Canine mesenchymal stem cells: state of the art, perspectives as therapy for dogs and as a model for man

Canine Mesenchymal Stromal Cell Exosomes: State-of-the-Art Characterization, Functional Analysis and Applications in Various Diseases

Canine mesenchymal stromal cells (MSCs) possess the capacity to differentiate into a variety of cell types and secrete a wide range of bioactive molecules in the form of soluble and membrane-bound exosomes. Extracellular vesicles/exosomes are nano-sized vesicles that carry proteins, lipids, and nucleic acids and can modulate recipient cell response in various ways. The process of exosome formation is a physiological interaction between cells. With a significant increase in basic research over the last two decades, there has been a tremendous expansion in research in MSC exosomes and their potential applications in canine disease models. The characterization of exosomes has demonstrated considerable variations in terms of source, culture conditions of MSCs, and the inclusion of fetal bovine serum or platelet lysate in the cell cultures. Furthermore, the amalgamation of exosomes with various nano-materials has become a novel approach to the fabrication of nano-exosomes. The fabrication of exosomes necessitates the elimination of extrinsic proteins, thus enhancing their potential therapeutic uses in a variety of disease models, including spinal cord injury, osteoarthritis, and inflammatory bowel disease. This review summarizes current knowledge on the characteristics, biological functions, and clinical relevance of canine MSC exosomes and their potential use in human and canine research. As discussed, exosomes have the ability to control lethal vertebrate diseases by administration directly at the injury site or through specific drug delivery mechanisms.

A Comprehensive Exploration of Therapeutic Strategies in Inflammatory Bowel Diseases: Insights from Human and Animal Studies

Inflammatory bowel disease (IBD) is a collective term for a group of chronic inflammatory enteropathies which are characterized by intestinal inflammation and persistent or frequent gastrointestinal signs. This disease affects more than 3.5 million humans worldwide and presents some similarities between animal species, in particular, dogs and cats. Although the underlying mechanism that triggers the disease is not yet well understood, the evidence suggests a multifactorial etiology implicating genetic causes, environmental factors, microbiota imbalance, and mucosa immune defects, both in humans and in dogs and cats. Conventional immunomodulatory drug therapies, such as glucocorticoids or immunosuppressants, are related with numerous adverse effects that limit its long-term use, creating the need to develop new therapeutic strategies. Mesenchymal stromal cells (MSCs) emerge as a promising alternative that attenuates intestinal inflammation by modulating inflammatory cytokines in inflamed tissues, and also due to their pro-angiogenic, anti-apoptotic, anti-fibrotic, regenerative, anti-tumor, and anti-microbial potential. However, this therapeutic approach may have important limitations regarding the lack of studies, namely in veterinary medicine, lack of standardized protocols, and high economic cost. This review summarizes the main differences and similarities between human, canine, and feline IBD, as well as the potential treatment and future prospects of MSCs.

Extracellular Vesicles in Domestic Animals: Cellular Communication in Health and Disease

Apoptotic and healthy cells of domestic animals release membrane-enclosed particles from their plasma membrane. These special structures, called extracellular vesicles, play an important role in intercellular communication. In the past, it was believed that their function was mainly to dispose unwanted cell contents and to help maintain cell homeostasis. However, we now know that they have important roles in health and disease and have diagnostic value as well as great potential for therapy in veterinary medicine. Extracellular vesicles facilitate cellular exchanges by delivering functional cargo molecules to nearby or distant tissues. They are produced by various cell types and are found in all body fluids. Their cargo reflects the state of the releasing parent cell, and despite their small size, this cargo is extraordinarily complex. Numerous different types of molecules contained in vesicles make them an extremely promising tool in the field of regenerative veterinary medicine. To further increase research interest and discover their full potential, some of the basic biological mechanisms behind their function need to be better understood. Only then will we be able to maximize the clinical relevance for targeted diagnostic and therapeutic purposes in various domestic animal species.

Overview of Equine Stem Cells: Sources, Practices, and Potential Safety Concerns

Over the past 2 decades, equine veterinarians are turning increasingly to stem cell therapies to repair damaged tissues or to promote healing through modulation of the immune system. Research is ongoing into optimizing practices associated with stem cell product transport, dosage, and administration. Culture-expanded equine mesenchymal stem cell therapies seem safe, even when used allogeneically, but various safety concerns should be considered. Stem cells and cellular reprogramming tools hold great promise for future equine therapies.

Mesenchymal Stem Cells: Generalities and Clinical Significance in Feline and Canine Medicine

Mesenchymal stem cells (MSCs) are multipotent cells: they can proliferate like undifferentiated cells and have the ability to differentiate into different types of cells. A considerable amount of research focuses on the potential therapeutic benefits of MSCs, such as cell therapy or tissue regeneration, and MSCs are considered powerful tools in veterinary regenerative medicine. They are the leading type of adult stem cells in clinical trials owing to their immunosuppressive, immunomodulatory, and anti-inflammatory properties, as well as their low teratogenic risk compared with pluripotent stem cells. The present review details the current understanding of the fundamental biology of MSCs. We focus on MSCs' properties and their characteristics with the goal of providing an overview of therapeutic innovations based on MSCs in canines and felines.

Characterization of canine adipose- and endometrium-derived Mesenchymal Stem/Stromal Cells and response to lipopolysaccharide

Mesenchymal stem/stromal cells (MSCs) are used for regenerative therapy in companion animals. Their potential was initially attributed to multipotency, but subsequent studies in rodents, humans and veterinary species evidenced that MSCs produce factors that are key mediators of immune, anti-infective and angiogenic responses, which are essential in tissue repair. MSCs preparations have been classically obtained from bone marrow and adipose tissue (AT) in live animals, what requires the use of surgical procedures. In contrast, the uterus, which is naturally exposed to external insult and infection, can be accessed nonsurgically to obtain samples, or tissues can be taken after neutering. In this study, we explored the endometrium (EM) as an alternative source of MSCs, which we compared with AT obtained from canine paired samples. Canine AT- and EM-MSCs, formed CFUs when seeded at low density, underwent tri-lineage differentiation into adipocytes, osteocytes and chondrocytes, and expressed the CD markers CD73, CD90 and CD105, at equivalent levels. The immune genes IL8, CCL2 and CCL5 were equally expressed at basal levels by both cell types. However, in the presence of the inflammatory stimulus lipopolysaccharide (LPS), expression of IL8 was higher in EM- than in AT-MSCs (p < 0.04) while the other genes were equally elevated in both cell types (p < 0.03). This contrasted with the results for CD markers, where the expression was unaltered by exposing the MSCs to LPS. Overall, the results indicate that canine EM-MSCs could serve as an alternative cell source to AT-MSCs in therapeutic applications.

In vitro investigation of canine periodontal ligament-derived mesenchymal stem cells: A possibility of promising tool for periodontal regeneration

Objectives

Recent investigations indicate that canine periodontal ligament-derived stem cells (cPDLSCs) may reveal a reliable strategy for repair of periodontal tissues via cell-based tissue engineering approaches. Due to limited research, this study aimed to demonstrate the phenotypic characterization of cPDLSc in comparison with canine bone marrow-derived mesenchymal stem cells (cBMSCs) in vitro.

Methods

Mesenchymal stem cells (MSCs) were obtained from PDL and BM of five male adult Mongrel dogs. In vitro isolation and expansion as well as biologic characterization including colony unit formation (CFU), osteogenic and adipogenic differentiation, flow cytometric analysis of CD34 and CD44, and RT-PCR of alkaline phosphatase (ALP), osteocalcin (OCN), periostin (POSTN) and S100A4 were performed. Furthermore, electron microscopy analysis was done to complement the comparative research.

