The transcription factor OCT6 promotes the dissolution of the naïve pluripotent state by repressing Nanog and activating a formative state gene regulatory network.

In the mouse embryo, the transition from the preimplantation to the postimplantation epiblast is governed by changes in the gene regulatory network (GRN) that lead to transcriptional, epigenetic, and functional changes. This transition can be faithfully recapitulated in vitro by the differentiation of mouse embryonic stem cells (mESCs) to epiblast-like cells (EpiLCs), that reside in naïve and formative states of pluripotency, respectively. However, the GRN that drives this conversion is not fully elucidated. Here we demonstrate that the transcription factor OCT6 is a key driver of this process. Firstly, we show that Oct6 is not expressed in mESCs but is rapidly induced as cells exit the naïve pluripotent state. By deleting Oct6 in mESCs, we find that knockout cells fail to acquire the typical morphological changes associated with the formative state when induced to differentiate. Additionally, the key naïve pluripotency TFs Nanog, Klf2, Nr5a2, Prdm14, and Esrrb were expressed at higher levels than in wild-type cells, indicating an incomplete dismantling of the naïve pluripotency GRN. Conversely, premature expression of Oct6 in naïve cells triggered a rapid morphological transformation mirroring differentiation, that was accompanied by the upregulation of the endogenous Oct6 as well as the formative genes Sox3, Zic2/3, Foxp1, Dnmt3A and FGF5. Strikingly, we found that OCT6 represses Nanog in a bistable manner and that this regulation is at the transcriptional level. Moreover, our findings also reveal that Oct6 is repressed by NANOG. Collectively, our results establish OCT6 as a key TF in the dissolution of the naïve pluripotent state and support a model where Oct6 and Nanog form a double negative feedback loop which could act as an important toggle mediating the transition to the formative state.

Peritumoral adipose tissue promotes lipolysis and white adipocytes browning by paracrine action.

Background: Stromal adipocytes and tumor breast epithelial cells undergo a mutual metabolic adaptation within tumor microenvironment. Therefore, browning and lipolysis occur in cancer associated adipocytes (CAA). However, the paracrine effects of CAA on lipid metabolism and microenvironment remodeling remain poorly understood. Methods: To analyze these changes, we evaluated the effects of factors in conditioned media (CM) derived from explants of human breast adipose tissue from tumor (hATT) or normal (hATN) on morphology, degree of browning, the levels of adiposity, maturity, and lipolytic-related markers in 3T3-L1 white adipocytes by Western blot, indirect immunofluorescence and lipolytic assay. We analyzed subcellular localization of UCP1, perilipin 1 (Plin1), HSL and ATGL in adipocytes incubated with different CM by indirect immunofluorescence. Additionally, we evaluated changes in adipocyte intracellular signal pathways. Results: We found that adipocytes incubated with hATT-CM displayed characteristics that morphologically resembled beige/brown adipocytes with smaller cell size and higher number of small and micro lipid droplets (LDs), with less triglyceride content. Both, hATT-CM and hATN-CM, increased Pref-1, C/EBPß LIP/LAP ratio, PPARγ, and caveolin 1 expression in white adipocytes. UCP1, PGC1α and TOMM20 increased only in adipocytes that were treated with hATT-CM. Also, hATT-CM increased the levels of Plin1 and HSL, while decreased ATGL. hATT-CM modified the subcellular localization of the lipolytic markers, favoring their relative content around micro-LDs and induced Plin1 segregation. Furthermore, the levels of p-HSL, p-ERK and p-AKT increased in white adipocytes after incubation with hATT-CM. Conclusions: In summary, these findings allow us to conclude that adipocytes attached to the tumor could induce white adipocyte browning and increase lipolysis as a means for endocrine/paracrine signaling. Thus, adipocytes from the tumor microenvironment exhibit an activated phenotype that could have been induced not only by secreted soluble factors from tumor cells but also by paracrine action from other adipocytes present in this microenvironment, suggesting a "domino effect".

EFFECTS OF BACTERIAL LIPOPOLYSACCHARIDE AND SHIGA TOXIN ON INDUCED PLURIPOTENT STEM CELL-DERIVED MESENCHYMAL STEM CELLS.

