CIViCdb 2022: evolution of an open-access cancer variant interpretation knowledgebase.

CIViC (Clinical Interpretation of Variants in Cancer; civicdb.org) is a crowd-sourced, public domain knowledgebase composed of literature-derived evidence characterizing the clinical utility of cancer variants. As clinical sequencing becomes more prevalent in cancer management, the need for cancer variant interpretation has grown beyond the capability of any single institution. CIViC contains peer-reviewed, published literature curated and expertly-moderated into structured data units (Evidence Items) that can be accessed globally and in real time, reducing barriers to clinical variant knowledge sharing. We have extended CIViC's functionality to support emergent variant interpretation guidelines, increase interoperability with other variant resources, and promote widespread dissemination of structured curated data. To support the full breadth of variant interpretation from basic to translational, including integration of somatic and germline variant knowledge and inference of drug response, we have enabled curation of three new Evidence Types (Predisposing, Oncogenic and Functional). The growing CIViC knowledgebase has over 300 contributors and distributes clinically-relevant cancer variant data currently representing >3200 variants in >470 genes from >3100 publications.

Large scale genotype- and phenotype-driven machine learning in Von Hippel-Lindau disease.

Von Hippel-Lindau (VHL) disease is a hereditary cancer syndrome where individuals are predisposed to tumor development in the brain, adrenal gland, kidney, and other organs. It is caused by pathogenic variants in the VHL tumor suppressor gene. Standardized disease information has been difficult to collect due to the rarity and diversity of VHL patients. Over 4100 unique articles published until October 2019 were screened for germline genotype-phenotype data. Patient data were translated into standardized descriptions using Human Genome Variation Society gene variant nomenclature and Human Phenotype Ontology terms and has been manually curated into an open-access knowledgebase called Clinical Interpretation of Variants in Cancer. In total, 634 unique VHL variants, 2882 patients, and 1991 families from 427 papers were captured. We identified relationship trends between phenotype and genotype data using classic statistical methods and spectral clustering unsupervised learning. Our analyses reveal earlier onset of pheochromocytoma/paraganglioma and retinal angiomas, phenotype co-occurrences and genotype-phenotype correlations including hotspots. It confirms existing VHL associations and can be used to identify new patterns and associations in VHL disease. Our database serves as an aggregate knowledge translation tool to facilitate sharing information about the pathogenicity of VHL variants.

Safety and immunomodulatory effects of allogeneic canine adipose-derived mesenchymal stromal cells transplanted into the region of the lacrimal gland, the gland of the third eyelid and the knee joint.

BACKGROUND AIMS: Mesenchymal stromal cells (MSCs) have been extensively studied as a cellular therapeutic for various pathologic conditions. However, there remains a paucity of data regarding regional and systemic safety of MSC transplantations, particularly with multiple deliveries of allogeneic cells. The purpose of this study was to investigate the safety and systemic immunomodulatory effects of repeated local delivery of allogeneic MSCs into the region of the lacrimal gland, the gland of the third eyelid and the knee joint in dogs. METHODS: Allogeneic adipose tissue-derived canine MSCs were delivered to the regions of the lacrimal gland and the third eyelid gland as well as in the knee joints of six healthy laboratory beagles as follows: six times with 1-week intervals for delivery to the lacrimal gland and the third eyelid gland regions and three to four times with 1- to 2-week intervals for intra-articular transplantations. Dogs were sequentially evaluated by clinical examination. At the conclusion of the study, dogs were humanely euthanized, and a complete gross and histopathologic examination of all organ systems was performed. Mixed leukocyte reactions were also performed before the first transplantation and after the final transplantation. RESULTS: Clinical and pathologic examinations found no severe consequences after repeated MSC transplantations. Results of mixed leukocyte reactions demonstrated suppression of T-cell proliferation after MSC transplantations. CONCLUSIONS: This is the first study to demonstrate regional and systemic safety and systemic immunomodulatory effects of repeated local delivery of allogeneic MSCs in vivo.