Results

CFU assay revealed that colonies of cPDLSCs presented 70% confluency with a more finite lifespan than BM-MSCs, showing a significant increase in cPDLSCs. Both types of MSCs showed osteogenic and adipogenic phenotypic characterized with clusters of mineralized depositions and lipid vacuoles, respectively. Both types of MSCs expressed CD44 with limited expression of CD34. RT-PCR of cPDLSCs revealed that expression of ALP, POSTN, OCN and S100A4 genes were significantly higher than those of BMSCs. In addition, comparison of SEM and revealed that cPDLSCs expressed more extracellular collagen fibers.

Conclusions

The current study indicated that cPDLSCs show potency as a novel cellular therapy for periodontal regeneration a large animal model.

Characterization and differentiation potential of mesenchymal stem cells isolated from multiple canine adipose tissue sources

Background

Mesenchymal stem cells (MSCs) are undifferentiated cells that can give rise to a mesoderm lineage. Adipose-derived MSCs are an easy and accessible source for MSCs isolation, although each source of MSC has its own advantages and disadvantages. Our study identifies a promising source for the isolation and differentiation of canines MSCs. For this purpose, adipose tissue from inguinal subcutaneous (SC), perirenal (PR), omental (OM), and infrapatellar fat pad (IPFP) was isolated and processed for MSCs isolation. In the third passage, MSCs proliferation/metabolism, surface markers expression, in vitro differentiation potential and quantitative reverse transcription PCR (CD73, CD90, CD105, PPARγ, FabP4, FAS, SP7, Osteopontin, and Osteocalcin) were evaluated.

Results

Our results showed that MSCs derived from IPFP have a higher proliferation rate, while OM-derived MSCs have higher cell metabolism. In addition, MSCs from all adipose tissue sources showed positive expression of CD73 (NT5E), CD90 (THY1), CD105 (ENDOGLIN), and very low expression of CD45. The isolated canine MSCs were successfully differentiated into adipogenic and osteogenic lineages. The oil-red-O quantification and adipogenic gene expression (FAS, FabP4, and PPARγ) were higher in OM-derived cells, followed by IPFP-MSCs. Similarly, in osteogenic differentiation, alkaline phosphatase activity and osteogenic gene (SP7 and Osteocalcin) expression were higher in OM-derived MSCs, while osteopontin expression was higher in PR-derived MSCs.

Conclusion

In summary, among all four adipose tissue sources, OM-derived MSCs have better differentiation potential toward adipo- and osteogenic lineages, followed by IPFP-MSCs. Interestingly, among all adipose tissue sources, MSCs derived from IPFP have the maximum proliferation potential. The characterization and differentiation potential of canine MSCs isolated from four different adipose tissue sources are useful to assess their potential for application in regenerative medicine.

Novel immortalization approach defers senescence of cultured canine adipose-derived mesenchymal stromal cells

In the last decades, the scientific community spared no effort to elucidate the therapeutic potential of mesenchymal stromal cells (MSCs). Unfortunately, in vitro cellular senescence occurring along with a loss of proliferative capacity is a major drawback in view of future therapeutic applications of these cells in the field of regenerative medicine. Even though insight into the mechanisms of replicative senescence in human medicine has evolved dramatically, knowledge about replicative senescence of canine MSCs is still scarce. Thus, we developed a high-content analysis workflow to simultaneously investigate three important characteristics of senescence in canine adipose-derived MSCs (cAD-MSCs): morphological changes, activation of the cell cycle arrest machinery, and increased activity of the senescence-associated β-galactosidase. We took advantage of this tool to demonstrate that passaging of cAD-MSCs results in the appearance of a senescence phenotype and proliferation arrest. This was partially prevented upon immortalization of these cells using a newly designed PiggyBac™ Transposon System, which allows for the expression of the human polycomb ring finger proto-oncogene BMI1 and the human telomerase reverse transcriptase under the same promotor. Our results indicate that cAD-MSCs immortalized with this new vector maintain their proliferation capacity and differentiation potential for a longer time than untreated cAD-MSCs. This study not only offers a workflow to investigate replicative senescence in eukaryotic cells with a high-content analysis approach but also paves the way for a rapid and effective generation of immortalized MSC lines. This promotes a better understanding of these cells in view of future applications in regenerative medicine.

Case Report: Successful Therapy of Spontaneously Occurring Canine Degenerative Lumbosacral Stenosis Using Autologous Adipose Tissue-Derived Mesenchymal Stem Cells

The management of degenerative lumbosacral stenosis (DLSS) in dogs usually requires aggressive, costly surgical treatments that may themselves present complications, while do not fully resolve the symptoms of the disease. In this study, the dog diagnosed with severe DLSS, with hind limb paresis, was treated using a new and least invasive treatment. Cultured autologous adipose tissue-derived mesenchymal stem cells (AT-MSCs) were injected bilaterally at the level of L7-S1, in the vicinity of the external aperture of the intervertebral foramen of DLSS patient. In the previously described treatments of spontaneous intervertebral disc degeneration in dogs, intradiscal injections of MSCs did not lead to positive effects. Here, we report a marked improvement in clinical outcome measures related to the ability of a dog to walk and trot, which were expressed by a numeric rating scale based on a veterinary assessment questionnaire. The improved status persisted throughout the observed time course of 4.5 years after the AT-MSC transplantation. To the best of our knowledge, this is the first case of successful therapy, with long-term positive effect, of spontaneously occurring canine DLSS using presented treatment that, we believe, represents a contribution to current knowledge in this field and may shape both animal and human DLSS treatment options.

Intrathecal Transplantation of Autologous and Allogeneic Bone Marrow-Derived Mesenchymal Stem Cells in Dogs

The route used in the transplantation of mesenchymal stem cells (MSCs) can directly affect the treatment success. The transplantation of MSCs via the intrathecal (IT) route can be an important therapeutic strategy for neurological disorders. The objective of this study was to evaluate the safety and feasibility of the IT transplantation of autologous (Auto-MSCs) and allogeneic (Allo-MSCs) bone marrow mesenchymal stem cells (BM-MSCs) in healthy dogs. Based on neurodisability score, cerebrospinal fluid (CSF) and magnetic resonance imaging (MRI), no significant differences from the control group were observed on day 1 or day 5 after IT Auto- or Allo-MSCs transplantation (P > 0.05). In addition, analysis of matrix metalloproteinase (MMP)-2 and MMP-9 expression in the CSF revealed no significant differences (P > 0.05) at 5 days after IT transplantation in the Auto- or Allo-MSCs group when compared to the control. Intrathecal transplantation of BM-MSCs in dogs provides a safe, easy and minimally invasive route for the use of cell-based therapeutics in central nervous system diseases.

The Effect of a 7 Year-Long Cryopreservation on Stemness Features of Canine Adipose-Derived Mesenchymal Stem Cells (cAD-MSC)

Mesenchymal stem cells (MSCs) are used in therapy in animal models and veterinary medicine, due to their capacity of inducing tissue regeneration and immunomodulation. Their clinical application requires a ready off-the-shelf amount of viable therapeutics doses. For this purpose, it is useful to cryopreserve MSCs to gain a ready and controlled source of abundant autologous stem cells. We evaluated the effect of 7 years cryopreservation using 10% dimethyl sulfoxide (DMSO) with different fetal bovine serum (FBS) concentrations (from 10 to 90%) on different passages of MSCs isolated from canine adipose tissue (cAD-MSCs). The study aimed to evaluate the most adequate cell passage and FBS percentage for the long-term cryopreservation of cells by maintaining the stemness features. Phenotype morphology, cell viability, osteogenic and adipogenic differentiation potentials, proliferative potential and expression of pluripotency markers were analyzed in thawed cells and compared with fresh ones. We demonstrated that cells cryopreserved with at least 80% FBS maintain unaltered the stemness characteristics of the freshly isolated cells. In particular, cells of P0-P1 passages have to be expanded in vitro and subsequently cryopreserved and cells of P2-P4 passages should be considered in the studies on therapeutic application and in vitro study of cAD-MSCs.

