brain functioning and development. Stem cells can be used to develop radically new treatments of neurodegenerative and cancer diseases of the brain.

Mature adipocytes may be a source of stem cells for tissue engineering

Adipose tissue contains a large portion of stem cells. These cells appear morphologically like fibroblasts and are primarily derived from the stromal cell fraction. Mature (lipid-filled) adipocytes possess the ability to become proliferative cells and have been shown to produce progeny cells that possess the same morphological (fibroblast-like) appearance as the stem cells from the stromal fraction. A closer examination of mature adipocyte-derived progeny cells may prove to be an emerging area of growth/metabolic physiology that may modify present thinking about adipose tissue renewal capabilities. Knowledge of these cells may also prove beneficial in cell-based therapies for tissue repair, regeneration, or engineering.

Fibroblast growth factor 2 promotes endothelial differentiation of adipose tissue-derived stem cells

INTRODUCTION

Adipose tissue-derived stem cells (ADSC) could potentially restore endothelial function in vasculogenic erectile dysfunction (ED). The mechanism for ADSC endothelial differentiation remained unidentified.

AIM

To test whether ADSC could differentiate into endothelial cells in the penis and to identify the underlying mechanism of ADSC endothelial differentiation.

METHODS

For in vivo endothelial differentiation, ADSC were labeled with bromodeoxyuridine (BrdU), injected into rat corpora cavernosa, and localized by immunofluorescence and phase-contrast microscopy. For in vitro endothelial differentiation, ADSC were grown in endothelial growth medium 2 (EGM2), stained for endothelial markers CD31, von Willebrand Factor (vWF), and endothelial nitric oxide synthase (eNOS), and assessed for the ability to form tube-like structures in Matrigel and to endocytose acetylated low-density lipoprotein (Ac-LDL). To identify factors that promote ADSC endothelial differentiation, ADSC were grown in various media, each of which contained a specific combination of supplemental factors and assessed for LDL-uptake. PD173074, a selective inhibitor of fibroblast growth factor 2 (FGF2) receptor, was used to confirm the importance of FGF2 signaling for ADSC endothelial differentiation.

MAIN OUTCOME MEASURES

In vivo endothelial differentiation was assessed by immunofluorescence microscopy. In vitro endothelial differentiation was assessed by immunofluorescence, Matrigel tube formation, and Ac-LDL uptake.

RESULTS

Injected ADSC were localized to the sinusoid endothelium, some of which stained positive for both BrdU and endothelial antigen rat endothelial cell antigen. ADSC proliferated at a faster rate in EGM2 than in standard DMEM, expressed endothelial markers CD31, vWF, and eNOS, formed tube-like structures in Matrigel, and endocytosed Ac-LDL. These properties were greatly diminished when ADSC were grown in the absence of FGF2 but were unaffected when grown in the absence of vascular endothelial growth factor, insulin-like growth factor, or epidermal growth factor. Furthermore, ADSC displayed similar endothelial properties when grown in FGF2-supplemented basic medium as in EGM2. Finally, blockade of FGF2 signaling with PD173074 abrogated ADSC endothelial differentiation.

CONCLUSIONS

ADSC could differentiate into endothelial cells in the penis. FGF2 signaling mediates ADSC endothelial differentiation.

FGF2-dependent neovascularization of subcutaneous Matrigel plugs is initiated by bone marrow-derived pericytes and macrophages

Vessel-like networks are quickly formed in subcutaneous FGF2-supplemented Matrigel plugs by two cell types: NG2(+) pericytes and F4/80(+) macrophages. Although not detected in these networks until 7 days after plug implantation, the appearance of CD31(+) endothelial cells marks the onset of vessel perfusion and the establishment of mature vessel morphology, with endothelial cells invested tightly by pericytes and more loosely by macrophages. Evidence that mature vessels develop from pericyte/macrophage networks comes from experiments in which 5-day plugs are transplanted into EGFP(+) recipients and allowed to mature. Fewer than 5% of pericytes in mature vessels are EGFP(+) in this paradigm, demonstrating their presence in the networks prior to plug transplantation. Endothelial cells represent the major vascular cell type recruited during later stages of vessel maturation. Bone marrow transplantation using EGFP(+) donors establishes that almost all macrophages and more than half of the pericytes in Matrigel vessels are derived from the bone marrow. By contrast, only 10% of endothelial cells exhibit a bone marrow origin. The vasculogenic, rather than angiogenic, nature of this neovascularization process is unique in that it is initiated by pericyte and macrophage progenitors, with endothelial cell recruitment occurring as a later step in the maturation process.