The Molecular Mechanisms Through Which Placental Mesenchymal Stem Cell-Derived Extracellular Vesicles Promote Myelin Regeneration.

Multiple sclerosis (MS) is a debilitating degenerative disease characterized by an immunological attack on the myelin sheath leading to demyelination and axon degeneration. Mesenchymal stem/stromal cells (MSCs) and secreted extracellular vesicles (EVs) have become attractive targets as therapies to treat neurodegenerative diseases such as MS due to their potent immunomodulatory and regenerative properties. The placenta is a unique source of MSCs (PMSCs), demonstrates "fetomaternal" tolerance during pregnancy, and serves as a novel source of MSCs for the treatment of neurodegenerative diseases. PMSCs and PMSC-EVs have been shown to promote remyelination in animal models of MS, however, the molecular mechanisms by which modulation of autoimmunity and promotion of myelination occurs have not been well elucidated. The current review will address the molecular mechanisms by which PMSC-EVs can promote remyelination in MS.

Engineering extracellular vesicles for Alzheimer's disease: An emerging cell-free approach for earlier diagnosis and treatment.

Alzheimer's disease (AD) is a debilitating neurodegenerative disorder affecting over five million people globally and has no established cure. Current AD-related treatments only alleviate cognitive and behavioral symptoms and do not address disease onset or progression, underlining the unmet need to create an effective, innovative AD therapeutic. Extracellular vesicles (EVs) have emerged as a new class of nanotherapeutics. These secreted, lipid-bound cellular signaling carriers show promise for potential clinical applications for neurodegenerative diseases like AD. Additionally, analyzing contents and characteristics of patient-derived EVs may address the unmet need for earlier AD diagnostic techniques, informing physicians of altered genetic expression or cellular communications specific to healthy and diseased physiological states. There are numerous recent advances in regenerative medicine using EVs and include bioengineering perspectives to modify EVs, target glial cells in neurodegenerative diseases like AD, and potentially use EVs to diagnose and treat AD earlier. This article is categorized under: Neurological Diseases > Biomedical Engineering Neurological Diseases > Molecular and Cellular Physiology Neurological Diseases > Stem Cells and Development.

Exosomal microRNAs from mesenchymal stem/stromal cells: Biology and applications in neuroprotection.

Mesenchymal stem/stromal cells (MSCs) are extensively studied as cell-therapy agents for neurological diseases. Recent studies consider exosomes secreted by MSCs as important mediators for MSCs' neuroprotective functions. Exosomes transfer functional molecules including proteins, lipids, metabolites, DNAs, and coding and non-coding RNAs from MSCs to their target cells. Emerging evidence shows that exosomal microRNAs (miRNAs) play a key role in the neuroprotective properties of these exosomes by targeting several genes and regulating various biological processes. Multiple exosomal miRNAs have been identified to have neuroprotective effects by promoting neurogenesis, neurite remodeling and survival, and neuroplasticity. Thus, exosomal miRNAs have significant therapeutic potential for neurological disorders such as stroke, traumatic brain injury, and neuroinflammatory or neurodegenerative diseases and disorders. This review discusses the neuroprotective effects of selected miRNAs (miR-21, miR-17-92, miR-133, miR-138, miR-124, miR-30, miR146a, and miR-29b) and explores their mechanisms of action and applications for the treatment of various neurological disease and disorders. It also provides an overview of state-of-the-art bioengineering approaches for isolating exosomes, optimizing their yield and manipulating the miRNA content of their cargo to improve their therapeutic potential.

The Unique Properties of Placental Mesenchymal Stromal Cells: A Novel Source of Therapy for Congenital and Acquired Spinal Cord Injury.

