Kyle D. Fink

Comprehensive Proteomic Analysis of Mesenchymal Stem Cell Exosomes Reveals Modulation of Angiogenesis via Nuclear Factor-KappaB Signaling.

Mesenchymal stem cells (MSC) are known to facilitate healing of ischemic tissue related diseases through proangiogenic secretory proteins. Recent studies further show that MSC derived exosomes function as paracrine effectors of angiogenesis, however, the identity of which components of the exosome proteome responsible for this effect remains elusive. To address this we used high‐resolution isoelectric focusing coupled liquid chromatography tandem mass spectrometry, an unbiased high throughput proteomics approach to comprehensively characterize the proteinaceous contents of MSCs and MSC derived exosomes. We probed the proteome of MSCs and MSC derived exosomes from cells cultured under expansion conditions and under ischemic tissue simulated conditions to elucidate key angiogenic paracrine effectors present and potentially differentially expressed in these conditions. In total, 6,342 proteins were identified in MSCs and 1,927 proteins in MSC derived exosomes, representing to our knowledge the first time these proteomes have been probed comprehensively. Multilayered analyses identified several putative paracrine effectors of angiogenesis present in MSC exosomes and increased in expression in MSCs exposed to ischemic tissue‐simulated conditions; these include platelet derived growth factor, epidermal growth factor, fibroblast growth factor, and most notably nuclear factor‐kappaB (NFkB) signaling pathway proteins. NFkB signaling was identified as a key mediator of MSC exosome induced angiogenesis in endothelial cells by functional in vitro validation using a specific inhibitor. Collectively, the results of our proteomic analysis show that MSC derived exosomes contain a robust profile of angiogenic paracrine effectors, which have potential for the treatment of ischemic tissue‐related diseases. Stem Cells 2016;34:601–613

Comprehensive Proteomic Analysis of Mesenchymal Stem Cell Exosomes Reveals Modulation of Angiogenesis via NFkB Signaling

Mesenchymal stem cells (MSC) are known to facilitate healing of ischemic tissue related diseases through proangiogenic secretory proteins. Recent studies further show that MSC derived exosomes function as paracrine effectors of angiogenesis, however, the identity of which components of the exosome proteome responsible for this effect remains elusive. To address this we used high‐resolution isoelectric focusing coupled liquid chromatography tandem mass spectrometry, an unbiased high throughput proteomics approach to comprehensively characterize the proteinaceous contents of MSCs and MSC derived exosomes. We probed the proteome of MSCs and MSC derived exosomes from cells cultured under expansion conditions and under ischemic tissue simulated conditions to elucidate key angiogenic paracrine effectors present and potentially differentially expressed in these conditions. In total, 6,342 proteins were identified in MSCs and 1,927 proteins in MSC derived exosomes, representing to our knowledge the first time these proteomes have been probed comprehensively. Multilayered analyses identified several putative paracrine effectors of angiogenesis present in MSC exosomes and increased in expression in MSCs exposed to ischemic tissue‐simulated conditions; these include platelet derived growth factor, epidermal growth factor, fibroblast growth factor, and most notably nuclear factor‐kappaB (NFkB) signaling pathway proteins. NFkB signaling was identified as a key mediator of MSC exosome induced angiogenesis in endothelial cells by functional in vitro validation using a specific inhibitor. Collectively, the results of our proteomic analysis show that MSC derived exosomes contain a robust profile of angiogenic paracrine effectors, which have potential for the treatment of ischemic tissue‐related diseases. Stem Cells 2016;34:601–613

Mesenchymal stem cell transplantation and DMEM administration in a 3NP rat model of Huntington's disease: morphological and behavioral outcomes.