ABSTRACT: Background : Mesenchymal stem cells (MSCs) can be activated by different bacterial toxins. Lipopolysaccharides and Shiga Toxin (Stx) are the main toxins necessary for hemolytic uremic syndrome development. The main etiological event in this disease is endothelial damage that causes glomerular destruction. Considering the repairing properties of MSC, we aimed to study the response of MSC derived from induced pluripotent stem cells (iPSC-MSC) to LPS and/or Stx and its effect on the restoration of injured endothelial cells. Methods : iPSC-MSC were treated with LPS and or/Stx for 24 h and secretion of cytokines, adhesion, and migration were measured in response to these toxins. In addition, conditioned media from treated iPSC-MSC were collected and used for proteomics analysis and evaluation of endothelial cell healing and tubulogenesis using human microvascular endothelial cells 1 as a source of endothelial cells. Results : The results obtained showed that LPS induced a proinflammatory profile on iPSC-MSC, whereas Stx effects were less evident, even though cells expressed the Gb 3 receptor. Moreover, LPS induced on iPSC-MSC an increment in migration and adhesion to a gelatin substrate. Addition of conditioned media of iPSC-MSC treated with LPS + Stx, decreased the capacity of human microvascular endothelial cells 1 to close a wound, and did not favor tubulogenesis. Proteomic analysis of iPSC-MSC treated with LPS and/or Stx revealed specific protein secretion patterns that support the functional results described. Conclusions : iPSC-MSC activated by LPS acquired a proinflammatory profile that induces migration and adhesion to extracellular matrix proteins but the addition of Stx did not activate any repair program to ameliorate endothelial damage, indicating that the use of iPSC-MSC to regenerate endothelial injury caused by LPS and/or Stx in hemolytic uremic syndrome could not be the best option to consider to regenerate a tissue injury.

Single cell transfection of human-induced pluripotent stem cells using a droplet-based microfluidic system.

Microfluidic tools have recently made possible many advances in biological and biomedical research. Research in fields such as physics, engineering, chemistry and biology have combined to produce innovation in microfluidics which has positively impacted diverse areas such as nucleotide sequencing, functional genomics, single-cell studies, single molecules assays and biomedical diagnostics. Among these areas, regenerative medicine and stem cells have benefited from microfluidics since these tools have had a profound impact on their applications. In this study, we present a high-performance droplet-based system for transfecting individual human-induced pluripotent stem cells. We will demonstrate that this system has great efficiency in single cells and captured droplets, like other microfluidic methods but with lower cost. Moreover, this microfluidic approach can be associated with the PiggyBac transposase-based system to increase its transfection efficiency. Our results provide a starting point for subsequent applications in more complex transfection systems, single-cell differentiation interactions, cell subpopulations and cell therapy, among other potential applications.

Extracellular vesicles from pluripotent stem cell-derived mesenchymal stem cells acquire a stromal modulatory proteomic pattern during differentiation.

Mesenchymal stem/stromal cells (MSCs) obtained from pluripotent stem cells (PSCs) constitute an interesting alternative to classical MSCs in regenerative medicine. Among their many mechanisms of action, MSC extracellular vesicles (EVs) are a potential suitable substitute for MSCs in future cell-free-based therapeutic approaches. Unlike cells, EVs do not elicit acute immune rejection, and they can be produced in large quantities and stored until ready to use. Although the therapeutic potential of MSC EVs has already been proven, a thorough characterization of MSC EVs is lacking. In this work, we used a label-free liquid chromatography tandem mass spectrometry proteomic approach to identify the most abundant proteins in EVs that are secreted from MSCs derived from PSCs (PD-MSCs) and from their parental induced PSCs (iPSCs). Next, we compared both datasets and found that while iPSC EVs enclose proteins that modulate RNA and microRNA stability and protein sorting, PD-MSC EVs are rich in proteins that organize extracellular matrix, regulate locomotion, and influence cell-substrate adhesion. Moreover, compared to their respective cells, iPSCs and iPSC EVs share a greater proportion of proteins, while the PD-MSC proteome appears to be more specific. Correlation and principal component analysis consistently aggregate iPSCs and iPSC EVs but segregate PD-MSC and their EVs. Altogether, these findings suggest that during differentiation, compared with their parental iPSC EVs, PD-MSC EVs acquire a more specific set of proteins; arguably, this difference might confer their therapeutic properties.