Spinal cord injury (SCI) is a devasting condition with no reliable treatment. Spina bifida is the most common cause of congenital SCI. Cell-based therapies using mesenchymal stem/stromal cells (MSCS) have been largely utilized in SCI. Several clinical trials for acquired SCI use adult tissue-derived MSC sources, including bone-marrow, adipose, and umbilical cord tissues. The first stem/stromal cell clinical trial for spina bifida is currently underway (NCT04652908). The trial uses early gestational placental-derived mesenchymal stem/stromal cells (PMSCs) during the fetal repair of myelomeningocele. PMSCs have been shown to exhibit unique neuroprotective, angiogenic, and antioxidant properties, all which are promising applications for SCI. This review will summarize the unique properties and current applications of PMSCs and discuss their therapeutic role for acquired SCI.

Placenta-derived multipotent mesenchymal stromal cells: a promising potential cell-based therapy for canine inflammatory brain disease.

BACKGROUND: Canine inflammatory brain disease (IBD) is a severe inflammatory disorder characterized by infiltration of activated immune cell subsets into the brain and spinal cord. Multipotent mesenchymal stromal cells (MSCs) are a promising therapy for IBD, based on their potent pro-angiogenic, neuroprotective, and immunomodulatory properties. The aims of this study were to compare the immunomodulatory attributes of canine adipose-derived MSCs (ASCs) and placenta-derived MSCs (PMSCs) in vitro. These data will serve as potency information to help inform the optimal MSC cell source to treat naturally occurring canine IBD. METHODS: Indoleamine 2,3 dioxygenase (IDO) activity and prostaglandin E2 (PGE2) concentration at baseline and after stimulation with interferon gamma (IFNγ) and/or tumor necrosis factor alpha (TNFα) were measured from canine ASC and PMSC cultures. Leukocyte suppression assays (LSAs) were performed to compare the ability of ASCs and PMSCs to inhibit activated peripheral blood mononuclear cell (PBMC) proliferation. IDO activity and PGE2; interleukin (IL)-2, IL-6, and IL-8; TNFα; and vascular endothelial growth factor (VEGF) concentrations were also measured from co-culture supernatants. Cell cycle analysis was performed to determine how ASCs and PMSCs altered lymphocyte proliferation. RESULTS: Activated canine MSCs from both tissue sources secreted high concentrations of IDO and PGE2, after direct stimulation with IFNγ and TNFα, or indirect stimulation by activated PBMCs. Both ASCs and PMSCs inhibited activated PBMC proliferation in LSA assays; however, PMSCs inhibited PBMC proliferation significantly more than ASCs. Blocking PGE2 and IDO in LSA assays determined that PGE2 is important only for ASC inhibition of PBMC proliferation. Activated ASCs increased IL-6 and VEGF secretion and decreased TNFα secretion, while activated PMSCs increased IL-6, IL-8, and VEGF secretion. ASCs inhibited lymphocyte proliferation via cell cycle arrest in the G0/G1 and PMSCs inhibited lymphocyte proliferation via induction of lymphocyte apoptosis. CONCLUSION: Our results demonstrate that ASCs and PMSCs have substantial in vitro potential as a cell-based therapy for IBD; however, PMSCs more potently inhibited lymphocyte proliferation by inducing apoptosis of activated lymphocytes. These data suggest that the mechanism by which ASCs and PMSCs downregulate PBMC proliferation differs. Additional studies may elucidate additional mechanisms by which canine MSCs modulate neuroinflammatory responses.

A multicenter experience using adipose-derived mesenchymal stem cell therapy for cats with chronic, non-responsive gingivostomatitis.

