Native Stem Cells Research Articles

Irreversible Electroporation for De-epithelialization of Murine Small Intestine

BackgroundNonthermal irreversible electroporation (NTIRE) has been shown to ablate the small intestinal epithelium while maintaining submucosal and muscularis propriae integrity. NTIRE is used here in a first-in-mouse study to eliminate the native intestinal stem cell population to understand optimal parameters and timeline of mucosal regeneration. MethodsAdult C57 background mice underwent laparotomy and electroporation of 1.5 cm of jejunum using a BTX 830 ECM electroporator and electrode calipers. Parameters were varied by voltage, pulse number, interval, and duration to determine optimal de-epithelialization. Electroporated segments were extracted 1 to 3 d after intervention with same-animal control segment. Cross sections were preserved, and measurements were taken to compare effects of parameters on villi height, crypt depth, crypt obliteration, and serosal thickness. ResultsMorbidity was limited at a standard set of electroporation parameters (14%), and increased with higher voltage, longer interval, and shorter or longer pulses. Serosa/muscularis thickness was unaffected by varying interventions. Crypt depth and obliterated crypts were most affected by modulating pulse number, intervals, and duration. Villi height was most significantly shortened by altering pulse duration, with limited recovery by day 3, otherwise mucosal regeneration was observed in most cases by this point. ConclusionsNTIRE is an effective method of denuding small intestinal epithelium in mice and temporarily ablating crypts while sparing the support scaffold for native regeneration. This first-in-mouse study of electroporation suggests it is a practical tool that can be utilized in a small mammalian system.

Fabrication, maturation, and implantation of composite tissue-engineered total discs formed from native and mesenchymal stem cell combinations

Low back pain arising from disc degeneration is one of the most common causes of limited function in adults. A number of tissue engineering strategies have been used to develop composite tissue engineered total disc replacements to restore native tissue structure and function. In this study we fabricated a composite engineered disc based on the combination of a porous polycaprolactone (PCL) foam annulus fibrosus (AF) and a hyaluronic acid (HA) hydrogel nucleus pulposus (NP). To evaluate whether native tissue cells or mesenchymal stem cells (MSCs) would perform better, constructs were seeded with native AF/NP cells or with MSCs in the foam and/or gel region. Maturation of these composite engineered discs was evaluated for 9 weeks in vitro culture by biochemical content, histological analysis and mechanical properties. To evaluate the performance of these constructs in the in vivo space, engineered discs were implanted into the caudal spines of athymic rats for 5 weeks. Our findings show that engineered discs comprised of AF/NP cells and MSCs performed similarly and maintained their structure after 5 weeks in vivo. However, for both cell types, loss of proteoglycan was evident in the NP region. These data support the continued development of the more clinically relevant MSCs population for disc replacement applications. Statement of SignificanceA number of tissue engineering strategies have emerged that are focused on the creation of a composite disc replacement. We fabricated a composite engineered disc based on the combination of a porous foam AF and a HA gel NP. We used these constructs to determine whether the combination of AF/NP cells or MSCs would mature to a greater extent in vitro and which cell type would best retain their phenotype after implantation. Engineered discs comprised of AF/NP cells and MSCs performed similarly, maintaining their structure after 5 weeks in vivo. These data support the successful fabrication and in vivo function of an engineered disc composed of a PCL foam AF and a hydrogel NP using either disc cells or MSCs.

Hyaluronic acid induction on breast cancer stem cells unfolds subtype specific variations in stemness and epithelial-to-mesenchymal transition

The reoccurrence of breast cancer is a major concern due to presence of cancer stem cells (CSCs). Considering the key role of hyaluronic acid (HA) in modulating the inflammation and cellular migration in cancer, the response of high molecular weight (HMW) and low molecular weight (LMW) HA towards various subtypes of breast cancer and breast cancer stem cells remain elusive. The aim of this study is to determine the effect of exogenous HMW-HA and LMW-HA on stemness of CSCs and epithelial-to-mesenchymal transition which may help in designing HA based therapeutic strategies. LMW-HA induces EMT in MCF-7 more prominently as compared to MDA-MB-231. However, HMW-HA did not show significant changes in the expression of EMT genes. Surprisingly, both HMW-HA and LMW-HA have shown to decrease the expression of EpCAM in MCF-7 cells and decrease the expression of CD44 in MDAMB-231 cells. HA has maintained the native stem cells phenotype of bCSCs isolated from MCF-7 only. The bCSCs isolated form MDAMB-231 showed a decrease in CD44. Luminal subtype has shown to follow Wnt/β-catenin whereas in the basal subtype localization of CD44 from surface to cytosol was observed in response to HA. Our study has demonstrated that bCSCs in luminal and basal cells follow differential intracellular signaling mechanisms in response to HA. This study could significantly influence the therapeutics involving HA in breast cancer.