Review: Mesenchymal Stem Cell Therapy in Canine Osteoarthritis Research: "Experientia Docet" (Experience Will Teach Us)

Osteoarthritis (OA) is currently an incurable and progressive condition in dogs causing chronic joint pain and possibly increasing disability. Due to the poor healing capacity of cartilage lesions that occur with OA, development of effective therapeutics is difficult. For this reason, current OA therapy is mostly limited to the management of pain and inflammation, but not directed ad disease modification. In the search for a safe and effective OA treatment, mesenchymal stem cells (MSCs) have been of great interest since these cells might be able to restore cartilage defects. The designs of OA studies on MSC usage, however, are not always consistent and complete, which limits a clear evaluation of MSC efficacy. The general study results show a tendency to improve lameness, joint pain and range of motion in dogs suffering from naturally-occurring OA. Assessment of the cartilage surface demonstrated the ability of MSCs to promote cartilage-like tissue formation in artificially created cartilage defects. Immunomodulatory capacities of MSCs also seem to play an important role in reducing pain and inflammation in dogs. It should be mentioned, however, that in the current studies in literature there are specific design limitations and further research is warranted to confirm these findings.

The lower in vitro chondrogenic potential of canine adipose tissue-derived mesenchymal stromal cells (MSC) compared to bone marrow-derived MSC is not improved by BMP-2 or BMP-6

Mesenchymal stromal cells (MSC) are used for cell-based treatment for canine osteoarthritis (OA). Compared with human MSCs, detailed information on the functional characterisation of canine MSCs is limited. In particular, the chondrogenic differentiation of canine adipose tissue-derived MSCs (cAT-MSCs) is challenging. In this study, we aimed to compare cAT-MSCs with bone marrow-derived MSCs (cBM-MSCs), focusing specifically on their in vitro chondrogenic potential, with or without bone morphogenetic proteins (BMP). cBM-MSCs and cAT-MSCs were characterised using flow cytometry and reverse transcription-quantitative polymerase chain reaction (RT-qPCR). The chondrogenic differentiation potential of all cMSC preparations in the presence of TGF-β1 alone or when supplemented with 10, 100, or 250 ng/mL BMP-2 or BMP-6 was investigated using RT-qPCR, and biochemical, histochemical and immunohistological analyses. Both cBM-MSCs and cAT-MSCs expressed the surface markers CD90, CD73, and CD29, and were negative for CD45 and CD34, although the expression of CD73 and CD271 varied with donor and tissue origin. Interestingly, expression of ACAN and SOX9 was higher in cBM-MSCs than cAT-MSCs. In contrast with cBM-MSCs, cAT-MSCs could not differentiate toward the chondrogenic lineage without BMP-2/-6, and their in vitro chondrogenesis was inferior to cBM-MSCs with BMP-2/-6. Thus, cAT-MSCs have lower in vitro chondrogenic capacity than cBM-MSC under the studied culture conditions with 10, 100, or 250 ng/mL BMP-2 or BMP-6. Therefore, further characterisation is necessary to explore the potential of cAT-MSCs for cell-based OA treatments.

Xenobiotic-Free Medium Guarantees Expansion of Adipose Tissue-Derived Canine Mesenchymal Stem Cells Both in 3D Fibrin-Based Matrices and in 2D Plastic Surface Cultures

Mesenchymal stem cells (MSCs) have been recently introduced in veterinary medicine as a potential therapeutic tool for several pathologies. The large-scale in vitro expansion needed to ensure the preparation of a suitable number of MSCs for clinical application usually requires the use of xenogeneic supplements like the fetal bovine serum (FBS). The substitution of FBS with species-specific supplements would improve the safety of implanted cells, reducing the risk of undesired immune responses following cell therapy. We have evaluated the effectiveness of canine adipose tissue-derived stromal vascular fraction (SVF) and MSCs (ADMSCs) expansion in the presence of canine blood-derived supplements. Cells were cultured on traditional plastic surface and inside a 3D environment derived from the jellification of different blood-derived products, i.e., platelet-poor plasma (PPP), platelet-rich plasma (PRP), or platelet lysate (PL). PPP, PRP, and PL can contribute to canine ADMSCs in vitro expansion. Both allogeneic and autologous PPP and PL can replace FBS for ADMSCs culture on a plastic surface, exhibiting either a similar (PPP) or a more effective (PL) stimulus to cell replication. Furthermore, the 3D environment based on homospecific blood-derived products polymerization provides a strong stimulus to ADMSCs replication, producing a higher number of cells in comparison to the plastic surface environment. Allogeneic or autologous blood products behave similarly. The work suggests that canine ADMSCs can be expanded in the absence of xenogeneic supplements, thus increasing the safety of cellular preparations. Furthermore, the 3D fibrin-based matrices could represent a simple, readily available environments for effective in vitro expansion of ADMSCs using allogeneic or autologous blood-products.

Administration of mesenchymal stem cells from adipose tissue at the hip joint of dogs with osteoarthritis: A systematic review

This systematic review aimed to determine the effects of intra-articular administration of mesenchymal stem cells from adipose tissue in dogs with hip joint osteoarthritis (OA). Clinical trials were systematically reviewed, using PubMed, EMBASE, Cochrane Library, LILACS, Web of Science, Scopus, Open Grey, Google Scholar, and ProQuest Dissertation and Thesis without publication year restrictions. References were screened and selected based on predefined eligibility criteria by two independent reviewers, according to PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines. Clinical outcomes were assessed quantitatively using clinical pain scores, physical examination, imaging examination, questionnaire responses, pain in manipulation, gait analysis, range of joint motion, and adverse effects. The risk of bias was assessed using the Joanna Briggs Institute Critical Appraisal Checklist. Out of 1483 articles, six met the inclusion criteria for qualitative analysis, with two randomized controlled trials and four before-and-after studies. All studies reported significantly better clinical outcomes in the adipose tissue stem cells (ADSC) group with improvements in pain and function and decreased evidence of hip OA. The risk of bias was categorized as high in the before-and-after studies and moderate to high in the randomized studies. The studies were considered heterogeneous owing to clinical results and methodology. Because of this heterogeneity, it was not possible to perform meta-analysis. Assessments of ADSC reports yielded positive clinical effects that showed improvements in pain and function and decreased evidence of hip osteoarthritis. More high-level, larger-cohort dog studies that utilize standardized protocols are needed.

Canine colostrum exosomes: characterization and influence on the canine mesenchymal stem cell secretory profile and fibroblast anti-oxidative capacity

Background

Canine colostrum milk (CCM) is a specific secretion of the mammary gland that is fundamental for the survival of the newborn. CCM has many described components (immunoglobulins, proteins or fat), but its small vesicles, named exosomes, are largely unknown.

Results

A characterization of CCM exosomes was performed. Exosomes were abundant in CCM and appeared with the characteristic cup-shaped morphology and well-defined round vesicles. The size distribution of exosomes was between 37 and 140 nm, and western blot analysis showed positive expression of specific exosomal markers. Proteomic analysis revealed a total of 826 proteins in exosome cargo. We also found that exosomes modified the proliferation and secretory profiles in canine mesenchymal stem cells derived from bone marrow (cBM-MSCs) and adipose tissue (cAd-MSCs). Additionally, CCM exosomes demonstrated a potent antioxidant effect on canine fibroblasts in culture.

Conclusions

Our findings highlight, for the first time, the abundant presence of exosomes in CCM and their ability to interact with mesenchymal stem cells (MSCs). The addition of exosomes to two types of MSCs in culture resulted in specific secretory profiles with functions related to angiogenesis, migration and chemotaxis of immune cells. In particular, the cAd-MSCs secretory profile showed higher potential in adipose tissue development and neurogenesis, while cBM-MSC production was associated with immunity, cell mobilization and haematopoiesis. Finally, exosomes also presented antioxidant capacity on fibroblasts against reactive oxygen species activity within the cell, demonstrating their fundamental role in the development and maturation of dogs in the early stages of their life.

