Clinicopathologic findings following intra-articular injection of autologous and allogeneic placentally derived equine mesenchymal stem cells in horses

Stem Cell-Based Therapies for Glaucoma Treatment: A Review Bridging the Gap in Veterinary Patients

Retinal diseases are characterized by progressive damage to retinal cells, leading to irreversible vision loss. Among these, glaucoma stands out as a multifactorial neurodegenerative disease involving elevated intraocular pressure, retinal ganglion cell apoptosis, and optic nerve damage, ultimately resulting in blindness in both humans and dogs. Stem cell-based therapies have emerged as a promising therapeutic option for such conditions due to their regenerative and neuroprotective potential. These therapies, particularly those based on mesenchymal stem cells, offer the potential to repair and protect retinal tissues through the bioactive molecules (growth factors, cytokines, chemokines) secreted, their secretome. However, research in this field, especially on the use of umbilical cord mesenchymal stem cells' secretome, remains sparse. Most clinical trials focus on human glaucomatous patients, leaving a significant gap in veterinary patients' application, especially in dogs, with additional research being needed to determine its usefulness in canine glaucoma treatment. Future studies should aim to evaluate these therapies across both human and veterinary contexts, broadening treatment possibilities for glaucoma.

Therapeutic Potential in Wound Healing of Allogeneic Use of Equine Umbilical Cord Mesenchymal Stem Cells

Wound healing after skin injury is a complex process, particularly in equines where leg wounds are prevalent and their repair is complicated due to the anatomical characteristics. Conventional treatments are not effective enough. The umbilical cord offers an unlimited source of adult mesenchymal stem cells (ucMSCs) from Wharton's jelly tissue. The present study aims to demonstrate the safety and therapeutic potential of the allogeneic use of equine ucMSCs (e-ucMSCs) in the healing of severe equine leg wounds. The methods employed were the isolation, culture and expansion of e-ucMSCs. Flow cytometry and a PCR assay were used for cell characterization. This study included an immunomodulation assay, a murine pre-clinical trial and the first phase of an equine clinical trial. Our results showed that e-ucMSCs express a functional HLA-G homolog, EQMHCB2. In the immunomodulation assay, the e-ucMSCs inhibited the proliferation of activated equine peripheral blood mononuclear cells (e-PBMCs). In the murine pre-clinical trial, e-ucMSCs reduced healing time by 50%. In the equine clinical trial, the injection of e-ucMSCs into severe leg lesions improved the closure time and quality of the tissues involved, regenerating them without fibrous tissue scar formation. In conclusion, the results of this study suggest that e-ucMSCs can be used allogeneically for wound healing by creating a tolerogenic environment.

Evaluation of stability and safety of equine mesenchymal stem cells derived from amniotic fluid for clinical application

Amniotic fluid mesenchymal stem cells (AF-MSCs), which can be obtained from fetal tissue, reportedly have self-renewal capacity and multi-lineage differentiation potential. The aim of this study was to identify the biological characteristics of AF-MSCs and evaluate their stability and safety in long-term culture. To confirm the biological characteristics of AF-MSCs, morphology, proliferation capacity, karyotype, differentiation capacity, gene expression level, and immunophenotype were analyzed after isolating AF-MSCs from equine amniotic fluid. AF-MSCs were differentiated into adipocytes, chondrocytes, and osteocytes. Immunophenotype analyses revealed expression levels of ≥95% and ≤ 2% of cells for a positive and negative marker, respectively. Analysis of the MSCs relative gene expression levels of AF-MSCs was approximately at least twice that of the control. The endotoxin level was measured to verify the safety of AF-MSCs and was found to be less than the standard value of 0.5 EU/ml. AF-MSCs were cultured for a long time without any evidence of abnormalities in morphology, proliferation ability, and karyotype. These results suggest that amniotic fluid is a competent source for acquiring equine MSCs and that it is valuable as a cell therapy due to its high stability.

Mesenchymal Stem Cells Isolated from Equine Hair Follicles Using a Method of Air-Liquid Interface

Equine mesenchymal stem cells (MSC) of various origins have been identified in horses, including MSCs from the bone marrow and adipose tissue. However, these stem cell sources are highly invasive in sampling, which thereby limits their clinical application in equine veterinary medicine. This study presents a novel method using an air-liquid interface to isolate stem cells from the hair follicle outer root sheath of the equine forehead skin. These stem cells cultured herewith showed high proliferation and asumed MSC phenotype by expressing MSC positive biomarkers (CD29, CD44 CD90) while not expressing negative markers (CD14, CD34 and CD45). They were capable of differentiating towards chondrogenic, osteogenic and adipogenic lineages, which was comparable with MSCs from adipose tissue. Due to their proliferative phenotype in vitro, MSC-like profile and differentiation capacities, we named them equine mesenchymal stem cells from the hair follicle outer root sheath (eMSCORS). eMSCORS present a promising alternative stem cell source for the equine veterinary medicine.

Effects of intra-articular injection of an acellular equine liquid amniotic allograft in healthy equine joints

OBJECTIVE

Evaluate effects of acellular equine liquid amnion allograft (ELAA) injected into healthy equine joints.

STUDY DESIGN

Randomized, blinded, controlled experiment.

ANIMALS

Eight healthy adult horses.

METHODS

One intercarpal joint (ICJ) of each horse was randomly assigned to be injected with 1.5 ml of ELAA (treatment) while the contralateral ICJ was injected with 1.5 ml of 0.9% NaCl (control). Subjective lameness evaluation, force plate analysis, and synovial fluid analysis, including interleukin-1 receptor antagonist (IL-1ra) analysis, were performed before (day 0) and at days 1, 3, 5, and 10. Synovial fluid analysis was also performed on days 20 and 30.

RESULTS

No difference in subjective lameness (P = .75) and no decrease in peak vertical force or vertical impulse were seen in any limb on any day. Total nucleated cell count (TNCC) was increased in treatment joints on days 1 (P = .0007; T: 6039 cells/μl, C: 240 cells/μl) and 3 (P < .0001; T: 1119 cells/μl, C: 240 cells/μl). Log-10 transformed values for IL-1ra were higher in treated joints on days 1 (P = .0005; T: 3553.7 pg/ml, C: 1890.1 pg/ml) and 3 (P = .01; T: 2283.2 pg/ml, C: 1250.7 pg/ml).

CONCLUSION

Injection of ELAA into the ICJ caused an increase in synovial fluid TNCC in comparison with saline control but no lameness was observed. There was increased IL-1ra on days 1 and 3 after ELAA injection.

CLINICAL SIGNIFICANCE

Intra-articular injection of ELAA into healthy equine joints results in no significant safety concerns. The observed increase in IL-1ra may provide beneficial effects in inflamed joints.

Production of extracellular vesicles from equine embryo-derived mesenchymal stromal cells

In brief

Mesenchymal stromal cell (MSC)-derived extracellular vesicles (EVs) have shown promise as off-the-shelf therapeutics; however, producing them in sufficient quantities can be challenging. In this study, MSCs were isolated from preimplantation equine embryos and used to produce EVs in two commercially available bioreactor designs.