Live-animal imaging of native haematopoietic stem and progenitor cells.

The biology of hematopoietic stem cells (HSCs) has predominantly been studied under transplantation conditions1,2. Particularly challenging has been the study of dynamic HSC behaviors given that live animal HSC visualization in the native niche still represents an elusive goal in the field. Here, we describe a dual genetic strategy in mice that restricts reporter labeling to a subset of the most quiescent long-term HSCs (LT-HSCs) and that is compatible with current intravital imaging approaches in the calvarial bone marrow (BM)3–5. We find that this subset of LT-HSCs resides in close proximity to both sinusoidal blood vessels and the endosteal surface. In contrast, multipotent progenitor cells (MPPs) display a broader distance distribution from the endosteum and are more likely to be associated with transition zone vessels. LT-HSCs are not found in BM niches with the deepest hypoxia and instead are found in similar hypoxic environments as MPPs. In vivo time-lapse imaging reveals that LT-HSCs display limited motility at steady-state. Following activation, LT-HSCs display heterogenous responses, with some cells becoming highly motile and a fraction of HSCs expanding clonally within spatially restricted domains. These domains have defined characteristics, as HSC expansion is found almost exclusively in a subset of BM cavities exhibiting bone-remodeling activities. In contrast, cavities with low bone-resorbing activities do not harbor expanding HSCs. These findings point to a new degree of heterogeneity within the BM microenvironment, imposed by the stages of bone turnover. Overall, our approach enables direct visualization of HSC behaviors and dissection of heterogeneity in HSC niches.

HEMATOPOIETIC STEM CELL TRANSPLANTATION IN PATIENTS WITH PRIMARY IMMUNODEFICIENCY DERIVED FROM AN ALTERNATIVE DONOR BY USING NEW TRANSPLANT ENGINEERING TECHNOLOGIES

Analysis of the results of hematopoietic stem cell transplantation (HSCT) derived from alternative donors in patients with primary immunodeficiency syndromes. 110 HSCTs for patients with PIDs derived from alternative donors (unrelated, n = 85, haploidentical, t = 25) were performed at the Dmitry Rogachev National Medical Research Centre within 2012-2017 timeframe. In all cases, there were used conditioning regimes with reduced toxicity based on threosulfan TCRotP+/CD19+ depletion with immunomagnetic method were used as the basic cell transplant preparation. The cumulative probability of acute GVHD was 17% (95% CI 10-25) (n = 18); however, it should be noted that in 16 of 18 cases, an acute GVHD, stage II, was observed, showing a good response to the first line therapy; but acute GVHD, stage III, was documented only in 2 patients. Reactivation of cytomegalovirus infection remained one of the serious issues, with a cumulative probability of its reactivation reaching up to 50% and CMV visceral infection rate found in 15.4% cases. The conditioning regimen in patients with Wiskott-Aldrich syndrome by using granulocyte colony-stimulating factor and plerixafor demonstrated a full control over transplant dysfunction compared to control group.Rate of immunological reconstitution upon inoculation of HSCT on the platform TCRotP+/CD19+ deletion did not differ in dynamics from that one after using undepleted HSCT together with native hematopoietic stem cell sources in a historical cohort. The overall survival probability for entire PID patient cohort was 84% (95% CI 77-92). No differences in patients transplanted from unrelated and haploidentical donors were revealed by assessing any of the studied parameters.Introduction of new HSCT technologies allows us to dramatically minimize adverse outcomes of PIDs and opens new avenues for further research in cellular regulation of autoinflammatory oncological and infectious disorders resulting in lethal outcome in PID patients.