Supplementary information

Supplementary information accompanies this paper at 10.1186/s12917-020-02623-w.

Canine Bone Marrow Mesenchymal Stem Cell Conditioned Media Affect Bacterial Growth, Biofilm-Associated Staphylococcus aureus and AHL-Dependent Quorum Sensing

The present study investigated the in vitro antibacterial, antibiofilm and anti-Quorum Sensing (anti-QS) activities of canine bone marrow mesenchymal stem cell-conditioned media (cBM MSC CM) containing all secreted factors <30 K, using a disc diffusion test (DDT), spectrophotometric Crystal Violet Assay (SCVA) and Bioluminescence Assay (BA) with QS-reporter Escherichia coli JM109 pSB1142. The results show a sample-specific bacterial growth inhibition (zones varied between 7–30 mm), statistically significant modulation of biofilm-associated Staphylococcus aureus and Escherichia coli bioluminescence (0.391 ± 0.062 in the positive control to the lowest 0.150 ± 0.096 in the experimental group, cf. 11,714 ± 1362 to 7753 ± 700, given as average values of absorbance A₅₅₀ ± SD versus average values of relative light units to growth RLU/A₅₅₀ ± SD). The proteomic analysis performed in our previous experiment revealed the presence of several substances with documented antibacterial, antibiofilm and immunomodulatory properties (namely, apolipoprotein B and D; amyloid-β peptide; cathepsin B; protein S100-A4, galectin 3, CLEC3A, granulin, transferrin). This study highlights that cBM MSC CM may represent an important new approach to managing biofilm-associated and QS signal molecule-dependent bacterial infections. To the best of our knowledge, there is no previous documentation of canine BM MSC CM associated with in vitro antibiofilm and anti-QS activity.

Is Stem Cell Commerce in Small Animal Therapies Scientifically and Morally Justified?

The lack of clear regulations for the use of veterinary stem cells has triggered the commercialization of unproven experimental therapies for companion animal diseases. Adult stem cells have complex biological characteristics that are directly related to the therapeutic application, but several questions remain to be answered. In order to regulate the use of these cells, well-conducted, controlled scientific studies that generate high-quality data should be performed, in order to assess the efficacy and safety of the intended treatment. This paper discusses the scientific challenges of mesenchymal stem cell therapy in veterinary regenerative medicine, and reviews published trials of adipose-tissue-derived stem cells in companion animal diseases that spontaneously occur.

Modular Orthopaedic Tissue Engineering With Implantable Microcarriers and Canine Adipose-Derived Mesenchymal Stromal Cells

Mesenchymal stromal cells (MSC) hold significant potential for tissue engineering applications. Modular tissue engineering involves the use of cellularized "building blocks" that can be assembled via a bottom-up approach into larger tissue-like constructs. This approach emulates more closely the complexity associated hierarchical tissues compared with conventional top-down tissue engineering strategies. The current study describes the combination of biodegradable porous poly(DL-lactide-co-glycolide) (PLGA) TIPS microcarriers with canine adipose-derived MSC (cAdMSC) for use as implantable conformable building blocks in modular tissue engineering applications. Optimal conditions were identified for the attachment and proliferation of cAdMSC on the surface of the microcarriers. Culture of the cellularized microcarriers for 21 days in transwell insert plates under conditions used to induce either chondrogenic or osteogenic differentiation resulted in self-assembly of solid 3D tissue constructs. The tissue constructs exhibited phenotypic characteristics indicative of successful osteogenic or chondrogenic differentiation, as well as viscoelastic mechanical properties. This strategy paves the way to create in situ tissue engineered constructs via modular tissue engineering for therapeutic applications.

A Protocol for the Isolation, Culture, and Cryopreservation of Umbilical Cord-Derived Canine Mesenchymal Stromal Cells: Role of Cell Attachment in Long-Term Maintenance

Mesenchymal stromal cells (MSCs) hold great promise in the field of regenerative medicine due to their ability to create a variable localized anti-inflammatory effect in injuries such as Crohn's disease and osteoarthritis or by incorporation in tissue engineered constructs. Currently, the MSC literature uses rodents for preclinical disease models. There is growing interest in using naturally occurring disease in large animals for modeling human disease. By review of the canine MSCs literature, it appears that canine MSCs can be difficult to maintain in culture for extended passages and this greatly varies between tissue sources, compared with human and rodent MSCs, and limited lifespan is an obstacle for preclinical investigation and therapeutic use. Research using canine MSCs has been focused on cells derived from bone marrow or adipose tissue, and the differences in manufacturing MSCs between laboratories are problematic due to lack of standardization. To address these issues, here, a stepwise process was used to optimize canine MSCs isolation, expansion, and cryopreservation utilizing canine umbilical cord-derived MSCs. The culture protocol utilizes coating of tissue culture surfaces that increases cellular adherence, increases colony-forming units-fibroblast efficiency, and decreases population doubling times. Canine MSCs isolated with our protocol could be maintained longer than published canine MSCs methods before senescing. Our improved cryopreservation protocols produce on average >90% viable MSCs at thaw. These methods enable master-bank and working-bank scenarios for allogeneic MSC testing in naturally occurring disease in dogs.

The Use of Allogenic Stromal Vascular Fraction (SVF) Cells in Degenerative Joint Disease of the Spine in Dogs

BACKGROUND/AIM

Stem cells are widely used in regenerative medicine and in clinical practice for the treatment of damaged nerve tissue, myocytes, tendons, and ligaments. The aim of the study was to monitor VEGF levels after the administration of allogenic cellular material (SVF) in the course of treatment of dogs suffering from degenerative joint disease in the spinal region.

MATERIALS AND METHODS

The study was conducted on 10 dogs of both genders, aged between 6 and 13 years in which allogenic stromal vascular fraction of stem cells (SVF) was administered intravenously. The control group was composed of 10 clinically healthy dogs. Before treatment and after 2- and 8-week intervals blood samples were obtained from the study group dogs in order to determine VEGF levels via immunoenzymatic test.

RESULTS

in a few days after the therapy, alleviation of pain symptoms and reduction of lameness were noticed. The VEGF level in 2 weeks after the therapy was significantly elevated (median: 38.77 pg/ml), while in 8 weeks a decrease was observed (median: 18.37 pg/ml). Conlusion: Administration of allogenic stem cells has a positive influence on elevation of the VEGF levels in the blood serum of affected animals as well as their regeneration capacity.

In vitro proliferation and differentiation of canine bone marrow derived mesenchymal stem cells over hydroxyl functionalized CNT substrates

Nanotopography of culture substrate acts as a positive cue in cell-biomaterial based tissue regeneration. Considering the potentiality of carbon nanotubes (CNTs) this study was designed to evaluate its two functionalized form by an in vitro culture condition using canine mesenchymal stem cells as cellular model. Cells were isolated and its behaviour, proliferation and differentiation processes were elucidated onto CNT substrates. Beside the variations in cellular behaviour it was remarkably noted that even though proliferation was reduced but osteogenic and chondrogenic differentiation was enhanced over multi-walled CNTs, whereas neuronal differentiation was better supported by single walled CNTs as evidenced by our cytochemical, immunocytochemical, gene expression and flow cytometry assays. The former one was noticed more cytocompatible by our different apoptosis studies. The outcome of these experiments collectively indicated that hydroxylated functionalized CNTs could be a potential scaffold constituent for future experimentations as well as for the application in regenerative medicine.

Mesenchymal stem cells therapy in companion animals: useful for immune-mediated diseases?