BACKGROUND: The ability of mesenchymal stem cells (MSCs) to modulate immune responses inspired a series of clinical trials addressing oral mucosal inflammation. We previously reported on the safety and efficacy of fresh, allogeneic and autologous, adipose-derived mesenchymal stem cells (ASCs) to treat feline gingivostomatitis (FCGS), an oral mucosal inflammatory disease that shares similarities with human oral lichen planus. METHODS: To meet clinical demand and goals for future commercialization, we determined the feasibility of shipping fresh ASCs to distant clinics and extended our pilot studies to expand safety and efficacy data for shipped and non-shipped ASCs in a cohort of 18 FCGS cats enrolled locally and at a few different locations within the USA. RESULTS: We found that ASCs retained their viability, phenotype, and function after shipment. ASCs administered systemically resulted in a 72% positive response rate, identical to that noted in our previous studies. Cats that responded to ASC therapy had a significant decrease in circulating globulin concentration and histological evidence of decreased CD3+ T cells and CD20+ B cells in the oral mucosa. Responder cats also had significantly decreased percentages of CD8lo cells in blood prior to and at 3 months post-ASC therapy. CD8lo cells may serve as a potential "predictor" for response to systemic ASC therapy. CONCLUSION: Fresh feline ASCs can be successfully shipped and administered to cats with FCGS. ASCs modulate the immune response and demonstrate efficacy for chronic oral mucosal inflammatory lesions that are characterized by CD8+ T cell inflammation and T cell activation. FCGS is a potentially useful naturally occurring large animal model of human oral inflammatory diseases.

Injectable mineralized microsphere-loaded composite hydrogels for bone repair in a sheep bone defect model.

The efficacy of cell-based therapies as an alternative to autologous bone grafts requires biomaterials to localize cells at the defect and drive osteogenic differentiation. Hydrogels are ideal cell delivery vehicles that can provide instructional cues via their composition or mechanical properties but commonly lack osteoconductive components that nucleate mineral. To address this challenge, we entrapped mesenchymal stromal cells (MSCs) in a composite hydrogel based on two naturally-derived polymers (alginate and hyaluronate) containing biomineralized polymeric microspheres. Mechanical properties of the hydrogels were dependent upon composition. The presentation of the adhesive tripeptide Arginine-Glycine-Aspartic Acid (RGD) from both polymers induced greater osteogenic differentiation of ovine MSCs in vitro compared to gels formed of RGD-alginate or RGD-alginate/hyaluronate alone. We then evaluated the capacity of this construct to stimulate bone healing when transplanting autologous, culture-expanded MSCs into a surgical induced, critical-sized ovine iliac crest bone defect. At 12 weeks post-implantation, defects treated with MSCs transplanted in composite gels exhibited significant increases in blood vessel density, osteoid formation, and bone formation compared to acellular gels or untreated defects. These findings demonstrate the capacity of osteoconductive hydrogels to promote bone formation with autologous MSCs in a large animal bone defect model and provide a promising vehicle for cell-based therapies of bone healing.

Placental Mesenchymal Stem Cell-Derived Extracellular Vesicles Promote Myelin Regeneration in an Animal Model of Multiple Sclerosis.

Mesenchymal stem/stromal cells (MSCs) display potent immunomodulatory and regenerative capabilities through the secretion of bioactive factors, such as proteins, cytokines, chemokines as well as the release of extracellular vesicles (EVs). These functional properties of MSCs make them ideal candidates for the treatment of degenerative and inflammatory diseases, including multiple sclerosis (MS). MS is a heterogenous disease that is typically characterized by inflammation, demyelination, gliosis and axonal loss. In the current study, an induced experimental autoimmune encephalomyelitis (EAE) murine model of MS was utilized. At peak disease onset, animals were treated with saline, placenta-derived MSCs (PMSCs), as well as low and high doses of PMSC-EVs. Animals treated with PMSCs and high-dose PMSC-EVs displayed improved motor function outcomes as compared to animals treated with saline. Symptom improvement by PMSCs and PMSC-EVs led to reduced DNA damage in oligodendroglia populations and increased myelination within the spinal cord of treated mice. In vitro data demonstrate that PMSC-EVs promote myelin regeneration by inducing endogenous oligodendrocyte precursor cells to differentiate into mature myelinating oligodendrocytes. These findings support that PMSCs' mechanism of action is mediated by the secretion of EVs. Therefore, PMSC-derived EVs are a feasible alternative to cellular based therapies for MS, as demonstrated in an animal model of the disease.

Standard operating procedure for curation and clinical interpretation of variants in cancer.