Transplantation of mesenchymal stem cells (MSCs) may offer a viable treatment for Huntingtons disease (HD). We tested the efficacy of MSC transplants to reduce deficits in a 3-nitropropionic acid (3NP) rat model of HD. Five groups of rats (Sham, 3NP, 3NP+vehicle, 3NP+TP(low), 3NP+TP(high)), were given PBS or 3NP intraperitoneally, twice daily for 42 days. On day 28, rats in all groups except Sham and 3NP, received intrastriatal injections of either 200,000 MSCs (TP(low)), 400,000 (TP(high)) MSCs or DMEM (VH, the vehicle for transplantation). MSCs survived 72 days without inducing a strong inflammatory response from the striatum. Behavioral sparing was observed on tests of supported-hindlimb-retraction, unsupported-hindlimb-retraction, visual paw placement and stepping ability for 3NP+TP(low) rats and on the unsupported-hindlimb-retraction and rotarod tasks for 3NP+VH rats. Relative to 3NP controls, all treated groups were protected from 3NP-induced enlargement of the lateral ventricles. In vitro, MSCs expressed transcripts for numerous neurotrophic factors. In vivo, increased striatal labeling in BDNF, collagen type-I and fibronectin (but not GDNF or CNTF) was observed in the brains of MSC-transplanted rats but not in DMEM-treated rats. In addition, none of the transplanted MSCs expressed neural phenotypes. These findings suggest that factors other than neuronal replacement underlie the behavioral sparing observed in 3NP rats after MSC transplantation.

Transplants of Adult Mesenchymal and Neural Stem Cells Provide Neuroprotection and Behavioral Sparing in a Transgenic Rat Model of Huntington's Disease

Stem cells have gained significant interest as a potential treatment of neurodegenerative diseases, including Huntingtons disease (HD). One source of these cells is adult neural stem cells (aNSCs), which differentiate easily into neuronal lineages. However, these cells are vulnerable to immune responses following transplantation. Another source is bone‐marrow‐derived mesenchymal stem cells (MSCs), which release neurotrophic factors and anti‐inflammatory cytokines following transplantation, and are less vulnerable to rejection. The goal of this study was to compare the efficacy of transplants of MSCs, aNSCs, or cotransplants of MSCs and aNSCs for reducing deficits in a transgenic rat model of HD. HD rats received intrastriatal transplantations of 400,000 MSCs, aNSCs, or a combination of MSCs/aNSCs, while wild‐type and HD controls were given vehicle. Rats were tested on the rotarod over the course of 20 weeks. The results indicated that transplants of: (a) aNSCs produced a strong immune response and conferred short‐term behavioral benefits; (b) MSCs elicited a relatively weak immune response, and provided a longer term behavioral benefit; and (c) combined MSCs and aNSCs conferred long‐term behavioral benefits and increased survival of the transplanted aNSCs. The finding that cotransplanting MSCs with aNSCs can prolong aNSC survival and provide greater behavioral sparing than when the transplants contains only aNSCs suggests that MSCs are capable of creating a more suitable microenvironment for aNSC survival. This cotransplantation strategy may be useful as a future therapeutic option for treating HD, especially if long‐term survival of differentiated cells proves to be critically important for preserving lasting functional outcomes. Stem Cells 2014;32:500–509

Human Mesenchymal Stem Cells Genetically Engineered to Overexpress Brain-derived Neurotrophic Factor Improve Outcomes in Huntington’s Disease Mouse Models