Abstract

Mesenchymal stromal cells (MSC) have recently been explored for their potential use as therapeutics in human and veterinary medicine applications, such as the treatment of endometrial inflammation and infertility. Allogeneic MSC-derived extracellular vesicles (EVs) may also provide therapeutic benefits with advantage of being an 'off-the-shelf' solution, provided they can be produced in large enough quantities, without contamination from bovine EVs contained in fetal bovine serum that is a common component of cell culture media. Toward this aim, we demonstrated the successful isolation and characterization of equine MSCs from preimplantation embryos. We also demonstrate that many of these lines can be propagated long-term in culture while retaining their differentiation potential and conducted a head-to-head comparison of two bioreactor systems for scalable EV production including in serum-free conditions. Based on our findings, the CELLine AD 1000 flasks enabled higher cell density cultures and significantly more EV production than the FiberCell system or conventional culture flasks. These findings will enable future isolation of equine MSCs and the scalable culture of their EVs for a wide range of applications in this rapidly growing field.

Mesenchymal Stem/Stromal Cells Derived from Human and Animal Perinatal Tissues-Origins, Characteristics, Signaling Pathways, and Clinical Trials

Mesenchymal stem/stromal cells (MSCs) are currently one of the most extensively researched fields due to their promising opportunity for use in regenerative medicine. There are many sources of MSCs, of which cells of perinatal origin appear to be an invaluable pool. Compared to embryonic stem cells, they are devoid of ethical conflicts because they are derived from tissues surrounding the fetus and can be safely recovered from medical waste after delivery. Additionally, perinatal MSCs exhibit better self-renewal and differentiation properties than those derived from adult tissues. It is important to consider the anatomy of perinatal tissues and the general description of MSCs, including their isolation, differentiation, and characterization of different types of perinatal MSCs from both animals and humans (placenta, umbilical cord, amniotic fluid). Ultimately, signaling pathways are essential to consider regarding the clinical applications of MSCs. It is important to consider the origin of these cells, referring to the anatomical structure of the organs of origin, when describing the general and specific characteristics of the different types of MSCs as well as the pathways involved in differentiation.

Immune response to allogeneic equine mesenchymal stromal cells

BACKGROUND

Mesenchymal stromal cells (MSCs) are believed to be hypoimmunogeneic with potential use for allogeneic administration.

METHODS

Bone marrow was harvested from Connemara (n = 1), Standardbred (n = 6), and Thoroughbred (n = 3) horses. MSCs were grouped by their level of expression of major histocompatibility factor II (MHC II). MSCs were then sub-grouped by those MSCs derived from universal blood donor horses. MSCs were isolated and cultured using media containing fetal bovine serum until adequate numbers were acquired. The MSCs were cultured in xenogen-free media for 48 h prior to use and during all assays. Autologous and allogeneic MSCs were then directly co-cultured with responder leukocytes from the Connemara horse in varying concentrations of MSCs to leukocytes (1:1, 1:10, and 1:100). MSCs were also cultured with complement present and heat-inactivated complement to determine whether complement alone would decrease MSC viability. MSCs underwent haplotyping of their equine leukocyte antigen (ELA) to determine whether the MHC factors were matched or mismatched between the donor MSCs and the responder leukocytes.

RESULTS

All allogeneic MSCs were found to be ELA mismatched with the responder leukocytes. MHC II-low and universal blood donor MSCs caused no peripheral blood mononuclear cell (PBMC) proliferation, no increase in B cells, and no activation of CD8 lymphocytes. Universal blood donor MSCs stimulated a significant increase in the number of T regulatory cells. Neutrophil interaction with MSCs showed that universal blood donor and MHC II-high allogeneic MSCs at the 6 h time point in co-culture caused greater neutrophil activation than the other co-culture groups. Complement-mediated cytotoxicity did not consistently cause MSC death in cultures with active complement as compared to those with inactivated complement. Gene expression assays revealed that the universal blood donor group and the MHC II-low MSCs were more metabolically active both in the anabolic and catabolic gene categories when cultured with allogeneic lymphocytes as compared to the other co-cultures. These upregulated genes included CD59, FGF-2, HGF, IDO, IL-10, IL-RA, IL-2, SOX2, TGF-β1, ADAMSTS-4, ADAMSTS-5, CCL2, CXCLB/IL-8, IFNγ, IL-1β, and TNFα.

CONCLUSIONS

MHC II-low MSCs are the most appropriate type of allogeneic MSC to prevent activation of the innate and cell-mediated component of the adaptive immune systems and have increased gene expression as compared to other allogeneic MSCs.

Bovine Fetal Mesenchymal Stem Cells Obtained From Omental Adipose Tissue and Placenta Are More Resistant to Cryoprotectant Exposure Than Those From Bone Marrow

Recent studies have shown promise for the development of cellular therapies with mesenchymal stem cells (MSCs) in livestock species, specifically bovines, and cryopreservation is highly relevant for the advancement of these applications. The use of permeable and/or non-permeable cryoprotectant solutions is necessary to reduce cell damage during freezing and thawing, but these same compounds can also cause negative effects on MSCs and their therapeutic properties. Another important factor to consider is the tissue source of MSCs, since it is now known that MSCs from different tissues of the same individual do not behave the same way, so optimizing the type and concentration of cryoprotectants for each cell type is essential to achieve a large and healthy population of MSCs after cryopreservation. Furthermore, sources of MSCs that could provide great quantities, non-invasively and without ethical concerns, such as placental tissue, have great potential for the development of regenerative medicine in livestock species, and have not been thoroughly evaluated. The objective of this study was to compare the viability of bovine fetal MSCs extracted from bone marrow (BM), adipose tissue (AT), and placenta (PT), following their exposure (15 and 30 min) to several solutions of permeable (dimethyl sulfoxide and ethylene glycol) and non-permeable (trehalose) cryoprotectants. Viability assays were performed with Trypan Blue to assess post-exposure plasma membrane integrity. The apoptotic potential was estimated analyzing the mRNA abundance of BAX and BCL-2 genes using quantitative rt-PCR. Based on the results of the study, BM-MSC exhibited significantly lower viability compared to AT-MSC and PT-MSC, at both 15 and 30 min of exposure to cryoprotectant solutions. Nevertheless, viability did not differ among treatments for any of the cell types or timepoints studied. BCL-2 expression was higher in BM-MSC compared to AT-MSC, however, BAX/BCL-2 ratio did not differ. In conclusion, AT-MSC and PT-MSC were more resistant that BM-MSC, which showed higher sensitivity to experimental conditions, regardless of the exposure times, and cryoprotectant solutions used in the study.

Preparation Technique Affects Recipient Immune Targeting of Autologous Mesenchymal Stem Cells

Fetal bovine serum (FBS) is used for MSC preparation in pre-clinical animal models and veterinary applications, recently in US clinical trials, and for MSC products with current foreign market authorizations. The effect of anti-bovine titers, which are common in animals and humans, has not been investigated. In the equine model, where anti-bovine titers are universally high due to routine vaccination, we evaluated the recipient immune response to autologous MSCs prepared with and without FBS. Preparation of MSCs with FBS resulted in post injection inflammation and antibody mediated cytotoxicity of MSCs when compared to MSCs prepared without FBS. Importantly, synovial MSC concentrations were reduced and LPS induced pain was higher, when FBS was used to prepare MSCs, demonstrating reduced efficacy of FBS prepared MSCs. Fetal bovine serum should no longer be utilized for MSC preparation in pre-clinical study, clinical study, or veterinary applications. The use of FBS in previously reported studies, and in MSC therapeutics with current foreign market authorization, should be considered when interpreting results.

Repeated intra-articular administration of equine allogeneic peripheral blood-derived mesenchymal stem cells does not induce a cellular and humoral immune response in horses

OBJECTIVE

The use of mesenchymal stem cells (MSCs) for the treatment of equine joint disease is widely investigated because of their regenerative and immunomodulatory potential. Allogeneic MSCs provide a promising alternative to autologous MSCs, since the former are immediately available and enable a thorough donor screening. However, questions have been raised concerning the immunogenic potential of allogeneic MSCs, especially after repeated administration.

