Atoh7 promotes retinal Müller cell differentiation into retinal ganglion cells

Glaucoma is one of the leading eye diseases due to the death of retinal ganglion cells. Increasing evidence suggests that retinal Müller cells exhibit the characteristics of retinal progenitor cells and can differentiate to neurons in injured retinas under certain conditions. However, the number of ganglion cells differentiated from retinal Müller cells falls far short of therapeutic needs. This study aimed to promote the differentiation of retinal Müller cells into ganglion cells by introducing Atoh7 into the stem cells dedifferentiated from retinal Müller cells. Rat retinal Müller cells were isolated and dedifferentiated into stem cells, which were transfected with PEGFP-N1 or PEGFP-N1-Atoh7 vector, and then further induced to differentiate into ganglion cells. The proportion of ganglion cells differentiated from Atoh7-tranfected stem cells was significantly higher than that of control transfected or untransfected cells. In summary, Atoh7 promotes the differentiation of retinal Müller cells into retinal ganglion cells. This may open a new avenue for gene therapy of glaucoma by promoting optic nerve regeneration.     

Growth differentiation factor 11 promotes differentiation of MSCs into endothelial‐like cells for angiogenesis

Growth differentiation factor 11 (GDF11) is a member of the transforming growth factor‐β super family. It has multiple effects on development, physiology and diseases. However, the role of GDF11 in the development of mesenchymal stem cells (MSCs) is not clear. To explore the effects of GDF11 on the differentiation and pro‐angiogenic activities of MSCs, mouse bone marrow–derived MSCs were engineered to overexpress GDF11 (MSC^GDF11) and their capacity for differentiation and paracrine actions were examined both in vitro and in vivo. Expression of endothelial markers CD31 and VEGFR2 at the levels of both mRNA and protein was significantly higher in MSC^GDF11 than control MSCs (MSC^Vector) during differentiation. More tube formation was observed in MSC^GDF11 as compared with controls. In an in vivo angiogenesis assay with Matrigel plug, MSC^GDF11 showed more differentiation into CD31⁺ endothelial‐like cells and better pro‐angiogenic activity as compared with MSC^Vector. Mechanistically, the enhanced differentiation by GDF11 involved activation of extracellular‐signal‐related kinase (ERK) and eukaryotic translation initiation factor 4E (EIF4E). Inhibition of either TGF‐β receptor or ERK diminished the effect of GDF11 on MSC differentiation. In summary, our study unveils the function of GDF11 in the pro‐angiogenic activities of MSCs by enhancing endothelial differentiation via the TGFβ‐R/ERK/EIF4E pathway.     

Tenogenic differentiation of equine adipose-tissue-derived stem cells under the influence of tensile strain, growth differentiation factors and various oxygen tensions

Mesenchymal stem cells have become extremely interesting for regenerative medicine and tissue engineering in the horse. Stem cell therapy has been proven to be a powerful and successful instrument, in particular for the healing of tendon lesions. We pre-differentiated equine adipose-tissue-derived stem cells (ASCs) in a collagen I gel scaffold by applying tensile strain, growth differentiation factors (GDFs) and various oxygen tensions in order to determine the optimal conditions for in vitro differentiation toward the tenogenic lineage. We compared the influence of 3% versus 21% oxygen tension, the use of GDF 5, GDF 6 and GDF 7 and the application of uniaxial tensile strain versus no mechanical stimulation on differentiation results as evaluated by cell morphology and by the expression of the tendon-relevant genes collagen I, collagen III, cartilage oligomeric matrix protein and scleraxis. The best results were obtained with an oxygen tension of 21%, tensile stimulation and supplementation with GDF 5 or GDF 7. This approach raises the hope that the in vivo application of pre-differentiated stem cells will improve healing and recovery time in comparison with treatment involving undifferentiated stem cells.     

Atoh7 promotes the differentiation of Müller cells-derived retinal stem cells into retinal ganglion cells in a rat model of glaucoma

Glaucoma is one of the leading eye diseases resulting in blindness due to the death of retinal ganglion cells. This study aimed to develop novel protocol to promote the differentiation of retinal Müller cells into ganglion cells in vivo in a rat model of glaucoma. The stem cells dedifferentiated from rat retinal Müller cells were randomized to receive transfection with empty lentivirus PGC-FU-GFP or lentivirus PGC-FU-Atoh7-GFP, or no transfection. The stem cells were induced further to differentiate. Ocular hypertension was induced using laser photocoagulation. The eyes were injected with Atoh7 expression vector lentivirus PGC-FU-Atoh7-GFP. Eyeball frozen sections, immunohistochemistry, RT-PCR, Western bolt, and apoptosis assay were performed. We found that the proportion of ganglion cells differentiated from Atoh7-tranfected stem cells was significantly higher than that of the other two groups. The mean intraocular pressure of glaucomatous eyes was elevated significantly compared with those of contralateral eyes. Some retinal Müller cells in the inner nuclear layer entered the mitotic cell cycle in rat chronic ocular hypertension glaucoma model. Atoh7 contributes to the differentiation of retinal Müller cells into retinal ganglion cells in rat model of glaucoma. In conclusion, Atoh7 promotes the differentiation of Müller cells-derived retinal stem cells into retinal ganglion cells in a rat model of glaucoma, thus opening up a new avenue for gene therapy and optic nerve regeneration in glaucoma.     