A Brief Review on 3D Bioprinted Skin Substitutes

The global escalating cases of skin donor shortage for patients with severe wounds warn the vital need for alternatives to skin allografts. Over the last three decades, research in the skin regeneration area has addressed the unmet need for artificial skin substitutes. 3D bioprinting is a promising innovative technology to accurately fabricate skin constructs based on natural or synthetic bioinks, whether loaded or not loaded with native skin cells (i.e., keratinocytes and fibroblasts) or stem cells in the prescribed 3D hierarchal structure to create artificial multilayer and single cell-laden construct. In this paper, the recent developments in 3D bioprinting for skin regeneration are reviewed to discuss different aspects of skin bioprinted substitutes, including 3D printing technology, bioink composition, and cell-laden constructs. The impact of 3D printing parameters on functionality of the skin substitute and cell viability is reviewed to provide insight into controlled fabrication as the critical component of advanced wound healing. We highlight the recent and ongoing research in skin bioprinting to address the progress in the translation of advanced wound healing from lab to clinic.

STEM-17. LOW GRADE ASTROCYTOMA MUTATIONS COOPERATE TO DISRUPT SOX2 GENOMIC ARCHITECTURE AND BLOCK DIFFERENTIATION VIA PREVIOUSLY UNIDENTIFIED ENHANCER ELEMENTS

Abstract Neomorphic mutations in isocitrate dehydrogenase I (IDH1) result in the formation of the oncometabolite 2-hydroxyglutarate (2HG) in a significant subset of gliomas and other tumors including acute myeloid leukemias. Preclinical evidence suggests that gliomas harboring IDH1 mutations undergo widespread, long-lasting modifications to the epigenome that persist following inhibition of 2HG production. However, the exact mechanism underlying gliomagenesis remains unclear. To address difficulties in growing these tumors in culture, our group generated a model of low-grade astrocytoma in human neural stem cells (NSCs). This model, referred to as 3-Hit NSCs, suggested a block in differentiation potential underlies gliomagenesis at the cellular level. This block is rescued by restoration of expression of the transcription factor (sex determining region Y)-box 2 (SOX2), which is transcriptionally downregulated during IDH mutant gliomagenesis. We believe that these changes occur secondary to profound alterations in 3-dimensional chromatin organization around the SOX2 genomic locus. Our preliminary data suggest SOX2 expression in control NSCs depends on 3-dimensional association of its promoter to an uncharacterized, distal enhancer located 600 kb telomeric to the SOX2 gene. We believe this association is disrupted in 3-Hit NSCs due to eviction of chromatin organizer CTCF from its motifs in the SOX2 topologically associating domain (TAD). To test this hypothesis, we used CRISPR-Cas9 technology to excise CTCF motifs immediately upstream of the SOX2 promoter and in the region of the putative enhancer in control NSCs. Excision of such motifs significantly reduced SOX2 mRNA levels and impaired growth of control NSCs. We are currently working on characterizing this novel SOX2-enhancer interaction in native stem cells, as well as tumors that depend on SOX2 expression. This works aims to elucidate the core epigenetic mechanisms underlying IDH mutant gliomagenesis. Our findings will be used to improve therapy in IDH-mutant glioma.

IL-17 alters the mesenchymal stem cell niche towards osteogenesis in cooperation with osteocytes.

Bone remodeling is a strictly regulated dynamic process that cycles between bone formation and resorption, and interleukin‐17 (IL‐17) critically orchestrates the activation and differentiation of both osteoblasts and osteoclasts. Mesenchymal stem cells (MSCs) within their native environment receive biochemical stimuli from surrounding cells that influences their differentiation into bone precursors, while the roles of osteocytes in regulating the osteogenic differentiation of MSCs remain unclear. This study investigated the specific roles of IL‐17 signaling cascades and osteocyte‐specific pathways in the osteogenesis of MSCs. Using a transwell coculture (CC) system, we explored the effects of osteocytes and osteoblasts on the osteogenesis of MSCs with and without IL‐17 supplementation. A polycaprolactone (PCL) three‐dimensional (3D) culture model was used to evaluate their osteogenic potential in the presence of osteocytes and IL‐17. Notably, IL‐17 induced osteogenesis in MSCs, which could be attenuated by blocking IL‐17 receptor A. The osteogenic differentiation of MSCs promoted by IL‐17 was further enhanced by CC with osteocytes. Moreover, proinflammatory cytokines IL‐6 and IL‐1β played an important role in IL‐17‐dependent differentiation, via the phosphorylation of AKT, signal transducer and activator of transcription 3, and extracellular signal‐regulated kinase 1/2 signaling pathways in the MSC niche. The present study confirms a synergistic effect of osteocytes and IL‐17 in the production of biochemical signals to stimulate the osteogenic differentiation of MSCs, which could be further promoted in the PCL 3D‐scaffold. These findings provide important insight into the mechanisms of MSCs activation and osteogenic differentiation within the native stem cell niche, and suggest a possible role of IL‐17 in bone tissue engineering.