METHODS

Current retrospective study assessed the cellular and humoral immunogenicity of ten jumping and dressage horses with naturally occurring degenerative joint disease which were treated 3 times intra-articularly with a 1 mL stem cell suspension containing 1.4-2.5 million chondrogenic induced equine allogeneic peripheral blood-derived MSCs (ciMSCs) combined with 1 mL equine allogeneic plasma. Stem cells from 2 donor horses were used. Horses were clinically evaluated for joint effusion, presence of pain to palpation and skin surface temperature at the local injection site, joint range of motion, occurrence of adverse events and the presence of ectopic tissue. The cellular immune response was analyzed using a modified mixed lymphocyte reaction and the humoral immune response was investigated using a flow cytometric crossmatch assay by which the presence of alloantibodies against the ciMSCs was evaluated. Presence of anti-bovine serum albumin antibodies was detected via ELISA.

RESULTS

Clinical evaluation of the horses revealed no serious adverse effects or suspected adverse drug reactions and no ectopic tissue formation at the local injection site or in other areas of the body. Generally, repeated administration led to a decrease of horses with joint effusion of the affected joint. Pain to palpation, skin surface temperature and joint range of motion did not increase or even decreased after treatment administration. Allogeneic ciMSCs did not induce a cellular immune response and no alloantibodies were detected in the recipients' serum, regardless the presence of BSA antibodies in 70 % of the horses.

CONCLUSION

Repeated intra-articular injections with allogeneic equine ciMSCs did not elicit clinically relevant adverse events. Furthermore, current study indicates the absence of a cellular or a humoral immune response following repeated intra-articular injections.

[Cell-based therapeutic strategies for osteoarthritis in equine patients - Basic knowledge for clinical practitioners]

Cell-based therapies for the treatment of osteoarthritis in equine patients experienced a real boom within the last few years. In every day medical practice, attending veterinary surgeons extract patient's blood or other autologous tissue samples and process the material for the purpose of administering the resulting product to the same patient under their own responsibility. Although being consistently classified as treatment option within the framework of regenerative medicine, the manufacturing processes, ingredients, and mechanisms of action remain highly diverse among cell-based therapies. Thus, sound knowledge about the latter ones forms the basis for therapeutic decision-making and best possible treatment regimes.

Mesenchymal Stem Cell and MicroRNA Therapy of Musculoskeletal Diseases

The therapeutic effects of mesenchymal stem cells (MSCs) in musculoskeletal diseases (MSDs) have been verified in many human and animal studies. Although some tissues contain MSCs, the number of cells harvested from those tissues and rate of proliferation in vitro are not enough for continuous transplantation. In order to produce and maintain stable MSCs, many attempts are made to induce differentiation from pluripotent stem cells (iPSCs) into MSCs. In particular, it is also known that the paracrine action of stem cell-secreted factors could promote the regeneration and differentiation of target cells in damaged tissue. MicroRNAs (miRNAs), one of the secreted factors, are small non-coding RNAs that regulate the translation of a gene. It is known that miRNAs help communication between stem cells and their surrounding niches through exosomes to regulate the proliferation and differentiation of stem cells. While studies have so far been underway targeting therapeutic miRNAs of MSDs, studies on specific miRNAs secreted from MSCs are still minimal. Hence, our ultimate goal is to obtain sufficient amounts of exosomes from iPSC-MSCs and develop them into therapeutic agents, furthermore to select specific miRNAs and provide safe cell-free clinical setting as a cell-free status with purpose of delivering them to target cells. This review article focuses on stem cell therapy on MSDs, specific microRNAs regulating MSDs and updates on novel approaches.

Fluid Analysis in the Equine Patient: Cerebrospinal, Synovial, and Peritoneal Fluids

Fluid analysis is an important part of the diagnostic work-up of equine patients presenting with disorders of the nervous system, musculoskeletal system, and abdominal cavity. Proper specimen handling and processing are paramount for complete and accurate interpretation of fluid samples. Normal cerebrospinal fluid is a low-cellularity, low-protein fluid requiring specific sample handling to ensure accurate results. Joint and abdominal fluid analyses are completed in practice or submitted for analysis to a reference laboratory. This article discusses fluid sample handling and processing considerations for the equine practitioner and reviews cytologic evaluation of normal and abnormal cerebrospinal, synovial, and peritoneal fluid samples.

Regenerative Medicine for Equine Musculoskeletal Diseases

Simple Summary

Lameness due to musculoskeletal disease is the most common diagnosis in equine veterinary practice. Many of these orthopaedic disorders are chronic problems, for which no clinically satisfactory treatment exists. Thus, high hopes are pinned on regenerative medicine, which aims to replace or regenerate cells, tissues, or organs to restore or establish normal function. Some regenerative medicine therapies have already made their way into equine clinical practice mainly to treat tendon injures, tendinopathies, cartilage injuries and degenerative joint disorders with promising but diverse results. This review summarises the current knowledge of commonly used regenerative medicine treatments and critically discusses their use.

Abstract

Musculoskeletal injuries and chronic degenerative diseases commonly affect both athletic and sedentary horses and can entail the end of their athletic careers. The ensuing repair processes frequently do not yield fully functional regeneration of the injured tissues but biomechanically inferior scar or replacement tissue, causing high reinjury rates, degenerative disease progression and chronic morbidity. Regenerative medicine is an emerging, rapidly evolving branch of translational medicine that aims to replace or regenerate cells, tissues, or organs to restore or establish normal function. It includes tissue engineering but also cell-based and cell-free stimulation of endogenous self-repair mechanisms. Some regenerative medicine therapies have made their way into equine clinical practice mainly to treat tendon injures, tendinopathies, cartilage injuries and degenerative joint disorders with promising results. However, the qualitative and quantitative spatiotemporal requirements for specific bioactive factors to trigger tissue regeneration in the injury response are still unknown, and consequently, therapeutic approaches and treatment results are diverse. To exploit the full potential of this burgeoning field of medicine, further research will be required and is ongoing. This review summarises the current knowledge of commonly used regenerative medicine treatments in equine patients and critically discusses their use.

Do allogeneic bone marrow derived mesenchymal stem cells diminish the inflammatory response to lipopolysaccharide infusion in horses? A pilot study

Endotoxemia is a leading cause of morbidity and mortality in the equine industry, with colic being the most common cause of endotoxemia in horses. The objective of this study was to evaluate the safety and potential efficacy of a single dose of allogeneic equine bone marrow derived mesenchymal stem cells (BM-MSCs) in horses after the IV administration of lipopolysaccharide (LPS). Six horses were administered an IV infusion of 30 ng/kg LPS (O55:B5 Escherichia coli) in 500 ml saline over 30 min. Immediately after infusion test horses (n = 3) were administered 100 × 10⁶ allogeneic BM-MSCs diluted in saline IV and control horses (n = 3) were administered saline. Clinicopathological data, pro-inflammatory cytokine measurements and sCD14 concentrations were compared between groups. No adverse reactions were observed in horses administered BM-MSCs intravenously. There were no significant differences between test and control horses with regard to clinicopathological values or pro-inflammatory cytokine production. At no time point did concentrations of sCD14 exceed the reference range in any horse. Results suggest that administration of a single IV dose of freshly cultured MSCs is safe and well-tolerated in horses with induced endotoxemia. Further study to evaluate their efficacy as a potential therapeutic in a larger number of horses with clinical disease is required.