Neuron differentiation in hydra involves dividing intermediates

The neuron differentiation pathway in hydra is usually assumed to be the following. A multipotent stem cell among the large interstitial cells becomes committed to neuron differentiation and divides. The two daughter cells, which are postmitotic small interstitial cells, subsequently differentiate into neurons. Herein the neuron pathway of the lower peduncle of Hydra oligactis was examined in some detail. In this region a substantial amount of neuron differentiation takes place, but very few large interstitial cells are present. It was found that small interstitial cells, which are capable of dividing, differentiate into neurons. The minimum time required to traverse the pathway from S phase of the last proliferating intermediate to a neuron is 18 hr. Thus, the neuron differentiation pathway in the lower peduncle involves dividing intermediates and is therefore more complex than usually assumed. Evidence for dividing small interstitial cells in the head, where the highest rate of neuron differentiation occurs, suggests that this more complex pathway may be common to all regions of the animal. A consequence of this finding is that the body of evidence concerning the commitment of multipotent stem cells to neurons and the control of this commitment requires reinterpretation.     

Comparison of murine dental follicle precursor and retinal progenitor cells after neural differentiation in vitro

Human dental stem or precursor cells can differentiate into multiple cell types like adipocytes, osteoblasts or chondrocytes. Recently, a number of different human dental stem cell lines were differentiated into neurons. This makes dental stem cells interesting as possible cell-based therapeutics for neural degenerative diseases. To test this hypothesis, we have investigated the neural differentiation potential of murine dental follicle precursor cells (mDFPCs). The mDFPC cell line was newly established without cell immortalization. After differentiation, neural cell marker expression in mDFPCs was checked and compared with that of murine retinal progenitor cells (mRPCs). Differentiated mDFPCs became neuron-like cells with small cell bodies and long/branching neurites, similar to differentiated mRPCs. However, mRPCs showed more complete neural differentiation. Furthermore, 5% of the differentiated mDFPCs and 37% of the differentiated mRPCs were positive for the glia cell marker GFAP (glial fibrillary acidic protein). The data presents new evidence of neural differentiation of mDFPCs, but only a small percentage of mDFPCs differentiated into glia cells, unlike mRPCs.     

In vitro survival and differentiation of neurons derived from epidermal growth factor-responsive postnatal hippocampal stem cells: Inducing effects of brain-derived neurotrophic factor

Neural stem cells proliferate in vitro and form neurospheres in the presence of epidermal growth factor (EGF), and are capable of differentiating into both neurons and glia when exposed to a substrate. We hypothesize that specific neurotrophic factors induce differentiation of stem cells from different central nervous system (CNS) regions into particular fates. We investigated differentiation of stem cells from the postnatal mouse hippocampus in culture using the following trophic factors (20 ng/mL): brain-derived neurotrophic factor (BDNF), neurotrophin-3 (NT-3) and glial-derived neurotrophic factor (GDNF). Without trophic factors, 32% of stem cells differentiated into neurons by 4 days in vitro (DIV), decreasing to 10% by 14 DIV. Addition of BDNF (starting at either day 0 or day 3) significantly increased neuron survival (31–43% by 14 DIV) and differentiation. Morphologically, many well-differentiated neurons resembled hippocampal pyramidal neurons. 5′-Bromodeoxyuridine labeling demonstrated that the pyramidal-like neurons originated from stem cells which had proliferated in EGF-containing cultures. However, similar application of NT-3 and GDNF did not exert such a differentiating effect. Addition of BDNF to stem cells from the postnatal cerebellum, midbrain, and striatum did not induce these neuronal phenotypes, though similar application to cortical stem cells yielded pyramidal-like neurons. Thus, BDNF supports survival of hippocampal stem cell-derived neurons and also can induce differentiation of these cells into pyramidal-like neurons. The presence of pyramidal neurons in BDNF-treated hippocampal and cortical stem cell cultures, but not in striatal, cerebellar, and midbrain stem cell cultures, suggests that stem cells from different CNS regions differentiate into region-specific phenotypic neurons when stimulated with an appropriate neurotrophic factor. © 1998 John Wiley & Sons, Inc. J Neurobiol 35: 395–425, 1998     

Insulin-like growth factor-1 regulation of retinal progenitor cell proliferation and differentiation

