Adipose-derived stem cells in veterinary medicine: characterization and therapeutic applications

Insights into the role of adipose-derived stem cells and secretome: potential biology and clinical applications in hypertrophic scarring

Scar tissue is the inevitable result of repairing human skin after it has been subjected to external destructive stimuli. It leads to localized damage to the appearance of the skin, accompanied by symptoms such as itching and pain, which reduces the quality of life of the patient and causes serious medical burdens. With the continuous development of economy and society, there is an increasing demand for beauty. People are looking forward to a safer and more effective method to eliminate pathological scarring. In recent years, adipose-derived stem cells (ADSCs) have received increasing attention from researchers. It can effectively improve pathological scarring by mediating inflammation, regulating fibroblast proliferation and activation, and vascular reconstruction. This review focuses on the pathophysiological mechanisms of hypertrophic scarring, summarizing the therapeutic effects of in vitro, in vivo, and clinical studies on the therapeutic effects of ADSCs in the field of hypertrophic scarring prevention and treatment, the latest application techniques, such as cell-free therapies utilizing ADSCs, and discussing the advantages and limitations of ADSCs. Through this review, we hope to further understand the characterization of ADSC and clarify the effectiveness of its application in hypertrophic scarring treatment, so as to provide clinical guidance.

Isolation and characterization of feline endometrial mesenchymal stem cells

BACKGROUND

Recently, there has been a growing interest in stem cells for human medicine. Limited feline endometrial mesenchymal stem cell (fEM-MSC) research in veterinary medicine necessitates reporting for future feline disease research and therapy.

OBJECTIVES

This study aimed to isolate fEM-MSCs from feline endometrial tissues and evaluate their morphology, proliferative ability, differentiation ability, and immunophenotype.

METHODS

Feline endometrial tissues were obtained from the ovariohysterectomies of healthy cats and isolated using an enzymatic method. The morphology and proliferative ability of the isolated cells were assessed using a doubling time (DT) assay from passages 3 to 6 (P3 - P6). We measured pluripotency gene expressions of cells in P2 using quantitative real-time polymerase chain reaction (qRT-PCR). To investigate MSC characteristics, a trilineage differentiation assay was conducted in P4, and cells in P4 were immunophenotyped using flow cytometry.

RESULTS

fEM-MSCs showed a typical spindle-shaped morphology under a microscope, and the DT was maintained from P3 to P6. fEM-MSCs could differentiate into adipocytes, osteoblasts, and chondrocytes, and expressed three pluripotency markers (OCT4, SOX2, and NANOG) by qRT-PCR. Immunophenotypic analysis showed that the fEM-MSCs were CD14 -, CD34 -, CD45 -, CD9+, and CD44+.

CONCLUSIONS

In this study, the feline endometrium was a novel source of MSCs, and to the best of our knowledge, this is the first report on the isolation method and characteristics of fEM-MSCs.

The Role of Mesenchymal Stem Cell Secretome (Extracellular Microvesicles and Exosomes) in Animals' Musculoskeletal and Neurologic-Related Disorders

The advances in regenerative medicine are very important for the development of medicine and the discovery of stem cells has shown a greater capacity to raise the level of therapeutic quality while their use becomes more accessible, especially in their mesenchymal form. In veterinary medicine, it is not different. The use of those cells, as well as recent advances related to the use of their extracellular vesicles, demonstrates a great opportunity to enhance therapeutic methods and ensure more life quality for patients, which can be in clinical or surgical treatments. Knowing the advances in these modalities and the growing clinical and surgery research and demands for innovations in orthopedic and neurology medicines, this paper aimed to review the literature about the methodologies of use and applications such as the pathways of action and the advances that were postulated for microvesicles and exosomes derived from mesenchymal stem cells in veterinary medicine, especially for musculoskeletal disorders and related injuries.