Mesenchymal Stem/Progenitor Cells: The Prospect of Human Clinical Translation

Mesenchymal stem/progenitor cells (MSCs) are key players in regenerative medicine, relying principally on their differentiation/regeneration potential, immunomodulatory properties, paracrine effects, and potent homing ability with minimal if any ethical concerns. Even though multiple preclinical and clinical studies have demonstrated remarkable properties for MSCs, the clinical applicability of MSC-based therapies is still questionable. Several challenges exist that critically hinder a successful clinical translation of MSC-based therapies, including but not limited to heterogeneity of their populations, variability in their quality and quantity, donor-related factors, discrepancies in protocols for isolation, in vitro expansion and premodification, and variability in methods of cell delivery, dosing, and cell homing. Alterations of MSC viability, proliferation, properties, and/or function are also affected by various drugs and chemicals. Moreover, significant safety concerns exist due to possible teratogenic/neoplastic potential and transmission of infectious diseases. Through the current review, we aim to highlight the major challenges facing MSCs' human clinical translation and shed light on the undergoing strategies to overcome them.

Veterinary Regenerative Medicine for Musculoskeletal Disorders: Can Mesenchymal Stem/Stromal Cells and Their Secretome Be the New Frontier?

Regenerative medicine aims to restore the normal function of diseased or damaged cells, tissues, and organs using a set of different approaches, including cell-based therapies. In the veterinary field, regenerative medicine is strongly related to the use of mesenchymal stromal cells (MSCs), which belong to the body repair system and are defined as multipotent progenitor cells, able to self-replicate and to differentiate into different cell types. This review aims to take stock of what is known about the MSCs and their use in the veterinary medicine focusing on clinical reports on dogs and horses in musculoskeletal diseases, a research field extensively reported in the literature data. Finally, a perspective regarding the use of the secretome and/or extracellular vesicles (EVs) in the veterinary field to replace parental MSCs is provided. The pharmaceuticalization of EVs is wished due to the realization of a Good Manufacturing Practice (GMP product suitable for clinical trials.

Stem Cells in Veterinary Medicine-Current State and Treatment Options

Regenerative medicine is a branch of medicine that develops methods to grow, repair, or replace damaged or diseased cells, organs or tissues. It has gained significant momentum in recent years. Stem cells are undifferentiated cells with the capability to self—renew and differentiate into tissue cells with specialized functions. Stem cell therapies are therefore used to overcome the body's inability to regenerate damaged tissues and metabolic processes after acute or chronic insult. The concept of stem cell therapy was first introduced in 1991 by Caplan, who proposed that massive differentiation of cells into the desired tissue could be achieved by isolation, cultivation, and expansion of stem cells in in vitro conditions. Among different stem cell types, mesenchymal stem cells (MSC) currently seem to be the most suitable for therapeutic purposes, based on their simple isolation and culturing techniques, and lack of ethical issues regarding their usage. Because of their remarkable immunomodulatory abilities, MSCs are increasingly gaining recognition in veterinary medicine. Developments are primarily driven by the limitations of current treatment options for various medical problems in different animal species. MSCs represent a possible therapeutic option for many animal diseases, such as orthopedic, orodental and digestive tract diseases, liver, renal, cardiac, respiratory, neuromuscular, dermal, olfactory, and reproductive system diseases. Although we are progressively gaining an understanding of MSC behavior and their mechanisms of action, some of the issues considering their use for therapy are yet to be resolved. The aim of this review is first to summarize the current knowledge and stress out major issues in stem cell based therapies in veterinary medicine and, secondly, to present results of clinical usage of stem cells in veterinary patients.

Mesenchymal stem cells for treatment of musculoskeletal disease in horses: Relative merits of allogeneic versus autologous stem cells

Mesenchymal stem cells (MSCs) are widely used for treatment of musculoskeletal diseases in horses, but there is ongoing debate regarding the relative safety and efficacy of allogeneic MSCs, compared with autologous equine MSCs. This review summarises the currently available published data regarding the therapeutic use of autologous and allogeneic MSCs in horses. Arguments that have been advanced against the use of allogeneic MSCs include higher risk of immunological reactions and shorter cell survival times following injection. Arguments favouring the use of allogeneic MSCs include the ability to bank cells and reduce the time to treatment, to collect MSCs from younger donor animals and the ability to manipulate banked cells prior to administration. In vitro studies and a limited set of experimental in vivo studies have indicated that adverse immunological reactions may occur when allogeneic MSCs are administered to horses. However, newer studies lack evidence of inflammatory reactions or adverse clinical responses when allogeneic MSCs are administered and compared with autologous MSCs. Thus, while the relative merits of allogeneic vs autologous MSCs for treatment of musculoskeletal injuries in horses have not been fully established, accumulating evidence from studies in horses suggests that allogeneic MSCs maybe a safe alternative to autologous MSCs. Large, properly designed, randomised trials in addition to careful immunological evaluation of short-term and long-term, local and systemic immune responses are needed to more fully resolve the issue.

Animal mesenchymal stem cell research in cartilage regenerative medicine - a review

Healing of articular cartilage is a major clinical challenge as it also lacks a direct vasculature and nerves, and carries a limited number of resident chondrocytes that do not proliferate easily. Damaged articular cartilages are usually replaced by fibrocartilages, which are mechanically and structurally weaker and less resilient. Regenerative medicine involving stem cells is considered to have a definitive potential to overcome the limitations associated with the currently available surgical methods of cartilage repair. Among various stem cell types, mesenchymal stem cells (MSCs) are preferred for clinical applications. These cells can be readily derived from various sources and have the ability to trans-differentiate into various tissue-specific cells, including those of the cartilage by the process of chondrogenesis. Compared to embryonic or induced pluripotent stem cells (iPSCs), no ethical or teratogenic issues are associated with MSCs. These stem cells are being extensively evaluated for the treatment of joint affections and the results appear promising. Unlike human medicine, in veterinary medicine, the literature on stem cell research for cartilage regeneration is limited. This review, therefore, aims to comprehensively discuss the available literature and pinpoint the achievements and limitations associated with the use of MSCs for articular cartilage repair in animal species.

Impact of Mesenchymal Stromal Cells and Their Extracellular Vesicles in a Rat Model of Kidney Rejection

Background

Mesenchymal stromal cells (MSCs) from different sources possess great therapeutic potential due to their immunomodulatory properties associated with allograft tolerance. However, a crucial role in this activity resides in extracellular vesicles (EVs) and signaling molecules secreted by cells. This study aimed to evaluate the immunomodulatory properties of donor and recipient MSCs isolated from adipose tissue (AD) or bone marrow (BM) and their EVs on kidney outcome in a rat kidney transplant model.

Methods

The heterotopic-kidney-transplant Fisher-to-Lewis rat model (F-L) was performed to study mixed cellular and humoral rejection. After kidney transplantation, Lewis recipients were assigned to 10 groups; two control groups; four groups received autologous MSCs (either AD- or BM- MSC) or EVs (derived from both cell types); and four groups received donor-derived MSCs or EVs. AD and BM-EVs were purified by ultracentrifugation. Autologous cell therapies were administered three times intravenously; immediately after kidney transplantation, 4 and 8 weeks, whereas donor-derived cell therapies were administered once intravenously immediately after transplantation. Survival and renal function were monitored. Twelve weeks after kidney transplantation grafts were harvested, infiltrating lymphocytes were analyzed by flow cytometry and histological lesions were characterized.