Strategies to improve retinal progenitor cell (RPC) capacity to yield proliferative and multipotent pools of cells that can efficiently differentiate into retinal neurons, including photoreceptors, could be vital for cell therapy in retinal degenerative diseases. In this study, we found that insulin-like growth factor-1 (IGF-1) plays a role in the regulation of proliferation and differentiation of RPCs. Our results show that IGF-1 promotes RPC proliferation via IGF-1 receptors (IGF-1Rs), stimulating increased phosphorylation in the PI3K/Akt and MAPK/Erk pathways. An inhibitor experiment revealed that IGF-1-induced RPC proliferation was inhibited when the PI3K/Akt and MAPK/Erk pathways were blocked. Furthermore, under the condition of differentiation, IGF-1-pretreated RPCs prefer to differentiate into retinal neurons, including photoreceptors, in vitro, which is crucial for visual formation and visual restoration. These results demonstrate that IGF-1 accelerates the proliferation of RPCs and IGF-1 pretreated RPCs may have shown an increased potential for retinal neuron differentiation, providing a novel strategy for regulating the proliferation and differentiation of retinal progenitors in vitro and shedding light upon the application of RPCs in retinal cell therapy.     

Efficient differentiation of mouse embryonic stem cells into motor neurons

Direct differentiation of embryonic stem (ES) cells into functional motor neurons represents a promising resource to study disease mechanisms, to screen new drug compounds, and to develop new therapies for motor neuron diseases such as spinal muscular atrophy (SMA) and amyotrophic lateral sclerosis (ALS). Many current protocols use a combination of retinoic acid (RA) and sonic hedgehog (Shh) to differentiate mouse embryonic stem (mES) cells into motor neurons. However, the differentiation efficiency of mES cells into motor neurons has only met with moderate success. We have developed a two-step differentiation protocol that significantly improves the differentiation efficiency compared with currently established protocols. The first step is to enhance the neuralization process by adding Noggin and fibroblast growth factors (FGFs). Noggin is a bone morphogenetic protein (BMP) antagonist and is implicated in neural induction according to the default model of neurogenesis and results in the formation of anterior neural patterning. FGF signaling acts synergistically with Noggin in inducing neural tissue formation by promoting a posterior neural identity. In this step, mES cells were primed with Noggin, bFGF, and FGF-8 for two days to promote differentiation towards neural lineages. The second step is to induce motor neuron specification. Noggin/FGFs exposed mES cells were incubated with RA and a Shh agonist, Smoothened agonist (SAG), for another 5 days to facilitate motor neuron generation. To monitor the differentiation of mESs into motor neurons, we used an ES cell line derived from a transgenic mouse expressing eGFP under the control of the motor neuron specific promoter Hb9. Using this robust protocol, we achieved 51 ± 0.8% of differentiation efficiency (n = 3; p < 0.01, Student's t-test). Results from immunofluorescent staining showed that GFP+ cells express the motor neuron specific markers, Islet-1 and choline acetyltransferase (ChAT). Our two-step differentiation protocol provides an efficient way to differentiate mES cells into spinal motor neurons.     

Transplantation of novel human GDF5-expressing CHO cells is neuroprotective in models of Parkinson's disease

Growth/differentiation factor 5 (GDF5) is a neurotrophic factor that promotes the survival of midbrain dopaminergic neurons in vitro and in vivo and as such is potentially useful in the treatment of Parkinson's disease (PD). This study shows that a continuous supply of GDF5, produced by transplanted GDF5-overexpressing CHO cells in vivo, has neuroprotective and neurorestorative effects on midbrain dopaminergic neurons following 6-hydroxydopamine (6-OHDA)-induced lesions of the adult rat nigrostriatal pathway. It also increases the survival and improves the function of transplanted embryonic dopaminergic neurons in the 6-OHDA-lesioned rat model of PD. This study provides the first proof-of-principle that sustained delivery of GDF5 in vivo may be useful in the treatment of PD.     

Betacellulin regulates the proliferation and differentiation of retinal progenitor cells in vitro

Retinal progenitor cells (RPCs) hold great potential for the treatment of retinal degenerative diseases. However, their proliferation capacity and differentiation potential towards specific retinal neurons are limited, which limit their future clinical applications. Thus, it is important to improve the RPCs’ ability to proliferate and differentiate. Currently, epidermal growth factor (EGF) is commonly used to stimulate RPC growth in vitro. In this study, we find that betacellulin (BTC), a member of the EGF family, plays important roles in the proliferation and differentiation of RPCs. Our results showed that BTC can significantly promote the proliferation of RPCs more efficiently than EGF. EGF stimulated RPC proliferation through the EGFR/ErbB2‐Erk pathway, while BTC stimulated RPC proliferation more powerfully through the EGFR/ErbB2/ErbB4‐Akt/Erk pathway. Meanwhile, under differentiated conditions, the BTC‐pre‐treated RPCs were preferentially differentiated into retinal neurons, including photoreceptors, one of the most important types of cells for retinal cell replacement therapy, compared to the EGF‐pre‐treated RPCs. In addition, knockdown of endogenous BTC expression can also obviously promote RPC differentiation into retinal neuronal cells. This data demonstrate that BTC plays important roles in promoting RPC proliferation and differentiation into retinal neurons. This study may provide new insights into the study of RPC proliferation and differentiation and make a step towards the application of RPCs in the treatment of retinal degenerative diseases.