In Situ Osteochondral Regeneration by Controlled Release of Stromal Cell-Derived Factor-1 Chemokine from Injectable Biomaterials: A Preclinical Evaluation in Animal Model

Osteochondral defect (OD) refers to damage in the area of articular cartilage extended to the subchondral bone, affecting millions of people worldwide. In situ osteochondral tissue engineering approach, which aims to activate the body's native stem cells and recruit them to the defective site by utilizing biomaterials, has become a potential strategy for repairing focal chondral lesions. However, due to the lack of cell-instructive potential, most of the biomaterials fail to recruit stem cells from the host environment and trigger the cellular and molecular functions necessary for tissue regeneration. In this study, the authors report a new formulation of injectable biomaterial system, based on stromal cell-derived factor-1 (SDF-1)-encapsulated poly(lactic-co-glycolic acid) (PLGA) microspheres loaded chitosan-gelatin (CS-GEL) composite hydrogel system (SDF-1/CS-GEL@PLGA), with the aim of imparting in situ cell-instructive and osteochondral tissue regenerative potential. The osteochondral regenerative potential of SDF-1/CS-GEL@PLGA was studied in rabbit as a model animal and the results were compared with the CS-GEL@PLGA without the SDF-1. The results of this study showed that the CS-GEL@PLGA hydrogel had better gelation time and longer release cycle (>30 days) than the CS-GEL. In addition, SDF-1/CS-GEL@PLGA hydrogels promoted the repair of osteochondral defects in rabbits within 12 weeks as compared to the CS-GEL@PLGA hydrogels. Therefore, based on the experimental data, SDF-1/CS-GEL@PLGA hydrogel is a promising injectable biomaterial system for osteochondral repair and regeneration.

Impact of Induced Pluripotent Stem Cells in Bone Repair and Regeneration.

The main objective of this article is to investigate the current trends in the use of induced pluripotent stem cells (iPSCs) for bone tissue repair and regeneration. Pluripotent stem cell-based tissue engineering has extended innovative therapeutic approaches for regenerative medicine. iPSCs have shown osteogenic differentiation capabilities and would be an innovative resource of stem cells for bone tissue regenerative applications. This review recapitulates the current knowledge and recent progress regarding utilization of iPSCs for bone therapy. A review of current findings suggests that a combination of a three-dimensional scaffolding system with iPSC technology to mimic the physiological complexity of the native stem cell niche is highly favorable for bone tissue repair and regeneration.

In Situ Modification of Tissue Stem and Progenitor Cell Genomes

SUMMARYIn vivo delivery of genome-modifying enzymes holds significant promise for therapeutic applications and functional genetic screening. Delivery to endogenous tissue stem cells, which provide an enduring source of cell replacement during homeostasis and regeneration, is of particular interest. Here, we use a sensitive Cre/lox fluorescent reporter system to test the efficiency of genome modification following in vivo transduction by adeno-associated viruses (AAVs) in tissue stem and progenitor cells. We combine immunophenotypic analyses with in vitro and in vivo assays of stem cell function to reveal effective targeting of skeletal muscle satellite cells, mesenchymal progenitors, hematopoietic stem cells, and dermal cell subsets using multiple AAV serotypes. Genome modification rates achieved through this system reached >60%, and modified cells retained key functional properties. This study establishes a powerful platform to genetically alter tissue progenitors within their physiological niche while preserving their native stem cell properties and regulatory interactions.