Results

Autologous AD- and BM-MSCs, but not their EVs, prolonged graft and recipient survival in a rat model of kidney rejection. Autologous AD- and BM-MSCs significantly improved renal function during the first 4 weeks after transplantation. The amelioration of graft function could be associated with an improvement in tubular damage, as well as in T, and NK cell infiltration. On the other side, the application of donor-derived AD-MSC was harmful, and all rats died before the end of the protocol. AD-EVs did not accelerate the rejection. Contrary to autologous MSCs results, the single dose of donor-derived BM-MSCs is not enough to ameliorate kidney graft damage.

Conclusion

EVs treatments did not exert any benefit in our experimental settings. In the autologous setting, BM-MSCs prompted as a potentially promising therapy to improve kidney graft outcomes in rats with chronic mixed rejection. In the donor-derived setting, AD-MSC accelerated progression to end-stage kidney disease. Further experiments are required to adjust timing and dose for better long-term outcomes.

Clinical safety of intratesticular transplantation of allogeneic bone marrow multipotent stromal cells in stallions

Although stem cell therapy is a promising alternative for treatment of degenerative diseases, there are just few reports on the use of stem cells therapy in horse's reproductive system. This study aims to evaluate the effect of intratesticular injection of bone marrow mesenchymal stromal/stem cells (MSCs) in healthy stallions, and its outcome on seminal parameters and fertility. In Experiment 1, 24 stallions were divided into treatment group (TG) and control group (CG). In the TG, an intratesticular application of MSC was performed, and in the CG, only PBS was used. Measurements of testicular volume, surface temperature and Doppler ultrasonography were performed 24 and 48 hr after treatments. Fifteen days after application, the testicles were removed and submitted to histological analysis. In Experiment 2, 3 fertile stallions received similarly treatment with MSCs. Physical examination and sperm analysis were performed weekly during 60 days after treatment, and at the end, semen from one of them was used for artificial inseminations of 6 healthy mares. In Experiment 1, clinical examinations showed no signals of acute inflammation on both groups according to the analysed variables (p > .05). Also, no signal of chronic inflammation was observed on histological evaluation. In Experiment 2, stallions presented no physical alterations or changes in sperm parameters, and a satisfactory fertility rate (83%; 5/6) was observed after AI. The results support the hypothesis that intratesticular application of bone marrow MSCs is a safe procedure, and this could be a promising alternative to treat testicular degenerative conditions.

The Potential of Mesenchymal Stem Cells to Treat Systemic Inflammation in Horses

One hallmark of mesenchymal stem cells (MSCs) is the ability to differentiate into multiple tissue types which assists in tissue regeneration. Another hallmark of MSCs is their potent anti-inflammatory and immunomodulatory properties and the potential to treat inflammatory, immune-mediated, and ischemic conditions. In equine practice, MSCs have shown efficacy in the treatment of musculoskeletal disorders such as tendinopathy, meniscal tears and cartilage injury. However, there are many equine disease processes and conditions that may benefit from the immunomodulatory properties of MSCs. Examples include conditions associated with overwhelming acute inflammatory response such as systemic inflammatory response syndrome to chronic diseases characterized by a prolonged low level of inflammation such as equine asthma and recurrent uveitis. For the acute inflammatory response processes, there is often high morbidity and mortality with no effective immunomodulatory treatment to prevent the overwhelming synthesis of proinflammatory mediators. For chronic inflammatory disease processes, frequently long-term corticosteroid treatment is the therapeutic mainstay, with serious potential complications. Thus, there is an unmet need for alternative anti-inflammatory treatments for both acute and chronic illnesses in horses. While MSCs show promise for such conditions, much research is needed before a clinically safe and effective treatment will be available. Optimal MSC tissue source, patient vs. donor source (autologous vs. allogeneic) and cell growth conditions need to be determined for each problem. For immediate use, allogeneic MSC treatments is preferable, but immune tolerance and adequate safety require further study. MSC collection and cryopreservation from horses before they are injured or ill, whether from umbilical cord tissue, bone marrow or adipose might become more widespread. Once these fundamental approaches to treating specific diseases with MSCs are determined, the route of administration, dose and timing of administration also need to be studied. To provide a framework for development of MSC immunomodulatory treatments, this article reviews the current understanding of equine MSC anti-inflammatory and immunomodulatory properties and proposes how MSC therapy may be further developed to treat acute onset systemic inflammatory processes and chronic inflammatory diseases.

Differentiation of equine induced pluripotent stem cells into mesenchymal lineage for therapeutic use

In previous work, we established an equine induced pluripotent stem cell line (E-iPSCs) from equine adipose-derived stem cells (ASCs) using a lentiviral vector encoding four transcription factors: Oct4, Sox2, Klf4, and c-Myc. In the current study, we attempted to differentiate these established E-iPSCs into mesenchymal stem cells (MSCs) by serial passaging using MSC-defined media for stem cell expansion. Differentiation of the MSCs was confirmed by analyzing expression levels of the MSC surface markers CD44 and CD29, and the pluripotency markers Nanog and Oct4. Results indicated that the E-iPSC-derived MSCs (E-iPSC-MSCs) retained the characteristics of MSCs, including the ability to differentiate into chondrogenic, osteogenic, or myogenic lineages. E-iPSC-MSCs were rendered suitable for therapeutic use by inhibiting immune rejection through exposure to transforming growth factor beta 2 (TGF-β2) in culture, which down-regulated the expression of major histocompatibility complex class I (MHC class I) proteins that cause immune rejection if they are incompatible with the MHC antigen of the recipient. We reported 16 cases of E-iPSC-MSC transplantations into injured horses with generally positive effects, such as reduced lameness and fraction lines. Our findings indicate that E-iPSC-MSCs can demonstrate MSC characteristics and be safely and practically used in the treatment of musculoskeletal injuries in horses.

Comparison of efficacy and safety of single versus repeated intra-articular injection of allogeneic neonatal mesenchymal stem cells for treatment of osteoarthritis of the metacarpophalangeal/metatarsophalangeal joint in horses: A clinical pilot study

The purpose of this prospective study was to evaluate the effects of single and repeated intra-articular administration of allogeneic, umbilical cord-derived, neonatal mesenchymal stem cells (MSC) in horses with lameness due to osteoarthritis (OA) of a metacarpophalangeal joint (MPJ).

Twenty-eight horses were included. Horses were divided into two groups. Horses in group MSC1 received an MSC injection at M0 and a placebo injection at M1 (1 month after M0). Horses in group MSC2 received MSC injections at M0 and at M1. Joint injections were performed with a blinded syringe. Clinical assessment was performed by the treating veterinarian at M1, M2 and M6 (2 and 6 months after M0), including lameness evaluation, palpation and flexion of the joint. Radiographic examination of the treated joints was performed at inclusion and repeated at M6. Radiographs were anonymized and assessed by 2 ECVDI LA associate members. Short term safety assessment was performed by owner survey. A 2-month rehabilitation program was recommended to veterinarians. There was a significant improvement of the total clinical score for horses in both groups. There was no significant difference in the total clinical score between groups MSC1 and MSC2 at any time point in the study. There was no significant difference in the total radiographic OA score, osteophyte score, joint space width score and subchondral bone score between inclusion and M6. Owner-detected adverse effects to MSC injection were recorded in 18% of the horses. Lameness caused by OA improved significantly over the 6-month duration of the study after treatment with allogeneic neonatal umbilical cord-derived MSCs combined with 8 weeks rest and rehabilitation. There is no apparent clinical benefit of repeated intra-articular administration of MSCs at a 1-month interval in horses with MPJ OA when compared to the effect of a single injection.