Mesenchymal stem cells are multipotent cells, with capacity for self-renewal and differentiation into tissues of mesodermal origin. These cells are possible therapeutic agents for autoimmune disorders, since they present remarkable immunomodulatory ability.The increase of immune-mediated diseases in veterinary medicine has led to a growing interest in the research of these disorders and their medical treatment. Conventional immunomodulatory drug therapy such as glucocorticoids or other novel therapies such as cyclosporine or monoclonal antibodies are associated with numerous side effects that limit its long-term use, leading to the need for developing new therapeutic strategies that can be more effective and safe.The aim of this review is to provide a critical overview about the therapeutic potential of these cells in the treatment of some autoimmune disorders (canine atopic dermatitis, feline chronic gingivostomatitis, inflammatory bowel disease and feline asthma) compared with their conventional treatment.Mesenchymal stem cell-based therapy in autoimmune diseases has been showing that this approach can ameliorate clinical signs or even cause remission in most animals, with the exception of canine atopic dermatitis in which little to no improvement was observed.Although mesenchymal stem cells present a promising future in the treatment of most of these disorders, the variability in the outcomes of some clinical trials has led to the current controversy among authors regarding their efficacy. Mesenchymal stem cell-based therapy is currently requiring a deeper and detailed analysis that allows its standardization and better adaptation to the intended therapeutic results, in order to overcome current limitations in future trials.

Canine Bone Marrow-derived Mesenchymal Stem Cells: Genomics, Proteomics and Functional Analyses of Paracrine Factors

Adult stem cells have become prominent candidates for treating various diseases in veterinary practice. The main goal of our study was therefore to provide a comprehensive study of canine bone marrow-derived mesenchymal stem cells (BMMSC) and conditioned media, isolated from healthy adult dogs of different breeds. Under well-defined standardized isolation protocols, the multipotent differentiation and specific surface markers of BMMSC were supplemented with their gene expression, proteomic profile, and their biological function. The presented data confirm that canine BMMSC express important genes for differentiation toward osteo-, chondro-, and tendo-genic directions, but also genes associated with angiogenic, neurotrophic, and immunomodulatory properties. Furthermore, using proteome profiling, we identify for the first time the dynamic release of various bioactive molecules, such as transcription and translation factors and osteogenic, growth, angiogenic, and neurotrophic factors from canine BMMSC conditioned medium. Importantly, the relevant genes were linked to their proteins as detected in the conditioned medium and further associated with angiogenic activity in chorioallantoic membrane (CAM) assay. In this way, we show that the canine BMMSC release a variety of bioactive molecules, revealing a strong paracrine component that may possess therapeutic potential in various pathologies. However, extensive experimental or preclinical trials testing canine sources need to be performed in order to better understand their paracrine action, which may lead to novel therapeutic strategies in veterinary medicine.

Mesenchymal stem cells in dogs with demyelinating leukoencephalitis as an experimental model of multiple sclerosis

Researchers have used dogs with neurological sequelae caused by distemper as an experimental model for multiple sclerosis, owing to the similarities of the neuropathological changes between distemper virus-induced demyelinating leukoencephalitis and multiple sclerosis in humans. However, little is known about the role of mesenchymal stem cells in treating such clinical conditions. Therefore, we investigated the use of mesenchymal stem cells in four dogs with neurological lesions caused by the distemper virus. During the first year after cellular therapy, the animals did not demonstrate significant changes in their locomotive abilities. However, the intense (Grade V) myoclonus in three animals was reduced to a moderate (Grade IV) level. At one year after the mesenchymal stem cell infusions, three animals regained functional ambulation (Grade I), and all four dogs started to move independently (Grades I and II). In two animals, the myoclonic severity had become mild (Grade III). It was concluded that the use of mesenchymal stem cells could improve the quality of life of dogs with neurological sequelae caused by canine distemper, thus presenting hope for similar positive results in human patients with multiple sclerosis.

Mesenchymal stem cell basic research and applications in dog medicine

The stem cells, owing to their special characteristics like self-renewal, multiplication, homing, immunomodulation, anti-inflammatory, and dedifferentiation are considered to carry an "all-in-one-solution" for diverse clinical problems. However, the limited understanding of cellular physiology currently limits their definitive therapeutic use. Among various stem cell types, currently mesenchymal stem cells are extensively studied for dog clinical applications owing to their readily available sources, easy harvesting, and ability to differentiate both into mesodermal, as well as extramesodermal tissues. The isolated, culture expanded, and characterized cells have been applied both at preclinical as well as clinical settings in dogs with variable but mostly positive results. The results, though positive, are currently inconclusive and demands further intensive research on the properties and their dependence on the applications. Further, numerous clinical conditions of dog resemble to that of human counterparts and thus, if proved rewarding in the former may act as basis of therapy for the latter. The current review throws some light on dog mesenchymal stem cell properties and their potential therapeutic applications.

Extracellular Vesicles from Wharton's Jelly Mesenchymal Stem Cells Suppress CD4 Expressing T Cells Through Transforming Growth Factor Beta and Adenosine Signaling in a Canine Model

Mesenchymal stem cells (MSCs) are widely investigated as potential therapeutic agents due to their potent immunomodulatory capacity. Although specific mechanisms by which MSC acts on immune cells are emerging, many questions remain, including the potential of extracellular vesicles (EVs) to mediate biological activities. Canine MSCs are of interest for both veterinary and comparative models of disease and have been shown to suppress CD4^pos T cell proliferation. The aim of this study was to determine whether EV isolated from canine Wharton's jelly-derived MSC (WJ-MSC EV) suppresses CD4^pos T cell proliferation using biochemical mechanisms previously ascribed to soluble mediators [transforming growth factor beta (TGF-β) and adenosine]. WJ-MSC EV exhibited mode of 125 nm diameter, low buoyant density (1.1 g/mL), and expression of EV proteins Alix and TSG101. Functionally, EVs inhibited CD4^pos T cell proliferation in a dose-dependent manner, which was absent in EV-depleted samples and EVs from non-MSC fibroblasts. EV suppression of CD4^pos T cell proliferation was inhibited by a TGF-βRI antagonist, neutralizing antibodies to TGF-β, or A2A adenosine receptor blockade. TGF-β was present on EVs as latent complexes most likely tethered to EV membrane by betaglycan. These data demonstrate that canine WJ-MSC EV utilizes TGF-β and adenosine signaling to suppress proliferation of CD4^pos T cell and will enable further investigation into mechanisms of immune cell modulation, as well as refinement of WJ-MSC and their EVs for therapeutic application.

Comparative analysis and characterization of soluble factors and exosomes from cultured adipose tissue and bone marrow mesenchymal stem cells in canine species

The two main sources of mesenchymal stem cell (MSCs) in the canine species are bone marrow (cBM-MSCs) and adipose tissue (cAd-MSCs). The secretion of multitude bioactive molecules, included under the concept of secretome and found in the cultured medium, play a predominant role in the mechanism of action of these cells on tissue regeneration. Although certain features of its characterization are well documented, their secretory profiles remain unknown. We described and compared, for the first time, the secretory profile and exosomes characterization in standard monolayer culture of MSCs from both sources of the same donor as well as its immunomodulatory potential. We found that despite the similarity in surface immunophenotyping and trilineage differentiation, there are several differences in terms of proliferation rate and secretory profile. cAd-MSCs have advantages in proliferative capacity, whereas cBM-MSCs showed a significantly higher secretory production of some soluble factors (IL-10, IL-2, IL-6, IL-8, IL-12p40, IFN-γ, VEGF-A, NGF-β, TGF-β, NO and PGE2) and exosomes under the same standard culture conditions. Proteomics analysis confirm that cBM-MSCs exosomes have a greater number of characterized proteins involved in metabolic processes and in the regulation of biological processes compared to cAd-MSCs. On the other hand, secretome from both sources demonstrate similar immunomodulatory capacity when tested in mitogen stimulated lymphocyte reaction, but not in their exosomes at the dose used. Considering that the use of secretome open as a new therapeutic strategy for different diseases, without the need to implant cells, those biological differences should be considered, when choosing the MSCs source, for either cellular implantation or direct use of secretome for a specific clinical application.

