Two faces of Schwann cell dedifferentiation in peripheral neurodegenerative diseases:pro-demyelinating and axon-preservative functions

Schwann cells are glial cells that are responsible for the synthesis and maintenance of the myelin sheath in the peripheral nerve system. Under pathological conditions, such as physical nerve injury and inflammatory neuropathies, Schwann cells undergo a substantial phenotype transformation that is not related to their intended function. For example, Schwann cells dedifferentiate into immature states and thereby cease to express myelin genes after nerve injury.

Pancreatic β cell regeneration induced by clinical and preclinical agents

Diabetes,one of the most common chronic diseases in the modern world,has pancreaticβcell deficiency as a major part of its pathophysiological mechanism.Pancreatic regeneration is a potential therapeutic strategy for the recovery ofβcell loss.However,endocrine islets have limited regenerative capacity,especially in adult humans.Almost all hypoglycemic drugs can protectβcells by inhibitingβcell apoptosis and dedifferentiation via correction of hyperglycemia and amelioration of the consequent inflammation and oxidative stress.Several agents,including glucagon-like peptide-1 andγ-aminobutyric acid,have been shown to promoteβcell proliferation,which is considered the main source of the regeneratedβcells in adult rodents,but with less clarity in humans.Pancreatic progenitor cells might exist and be activated under particular circumstances.Artemisinins andγ-aminobutyric acid can induceα-to-βcell conversion,although some disputes exist.Intestinal endocrine progenitors can transdeterminate into insulin-producing cells in the gut after FoxO1 deletion,and pharmacological research into FoxO1 inhibition is ongoing.Other cells,including pancreatic acinar cells,can transdifferentiate intoβcells,and clinical and preclinical strategies are currently underway.In this review,we summarize the clinical and preclinical agents used in different approaches forβcell regeneration and make some suggestions regarding future perspectives for clinical application.

Dedifferentiated fat cells:A cell source for regenerative medicine

The identification of an ideal cell source for tissue regeneration remains a challenge in the stem cell field. The ability of progeny cells to differentiate into other cell types is important for the processes of tissue reconstruction and tissue engineering and has clinical, biochemical or molecular implications. The adaptation of stem cells from adipose tissue for use in regenerative medicine has created a new role for adipocytes. Mature adipocytes can easily be isolated from adipose cell suspensions and allowed to dedifferentiate into lipidfree multipotent cells, referred to as dedifferentiated fat(DFAT) cells. Compared to other adult stem cells, the DFAT cells have unique advantages in their abundance, ease of isolation and homogeneity. Under proper condition in vitro and in vivo, the DFAT cells have exhibited adipogenic, osteogenic, chondrogenic, cardiomyogenc, angiogenic, myogenic, and neurogenic potentials. In this review, we first discuss the phenomena of dedifferentiation and transdifferentiation of cells, and then dedifferentiation of adipocytes in particular. Understanding the dedifferentiation process itself may contribute to our knowledge of normal growth processes, as well as mechanisms of disease. Second, we highlight new developments in DFAT cell culture and summarize the current understanding of DFAT cell properties. The unique features of DFAT cells are promising for clinical applications such as tissue regeneration.

Dedifferentiated fat cells: an alternative source of adult multipotent cells from the adipose tissues

When adipose-derived stem cells （ASCs） arc retrieved from the stromal vascular portion of adipose tissue, a large amount of mature adipocytes are often discarded. However, by modified ceiling culture technique based on their buoyancy, mature adipocytes can be easily isolated from the adipose cell suspension and dediffercn- tiated into lipid-frce fibroblast-like cells, named dediffercntiated fat （DFAT） cells. DFAT cells rc-establish active proliferation ability and undertake multipotent capacities. Compared with ASCs and other adult stem cells, DFAT cells showed unique advantages in their abundance, isolation and homogeneity. In this concise review, the establishment and culture methods of DFAT cells arc introduced and the current profiles of their cellular nature are summarized. Under proper inducti~,n culture in vitro or environment in vivo, DFAT cells could demonstrate adipogenic, osteogenic, chondrogenie and myogenic potentials. In angiogenie conditions, DFAT cells could exhibit perivascular characteristics antt elicit neovascularization. Our preliminary findings also suggested the pericyte phenotype underlying such cell lineage, which supported a novel interpretation about the common origin of mesenchymal stem cells and tissue-specific stem cells within blood vessel walls. Current research on DFAT cells indicated that this alternative source of adult multipotent cells has great potential in tissue engineering and regenerative medicine.