The Use of Stromal Vascular Fraction in Long Bone Defect Healing in Sheep

The objectives of the present study were to evaluate (a) the feasibility of using stromal vascular fraction (SVF) and nanocrystalline hydroxyapatite (nHA) paste in combination for the treatment of segmental bone defect, (b) the quality of the callus produced, (c) the potential improvement of the autograft technique, and (d) the direct comparison of the biomaterial to the use of autogenous cancellous bone. Unilateral, segmental mid-diaphyseal bone defect was created on the right metatarsus of skeletally mature sheep animals (n = 24) under anesthesia (D0). Residual segments were stabilized by stainless-steel plates and appropriate screws. Defects were managed as follows: group A: use of nHA paste to filling, group B: use of autogenous bone graft mixed with nHA bone paste, placed in defect, group C: use of SVF mixed with nHA bone paste injected into defect, group D: use of bone graft and SVF with nHA paste before apposition in bone defect. SVF had been previously isolated from adipose tissue of the animals intra-operatively after digestion with collagenase solution and neutralization. Animals were evaluated clinically and by X-raying and ultrasonographic examination of the defect, at regular intervals, until D90. Ultrasonographic assessment performed along the length of the defect included calculation of the length of the bone defect and assessment of vascularization. SVF was successfully isolated from group C and D animals, with the average yield being 1.77 × 106 cells. The comparison of clinical scores (based on the 'Kaler scale') on each post-operative day indicated significant differences between the four groups on D1 to D30 (p < 0.01); the median clinical score within group A was 2.5 for D1-D30 and 1 for the entire period; respective scores for other groups were 1.5 (p = 0.07) and 0 (p = 0.033). Differences in radiographic assessment scores were significant for scores obtained on D60 (p = 0.049) and D90 (p = 0.006). There was a significant difference between the four groups in the length of the bone defect, as assessed ultrasonographically, for the entire length of the study; median values were 8, 8.5, 6, and 8 mm for groups A, B, C, and D, respectively (p = 0.008). There was a significance in the differences between median scores obtained during the histopathological examination: 2, 11, 13.5, and 12 for group A, B, C, and D (p = 0.022). There was an inverse correlation between the overall scores of histopathological evaluations and the length of the bone defect (observed on D90) (p < 0.0001) and a correlation between the overall scores and the radiographic assessment scores (obtained on D90) (p < 0.0001). This is the first study in which the efficacy of fresh autologous Stromal Vascular Fraction (SVF) from adipose tissue in enhancing bone healing in a long, weight-bearing, diaphyseal bone was evaluated. It is concluded that the lumbosacral region was an attractive site for harvesting adipose tissue, the use of SVF contributed to faster rehabilitation post-operatively, and SVF significantly enhanced bone formation; in general, the results indicated an osteogenic potential of SVF comparable to the gold standard autologous bone graft.

Outlook of Adipose-Derived Stem Cells: Challenges to Their Clinical Application in Horses

Adipose tissue is recognized as the major endocrine organ, potentially acting as a source of mesenchymal stem cells for various applications in regenerative medicine. Athletic horses are often exposed to traumatic injuries, resulting in severe financial losses. The development of adipose-derived stem cells' regenerative potential depends on many factors. The extraction of stem cells from subcutaneous adipose tissue is non-invasive, non-traumatic, cheaper, and safer than other sources. Since there is a lack of unique standards for identification, the isolated cells and applied differentiation protocols are often not species-specific; therefore, the cells cannot reveal their multipotent properties, so their stemness features remain questionable. The current review discusses some aspects of the specificity of equine adipose stem cells concerning their features, immunophenotyping, secretome profile, differentiation abilities, culturing conditions, and consequent possibilities for clinical application in concrete disorders. The presented new approaches elucidate the possibility of the transition from cell-based to cell-free therapy with regenerative purposes in horses as an alternative treatment to cellular therapy. In conclusion, their clinical benefits should not be underestimated due to the higher yield and the physiological properties of adipose-derived stem cells that facilitate the healing and tissue regeneration process and the ability to amplify the effects of traditional treatments. More profound studies are necessary to apply these innovative approaches when treating traumatic disorders in racing horses.