The use of canine mesenchymal stem cells for the autologous treatment of osteoarthritis

Mesenchymal stem cells (MSCs) hold enormous potential for cell-based therapy in the treatment of various diseases, particularly those which currently cannot be cured and result in poor outcomes or invasive surgery. Here we present results of the application of autologous, culture-expanded, adipose tissue (AT)-derived MSCs for the osteoarthritis (OA) treatment of 10 canine patients. The stemness of isolated cells has been confirmed by their ability to differentiate into osteo- and chondrocytic lineages. The clinical effect of a single injection of ATMSCs into the symptomatic joints was evaluated by a veterinarian for five disabilities characteristic of OA at 30, 60 and 90 days after treatment, which has been designated as the initial evaluation period. Functional outcomes for all analysed characteristics improved significantly at the end of this evaluation compared with the baseline. In addition, for 5 of these 10 patients, an extended follow-up study was performed from 1 to 4 years after the initial evaluation period. We detected long-lasting positive effects on two out of five analysed characteristics. The results demonstrate that the use of autologous AT-MSCs is a successful approach to canine OA therapy.

A canine in vitro model for evaluation of marrow-derived mesenchymal stromal cell-based bone scaffolds

Tissue engineered bone grafts based on bone marrow mesenchymal stromal cells (MSCs) are being actively developed for craniomaxillofacial (CMF) applications. As for all tissue engineered implants, the bone-regenerating capacity of these MSC-based grafts must first be evaluated in animal models prior to human trials. Canine models have traditionally resulted in improved clinical translation of CMF grafts relative to other animal models. However, the utility of canine CMF models for evaluating MSC-based bone grafts rests on canine MSCs (cMSCs) responding in a similar manner to scaffold-based stimuli as human MSCs (hMSCs). Herein, cMSC and hMSC responses to polyethylene glycol (PEG)-based scaffolds were therefore compared in the presence or absence of osteoinductive polydimethylsiloxane (PDMS). Notably, the conjugation of PDMS to PEG-based constructs resulted in increases in both cMSC and hMSC osteopontin and calcium deposition. Based on these results, cMSCs were further used to assess the efficacy of tethered bone morphogenic protein 2 (BMP2) in enhancing PEG-PDMS scaffold osteoinductivity. Addition of low doses of tethered BMP2 (100 ng/mL) to PEG-PDMS systems increased cMSC expression of osterix and osteopontin compared to both PEG-PDMS and PEG-BMP2 controls. Furthermore, these increases were comparable to effects seen with up to five-times higher BMP2 doses noted in literature. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 106A:2382-2393, 2018.

Beneficial and detrimental impact of transplanted canine adipose-derived stem cells in a virus-induced demyelinating mouse model

In recent years stem cell therapies have been broadly applied in various disease models specifically immune mediated and degenerative diseases. Whether adipose-derived stem cells might represent a useful therapeutic option in virus-triggered central nervous system diseases has not been investigated so far. Theiler's murine encephalomyelitis (TME) and canine distemper encephalitis are established, virus-mediated animal models sharing many similarities with multiple sclerosis (MS). Canine adipose-derived stem cells (ASC) were selected since dogs might serve as an important translational model for further therapeutic applications. The aim of the present study was to investigate whether canine ASC influence clinical signs, axonal damage, demyelination and inflammation during TME. ASC were transplanted intravenously (iv) or intra-cerebroventricularly (icv) at 7 (early) or 42 (late) days post infection (dpi) in TME virus (TMEV) infected mice. TMEV/ASC iv animals transplanted at 7dpi displayed a transient clinical deterioration in rotarod performance compared to TMEV/control animals. Worsening of clinical signs was associated with significantly increased numbers of microglia/macrophages and demyelination in the spinal cord. In contrast, late transplantation had no influence on clinical findings of TMEV-infected animals. However, late TMEV/ASC iv transplanted animals showed reduced axonal damage compared to TMEV/control animals. Screening of spinal cord and peripheral organs for transplanted ASC revealed no positive cells. Surprisingly, iv transplanted animals showed pulmonary follicular aggregates consisting of T- and B-lymphocytes. Thus, our data suggest that following intravenous application, the lung as priming organ for lymphocytes seems to play a pivotal role in the pathogenesis of TME. Consequences of T-lymphocyte priming in the lung depend on the disease phase and may be responsible for disease modifying effects of ASC.

Mesenchymal Stem Cells Form 3D Clusters Following Intraventricular Transplantation

Mesenchymal stem cells (MSCs) are regarded as an immune privileged cell type with numerous regeneration-promoting effects. The in vivo behavior of MSC and underlying mechanisms leading to their regenerative effects are largely unknown. The aims of this study were to comparatively investigate the in vivo behavior of canine (cMSC), human (hMSC), and murine MSC (mMSC) following intra-cerebroventricular transplantation. At 7 days post transplantation (dpt), clusters of cMSC, hMSC, and mMSC were detected within the ventricular system. At 49 dpt, cMSC-transplanted mice showed clusters mostly consisting of extracellular matrix lacking transplanted MSC. Similarly, hMSC-transplanted mice lacked MSC clusters at 49 dpt. Xenogeneic MSC transplantation was associated with a local T lymphocyte-dominated immune reaction at both time points. Interestingly, no associated inflammation was observed following syngeneic mMSC transplantation. In conclusion, transplanted MSC formed intraventricular cell clusters and exhibited a short life span in vivo. Xenogeneically in contrast to syngeneically transplanted MSC triggered a T cell-mediated graft rejection indicating that MSCs are not as immune privileged as previously assumed. However, MSC may mediate their effects by a "hit and run" mechanism and future studies will show whether syngeneically or xenogeneically transplanted MSCs exert better therapeutic effects in animals with CNS disease.

Safety and efficacy of the mesenchymal stem cell in feline eosinophilic keratitis treatment

Background

Feline eosinophilic keratitis (FEK) is a chronic keratopathy caused by a suspected immune mediated response to an unknown antigenic stimulus. The purpose of this study was to investigate the safety and therapeutic effects of allogeneic feline adipose-derived mesenchymal stromal cells (fAd-MSCs) implanted subconjunctival around the ocular surface lesion in five cats with FEK refractory to current available treatments.

Results

FEK was diagnosed by clinical appearance and evidence of eosinophil and/or mast cells in corneal cytology. Each animal was treated with two applications of 2 × 10⁶ million of fAd-MSCs 2 months apart. Ocular surface integrity was assessed before treatment and at 1, 3, 6 and 11 months after treatment. Clinical signs showed a significant change during the follow-up with resolution of the corneal and conjunctiva lesions and there were no signs of regression or worsening.

Conclusions

Implanted cells were well-tolerated and effective reducing clinical signs of FEK with a sustained effect during the study period. None of the animals showed systemic or local complications during the study. To our knowledge, this is the first time in literature that local implantation of allogeneic fAd-MSCs has been found as an effective therapeutic alternative to treat cats with FEK.

In-vitro characterization of canine multipotent stromal cells isolated from synovium, bone marrow, and adipose tissue: a donor-matched comparative study

Background

The dog represents an excellent large animal model for translational cell-based studies. Importantly, the properties of canine multipotent stromal cells (cMSCs) and the ideal tissue source for specific translational studies have yet to be established. The aim of this study was to characterize cMSCs derived from synovium, bone marrow, and adipose tissue using a donor-matched study design and a comprehensive series of in-vitro characterization, differentiation, and immunomodulation assays.

Methods

Canine MSCs were isolated from five dogs with cranial cruciate ligament rupture. All 15 cMSC preparations were evaluated using colony forming unit (CFU) assays, flow cytometry analysis, RT-PCR for pluripotency-associated genes, proliferation assays, trilineage differentiation assays, and immunomodulation assays. Data were reported as mean ± standard deviation and compared using repeated-measures analysis of variance and Tukey post-hoc test. Significance was established at p < 0.05.