Intra-Articular Injection of 2 Different Dosages of Autologous and Allogeneic Bone Marrow- and Umbilical Cord-Derived Mesenchymal Stem Cells Triggers a Variable Inflammatory Response of the Fetlock Joint on 12 Sound Experimental Horses

Osteoarthritis is a significant and costly cause of pain for both humans and horses. The horse has been identified as a suitable model for human osteoarthritis. Regenerative therapy with allogeneic mesenchymal stem cells (MSCs) is a promising treatment, but the safety of this procedure continues to be debated. The aim of this study is to evaluate the safety of intra-articular injections of allogeneic MSCs on healthy joints by comparing two different dosages and two different tissue sources, namely, bone marrow and umbilical cord blood, with a placebo treatment on the same individuals. We also assessed the influence of autologous versus allogeneic cells for bone marrow-derived MSC treatment. Twelve clinically sound horses were subjected to injections in their 4 fetlock joints. Each of the three fetlocks was administered a different MSC type, and the remaining fetlock was injected with phosphate-buffered saline as a control. Six horses received 10 million cells per joint, and the 6 other horses received 20 million cells per joint. Clinical and ultrasound monitoring revealed that allogeneic bone marrow-derived MSCs induced significantly more synovial effusion compared to umbilical cord blood-derived MSCs but no significant difference was noted within the synovial fluid parameters. The administration of 10 million cells in horses triggered significantly more inflammatory signs than the administration of 20 million cells. Mesenchymal stem cell injections induced mild to moderate local inflammatory signs compared to the placebo, with individual variability in the sensitivity to the same line of MSCs. Understanding the behavior of stem cells when injected alone is a step towards the safer use of new strategies in stem cell therapy, where the use of either MSC secretome or MSCs combined with biomaterials could enhance their viability and metabolic activity.

Generation and miRNA Characterization of Equine Induced Pluripotent Stem Cells Derived from Fetal and Adult Multipotent Tissues

Introduction

Pluripotent stem cells are believed to have greater clinical potential than mesenchymal stem cells due to their ability to differentiate into almost any cell type of an organism, and since 2006, the generation of patient-specific induced pluripotent stem cells (iPSCs) has become possible in multiple species.

Objectives

We hypothesize that different cell types respond differently to the reprogramming process; thus, the goals of this study were to isolate and characterize equine adult and fetal cells and induce these cells to pluripotency for future regenerative and translational purposes.

Methods

Adult equine fibroblasts (eFibros) and mesenchymal cells derived from the bone marrow (eBMmsc), adipose tissue (eADmsc), and umbilical cord tissue (eUCmsc) were isolated, their multipotency was characterized, and the cells were induced in vitro into pluripotency (eiPSCs). eiPSCs were generated through a lentiviral system using the factors OCT4, SOX2, c-MYC, and KLF4. The morphology and in vitro pluripotency maintenance potential (alkaline phosphatase detection, embryoid body formation, in vitro spontaneous differentiation, and expression of pluripotency markers) of the eiPSCs were characterized. Additionally, a miRNA profile analysis of the mesenchymal and eiPSCs was performed.

Results

Multipotent cells were successfully isolated, but the eBMmsc failed to generate eiPSCs. The eADmsc-, eUCmsc-, and eFibros-derived iPSCs were positive for alkaline phosphatase, OCT4 and NANOG, were exclusively dependent on bFGF, and formed embryoid bodies. The miRNA profile revealed a segregated pattern between the eiPSCs and multipotent controls: the levels of miR-302/367 and the miR-92 family were increased in the eiPSCs, while the levels of miR-23, miR-27, and miR-30, as well as the let-7 family were increased in the nonpluripotent cells.

Conclusions

We were able to generate bFGF-dependent iPSCs from eADmsc, eUCmsc, and eFibros with human OSKM, and the miRNA profile revealed that clonal lines may respond differently to the reprogramming process.

Placental Stem Cells from Domestic Animals: Translational Potential and Clinical Relevance

The field of regenerative medicine is moving toward clinical practice in veterinary science. In this context, placenta-derived stem cells isolated from domestic animals have covered a dual role, acting both as therapies for patients and as a valuable cell source for translational models. The biological properties of placenta-derived cells, comparable among mammals, make them attractive candidates for therapeutic approaches. In particular, stemness features, low immunogenicity, immunomodulatory activity, multilineage plasticity, and their successful capacity for long-term engraftment in different host tissues after autotransplantation, allo-transplantation, or xenotransplantation have been demonstrated. Their beneficial regenerative effects in domestic animals have been proven using preclinical studies as well as clinical trials starting to define the mechanisms involved. This is, in particular, for amniotic-derived cells that have been thoroughly studied to date. The regenerative role arises from a mutual tissue-specific cell differentiation and from the paracrine secretion of bioactive molecules that ultimately drive crucial repair processes in host tissues (e.g., anti-inflammatory, antifibrotic, angiogenic, and neurogenic factors). The knowledge acquired so far on the mechanisms of placenta-derived stem cells in animal models represent the proof of concept of their successful use in some therapeutic treatments such as for musculoskeletal disorders. In the next future, legislation in veterinary regenerative medicine will be a key element in order to certify those placenta-derived cell-based protocols that have already demonstrated their safety and efficacy using rigorous approaches and to improve the degree of standardization of cell-based treatments among veterinary clinicians.

Equine Allogeneic Chondrogenic Induced Mesenchymal Stem Cells Are an Effective Treatment for Degenerative Joint Disease in Horses

Degenerative joint disease is one of the main causes of equine early retirement from pleasure riding or a performance career. The disease is initially triggered by an abnormal loading of normal cartilage or a normal loading of abnormal cartilage. This primary insult is accompanied with joint inflammation, which leads to further progressive degeneration of the articular cartilage and changes in the surrounding tissues. Therefore, in search for an effective treatment, 75 adult horses with early signs of degenerative fetlock joint disease were enrolled in a randomized, multicenter, double-blinded, and placebo-controlled study. Fifty animals were injected intra-articularly with the investigational veterinary product (IVP) consisting of allogeneic chondrogenic induced mesenchymal stem cells (ciMSCs) with equine allogeneic plasma, and 25 horses were injected with 0.9% NaCl (saline) control product. From week 3 to 18 after treatment, lameness scores (P < 0.001), flexion test responses (P < 0.034), and joint effusion scores (P < 0.001) were remarkably superior in IVP-treated horses. Besides nasal discharge in both treatment groups, no adverse events were observed during the entire study period. On long-term follow-up (1 year), significantly more investigational product-treated horses were working at training level or were returned to their previous level of work (P < 0.001).

Persistence of fluorescent nanoparticle-labelled bone marrow mesenchymal stem cells in vitro and after intra-articular injection

Mesenchymal stem cells (MSCs) improve the osteoarthritis condition, but the fate of MSCs after intra-articular injection is unclear. We used fluorescent nanoparticles (quantum dots [QDs]) to track equine MSCs (QD-labelled MSCs [QD-MSCs]) in vivo after intra-articular injection into normal and osteoarthritic joints. One week after injection of QD-MSCs, unlabelled MSCs, or vehicle, we determined the presence of QD-MSCs in synovium and articular cartilage histologically. In vitro, we evaluated the persistence of QDs in MSCs and whether QDs affected proliferation, immunophenotype, or differentiation. In joints injected with QD-MSCs, labelled cells were identified on the synovial membrane and significantly less often on articular cartilage, without differences between normal and osteoarthritic joints. Joints injected with QD-MSCs and MSCs had increased synovial total nucleated cell count and protein compared with vehicle-injected joints. In vitro, QDs persisted in nonproliferating cells for up to 8 weeks (length of the study), but QD fluorescence was essentially absent from proliferating cells within two passages (approximately 3 to 5 days). QD labelling did not affect MSC differentiation into chondrocytes, adipocytes, and osteocytes. QD-MSCs had slightly different immunophenotype from control cells, but whether this was due to an effect of the QDs or to drift during culture is unknown. QD-MSCs can be visualized in histological sections 1 week after intra-articular injection and are more frequently found in the synovial membrane versus cartilage in both normal and osteoarthritic joints. QDs do not alter MSC viability and differentiation potential in vitro. However, QDs are not optimal markers for long-term tracking of MSCs, especially under proliferative conditions.