Manually curated variant knowledgebases and their associated knowledge models are serving an increasingly important role in distributing and interpreting variants in cancer. These knowledgebases vary in their level of public accessibility, and the complexity of the models used to capture clinical knowledge. CIViC (Clinical Interpretation of Variants in Cancer - www.civicdb.org) is a fully open, free-to-use cancer variant interpretation knowledgebase that incorporates highly detailed curation of evidence obtained from peer-reviewed publications and meeting abstracts, and currently holds over 6300 Evidence Items for over 2300 variants derived from over 400 genes. CIViC has seen increased adoption by, and also undertaken collaboration with, a wide range of users and organizations involved in research. To enhance CIViC's clinical value, regular submission to the ClinVar database and pursuit of other regulatory approvals is necessary. For this reason, a formal peer reviewed curation guideline and discussion of the underlying principles of curation is needed. We present here the CIViC knowledge model, standard operating procedures (SOP) for variant curation, and detailed examples to support community-driven curation of cancer variants.

Safety and tracking of intrathecal allogeneic mesenchymal stem cell transplantation in healthy and diseased horses.

BACKGROUND: It is currently unknown if the intrathecal administration of a high dose of allogeneic mesenchymal stem cells (MSCs) is safe, how MSCs migrate throughout the vertebral canal after intrathecal administration, and whether MSCs are able to home to a site of injury. The aims of the study were: 1) to evaluate the safety of intrathecal injection of 100 million allogeneic adipose-derived MSCs (ASCs); 2) to assess the distribution of ASCs after atlanto-occipital (AO) and lumbosacral (LS) injection in healthy horses; and 3) to determine if ASCs homed to the site of injury in neurologically diseased horses. METHODS: Six healthy horses received 100 × 106 allogeneic ASCs via AO (n = 3) or LS injection (n = 3). For two of these horses, ASCs were radiolabeled with technetium and injected AO (n = 1) or LS (n = 1). Neurological examinations were performed daily, and blood and cerebrospinal fluid (CSF) were evaluated prior to and at 30 days after injection. Scintigraphic images were obtained immediately postinjection and at 30 mins, 1 h, 5 h, and 24 h after injection. Three horses with cervical vertebral compressive myelopathy (CVCM) received 100 × 106 allogeneic ASCs labeled with green fluorescent protein (GFP) via AO injection and were euthanized 1-2 weeks after injection for a full nervous system necropsy. CSF parameters were compared using a paired student's t test. RESULTS: There were no significant alterations in blood, CSF, or neurological examinations at any point after either AO or LS ASC injections into healthy horses. The radioactive signal could be identified all the way to the lumbar area after AO ASC injection. After LS injection, the signal extended caudally but only a minimal radioactive signal extended further cranially. GFP-labeled ASCs were not present at the site of disease at either 1 or 2 weeks following intrathecal administration. CONCLUSIONS: The intrathecal injection of allogeneic ASCs was safe and easy to perform in horses. The AO administration of ASCs resulted in better distribution within the entire subarachnoid space in healthy horses. ASCs could not be found after 7 or 15 days of injection at the site of injury in horses with CVCM.

Allogeneic Stem Cells Alter Gene Expression and Improve Healing of Distal Limb Wounds in Horses.

Distal extremity wounds are a significant clinical problem in horses and humans and may benefit from mesenchymal stem cell (MSC) therapy. This study evaluated the effects of direct wound treatment with allogeneic stem cells, in terms of gross, histologic, and transcriptional features of healing. Three full-thickness cutaneous wounds were created on each distal forelimb in six healthy horses, for a total of six wounds per horse. Umbilical cord-blood derived equine MSCs were applied to each wound 1 day after wound creation, in one of four forms: (a) normoxic- or (b) hypoxic-preconditioned cells injected into wound margins, or (c) normoxic- or (d) hypoxic-preconditioned cells embedded in an autologous fibrin gel and applied topically to the wound bed. Controls were one blank (saline) injected wound and one blank fibrin gel-treated wound per horse. Data were collected weekly for 6 weeks and included wound surface area, thermography, gene expression, and histologic scoring. Results indicated that MSC treatment by either delivery method was safe and improved histologic outcomes and wound area. Hypoxic-preconditioning did not offer an advantage. MSC treatment by injection resulted in statistically significant increases in transforming growth factor beta and cyclooxygenase-2 expression at week 1. Histologically, significantly more MSC-treated wounds were categorized as pro-healing than pro-inflammatory. Wound area was significantly affected by treatment: MSC-injected wounds were consistently smaller than gel-treated or control wounds. In conclusion, MSC therapy shows promise for distal extremity wounds in horses, particularly when applied by direct injection into the wound margin. Stem Cells Translational Medicine 2018;7:98-108.