Results

All tissue samples produced plastic adherent, spindle-shaped preparations of cMSCs. Cells were negative for CD34, CD45, and STRO-1 and positive for CD9, CD44, and CD90, whereas the degree to which cells were positive for CD105 was variable depending on tissue of origin. Cells were positive for the pluripotency-associated genes NANOG, OCT4, and SOX2. Accounting for donor and tissue sources, there were significant differences in CFU potential, rate of proliferation, trilineage differentiation, and immunomodulatory response. Synovium and marrow cMSCs exhibited superior early osteogenic activity, but when assessing late-stage osteogenesis no significant differences were detected. Interestingly, bone morphogenic protein-2 (BMP-2) supplementation was necessary for early-stage and late-stage osteogenic differentiation, a finding consistent with other canine studies. Additionally, synovium and adipose cMSCs proliferated more rapidly, displayed higher CFU potential, and formed larger aggregates in chondrogenic assays, although proteoglycan and collagen type II staining were subjectively decreased in adipose pellets as compared to synovial and marrow pellets. Lastly, cMSCs derived from all three tissue sources modulated murine macrophage TNF-α and IL-6 levels in a lipopolysaccharide-stimulated coculture assay.

Conclusions

While cMSCs from synovium, marrow, and adipose tissue share a number of similarities, important differences in proliferation and trilineage differentiation exist and should be considered when selecting cMSCs for translational studies. These results and associated methods will prove useful for future translational studies involving the canine model.

Electronic supplementary material

The online version of this article (doi:10.1186/s13287-017-0639-6) contains supplementary material, which is available to authorized users.

A canine liver fibrosis model to develop a therapy for liver cirrhosis using cultured bone marrow-derived cells

We have been developing a therapy for liver cirrhosis using cultured autologous bone marrow-derived mesenchymal stem cells (BMSCs). Before human clinical trials can be considered, the safety and efficacy of BMSC infusion in medium to large animals must be confirmed; thus, we developed a canine liver fibrosis model. A small amount of bone marrow fluid was aspirated from the canine humerus to assess the characteristics of BMSCs. We implanted a venous catheter in the stomach and a subcutaneous infusion port in the back of the neck of each canine. Repeated injection of CCl₄ through the catheter was performed to induce liver cirrhosis. After 10 weeks of CCl₄ injection, eight canines were equally divided into two groups: no cell infusion (control group) and autologous BMSC infusion through the peripheral vein (BMSC group). A variety of assays were carried out before and 4 weeks after the infusion. The area of liver fibrosis stained with sirius red was significantly reduced in the BMSC group 4 weeks after BMSC infusion, consistent with a significantly shortened half-life of indocyanine green and improved liver function. Conclusion: We established a useful canine liver fibrosis model and confirmed that cultured autologous BMSC infusion improved liver fibrosis without adverse effects. (Hepatology Communications 2017;1:691-703).

Functionalized carbon nanotubes as suitable scaffold materials for proliferation and differentiation of canine mesenchymal stem cells

In the field of regenerative medicine, numerous potential applications of mesenchymal stem cells (MSCs) can be envisaged, due to their ability to differentiate into a range of tissues on the basis of the substrate on which they grow. With the advances in nanotechnology, carbon nanotubes (CNTs) have been widely explored for use as cell culture substrate in tissue engineering applications. In this study, canine bone marrow-derived MSCs were considered as the cellular model for an in vitro study to elucidate the collective cellular processes, using three different varieties of thin films of functionalized carbon nanotubes (COOH-single-walled CNTs [SWCNTs], COOH-multiwalled CNTs [MWCNTs] and polyethylene glycol [PEG]-SWCNTs), which were spray dried onto preheated cover slips. Cells spread out better on the CNT films, resulting in higher cell surface area and occurrence of filopodia, with parallel orientation of stress fiber bundles. Canine MSCs proliferated at a slower rate on all types of CNT substrates compared to the control, but no decline in cell number was noticed during the study period. Expression of apoptosis-associated genes decreased on the CNT substrates as time progressed. On flow cytometry after AnnexinV-fluorescein isothiocyanate/propidium iodide (PI) staining, total number of apoptotic and necrotic cells remained lower in COOH-functionalized films compared to PEG-functionalized ones. Collectively, these results indicate that COOH-MWCNT substrate provided an environment of low cytotoxicity. Canine MSCs were further induced to differentiate along osteogenic, chondrogenic, and neuronal lineages by culturing under specific differentiation conditions. The cytochemical and immunocytochemical staining results, as well as the expression of the bone marker genes, led us to hypothesize that the COOH-MWCNT substrate acted as a better cue, accelerating the osteogenic differentiation process. However, while chondrogenesis was promoted by COOH-SWCNT, neuronal differentiation was promoted by both COOH-SWNCT and COOH-MWCNT. Taken together, these findings suggest that COOH-functionalized CNTs represent a promising scaffold component for future utilization in the selective differentiation of canine MSCs in regenerative medicine.

From skeletal muscle to stem cells: an innovative and minimally-invasive process for multiple species

Bone marrow and adipose tissue represent the two most commonly exploited sources of adult mesenchymal stem cells for musculoskeletal applications. Unfortunately the sampling of bone marrow and fat tissue is invasive and does not always lead to a sufficient number of cells. The present study describes a novel sampling method based on microbiopsy of skeletal muscle in man, pigs, dogs and horses. The process includes explant of the sample, Percoll density gradient for isolation and subsequent culture of the cells. We further characterized the cells and identified their clonogenic and immunomodulatory capacities, their immune-phenotyping behavior and their capability to differentiate into chondroblasts, osteoblasts and adipocytes. In conclusion, this report describes a novel and easy-to-use technique of skeletal muscle-derived mesenchymal stem cell harvest, culture, characterization. This technique is transposable to a multitude of different animal species.

Canine Adipose Derived Mesenchymal Stem Cells Transcriptome Composition Alterations: A Step towards Standardizing Therapeutic

Although canine adipose derived stem cells (cASCs) morphology characteristics and differentiation ability are well documented, transcriptome alterations of undifferentiated cASCs during ex vivo cultivation remain unknown. Here we demonstrate, for the first time, the transcriptome composition of isolated cASCs in undifferentiated state originating from six donors. Transcriptome changes were monitored during ex vivo cultivation between passage 3 (P3) and P5, which are mostly used in therapy. Influence of donors' age in given passage number on transcriptome composition was also investigated. Cultivation from P3 to P5 resulted in 16 differentially expressed genes with cooverexpression of pluripotency and self-renewal transcription factors genes SOX2 and POU5F1 dominant in old donors' cells. Furthermore, cASCs demonstrated upregulation of IL-6 in young and old donors' cells. In addition, ex vivo cultivation of cASCs revealed well-known morphological alterations accompanied with decrease in expression of CD90 and CD44 markers in P4 and higher monitored by flow cytometry and successful osteo- and chondrodifferentiation but inefficient adipodifferentiation in P3. Our results revealed the impact of ex vivo cultivation on nature of cells. Correlation of transcriptome changes with secretome composition is needed and its further impact on therapeutic potential of cASCs remains to be evaluated in clinical trials.

Companion animals: Translational scientist's new best friends

Knowledge and resources derived from veterinary medicine represent an underused resource that could serve as a bridge between data obtained from diseases models in laboratory animals and human clinical trials. Naturally occurring disease in companion animals that display the defining attributes of similar, if not identical, diseases in humans hold promise for providing predictive proof of concept in the evaluation of new therapeutics and devices. Here we outline comparative aspects of naturally occurring diseases in companion animals and discuss their current uses in translational medicine, benefits, and shortcomings. Last, we envision how these natural models of disease might ultimately decrease the failure rate in human clinical trials and accelerate the delivery of effective treatments to the human clinical market.