Effect of glucose on the expression of CD24 marker in Umbilical-cord derived Mesenchymal Stem Cells

Diabetes Mellitus (DM) is a chronic metabolic disease with high morbidity and significant mortality. The prevalence of DM is quite alarming with around 347 million people affected worldwide, the largest contributors to the disease load being India (65.1 million people affected in 2013) and China. Though the prevalence in India of 9.1% is only marginally higher than the worldwide prevalence of 8.3% the massive population contributes to the disease load. Though many drugs are available, insulin is the better choice to reduce blood sugar levels. Insulin administered through syringes and pumps is discharged at doses adjusted according to blood sugar levels estimated either once daily or once in two weeks. However, there occur periods of variation in glucose level at the cellular level which is responsible for long term complications. The only definitive treatment option is a source of islet cells that discharges human insulin according to the changing milieu in the body to maintain sugar levels. The difficulties encountered with islet allograft transplants are the availability of cadaver donor, need for immune suppressants, graft cell loss, and autoimmunity. Hence it is the need of the hour to manufacture islet cells in vitro to have a constant source of supply replacing the currently available therapeutic measures. The development of in vitro islets requires a viable source of stem cells. The perinatal tissues which include umbilical cord and placenta are wasted every day in tons. They are rich sources of MSCs which are immunologically naive and obtaining consent is relatively easy, as these tissues are only discarded otherwise. At the initial stage of the process, the MSCs have to be isolated. Though there are different protocols defined by researchers to isolate MSCs from the umbilical cord, no standardized protocol is available yet. Currently, islets cultured from human stem cells are quite fragile and have a limited shelf life of only 72 hours. Also, the characterization, culture, and storage protocols have to be standardized. By studying pancreatic progenitor cells and development pathways we may find methods to improve our culture and storage techniques. Novel markers identify pancreatic precursor cells. Based on the observations made in the present study and review of literature about other studies done so far, it seems that MSCs express CD24. These cells may develop into a clone of pancreatic progenitors, neural stem cells, or cancer stem cells. This development depends on the environmental conditions and differentiating factors available. It is known that elevated glucose concentrations impair cellular functions and induce apoptosis and is supposed to be the cause of further degeneration of pancreatic beta cells and all the long term complications in DM. It is hypothesized that high blood glucose levels also affect the body’s native stem cells through mechanisms still under study. Controversial reports on the toxic effects of glucose on MSCs both in vivo and in vitro are available. It had been reported by Stolzing, et al. that high glucose is toxic to MSCs derived from rats while cell proliferation increased and the rate of apoptosis decreased when glucose concentration was reduced. Li, et al. cultured bone marrow-derived human MSCs in media containing 5, 6, 11, 25, and 40 mmol concentration of glucose and measured the rate of proliferation and apoptosis. The inhibitory effect on cell apoptosis was noticed on short term exposure to high glucose medium but there was no effect on cell proliferation and apoptosis in long term cultures. Also Dhanasekaran, et al. reported retention of MSC surface marker characteristics, proliferation, and differentiation potential in bone marrow and adipose-derived MSCs cultured at 25 mmol glucose concentration.

Intracavernous Stem Cell Transplantation in Erectile Dysfunction: Modification of Adhesive Properties of Stem Cells Increases Their Ability to Restore Contractile and Phosphatase Activity of Cavernous Tissue Damaged by Hyperglycemia

A comparative study of the effect on the contractile and phosphate activity of the cavernous tissue of four intracavernous injections (ICI) (1×106 cells once a week) of native stem cells (SC) and cells, with SYT1/SYT2 molecules, integrated into the cell membrane (SC-m-SYT1/SYT2), was performed in two groups (n=10; 1:1) of sexually mature Wistar rats weighing 160-180 gwith induced hyperglycemia (>8 mmol/l). It was found that, at the end of the ICI in the group of animals receiving SC-m-SYT1/SYT2, the median amplitude of contractions was 1.6 times greater (P<0.05, Wilcoxon’s test), and the intensity mediants for ATPase and LF, respectively, 2 and 1 points greater than in the group where native SCs were introduced (P<0.05, Wilcoxon’s test). ICI of native and modified SC did not affect the level of glycemia. Modification of the adhesive properties of SC by SYT1/SYT2 molecules increases their ability to restore contractile and phosphatase activity of cavernous tissue damaged by hyperglycemia. Further research is needed on the processes of homing and differentiation of SC, modified with SYT1/SYT2 molecules, in intact and pathologically altered cavernous tissue in vitro and in vivo.

Bone morphogenetic protein-12 inducing tenogenic differentiation of mesenchymal stem cells enhances healing of linea alba incision.