Photopolymerizable Injectable Cartilage Mimetic Hydrogel for the Treatment of Focal Chondral Lesions: A Proof of Concept Study in a Rabbit Animal Model

BACKGROUND

In this study, we investigate the in vitro and in vivo chondrogenic capacity of a novel photopolymerizable cartilage mimetic hydrogel, enhanced with extracellular matrix analogs, for cartilage regeneration.

PURPOSE

To (1) determine whether mesenchymal stem cells (MSCs) embedded in a novel cartilage mimetic hydrogel support in vitro chondrogenesis, (2) demonstrate that the proposed hydrogel can be delivered in situ in a critical chondral defect in a rabbit model, and (3) determine whether the hydrogel with or without MSCs supports in vivo chondrogenesis in a critical chondral defect.

STUDY DESIGN

Controlled laboratory study.

METHODS

Rabbit bone marrow-derived MSCs were isolated, expanded, encapsulated in the hydrogel, and cultured in chondrogenic differentiation medium for 9 weeks. Compressive modulus was evaluated at day 1 and at weeks 3, 6, and 9. Chondrogenic differentiation was investigated via quantitative polymerase reaction, safranin-O staining, and immunofluorescence. In vivo, a 3 mm-wide × 2-mm-deep chondral defect was created bilaterally on the knee trochlea of 10 rabbits. Each animal had 1 defect randomly assigned to be treated with hydrogel with or without MSCs, and the contralateral knee was left untreated. Hence, each rabbit served as its own matched control. Three groups were established: group A, hydrogel (n = 5); group B, hydrogel with MSCs (n = 5); and group C, control (n = 10). Repair tissue was evaluated at 6 months after intervention.

RESULTS

In vitro, chondrogenesis and the degradable behavior of the hydrogel by MSCs were confirmed. In vivo, the hydrogel could be delivered intraoperatively in a sterile manner. Overall, the hydrogel group had the highest scores on the modified O'Driscoll scoring system (group A, 17.4 ± 4.7; group B, 13 ± 3; group C, 16.7 ± 2.9) ( P = .11) and showed higher safranin-O staining (group A, 49.4% ± 20%; group B, 25.8% ± 16.4%; group C, 36.9% ± 25.2%) ( P = .27), although significance was not detected for either parameter.

CONCLUSION

This study provides the first evidence of the ability to photopolymerize this novel hydrogel in situ and assess its ability to provide chondrogenic cues for cartilage repair in a small animal model. In vitro chondrogenesis was evident when MSCs were encapsulated in the hydrogel.

CLINICAL RELEVANCE

Cartilage mimetic hydrogel may offer a tissue engineering approach for the treatment of osteochondral lesions.

Equine Mesenchymal Stem Cells: Properties, Sources, Characterization, and Potential Therapeutic Applications

Properties like sustained multiplication and self-renewal, and homing and multilineage differentiation to undertake repair of the damaged tissues make stem cells the lifeline for any living system. Therefore, stem cell therapy is regarded to carry immense therapeutic potential. Though the dearth of understanding about the basic biological properties and pathways involved in therapeutic benefits currently limit the application of stem cells in humans as well as animals, there are innumerable reports that suggest clinical benefits of stem cell therapy in equine. Among various stem cell sources, currently adult mesenchymal stem cells (MSCs) are preferred for therapeutic application in horse owing to their easy availability, capacity to modulate inflammation, and promote healing. Also the cells carry very limited teratogenic risk compared to the pluripotent stem cells. Mesenchymal stem cells were earlier considered mainly for musculoskeletal tissues, but now may also be utilized in other diverse clinical problems in horse, and the results may be extrapolated even for human medicine. The current review highlights biological properties, sources, mechanisms, and potential therapeutic applications of stem cells in equine practice.

Differences in the intrinsic chondrogenic potential of equine umbilical cord matrix and cord blood mesenchymal stromal/stem cells for cartilage regeneration

Umbilical cord blood mesenchymal stromal/stem cells (UCB-MSCs) and umbilical cord matrix MSCs (UCM-MSCs) have chondrogenic potential and are alternative sources to standard surgically derived bone marrow or adipose tissue collection for cartilage engineering. However, the majority of comparative studies explore neonatal MSCs potential only on ISCT benchmark assays accounting for some bias in the reproducibility between in vitro and in clinical studies. Therefore, we characterized equine UCB-MSCs and UCM-MSCs and investigated with particular attention their chondrogenesis potential in 3D culture with BMP-2 + TGF-ß1 in normoxia or hypoxia. We carried out an exhaustive characterization of the extracellular matrix generated by both these two types of MSCs after the induction of chondrogenesis through evaluation of hyaline cartilage, hypertrophic and osteogenic markers (mRNA, protein and histology levels). Some differences in hypoxia sensitivity and chondrogenesis were observed. UCB-MSCs differentiated into chondrocytes express an abundant, dense and a hyaline-like cartilage matrix. By contrast, despite their expression of cartilage markers, UCM-MSCs failed to express a relevant cartilage matrix after chondrogenic induction. Both MSCs types also displayed intrinsic differences at their undifferentiated basal status, UCB-MSCs expressing higher levels of chondrogenic markers whereas UCM-MSCs synthesizing higher amounts of osteogenic markers. Our results suggest that UCB-MSCs should be preferred for ex-vivo horse cartilage engineering. How those results should be translated to in vivo direct cartilage regeneration remains to be determined through dedicated study.

Retrospective analysis of local injection site adverse reactions associated with 230 allogenic administrations of bone marrow-derived mesenchymal stem cells in 164 horses

BACKGROUND

Bone marrow-derived mesenchymal stem cells (BM-MSCs) are frequently used in the treatment of musculoskeletal injuries. Fully characterised cells that are readily available for use is optimum. Allogenic BM-MSCs can satisfy the need for rapid treatment, however, their safety has been questioned.

OBJECTIVES

Objectives were to characterise BM-MSCs from an adult donor horse, in vitro, and to identify and describe adverse reactions that occurred following their injection into other horses. We hypothesised that BM-MSCs capable of proliferation, differentiation and lacking MHC II from one donor could be implanted into another individual without significant adverse reactions and the frequency of adverse reactions in clinical cases would be similar to that previously reported for autologous BM-MSCs.

STUDY DESIGN

Retrospective clinical study.

METHODS

BM-MSCs were proliferated and characterised from one donor and cryopreserved for clinical use. Medical records for horses injected with allogenic BM-MSCs from this donor at a single hospital were used. After routine lameness exam, lesions were identified using diagnostic ultrasound or MRI. Post injection reaction was defined as increased pain, swelling, or heat at or near injection site, or increased lameness. Treatments required for each reaction were noted.

RESULTS

BM-MSCs proliferated and underwent differentiation. Cells were found to be negative for MHC-II (<2%) and were viable after cryopreservation and shipping. Ten of 230 (4.35%) injections were noted to be associated with an adverse reaction. Adverse reactions occurred in synovial structures (n = 3) and in soft tissues (n = 7).

MAIN LIMITATIONS

This investigation could underestimate the number and severity of reactions. Mild reactions, such as synovitis, may have been missed. Also, anti-inflammatory drugs could overshadow mild reactions, making them less likely to be detected.