Retinoic acid induces the osteogenic differentiation of cat adipose tissue-derived stromal cells from distinct anatomical sites

Mesenchymal stromal cells-based regenerative orthopedic therapies have been used in cats as a promising and innovative therapeutic approach to enhance the repair of bone defects. Adipose tissue-derived stromal cells (ADSCs) can be obtained from two main sites-subcutaneous and visceral-with established differences regarding structure, composition, cell content, and functionality. However, in cats, to the best of the authors' knowledge, no studies have been conducted to compare the functional activity of the ADSCs isolated from the two sites, and the impact of these differences on the induced osteogenic potential. Additionally, retinoic acid has been recently regarded as a new osteogenic inducer within cells of distinct species, with undisclosed functionality on cat-derived cell populations. Thus, the present study aimed to evaluate the functional activity of ADSCs isolated from the subcutaneous and visceral adipose sites (SCAT and VAT, respectively) of the cat, as well as the effects of two osteogenic-inducing conditions-the classic dexamethasone, β-glycerophosphate and ascorbic acid-supplemented media (Dex + β + AAM), and Retinoic Acid-supplemented media (RAM). The adipose tissue of subcutaneous and visceral origin was isolated, characterized, and ADSCs were isolated and grown in the presence of the two osteogenic-inducing conditions, and characterized in terms of proliferation, metabolic activity, morphology, and osteogenic activity. Our results demonstrated a distinct biological profile of the two adipose tissue sites regarding cell size, vascularization, and morphology. Further, osteogenic-induced ADSCs from both sites presented an increased expression of alkaline phosphatase activity (ALP) and cytochemical staining, as compared with control. Overall, RAM induced higher levels of ALP activity than Dex + β + AAM, supporting an increased osteogenic activation. Additionally, VAT was the tissue with the best osteogenic potential, showing higher levels of ALP expression, particularly with RAM. In conclusion, different characteristics were found between the two adipose tissue sites-SCAT and VAT, which probably reflect the differences found in the functionality of isolated ADSCs from both tissues. Furthermore, for cat, VAT shows a greater osteogenic-inductive capacity than SCAT, particularly with RAM, which can be of therapeutic relevance for regenerative medicine applications.

Immortalized Canine Adipose-Derived Mesenchymal Stem Cells as a Novel Candidate Cell Source for Mesenchymal Stem Cell Therapy

Mesenchymal stem cells are expected to be a cell source for stem cell therapy of various diseases in veterinary medicine. However, donor-dependent cell heterogenicity has been a cause of inconsistent therapeutic efficiency. Therefore, we established immortalized cells from canine adipose tissue-derived mesenchymal stem cells (ADSCs) to minimize cellular heterogeneity by reducing the number of donors, evaluated their properties, and compared them to the primary cells with RNA-sequencing. Immortalized canine ADSCs were established by transduction with combinations of the R24C mutation of human cyclin-dependent kinase 4 (CDKR24C), canine cyclin D1, and canine TERT. The ADSCs transduced with CDK4R24C, cyclin D1, and TERT (ADSC-K4DT) or with CDK4R24C and cyclin D1 (ADSC-K4D) showed a dramatic increase in proliferation (population doubling level >100) without cellular senescence compared to the primary ADSCs. The cell surface markers, except for CD90 of the ADSC-K4DT and ADSC-K4D cells, were similar to those of the primary ADSCs. The ADSC-K4DT and ADSC-K4D cells maintained their trilineage differentiation capacity and chromosome condition, and did not have a tumorigenic development. The ability to inhibit lymphocyte proliferation by the ADSC-K4D cells was enhanced compared with the primary ADSCs and ADSC-K4DT cells. The pathway analysis based on RNA-sequencing revealed changes in the pathways mainly related to the cell cycle and telomerase. The ADSC-K4DT and ADSC-K4D cells had decreased CD90 expression, but there were no obvious defects associated with the decreased CD90 expression in this study. Our results suggest that ADSC-K4DT and ADSC-K4D cells are a potential novel cell source for mesenchymal stem cell therapy.