The objective of this study was to investigate the curative effects of mesenchymal stem cells' tenogenic differentiation on linea alba incision healing induced by bone morphogenetic protein-12. Mesenchymal stem cells were isolated and induced by 10 ng/ml of bone morphogenetic protein-12 for 48 h. Expression of scleraxis, collagen I and collagen III were examined at 48 h, 5 and 7 days to investigate the tenogenic differentiation. The expression of scleraxis increases continually even in the absence of bone morphogenetic protein-12 for 5 days (P<0.01). The expression of collagen I and III requires persistent inducing. Then fifty Sprague-Dawley rats were randomly divided into five groups: negative control, positive control, sham group, native mesenchymal stem cells and tenogenically differentiated mesenchymal stem cells. Tensiometric testing and modified semiquantitative histological analysis were performed to explore the curative effects. The tension levels in the positive control, sham, native mesenchymal stem cells and tenogenically differentiated mesenchymal stem cells were 44, 41.8, 51.6 and 69.7%, respectively, compared with the negative control. Tenogenically differentiated mesenchymal stem cells exhibited a greater increase in tension compared with positive control, sham and native mesenchymal stem cell groups (P<0.05). From the sections stained with Masson's Trichrome, collagen organization and amount of tenogenically differentiated mesenchymal stem cells was better than the other three groups (P<0.05). In conclusion, mesenchymal stem cells' tenogenic differentiation induced by bone morphogenetic protein-12 can enhance linea alba incision healing.

Hydrogel from Acellular Porcine Adipose Tissue Accelerates Wound Healing by Inducing Intradermal Adipocyte Regeneration

As an important component of the skin, intradermal adipocytes are closely associated with skin homeostasis and wound healing. Although studies have focused on the role of fibroblasts, keratinocytes, and inflammatory cells in wound healing, the role of adipocytes has not been fully investigated. Here, we verified whether the induction of adipocyte regeneration in a wound bed can effectively promote wound healing, finding that the hydrogel from acellular porcine adipose tissue in combination with adipose-derived stem cells can induce in situ adipogenesis in the wound microenvironment. The newly regenerated adipocytes enhanced fibroblast migration, accelerated wound closing, and enhanced wound epithelialization. More importantly, newly formed intact skin structure was observed after treating the wound with adipose-derived stem cell-loaded hydrogel from acellular porcine adipose tissue. These results show that hydrogel from acellular porcine adipose tissue might substantially improve re-epithelialization, angiogenesis, and skin-appendage regeneration, making it a promising therapeutic biomaterial for skin wound healing.

Ultra-High Signal Detection of Human Embryonic Stem Cells Driven by Two-Dimensional Materials.

We observed a unique bioelectric signal of human embryonic stem cells using direct current-voltage measurements facilitated by few-layered 2D-MoS2 sheets. A 1.828 mA cell signal was achieved (2 orders of magnitude higher than previous electrical-based detection methods) as well as multiple cell reading cycles demonstrating I ∼ 1.9 mA. Native stem cell proliferation, viability, and pluripotency were preserved. Molecular dynamics simulations elucidated the origin of the 2D-MoS2 sheet-assisted increase in current flow. This paves the way for the development of a broadly applicable, fast, and damage-free stem cell detection method capable of identifying pluripotency with virtually any complementary-metal-oxide-semiconductor circuits.

Neighboring cells override 3D hydrogel matrix cues to drive human MSC quiescence

Physical properties of modifiable hydrogels can be tuned to direct stem cell differentiation in a role akin to that played by the extracellular matrix in native stem cell niches. However, stem cells do not respond to matrix cues in isolation, but rather integrate soluble and non-soluble signals to balance quiescence, self-renewal and differentiation. Here, we encapsulated single cell suspensions of human mesenchymal stem cells (hMSC) in hyaluronic acid-based hydrogels at high and low densities to unravel the contributions of matrix- and non-matrix-mediated cues in directing stem cell response. We show that in high-density (HD) cultures, hMSC do not rely on hydrogel cues to guide their fate. Instead, they take on characteristics of quiescent cells and secrete a glycoprotein-rich pericellular matrix (PCM) in response to signaling from neighboring cells. Preventing quiescence precluded the formation of a glycoprotein-rich PCM and forced HD cultures to differentiate in response to hydrogel composition. Our observations may have important implications for tissue engineering as neighboring cells may act counter to matrix cues provided by scaffolds. Moreover, as stem cells are most regenerative if activated from a quiescent state, our results suggest that ex vivo native-like niches that incorporate signaling from neighboring cells may enable the production of clinically relevant, highly regenerative cells.