Comparison of Mesenchymal Stem Cell Surface Markers from Bone Marrow Aspirates and Adipose Stromal Vascular Fraction Sites

The objective of this study was to subjectively evaluate the harvest of two areas of adipose collection and three areas of bone marrow collection as potential sites for clinical harvest of adipose stromal vascular fraction (SVF) and bone marrow concentrate for clinical use by quantifying the amount of tissue harvested, subjective ease of harvest, the variation of each site, and determining the cell surface marker characteristics using commercially available antibodies. Bone marrow and adipose tissue samples were collected from 10 adult mixed breed dogs. Adipose tissue was collected from the caudal scapular region and falciform fat ligament. Bone marrow aspirates were collected from the ilium, humerus, and tibia. Tissues were weighed (adipose) or measured by volume (bone marrow), processed to isolate the SVF or bone marrow concentrate, and flow cytometry was performed to quantitate the percentage of cells that were CD90, CD44 positive, and CD45 negative. Sites and tissue types were compared using matched pairs t-test. Subjectively subcutaneous fat collection was the most difficult and large amounts of tissue dissection were necessary. Additionally the subcutaneous area yielded less than the goal amount of tissue. The bone marrow harvest ranged from 10 to 27.5 ml. Adipose tissue had the highest concentration of cells with CD90⁺, CD44⁺, and CD45⁻ markers (P < 0.05), and bone marrow had the highest total number of these cells at harvest (P < 0.05). Variation was high for all sites, but the adipose collection yielded more consistent results. These results describe the relative cellular components in the SVF of adipose tissue and bone marrow as defined by the biomarkers chosen. Although bone marrow yielded higher absolute cell numbers on average, adipose tissue yielded more consistent results. Fat from the falciform ligament was easily obtained with less dissection and therefore created less perceived relative patient trauma.

Characterization and Comparison of Canine Multipotent Stromal Cells Derived from Liver and Bone Marrow

Liver-derived multipotent stromal cells (L-MSCs) may prove preferable for treatment strategies of liver diseases, in comparison to the widely studied bone marrow-derived MSCs (BM-MSCs). Canines are a large animal model, in which the pathologies of liver diseases are similar to man. This study further promotes the implementation of canine models in MSC-based treatments of liver diseases. L-MSCs were characterized and compared to BM-MSCs from the same individual. Both cell types demonstrated a spindle-shaped fibroblast-like morphology, possessed the same growth potential, and demonstrated similar immunomodulation gene expression of CD274, PTGS-1, and PTGS-2. Marked differences in cell surface markers, CD105 and CD146, distinguished these two cell populations, and L-MSCs retained a liver-specific imprinting, observed by expression of CK18 and CK19. Finally, both populations differentiated toward the osteogenic and adipogenic lineage; however, L-MSCs failed to differentiate into the chondrogenic lineage. In conclusion, characterization of canine L-MSCs and BM-MSCs demonstrated that the two cell type populations are highly comparable. Although it is still unclear which cell source is preferred for clinical application in liver treatment strategies, this study provides a foundation for future controlled studies with MSC therapy in various liver diseases in dogs before their application in man.

Mesenchymal stem cells do not exert direct beneficial effects on CNS remyelination in the absence of the peripheral immune system

Remyelination is the natural repair mechanism in demyelinating disorders such as multiple sclerosis (MS) and it was proposed that it might protect from axonal loss. For unknown reasons, remyelination is often incomplete or fails in MS lesions and therapeutic treatments to enhance remyelination are not available. Recently, the transplantation of exogenous mesenchymal stem cells (MSC) has emerged as a promising tool to enhance repair processes. This included the animal model experimental autoimmune encephalomyelitis (EAE), a commonly used model for the autoimmune mechanisms of MS. However, in EAE it is not clear if the beneficial effect of MSC derives from a direct influence on brain resident cells or if this is an indirect phenomenon via modulation of the peripheral immune system. The aim of this study was to determine potential regenerative functions of MSC in the toxic cuprizone model of demyelination that allows studying direct effects on de- and remyelination without the influence of the peripheral immune system. MSC from three different species (human, murine, canine) were transplanted either intraventricularly into the cerebrospinal fluid or directly into the lesion of the corpus callosum at two time points: at the onset of oligodendrocyte progenitor cell (OPC) proliferation or the peak of OPC proliferation during cuprizone induced demyelination. Our results show that MSC did not exert any regenerative effects after cuprizone induced demyelination and oligodendrocyte loss. During remyelination, MSC did not influence the dynamics of OPC proliferation and myelin formation. In conclusion, MSC did not exert direct regenerative functions in a mouse model where peripheral immune cells and especially T lymphocytes do not play a role. We thus suggest that the peripheral immune system is required for MSC to exert their effects and this is independent from a direct influence of the central nervous system.

Regenerative therapy for the management of a large skin wound in a dog

Extensive full-thickness skin wounds are quite common in domestic animals. In these report, following the failure of reconstructive surgery, adipose tissue-derived mesenchymal stem cells, and platelet-rich plasma were successfully used in a dog to improve speed and quality of skin tissue healing, avoiding suffering, and debilitating effects.

Adenovirus-mediated expression of human sodium-iodide symporter gene permits in vivo tracking of adipose tissue-derived stem cells in a canine myocardial infarction model

INTRODUCTION

In vivo tracking of the transplanted stem cells is important in pre-clinical research of stem cell therapy for myocardial infarction. We examined the feasibility of adenovirus-mediated sodium iodide symporter (NIS) gene to cell tracking imaging of transplanted stem cells in a canine infarcted myocardium by clinical single photon emission computed tomography (SPECT).

METHODS

Beagle dogs were injected intramyocardially with NIS-expressing adenovirus-transfected canine stem cells (Ad-hNIS-canine ADSCs) a week after myocardial infarction (MI) development. (99m)Tc-methoxyisobutylisonitrile ((99m)Tc-MIBI) and (99m)Tc-pertechnetate ((99m)TcO4(-)) SPECT imaging were performed for assessment of infarcted myocardium and viable stem cell tracking. Transthoracic echocardiography was performed to monitor any functional cardiac changes.

RESULTS

Left ventricular ejection fraction (LVEF) was decreased after LAD ligation. There was no significant difference in EF between the groups with the stem cell or saline injection. (125)I uptake was higher in Ad-hNIS-canine ADSCs than in non-transfected ADSCs. Cell proliferation and differentiation were not affected by hNIS-carrying adenovirus transfection. (99m)Tc-MIBI myocardial SPECT imaging showed decreased radiotracer uptake in the infarcted apex and mid-anterolateral regions. Ad-hNIS-canine ADSCs were identified as a region of focally increased (99m)TcO4(-) uptake at the lateral wall and around the apex of the left ventricle, peaked at 2 days and was observed until day 9.

CONCLUSIONS

Combination of adenovirus-mediated NIS gene transfection and clinical nuclear imaging modalities enables to trace the fate of transplanted stem cells in infarcted myocardium for translational in vivo cell tracking study for prolonged duration.

Use of adipose-derived mesenchymal stem cells in keratoconjunctivitis sicca in a canine model

Keratoconjunctivitis sicca (KCS) or dry eye disease (DED) is an immune-mediated multifactorial disease, with high level of prevalence in humans and dogs. Our aim in this study was to investigate the therapeutic effects of allogeneic adipose-derived mesenchymal stromal cells (Ad-MSCs) implanted around the lacrimal glands in 12 dogs (24 eyes) with KCS, which is refractory to current available treatments. Schirmer tear test (STT) and ocular surface integrity were assessed at 0 (before treatment), 3, 6, and 9 months after treatment. Average STT values and all clinical signs showed a statistically significant change (P < 0.001) during the follow-up with reduction in all ocular parameters scored: ocular discharge, conjunctival hyperaemia, and corneal changes, and there were no signs of regression or worsening. Implanted cells were well tolerated and were effective reducing clinical signs of KCS with a sustained effect during the study period. None of the animals showed systemic or local complications during the study. To our knowledge, this is the first time in literature that implantation of allogeneic Ad-MSCs around lacrimal glands has been found as an effective therapeutic alternative to treat dogs with KCS. These results could reinforce a good effective solution to be extrapolated to future studies in human.