Project description:Human pluripotent stem cells (hPSCs) are a promising source of cells for applications in regenerative medicine. Directed differentiation of hPSCs into specialized cells such as spinal motoneurons or midbrain dopamine (DA) neurons has been achieved. However the effective use of hPSCs for cell therapy has lagged far behind. While mouse PSC-derived DA neurons have shown efficacy in models of Parkinson’s disease, DA neurons derived from human PSCs generally display poor in vivo performance. There are also considerable safety concerns for hPSCs related to their potential for teratoma formation or neural overgrowth. Here we present a novel floor plate-based strategy for the derivation of human DA neurons that efficiently engraft, suggesting that past failures were due to incomplete specification rather than a specific vulnerability of the cells. Midbrain floor plate precursors are derived from hPSCs in days following exposure to small molecule activators of sonic hedgehog (SHH) and canonical WNT signaling. Engraftable midbrain DA neurons are obtained by day 25 and can be maintained in vitro for several months. Extensive in vitro molecular profiling, biochemical and electrophysiological data define developmental progression and confirm identity of hPSC-derived midbrain DA neurons. In vivo survival and function is demonstrated in PD animal models in three host species. Long-term engraftment in 6-OHDA-lesioned mouse and rats demonstrates robust survival of midbrain DA neurons, complete restoration of amphetamine-induced rotation behavior and improvements in tests of forelimb use and akinesia. Finally, scalability is demonstrated by transplantation into Parkinsonian monkeys. Excellent DA neuron survival, function and lack of neural overgrowth in the three animal models tested indicate considerable promise for the development of cell based therapies in PD. Differentiated hESC with three conditions (LSB, LSB/S/F8, LSB/S/F8/CHIR) were subjected to RNA extraction in specific timepoint (day 0, 1, 3, 5, 7, 11, 13, 25) and hybridization on Illumina microarrays. Each sample has 3 or 4 biological repeats. Based on previous study* of dual SMAD inhibition neural induction, we developed new midbrain dopamine neuron protocol. It depends on time specific treatment of below factors (LSB/S/F8/CHIR): L (LDN193189 (BMP inhibitor) , day 0-11), SB (SB431542 (TGF-b signal inhibitor), day 0-5), S (SHH + Purmorphamine (Smo agonist), day 1-7), F8 (FGF8, day 1-7) and CHIR (CHIR99021 (GSK3b inhibitor), day 3-13) LSB and LSB/S/F8 are limited control conditions of dual SMAD only (LSB) or traditional patterning with Sonic and FGF (LSB/S/F8) *Chambers,S.M. et al. Highly efficient neural conversion of human ES and iPS cells by dual inhibition of SMAD signaling. Nat. Biotechnol. 27, 275-280 (2009).

Project description:Biofilms have been implicated in delayed wound healing, although the mechanisms by which biofilms impair wound healing are poorly understood. Many species of bacteria produce exotoxins and exoenzymes that may inhibit healing. In addition, oxygen consumption by biofilms, as well as responding leukocytes, may impede wound healing. In this study, we used oxygen microsensors to measure oxygen transects through in vitro-cultured biofilms, biofilms formed in vivo within scabs from a diabetic (db/db) mouse model, and ex vivo human chronic wound specimens. The results show that oxygen levels within mouse scabs had steep gradients that reached minima ranging from 17-72 mmHg on live mice and 6.4-1.1 mmHg on euthanized mice. The oxygen gradients in the mouse scabs were similar to those observed for clinical isolates cultured in vitro and for human ex vivo specimens. No oxygen gradients were observed for heat-killed mouse scabs, suggesting that active metabolism by the viable bacteria and host cells contributed to the reduced oxygen partial pressure of the scabs. To characterize the metabolic activities of the bacteria in the mouse scabs, we performed transcriptomics analyses of Pseudomonas aeruginosa biofilms associated with the db/db mice wounds using Affymetrix microarrays. The results demonstrated that the bacteria expressed genes for metabolic activities associated with cell growth. Interestingly, the transcriptome results indicated that the bacteria within the wounds also experienced oxygen-limitation stress. Among the bacterial genes that were expressed in vivo were genes associated with the Anr-mediated hypoxia-stress response. Other bacterial stress response genes highly expressed in vivo were genes associated with stationary-phase growth, osmotic stress, and RpoH-mediated heat shock stress. Overall, the results support the hypothesis that bacterial biofilms in chronic wounds promote chronicity by contributing to the maintenance of localized low oxygen tensions. Transcriptional profiling of two independent biological replicates of Pseudomonas aeruginosa biofilms, as grown to 72 hours and used as inocula applied to the murine wounds, was performed. A principle components analysis (PCA) was used to provide an overview of the transcriptome data from the 28-day mouse wound scab, comparing the data to the biofilm inoculum, and to published reports of P. aeruginosa biofilm and planktonic samples. The analysis shows that the transcriptome of the mouse wound scab was distinct from the biofilm inoculum that was applied to the wound, demonstrating a shift in biofilm gene expression following 28 days of infection. We sought to characterize P. aeruginosa activity within biofilms in the mouse wound model by isolating and identifying mRNA from the biofilms used as inocula and from the wound scabs 28 days post infection.

Project description:Biofilms have been implicated in delayed wound healing, although the mechanisms by which biofilms impair wound healing are poorly understood. Many species of bacteria produce exotoxins and exoenzymes that may inhibit healing. In addition, oxygen consumption by biofilms, as well as responding leukocytes, may impede wound healing. In this study, we used oxygen microsensors to measure oxygen transects through in vitro-cultured biofilms, biofilms formed in vivo within scabs from a diabetic (db/db) mouse model, and ex vivo human chronic wound specimens. The results show that oxygen levels within mouse scabs had steep gradients that reached minima ranging from 17-72 mmHg on live mice and 6.4-1.1 mmHg on euthanized mice. The oxygen gradients in the mouse scabs were similar to those observed for clinical isolates cultured in vitro and for human ex vivo specimens. No oxygen gradients were observed for heat-killed mouse scabs, suggesting that active metabolism by the viable bacteria and host cells contributed to the reduced oxygen partial pressure of the scabs. To characterize the metabolic activities of the bacteria in the mouse scabs, we performed transcriptomics analyses of Pseudomonas aeruginosa biofilms associated with the db/db mice wounds using Affymetrix microarrays. The results demonstrated that the bacteria expressed genes for metabolic activities associated with cell growth. Interestingly, the transcriptome results indicated that the bacteria within the wounds also experienced oxygen-limitation stress. Among the bacterial genes that were expressed in vivo were genes associated with the Anr-mediated hypoxia-stress response. Other bacterial stress response genes highly expressed in vivo were genes associated with stationary-phase growth, osmotic stress, and RpoH-mediated heat shock stress. Overall, the results support the hypothesis that bacterial biofilms in chronic wounds promote chronicity by contributing to the maintenance of localized low oxygen tensions.

Dataset Information

RNA-seq of mouse wounds from different time points, treatment and genotype

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