Origins of Metaplasia in Barrett’s Esophagus: Is this an Esophageal Stem or Progenitor Cell Disease?

The incidence of esophageal adenocarcinoma has been increasing in Western countries over the past several decades. Though Barrett'sesophagus, in which the normal esophageal squamous epithelium is replaced withmetaplastic intestinalized columnar cells due to chronic damage from gastroesophageal reflux, is accepted as the requisite precursor lesion foresophageal adenocarcinoma, the Barrett's esophagus cell of origin and the molecular mechanism underlying esophageal epithelial metaplasia remain controversial. Much effort has been dedicated towards identifying the Barrett's esophagus cell of origin since this could lead to more effective prevention and treatment strategies for both Barrett's esophagus and esophageal adenocarcinoma. Previously, it was hypothesized that terminally differentiated esophageal squamous cells might undergo direct conversion into specialized intestinal columnar cells via the process of transdifferentiation. However, there is increasing evidence that stem and/or progenitor cells are molecularly reprogrammed through the process of transcommitment to differentiate into the columnar cell lineages that characterize Barrett's esophagus. Given that Barrett's esophagus originates at the gastroesophageal junction, the boundary between the distal esophagus and gastric cardia, potential sources of these stem and/or progenitor cells include columnar cells from the squamocolumnar junction or neighboring gastric cardia, native esophageal squamous cells, native esophageal cuboidal or columnar cells from submucosal glands or ducts, or circulating bone marrow-derived cells. In this review, we focus on native esophageal specific stem and/or progenitor cells and detail molecular mediators of transcommitment based on recent insights gained from novel mouse models and clinical observations from patients.

Directly injected native bone-marrow stem cells cannot incorporate into acetaminophen-induced liver injury

The paucity of liver donation highlights the use of cell-based strategies for end-stage liver failure. We recently showed that bone marrow-derived aggregates (BMDAs) can completely restore the hematopoietic system in gamma-irradiated mice. These aggregates are stem and progenitor cells in the bone marrow (BM), composed of both hematopoietic and non-hematopoietic lineages. Furthermore, reports showed that resident BM cells migrate to the liver and integrate themselves into the tissue in small numbers. Hence, we hypothesized that direct delivery of BMDAs to the damaged liver might enhance the integration of BM cells in the liver because of its stemness property, intact BM architecture, the physical proximity of these niche-like structures to the damaged sites and the existence of liver paracrine factors. To this aim, we made an acute liver model by intraperitoneal injection of acetaminophen. Then, GFP-expressing BMDAs were intrahepatically injected. Despite the detection of GFP-expressing cells five days after intrahepatic injection, these cells were not detectable at days 15 and 60, indicating that the puzzle of BM cell integration in the liver still has more missing pieces other than stemness, physical proximity, and paracrine factors. Actually, it seems that even intact BM structures need further signals to be qualified for integration.

Tenogenic differentiation of mesenchymal stem cells improves healing of linea alba incision

OBJECTIVE: The aim of this study is to investigate the curative effects of mesenchymal stem cells' (MSCs') tenogenic differentiation on Linea alba incision healing. MATERIALS AND METHODS: Autologous MSCs were isolated from rat bone marrow and cultured and induced by 10 ng/mL of bone morphogenetic protein-12 (BMP-12) for 48 h. Expression of scleraxis (SCX), collagen I, and collagen III was examined at 48 h, 5 days, and 7 days to investigate the tenogenic differentiation. Fifty Sprague-Dawley rats were randomly divided into five groups: tenogenically differentiated (group E) or native mesenchymal stem cells (group D) seeded onto collagen sponge scaffolds or only sponge scaffolds (group C) were transplanted into the linea alba incision; rats that underwent operation without implantation of anything served as the sham group (group B), and rats that did not undergo operation were used as the control group (group A). Histological analysis was performed to explore the curative effects. RESULTS: The expression of SCX increases continually even in the absence of BMP-12 for 5 days (P CONCLUSIONS: In animal experiments, MSCs' tenogenic differentiation induced by BMP-12 can dramatically enhance linea alba incision healing.