Drosophila dyskerin is required for somatic stem cell homeostasis.

Drosophila represents an excellent model to dissect the roles played by the evolutionary conserved family of eukaryotic dyskerins. These multifunctional proteins are involved in the formation of H/ACA snoRNP and telomerase complexes, both involved in essential cellular tasks. Since fly telomere integrity is guaranteed by a different mechanism, we used this organism to investigate the specific role played by dyskerin in somatic stem cell maintenance. To this aim, we focussed on Drosophila midgut, a hierarchically organized and well characterized model for stemness analysis. Surprisingly, the ubiquitous loss of the protein uniquely affects the formation of the larval stem cell niches, without altering other midgut cell types. The number of adult midgut precursor stem cells is dramatically reduced, and this effect is not caused by premature differentiation and is cell-autonomous. Moreover, a few dispersed precursors found in the depleted midguts can maintain stem identity and the ability to divide asymmetrically, nor show cell-growth defects or undergo apoptosis. Instead, their loss is mainly specifically dependent on defective amplification. These studies establish a strict link between dyskerin and somatic stem cell maintenance in a telomerase-lacking organism, indicating that loss of stemness can be regarded as a conserved, telomerase-independent effect of dyskerin dysfunction.

Robot-assisted treatment of splenic artery aneurysms.

BACKGROUND: Although splenic artery aneurysms (SAAs) are relatively uncommon, they are clinically relevant because of the risk of rupture. Optimal management is a matter of debate and involves the use of percutaneous endovascular stenting, which has limitations, versus the open surgical approach which can lead to significant morbidity. The present study reports the outcomes of robot-assisted surgery for SAA and its role in overcoming many of the limitations of laparoscopy. METHODS: A total of nine patients with incidentally detected SAAs underwent a surgery between September 2001 and November 2007. Six of these nine patients underwent a robot-assisted splenic aneurysm resection with vascular reconstruction. The remaining three cases included one robotic arterial ligation, one robotic partial splenectomy, and one laparoscopic splenectomy. RESULTS: The mean operating time was 212 ± 61 minutes (range: 90-300), mean intraoperative blood loss was 186.6 ± 202.4 mL (range: 0-500), and mean hospital stay was 7.1 ± 3.7 days (range: 3-14). The morbidity rate was 11.1% and no mortality was reported. Doppler-ultrasonography surveillance showed regular organ perfusion in all patients with vascular reconstruction. CONCLUSION: Robot-assisted surgery for SAA represents one of the most advanced developments among minimally invasive procedures and can become an important option for the treatment of this disease.

Robot-assisted laparoscopic repair of renal artery aneurysms.