CONCLUSIONS

Fully characterised allogenic BM-MSCs originating from a single donor horse can be administered to horses with soft tissue injuries with a low rate of adverse reaction. The Summary is available in Portuguese - see Supporting Information.

Practical considerations for clinical use of mesenchymal stem cells: From the laboratory to the horse

Since the clinical use of mesenchymal stem cells (MSCs) for treating musculoskeletal injuries is gaining popularity, practitioners should be aware of the factors that may affect MSCs from tissue harvesting for MSC isolation to cell delivery into the injury site. This review provides equine practitioners with up-to-date, practical knowledge for the treatment of equine patients using MSCs. A brief overview of laboratory procedures affecting MSCs is provided, but the main focus is on shipping conditions, routes of administration, injection methods, and which commonly used products can be combined with MSCs and which products should be avoided as they have deleterious effects on cells. There are still several knowledge gaps regarding MSC-based therapies in horses. Therefore, it is important to properly manage the factors which are currently known to affect MSCs, to further strengthen the evidence basis of this treatment.

Cell-Based Therapies for Joint Disease in Veterinary Medicine: What We Have Learned and What We Need to Know

Biological cell-based therapies for the treatment of joint disease in veterinary patients include autologous-conditioned serum, platelet-rich plasma, and expanded or non-expanded mesenchymal stem cell products. This narrative review outlines the processing and known mechanism of action of these therapies and reviews current preclinical and clinical efficacy in joint disease in the context of the processing type and study design. The significance of variation for biological activity and consequently regulatory approval is also discussed. There is significant variation in study outcomes for canine and equine cell-based products derived from whole blood or stem cell sources such as adipose and bone marrow. Variation can be attributed to altering bio-composition due to factors including preparation technique and source. In addition, study design factors like selection of cases with early vs. late stage osteoarthritis (OA), or with intra-articular soft tissue injury, influence outcome variation. In this under-regulated field, variation raises concerns for product safety, consistency, and efficacy. Cell-based therapies used for OA meet the Food and Drug Administration’s (FDA’s) definition of a drug; however, researchers must consider their approach to veterinary cell-based research to meet future regulatory demands. This review explains the USA’s FDA guidelines as an example pathway for cell-based therapies to demonstrate safety, effectiveness, and manufacturing consistency. An understanding of the variation in production consistency, effectiveness, and regulatory concerns is essential for practitioners and researchers to determine what products are indicated for the treatment of joint disease and tactics to improve the quality of future research.

A Comparison of Bone Marrow and Cord Blood Mesenchymal Stem Cells for Cartilage Self-Assembly

Joint injury is a common cause of premature retirement for the human and equine athlete alike. Implantation of engineered cartilage offers the potential to increase the success rate of surgical intervention and hasten recovery times. Mesenchymal stem cells (MSCs) are a particularly attractive cell source for cartilage engineering. While bone marrow-derived MSCs (BM-MSCs) have been most extensively characterized for musculoskeletal tissue engineering, studies suggest that cord blood MSCs (CB-MSCs) may elicit a more robust chondrogenic phenotype. The objective of this study was to determine a superior equine MSC source for cartilage engineering. MSCs derived from bone marrow or cord blood were stimulated to undergo chondrogenesis through aggregate redifferentiation and used to generate cartilage through the self-assembling process. The resulting neocartilage produced from either BM-MSCs or CB-MSCs was compared by measuring mechanical, biochemical, and histological properties. We found that while BM constructs possessed higher tensile properties and collagen content, CB constructs had superior compressive properties comparable to that of native tissue and higher GAG content. Moreover, CB constructs had alkaline phosphatase activity, collagen type X, and collagen type II on par with native tissue suggesting a more hyaline cartilage-like phenotype. In conclusion, while both BM-MSCs and CB-MSCs were able to form neocartilage, CB-MSCs resulted in tissue more closely resembling native equine articular cartilage as determined by a quantitative functionality index. Therefore, CB-MSCs are deemed a superior source for the purpose of articular cartilage self-assembly.

Concepts and challenges in the use of mesenchymal stem cells as a treatment for cartilage damage in the horse

Osteoarthritis (OA), the most common form of joint disease affecting humans and horses, is characterized by the advance and decline of cartilage and loss of function of the affected joint. The progression of OA is steadily accompanied with biochemical events, which interfere with the cytokines and proteolytic enzymes responsible for progress of the disease. Recently, regenerative therapies have been used with an assumption that mesenchymal stem cells (MSCs) possess the potential to prevent the advancement of cartilage damage and potentially regenerate the injured tissue with an ultimate goal of preventing OA. We believe that despite various challenges, the use of allogenic versus autologous MSCs in cartilage regeneration, is a major issue which can directly or indirectly affect the other factors including, the timing of implantation, dose or cell numbers for implantation, and the source of MSCs. Current knowledge reporting some of these challenges that the clinicians might face in the treatment of cartilage damage in horses are presented. In this regard we conducted two independent studies. In the first study we compared donor matched bone marrow and synovial fluid - derived equine MSCs in vitro, and showed that the SFMSCs were similar to the BMMSCs in their proliferation, expression of CD29, CD44 and CD90, but, exhibited a significantly different chondrogenesis. Additionally, 3.2-21% of all SFMSCs were positive for MHC II, whereas, BMMSCs were negative. In the second study we observed that injection of both the autologous and allogenic SFMSCs into the tarsocrural joint resulted in elevated levels of total protein and total nucleated cell counts. Further experiments to evaluate the in vivo acute or chronic response to allogenic or autologous MSCs are imperative.

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.

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.

Tenogenically Induced Allogeneic Peripheral Blood Mesenchymal Stem Cells in Allogeneic Platelet-Rich Plasma: 2-Year Follow-up after Tendon or Ligament Treatment in Horses

Poor healing of tendon and ligament lesions often results in early retirement of sport horses. Therefore, regenerative therapies are being explored as potentially promising treatment for these injuries. In this study, an intralesional injection was performed with allogeneic tenogenically induced mesenchymal stem cells and platelet-rich plasma 5-6 days after diagnosis of suspensory ligament (SL) (n = 68) or superficial digital flexor tendon (SDFT) (n = 36) lesion. Clinical, lameness and ultrasonographic evaluation was performed at 6 and 12 weeks. Moreover, a survey was performed 12 and 24 months after treatment to determine how many horses were competing at original level and how many were re-injured. At 6 weeks, 88.2% of SL (n = 68) and 97.3% of SDFT lesions (n = 36) demonstrated moderate ultrasonographic improvement. At 12 weeks, 93.1% of SL (n = 29) and 95.5% of SDFT lesions (n = 22) improved convincingly. Moreover, lameness was abolished in 78.6% of SL (n = 28) and 85.7% (n = 7) of SDFT horses at 12 weeks. After 12 months (n = 92), 11.8% of SL and 12.5% of SDFT horses were re-injured, whereas 83.8 of SL and 79.2% of SDFT returned to previous performance level. At 24 months (n = 89) after treatment, 82.4 (SL) and 85.7% (SDFT) of the horses returned to previous level of performance. A meta-analysis was performed on relevant published evidence evaluating re-injury 24 months after stem cell-based [17.6% of the SL and 14.3% of the SDFT group (n = 89)] versus conventional therapies. Cell therapies resulted in a significantly lower re-injury rate of 18% [95% confidence interval (CI), 0.11-0.25] 2 years after treatment compared to the 44% re-injury rate with conventional treatments (95% CI, 0.37-0.51) based on literature data (P < 0.0001).