Therapeutic Efficacy of Fresh, Allogeneic Mesenchymal Stem Cells for Severe Refractory Feline Chronic Gingivostomatitis.

Mesenchymal stem cells (MSCs) have potent immunomodulatory functions and are a promising therapy for immune-mediated inflammatory disorders. We previously demonstrated the efficacy of fresh, autologous, adipose-derived MSCs (ASCs) to treat feline chronic gingivostomatitis (FCGS), a chronic oral mucosal inflammatory disease similar to human oral lichen planus. Here, we investigate the use of fresh allogeneic ASCs for treatment of FCGS in seven cats. Radiolabeled ASCs were also tracked systemically. Each cat received two intravenous injections of 20 million ASCs, 1 month apart. Oral inflammation, blood lymphocyte subsets, anti-fetal bovine serum antibody levels, ASC crossmatching and serum proteins and cytokine concentrations were determined. Four of the 7 cats (57%) responded to treatment [complete clinical remission (n = 2) or substantial clinical improvement (n = 2)]. Three cats were nonresponders. Prior to therapy, most cats had increased circulating CD8+ T cells, decreased CD8lo cells, and a decreased CD4/CD8 ratio, however clinical resolution was not associated with normalization of these parameters. Nonresponders showed more severe systemic inflammation (neutrophilia, hyperglobulinemia and increased interferon gamma and tumor necrosis factor alpha concentration) prior to ASC therapy. Clinical remission took up to 20 months and no clinical relapse has occurred. A higher fraction of radiolabeled ASCs were identified in the oral cavity of FCGS affected cats than the control cat. The administration of fresh, allogenic ASCs appeared to have lower clinical efficacy with a delayed response as compared to the fresh, autologous ASCs. In addition, the mechanism(s) of action for autologous and allogenic ASCs may differ in this model of oral inflammation. Stem Cells Translational Medicine 2017;6:1710-1722.

Human and feline adipose-derived mesenchymal stem cells have comparable phenotype, immunomodulatory functions, and transcriptome.

BACKGROUND: Adipose-derived mesenchymal stem cells (ASCs) are a promising cell therapy to treat inflammatory and immune-mediated diseases. Development of appropriate pre-clinical animal models is critical to determine safety and attain early efficacy data for the most promising therapeutic candidates. Naturally occurring diseases in cats already serve as valuable models to inform human clinical trials in oncologic, cardiovascular, and genetic diseases. The objective of this study was to complete a comprehensive side-by-side comparison of human and feline ASCs, with an emphasis on their immunomodulatory capacity and transcriptome. METHODS: Human and feline ASCs were evaluated for phenotype, immunomodulatory profile, and transcriptome. Additionally, transwells were used to determine the role of cell-cell contact in ASC-mediated inhibition of lymphocyte proliferation in both humans and cats. RESULTS: Similar to human ASCs, feline ASCs were highly proliferative at low passages and fit the minimal criteria of multipotent stem cells including a compatible surface protein phenotype, osteogenic capacity, and normal karyotype. Like ASCs from all species, feline ASCs inhibited mitogen-activated lymphocyte proliferation in vitro, with or without direct ASC-lymphocyte contact. Feline ASCs mimic human ASCs in their mediator secretion pattern, including prostaglandin E2, indoleamine 2,3 dioxygenase, transforming growth factor beta, and interleukin-6, all augmented by interferon gamma secretion by lymphocytes. The transcriptome of three unactivated feline ASC lines were highly similar. Functional analysis of the most highly expressed genes highlighted processes including: 1) the regulation of apoptosis; 2) cell adhesion; 3) response to oxidative stress; and 4) regulation of cell differentiation. Finally, feline ASCs had a similar gene expression profile to noninduced human ASCs. CONCLUSIONS: Findings suggest that feline ASCs modulate lymphocyte proliferation using soluble mediators that mirror the human ASC secretion pattern. Uninduced feline ASCs have similar gene expression profiles to uninduced human ASCs, as revealed by transcriptome analysis. These data will help inform clinical trials using cats with naturally occurring diseases as surrogate models for human clinical trials in the regenerative medicine arena.