OBJECTIVE: The aim of this article is to report our experience in the repair of renal artery aneurysms using robot-assisted surgery. METHODS: Between December 2002 and March 2009, five women with a mean age of 63.8 years (range, 57-78 years) underwent robot-assisted laparoscopic repair of renal artery aneurysms by the same surgeon at two different institutions, the Department of General Surgery, Misericordia Hospital, Grosseto, Italy (three patients) and the Division of Minimally Invasive and Robotic Surgery at the University of Illinois, Chicago (two patients). The mean size of the lesions was 19.4 mm (range, 9-28 mm). Four of the lesions were complex aneurysms involving the renal artery bifurcation. Two patients were symptomatic and three had hypertension. In situ repair by aneurysmectomy was performed in all cases, followed by revascularization. In complex aneurysms, an autologous saphenous vein graft was used for the reconstruction. RESULTS: The mean operative time was 288 minutes (range, 170-360 min) and the estimated surgical blood loss was 100 ml (range, 50-300 ml). Warm ischemia time was 10 minutes in the patient treated by aneurysmectomy, followed by direct reconstruction. The average warm ischemia time was 38.5 minutes (range, 20-60 min) for patients treated with saphenous vein graft interposition. The mean time to resume a regular diet was 1.6 days (range, 1-2 days). The mean postoperative length of hospital stay was 5.6 days (range, 3-7 days). No postoperative morbidity was noted. The mean follow-up time for the entire series was 28 months (range, 6-48 months). Color Doppler ultrasonography examination showed patency in all reconstructed vessels. One patient had stenosis of one of the reconstructed branches, which was treated with percutaneous angioplasty. CONCLUSIONS: Robot-assisted laparoscopic repair of renal artery aneurysms is feasible, safe and effective. The technical advantages of the robotic system allows for microvascular reconstruction to be performed using a minimally invasive approach, even in complex cases. This approach may also allow for improved postoperative recovery and reduce the morbidity correlated with open repair of renal artery aneurysms. Although more experience and technical refinements are necessary, robot-assisted laparoscopic repair of renal artery aneurysms represents a valid alternative to open surgery.

Well-differentiated endocrine tumor of the distal common bile duct: a case study and literature review.

Primary carcinoid tumors of the extrahepatic biliary tree are exceedingly rare, accounting for 0.2-2% of all digestive carcinoids. The authors in this study describe a case of biliary duct primary well-differentiated endocrine tumor in a 30-year-old man with symptoms of biliary obstruction and watery diarrhoea. Abdominal ultrasound showed a 2-cm solid lesion in the head of the pancreas, compressing the distal common bile duct. A computed tomography scan confirmed these findings, revealing the hypervascular pattern of the tumor. Gastrointestinal hormonal screening demonstrated an increase in plasma serotonin. The patient underwent standard pylorus-preserving pancreatoduodenectomy. Pathological examination showed a neuroendocrine tumor of the distal common bile duct measuring 1.8 cm in greatest dimension. The tumor cells were immunopositive for neuron-specific enolase (NSE), chromogranin A, synaptophysin, serotonin, and cytokeratin. Stains for gastrin and somatostatin were negative. Seven years later, the patient is well, with no evidence of disease. Given the site of these tumors and the difficulty in differentiating them from periampullary lesions, decisions as to the appropriate surgical approach may be problematic. After an exhaustive review of the literature, the authors conclude that pancreatoduodenectomy is the treatment of choice.

Tropomyosin expression in the ileal pouch: a relationship with the development of pouchitis in ulcerative colitis.

OBJECTIVE: Human tropomyosin isoform 5 (hTM5) is a cytoskeletal protein expressed in normal epithelial cells, predominantly in the colon. An autoimmune response toward hTM5 has been reported in ulcerative colitis (UC). Whether hTM5 expression in the ileum is involved in pouchitis is unknown. We assessed hTM5 expression on ileal epithelial cells at surgery and subsequently on development of pouchitis in UC. METHODS: In a prospective longitudinal study, 28 UC patients undergoing ileal pouch procedures were included. Biopsy samples were taken from the rectum at surgery, as well as from the ileal pouch at surgery and at 6 months. The specimens were stained by immunoperoxidase using the anti-hTM5 monoclonal antibody CG3. Pouchitis was assessed by the Pouchitis Disease Activity Index and hTM5 expression on a scale of 0-3. RESULTS: At surgery, in rectal samples, hTM5 expression was strong in all epithelial cells including the luminal surface, whereas in ileal samples hTM5 was not expressed or focally expressed only in the goblet cells. At 6 months, the ileum was found to have undergone morphological changes, becoming similar to the colon and showing shortening or reduced number of villi. These changes were associated with a diffuse hTM5 staining in the goblet cells and in the nongoblet epithelial cells lining the crypts and the lumen. The hTM5 score was related to the Pouchitis Disease Activity Index at 6 months (r = 0.82; p = 0.01). CONCLUSIONS: Expression of hTM5 shows a different pattern in the ileal pouch in UC after surgery. This event is associated with morphological changes of the ileum toward colonic epithelium, related to the development of pouchitis.