miR-30c promotes Schwann cell remyelination following peripheral nerve injury

Differential expression of mi RNAs occurs in injured proximal nerve stumps and includes mi RNAs that are firstly down-regulated and then gradually up-regulated following nerve injury.These mi RNAs might be related to a Schwann cell phenotypic switch.mi R-30 c,as a member of this group,was further investigated in the current study.Sprague-Dawley rats underwent sciatic nerve transection and proximal nerve stumps were collected at 1,4,7,14,21,and 28 days post injury for analysis.Following sciatic nerve injury,mi R-30 c was down-regulated,reaching a minimum on day 4,and was then upregulated to normal levels.Schwann cells were isolated from neonatal rat sciatic nerve stumps,then transfected with mi R-30 c agomir and co-cultured in vitro with dorsal root ganglia.The enhanced expression of mi R-30 c robustly increased the amount of myelin-associated protein in the co-cultured dorsal root ganglia and Schwann cells.We then modeled sciatic nerve crush injury in vivo in Sprague-Dawley rats and tested the effect of perineural injection of mi R-30 c agomir on myelin sheath regeneration.Fourteen days after surgery,sciatic nerve stumps were harvested and subjected to immunohistochemistry,western blot analysis,and transmission electron microscopy.The direct injection of mi R-30 c stimulated the formation of myelin sheath,thus contributing to peripheral nerve regeneration.Overall,our findings indicate that mi R-30 c can promote Schwann cell myelination following peripheral nerve injury.The functional study of mi R-30 c will benefit the discovery of new therapeutic targets and the development of new treatment strategies for peripheral nerve regeneration.

Adipose tissue in bone regeneration-stem cell source and beyond

Adipose tissue(AT)is recognized as a complex organ involved in major homeostatic body functions,such as food intake,energy balance,immunomodulation,development and growth,and functioning of the reproductive organs.The role of AT in tissue and organ homeostasis,repair and regeneration is increasingly recognized.Different AT compartments(white AT,brown AT and bone marrow AT)and their interrelation with bone metabolism will be presented.AT-derived stem cell populations-adipose-derived mesenchymal stem cells and pluripotentlike stem cells.Multilineage differentiating stress-enduring and dedifferentiated fat cells can be obtained in relatively high quantities compared to other sources.Their role in different strategies of bone and fracture healing tissue engineering and cell therapy will be described.The current use of AT-or AT-derived stem cell populations for fracture healing and bone regenerative strategies will be presented,as well as major challenges in furthering bone regenerative strategies to clinical settings.

Emerging targets for glioblastoma stem cell therapy

Glioblastoma multiforme（GBM）,designated as World Health Organization（WHO）grade IV astrocytoma,is a lethal and therapy-resistant brain cancer comprised of several tumor cell subpopulations,including GBM stem cells（GSCs）which are believed to contribute to tumor recurrence following initial response to therapies.Emerging evidence demonstrates that GBM tumors are initiated from GSCs.The development and use of novel therapies including small molecule inhibitors of specific proteins in signaling pathways that regulate sternness,proliferation and migration of GSCs,immunotherapy,and non-coding microRNAs may provide better means of treating GBM.Identification and characterization of GSC-specific signaling pathways would be necessary to identify specific therapeutic targets which may lead to the development of more efficient therapies selectively targeting GSCs.Several signaling pathways including mTOR,AKT,maternal embryonic leucine zipper kinase（MELK）,NOTCH1 and Wnt/β-catenin as well as expression of cancer stem cell markers CD133,CD44,Oct4,Sox2,Nanog,and ALDHlA1 maintain GSC properties.Moreover,the data published in the Cancer Genome Atlas（TCGA）specifically demonstrated the activated PI3K/AKT/mTOR pathway in GBM tumorigenesis.Studying such pathways may help to understand GSC biology and lead to the development of potential therapeutic interventions to render them more sensitive to chemotherapy and radiation therapy.Furthemore,recent demonstration of dedifferentiation of GBM cell lines into CSC-like cells prove that any successful therapeutic agent or combination of drugs for GBM therapy must eliminate not only GSCs,but the differentiated GBM cells and the entire bulk of tumor cells.

Regeneration of β cells from cell phenotype conversion among the pancreatic endocrine cells

The prevalence of diabetes has increased dramatically, with over 537 million adults affected worldwide.1 In both type 1 and type 2 diabetes, pancreatic islet β cell dysfunction is common pathogenesis.

Submergence promotes auxin-induced callus formation through ethylene-mediated post-transcriptional control of auxin receptors

Plant cells in damaged tissue can be reprogrammed to acquire pluripotency and induce callus formation.However,in the aboveground organs of many species,somatic cells that are distal to the wound site become less sensitive to auxin-induced callus formation,suggesting the existence of repressive regulatory mechanisms that are largely unknown.Here we reveal that submergence-induced ethylene signals promote callus formation by releasing post-transcriptional silencing of auxin receptor transcripts in non-wounded regions.We determined that short-term submergence of intact seedlings induces auxin-mediated cell dedifferentiation across the entirety of Arabidopsis thaliana explants.The constitutive triple response 1-1(ctr1-1)mutation induced callus formation in explants without submergence,suggesting that ethylene facilitates cell dedifferentiation.We show that ETHYLENE-INSENSITIVE 2(EIN2)post-transcriptionally regulates the abundance of transcripts for auxin receptor genes by facilitating microRNA393 degradation.Submergence-induced calli in non-wounded regions were suitable for shoot regeneration,similar to those near the wound site.We also observed submergence-promoted callus formation in Chinese cabbage(Brassica rapa),indicating that this may be a conserved mechanism in other species.Our study identifies previously unknown regulatory mechanisms by which ethylene promotes cell dedifferentiation and provides a new approach for boosting callus induction efficiency in shoot explants.