Insulin growth factor signaling mediates neuron-like differentiation of adipose-tissue-derived stem cells

Our previous study showed that adipose tissue-derived stem cells (ADSC) could be induced by isobutylmethylxanthine (IBMX) to differentiate into neuron-like cells. In the present study, ADSC were treated with IBMX in the presence or in the absence of each of eight specific inhibitors of different signaling pathways (JAK/STAT, PKA, PI3K, MEK, Wnt/Frizzled, ERK/MAPK, TGF-beta, and insulin growth factor [IGF]-I). PPP, a specific inhibitor of IGF-I signaling, was the only inhibitor that showed significant inhibition of IBMX-induced ADSC neuronal differentiation, as determined by changes in cell morphology in the initial screening. Further examination by immunofluorescence staining showed that the neuronal marker, beta-III-tubulin, was highly induced in IBMX-treated ADSC, and the induction was significantly suppressed by PPP. Western blotting, followed by densitometry showed that PPP suppressed IBMX-induced beta-III-tubulin expression by 43%, 88%, and 84% when used to treat the cells for 1, 3, and 24 hr, respectively. Treatment of ADSC with IBMX also led to the phosphorylation of IGF-I receptor at tyrosine 1136 (Y1136), as determined by immunofluorescence staining with an antibody that reacts specifically with Y1136. This effect was also abrogated by PPP. Thus, the IBMX-induced neuron-like differentiation of ADSC is mediated by IGF signaling through the phosphorylation of IGF-IR at Y1136.

Autologous transplants of Adipose-Derived Adult Stromal (ADAS) cells afford dopaminergic neuroprotection in a model of Parkinson's disease

Adult adipose contains stromal progenitor cells with neurogenic potential. However, the stability of neuronal phenotypes adopted by Adipose-Derived Adult Stromal (ADAS) cells and whether terminal neuronal differentiation is required for their consideration as alternatives in cell replacement strategies to treat neurological disorders is largely unknown. We investigated whether in vitro neural induction of ADAS cells determined their ability to neuroprotect or restore function in a lesioned dopaminergic pathway. In vitro-expanded naïve or differentiated ADAS cells were autologously transplanted into substantia nigra 1 week after an intrastriatal 6-hydroxydopamine injection. Neurochemical and behavioral measures demonstrated neuroprotective effects of both ADAS grafts against 6-hydroxydopamine-induced dopaminergic neuron death, suggesting that pre-transplantation differentiation of the cells does not determine their ability to survive or neuroprotect in vivo. Therefore, we investigated whether equivalent protection by naïve and neurally-induced ADAS grafts resulted from robust in situ differentiation of both graft types into dopaminergic fates. Immunohistological analyses revealed that ADAS cells did not adopt dopaminergic cell fates in situ, consistent with the limited ability of these cells to undergo terminal differentiation into electrically active neurons in vitro. Moreover, re-exposure of neurally-differentiated ADAS cells to serum-containing medium in vitro confirmed ADAS cell phenotypic instability (plasticity). Lastly, given that gene expression analyses of in vitro-expanded ADAS cells revealed that both naïve and differentiated ADAS cells express potent dopaminergic survival factors, ADAS transplants may have exerted neuroprotective effects by production of trophic factors at the lesion site. ADAS cells may be ideal for ex vivo gene transfer therapies in Parkinson's disease treatment.