Canine and Equine Mesenchymal Stem Cells Grown in Serum Free Media Have Altered Immunophenotype.

Mesenchymal stem cell (MSC) therapy is being increasingly used to treat dogs and horses with naturally-occurring diseases. However these animals also serve as critical large animal models for ongoing translation of cell therapy products to the human market. MSC manufacture for clinical use mandates improvement in cell culture systems to meet demands for higher MSC numbers and removal of xeno-proteins (i.e. fetal bovine serum, FBS). While serum-free media (SFM) is commercially available, its affects on MSC phenotype and immunomodulatory functions are not fully known. The objective of this study was to determine if specific MSC culture conditions, MSC expansion in HYPERFlasks® or MSC expansion in a commercially available SFM, would alter MSC proliferation, phenotype or immunomodulatory properties in vitro. MSCs cultured in HYPERFlasks® were similar in phenotype, proliferative capacity and immunomodulatory functions to MSCs grown in standard flasks however MSC yield was markedly increased. HYPERFlasks® therefore provide a viable option to generate greater cell numbers in a streamlined manner. Canine and equine MSCs expanded in SFM displayed similar proliferation, surface phenotype and inhibitory effect on lymphocyte proliferation in vitro. However, MSCs cultured in the absence of FBS secreted significantly less PGE2, and were significantly less able to inhibit IFNγ secretion by activated T-cells. Immunomodulatory functions altered by expansion in SFM were species dependent. Unlike equine MSCs, in canine adipose-derived MSCs, the inhibition of lymphocyte proliferation was not principally modulated by PGE2. The removal of FBS from both canine and equine MSC culture systems resulted in altered immunomodulatory properties in vitro and warrants further investigation prior to moving towards FBS-free culture conditions.

Feline foamy virus adversely affects feline mesenchymal stem cell culture and expansion: implications for animal model development.

Mesenchymal stem cells (MSCs) are a promising therapeutic option for various immune-mediated and inflammatory disorders due to their potent immunomodulatory and trophic properties. Naturally occurring diseases in large animal species may serve as surrogate animal models of human disease, as they may better reflect the complex genetic, environmental, and physiologic variation present in outbred populations. We work with naturally occurring diseases in large animal species to better understand how MSCs work and to facilitate optimal translation of MSC-based therapies. We are investigating the use of MSC therapy for a chronic oral inflammatory disease in cats. During our efforts to expand fat-derived feline MSCs (fMSCs), we observed that∼50% of the cell lines developed giant foamy multinucleated cells in later passages. These morphologic alterations were associated with proliferation arrest. We hypothesized that the cytopathic effects were caused by infection with a retrovirus, feline foamy virus (FFV). Using transmission electron microscopy, polymerase chain reaction, and in vitro assays, we determined that syncytial cell formation and proliferation arrest in fMSCs were caused by FFV strains that were highly homologous to previously reported FFV strains. We determined that the antiretroviral drug, tenofovir, may be used to support ex vivo expansion and salvage of FFV-infected fMSC lines. MSC lines derived from specific pathogen-free cats do not appear to be infected with FFV and may be a source of allogeneic fMSCs for clinical application. FFV infection of fMSC lines may hinder large-scale expansion of autologous MSC for therapeutic use in feline patients.