Huntingtons disease (HD) is a fatal degenerative autosomal dominant neuropsychiatric disease that causes neuronal death and is characterized by progressive striatal and then widespread brain atrophy. Brain-derived neurotrophic factor (BDNF) is a lead candidate for the treatment of HD, as it has been shown to prevent cell death and to stimulate the growth and migration of new neurons in the brain in transgenic mouse models. BDNF levels are reduced in HD postmortem human brain. Previous studies have shown efficacy of mesenchymal stem/stromal cells (MSC)/BDNF using murine MSCs, and the present study used human MSCs to advance the therapeutic potential of the MSC/BDNF platform for clinical application. Double-blinded studies were performed to examine the effects of intrastriatally transplanted human MSC/BDNF on disease progression in two strains of immune-suppressed HD transgenic mice: YAC128 and R6/2. MSC/BDNF treatment decreased striatal atrophy in YAC128 mice. MSC/BDNF treatment also significantly reduced anxiety as measured in the open-field assay. Both MSC and MSC/BDNF treatments induced a significant increase in neurogenesis-like activity in R6/2 mice. MSC/BDNF treatment also increased the mean lifespan of the R6/2 mice. Our genetically modified MSC/BDNF cells set a precedent for stem cell-based neurotherapeutics and could potentially be modified for other neurodegenerative disorders such as amyotrophic lateral sclerosis, Alzheimers disease, and some forms of Parkinsons disease. These cells provide a platform delivery system for future studies involving corrective gene-editing strategies.Huntingtons disease (HD) is a fatal degenerative autosomal dominant neuropsychiatric disease that causes neuronal death and is characterized by progressive striatal and then widespread brain atrophy. Brain-derived neurotrophic factor (BDNF) is a lead candidate for the treatment of HD, as it has been shown to prevent cell death and to stimulate the growth and migration of new neurons in the brain in transgenic mouse models. BDNF levels are reduced in HD postmortem human brain. Previous studies have shown efficacy of mesenchymal stem/stromal cells (MSC)/BDNF using murine MSCs, and the present study used human MSCs to advance the therapeutic potential of the MSC/BDNF platform for clinical application. Double-blinded studies were performed to examine the effects of intrastriatally transplanted human MSC/BDNF on disease progression in two strains of immune-suppressed HD transgenic mice: YAC128 and R6/2. MSC/BDNF treatment decreased striatal atrophy in YAC128 mice. MSC/BDNF treatment also significantly reduced anxiety as measured in the open-field assay. Both MSC and MSC/BDNF treatments induced a significant increase in neurogenesis-like activity in R6/2 mice. MSC/BDNF treatment also increased the mean lifespan of the R6/2 mice. Our genetically modified MSC/BDNF cells set a precedent for stem cell-based neurotherapeutics and could potentially be modified for other neurodegenerative disorders such as amyotrophic lateral sclerosis, Alzheimers disease, and some forms of Parkinsons disease. These cells provide a platform delivery system for future studies involving corrective gene-editing strategies.

Developing stem cell therapies for juvenile and adult-onset Huntington's disease

Stem cell therapies have been explored as a new avenue for the treatment of neurologic disease and damage within the CNS in part due to their native ability to mimic repair mechanisms in the brain. Mesenchymal stem cells have been of particular clinical interest due to their ability to release beneficial neurotrophic factors and their ability to foster a neuroprotective microenviroment. While early stem cell transplantation therapies have been fraught with technical and political concerns as well as limited clinical benefits, mesenchymal stem cell therapies have been shown to be clinically beneficial and derivable from nonembryonic, adult sources. The focus of this review will be on emerging and extant stem cell therapies for juvenile and adult-onset Huntington’s disease.

The effects of acute voluntary wheel running on recovery of function following medial frontal cortical contusions in rats.

PURPOSE Traumatic brain injury (TBI) produces significant deficits in executive function, sensory-motor function, and on spatial learning tasks. We wish to study if recovery from TBI can be benefited by voluntary exercise. METHODS A variation of the stop-signal reaction time (SSRT) task was employed to measure rats ability to obtain maximum reinforcers in a complex behavioral task. A 2 × 2 (lesion × treatment) experimental design was constructed with 31 weight restricted male Long-Evans rats which received either bilateral cortical contusions to the medial frontal cortex or sham preparations following the acquisition of the SSRT task (matched based on pre-surgical performance). Following surgery, rats were randomly assigned to either an environment with free access to running wheels or traditional single housing without running wheels. RESULTS Rats receiving a bilateral TBI performed significantly worse than sham operated rats on a complex task. Contrary to our original hypothesis, acute exercise following injury exacerbated the deficits in the complex task that did not return to levels of the injured rats without access to running wheels until post-TBI day 13. CONCLUSION We found a significant interaction between severe bilateral TBI and the introduction of voluntary exercise immediately post-injury. In this paradigm, voluntary wheel running exacerbated the TBI-induced deficit, rather than reducing it.

Intrastriatal Transplantation of Adenovirus-Generated Induced Pluripotent Stem Cells for Treating Neuropathological and Functional Deficits in a Rodent Model of Huntington’s Disease