Adipose-derived stem cells differentiate into a Schwann cell phenotype and promote neurite outgrowth in vitro

Experimentally, peripheral nerve repair can be enhanced by Schwann cell transplantation but the clinical application is limited by donor site morbidity and the inability to generate a sufficient number of cells quickly. We have investigated whether adult stem cells, isolated from adipose tissue, can be differentiated into functional Schwann cells. Rat visceral fat was enzymatically digested to yield rapidly proliferating fibroblast-like cells, a proportion of which expressed the mesenchymal stem cell marker, stro-1, and nestin, a neural progenitor protein. Cells treated with a mixture of glial growth factors (GGF-2, bFGF, PDGF and forskolin) adopted a spindle-like morphology similar to Schwann cells. Immunocytochemical staining and western blotting indicated that the treated cells expressed the glial markers, GFAP, S100 and p75, indicative of differentiation. When co-cultured with NG108-15 motor neuron-like cells, the differentiated stem cells enhanced the number of NG108-15 cells expressing neurites, the number of neurites per cell and the mean length of the longest neurite extended. Schwann cells evoked a similar response whilst undifferentiated stem cells had no effect. These results indicate adipose tissue contains a pool of regenerative stem cells which can be differentiated to a Schwann cell phenotype and may be of benefit for treatment of peripheral nerve injuries.

Stem cells: a revolution in therapeutics-recent advances in stem cell biology and their therapeutic applications in regenerative medicine and cancer therapies

Basic and clinical research accomplished during the last few years on embryonic, fetal, amniotic, umbilical cord blood, and adult stem cells has constituted a revolution in regenerative medicine and cancer therapies by providing the possibility of generating multiple therapeutically useful cell types. These new cells could be used for treating numerous genetic and degenerative disorders. Among them, age-related functional defects, hematopoietic and immune system disorders, heart failures, chronic liver injuries, diabetes, Parkinson's and Alzheimer's diseases, arthritis, and muscular, skin, lung, eye, and digestive disorders as well as aggressive and recurrent cancers could be successfully treated by stem cell-based therapies. This review focuses on the recent advancements in adult stem cell biology in normal and pathological conditions. We describe how these results have improved our understanding on critical and unique functions of these rare sub-populations of multipotent and undifferentiated cells with an unlimited self-renewal capacity and high plasticity. Finally, we discuss some major advances to translate the experimental models on ex vivo and in vivo expanded and/or differentiated stem cells into clinical applications for the development of novel cellular therapies aimed at repairing genetically altered or damaged tissues/organs in humans. A particular emphasis is made on the therapeutic potential of different tissue-resident adult stem cell types and their in vivo modulation for treating and curing specific pathological disorders.

Tyrosine hydroxylase: human isoforms, structure and regulation in physiology and pathology

TH is a tetrahydrobiopterin-requiring, iron-containing monooxygenase. It catalyses the conversion of L-tyrosine to L-dopa, which is the first, rate-limiting step in the biosynthesis of catecholamines (dopamine, noradrenaline and adrenaline), the central and sympathetic neurotransmitters and adrenomedullary hormones. The cofactor of TH is tetrahydrobiopterin, which is synthesized from GTP in three steps. The TH gene consists of 14 exons only in humans and 13 exons in animals. Human TH exists in four isoforms (hTH1-4) that are produced by alternative mRNA splicing from a single gene. A single mRNA and protein corresponding to hTH1 exists in non-primates. Monkey TH exists in two isoforms, corresponding to hTH1 and hTH2. TH activity is regulated in the short term by feedback inhibition of catecholamines in competition with tetrahydrobiopterin, and by activation and deactivation due to phosphorylation and dephosphorylation, mainly at Ser-19 and Ser-40 of hTH1. The multiple TH isoforms in humans and monkeys have additional phosphorylation, resulting in more subtle regulation. In long-term regulation under stress conditions, TH protein is induced. CRE and AP1 in the 5' flanking region of the TH gene may be the main functional elements for TH gene expression. TH may be closely related to the pathogenesis of neurological diseases, such as dystonia and Parkinson's disease, psychiatric diseases, such as affective disorders and schizophrenia, as well as cardiovascular diseases. The TH gene may prove useful in gene therapy to compensate for decreased levels of catecholamines in neurological diseases, for example, for supplementation of dopamine in Parkinson's disease.