Induced pluripotent stem cells (iPSCs) show considerable promise for cell replacement therapies for Huntingtons disease (HD). Our laboratory has demonstrated that tail‐tip fibroblasts, reprogrammed into iPSCs via two adenoviruses, can survive and differentiate into neuronal lineages following transplantation into healthy adult rats. However, the ability of these cells to survive, differentiate, and restore function in a damaged brain is unknown. To this end, adult rats received a regimen of 3‐nitropropionic acid (3‐NP) to induce behavioral and neuropathological deficits that resemble HD. At 7, 21, and 42 days after the initiation of 3‐NP or vehicle, the rats received intrastriatal bilateral transplantation of iPSCs. All rats that received 3‐NP and vehicle treatment displayed significant motor impairment, whereas those that received iPSC transplantation after 3‐NP treatment had preserved motor function. Histological analysis of the brains of these rats revealed significant decreases in optical densitometric measures in the striatum, lateral ventricle enlargement, as well as an increase in striosome size in all rats receiving 3‐NP when compared with sham rats. The 3‐NP‐treated rats given transplants of iPSCs in the 7‐ or 21‐day groups did not exhibit these deficits. Transplantation of iPSCs at the late‐stage (42‐day) time point did not protect against the 3‐NP‐induced neuropathology, despite preserving motor function. Transplanted iPSCs were found to survive and differentiate into region‐specific neurons in the striatum of 3‐NP rats, at all transplantation time points. Taken together, these results suggest that transplantation of adenovirus‐generated iPSCs may provide a potential avenue for therapeutic treatment of HD.

Survival and differentiation of adenovirus-generated induced pluripotent stem cells transplanted into the rat striatum.

Induced pluripotent stem cells (iPSCs) offer certain advantages over embryonic stem cells in cell replacement therapy for a variety of neurological disorders. However, reliable procedures, whereby transplanted iPSCs can survive and differentiate into functional neurons, without forming tumors, have yet to be devised. Currently, retroviral or lentiviral reprogramming methods are often used to reprogram somatic cells. Although the use of these viruses has proven to be effective, formation of tumors often results following in vivo transplantation, possibly due to the integration of the reprogramming genes. The goal of the current study was to develop a new approach, using an adenovirus for reprogramming cells, characterize the iPSCs in vitro, and test their safety, survivability, and ability to differentiate into region-appropriate neurons following transplantation into the rat brain. To this end, iPSCs were derived from bone marrow-derived mesenchymal stem cells and tail-tip fibroblasts using a single cassette lentivirus or a combination of adenoviruses. The reprogramming efficiency and levels of pluripotency were compared using immunocytochemistry, flow cytometry, and real-time polymerase chain reaction. Our data indicate that adenovirus-generated iPSCs from tail-tip fibroblasts are as efficient as the method we used for lentiviral reprogramming. All generated iPSCs were also capable of differentiating into neuronal-like cells in vitro. To test the in vivo survivability and the ability to differentiate into region-specific neurons in the absence of tumor formation, 400,000 of the iPSCs derived from tail-tip fibroblasts that were transfected with the adenovirus pair were transplanted into the striatum of adult, immune-competent rats. We observed that these iPSCs produced region-specific neuronal phenotypes, in the absence of tumor formation, at 90 days posttransplantation. These results suggest that adenovirus-generated iPSCs may provide a safe and viable means for neuronal replacement therapies.

Early cognitive dysfunction in the HD 51 CAG transgenic rat model of Huntington's disease.

Huntingtons disease (HD) is a neurodegenerative disorder in humans caused by an expansion of a CAG trinucleotide repeat that produces choreic movements, which are preceded by cognitive deficits. The HD transgenic rat (tgHD), which contains the human HD mutation with a 51 CAG repeat allele, exhibits motor deficits that begin when these rats are 12 months of age. However, there are no reports of cognitive dysfunction occurring prior to this. To assess whether cognitive dysfunction might precede motor deficits in tgHD rats, one group of 9-month-old male rats with homozygotic mutated genes and one group of wild-type (WT) rats underwent three testing phases in a unique Spatial Operant Reversal Test (SORT) paradigm, as well as assessment of spontaneous motor activity. After testing, morphological and histological examination of the brains were made. Results indicated that tgHD rats acquired the cued-response (Phase 1) portion of the SORT, but made significantly more errors during the reversal (Phase 2) and during the pseudorandomized reversals (Phase 3) portion of the study, when compared to WT rats. Analysis of the data using mathematical principles of reinforcement revealed no memory, motor, or motivational deficits. These results indicate that early cognitive dysfunction, as measured by the SORT, occur prior to motor deficits, gross anatomical changes, or cell loss in the tgHD rat with 51 CAG repeats, and suggest that this protocol could provide a useful screen for therapeutic studies.