Osteogenic Differentiation of Canine Adipose Derived Mesenchymal Stem Cells on B-TCP and B-TCP/Collagen Biomaterials

Mesenchymal stem cells are adult stem cells that have the ability to differentiate into osteogenic, chondrogenic, adipogenic and myogenic lineages. In the field of orthopedics and traumatology, mesenchymal stem cells in combination with biomaterials are used especially for the treatment of bone fractures and diseases in both humans and animals. The purpose of this study is to promote growth, proliferation and osteogenic differentiation of mesenchymal stem cells that were isolated from the adipose tissue of canines on B-TCP (Beta-tricalcium phosphate) and B-TCP/Collagen biomaterials. MTT analysis was performed to test the cell adhesion and proliferation on B-TCP and B-TCP/Collagen biomaterials that were used to mimic the extracellular matrix of three-dimensional bone tissue. Scanning electron microscope analysis was performed to show general surface characters of B-TCP and B-TCP /Collagen biomaterials. The osteoinductive capacities of the B-TCP and B-TCP/Collagen biomaterials were determined by alkaline phosphatase and Von Kossa stainings, and RT-PCR analysis. The ALP activity of the B-TCP/Col containing material was significantly higher than the B-TCP on the first days. In terms of gene expression, there were no significant differences except 14th-day SPARC gene expression. The results of Von Kossa staining indicate that B-TCP/Col has above the desired level degradation capacity. As a result of this research, although it is advantageous in terms of alkaline phosphatase activity and osteogenic gene expression compared to B-TCP material, it is thought that B-TCP/Collagen biomaterial should be developed for use in bone tissue engineering due to its high degradation property.

Clinical applications of adipose-derived stromal vascular fraction in veterinary practice

Adipose tissue-derived stromal vascular fraction (AdSVF) comprises a heterogeneous cell population, including the multipotent mesenchymal stem cells, hematopoietic stem cells, immune cells, endothelial cells, fibroblasts, and pericytes. As such, multipotent adipose tissue-derived mesenchymal stem cells (AdMSCs), are one of the important components of AdSVF. Commonly used techniques to harvest AdSVF involve enzymatic or non-enzymatic methods. The enzymatic method is considered to be the gold standard technique due to its higher yield. The cellular components of AdSVF can be resuspended in normal saline, platelet-rich plasma, or phosphate-buffered saline to produce a ready-to-use solution. Freshly isolated AdSVF has exhibited promising osteogenic and vasculogenic capacity. AdSVF has already been proven to possess therapeutic potential for osteoarthritis management. It is also an attractive therapeutic option for enhancing wound healing. In addition, the combined use of AdSVF and platelet-rich plasma has an additive stimulatory effect in accelerating wound healing and can be considered an alternative to AdMSC treatment. It is also widely used for managing various orthopaedic conditions in clinical settings and has the potential for regenerating bone, cartilage, and tendons. Autologous AdSVF cells are used along with bone substitutes and other biological factors as an alternative to conventional bone grafting techniques owing to their promising osteogenic and vasculogenic capacity. It can also be used for treating osteonecrosis, meniscus tear, chondromalacia, and tendon injuries in veterinary practice. It has several advantages over in vitro expanded AdMSC, including precluding the need for culturing, reduced risk of cell contamination, and cost-effectiveness, making it ideal for clinical use.

An Outstanding Role of Adipose Tissue in Canine Stem Cell Therapy

Adipose tissue, previously known as connective tissue with a role in energy storage, is currently changing the course of treatments in veterinary medicine. Recent studies have revealed one particularly impressive function among all the newly discovered functions of adipose tissue. The interactive cells hosted by adipose tissue, the stromal vascular fraction (SVF), and their role in treating numerous diseases have provided a prospective course of research with positive outcomes in regenerative veterinary medicine (RVM). This review describes the main features of adipose tissue, emphasizing an eclectic combination of cells within the SVF and its thus far researched therapeutic possibilities in canine RVM. An afterwards focus is on a highly researched component of the SVF, adipose-derived mesenchymal stem cells (ASCs), which were shown to have an extraordinary impact relying on several proposed mechanisms of action on mitigating pathologies in canines. Furthermore, ASC therapy showed the most significant results in the orthopaedics field and in neurology, dermatology, ophthalmology, gastroenterology, and hepatology, which elevates the possibilities of ASC therapy to a whole new level. Therefore, this review article aims to raise awareness of the importance of research on cellular components, within abundant and easily accessible adipose tissue, in the direction of regenerative therapy in canines, considering the positive outcomes so far. Although the focus is on the positive aspects of cellular therapy in canines, the researchers should not forget the importance of identifying the potential negative aspects within published and upcoming research. Safe and standardized treatment represents a fundamental prerequisite for positively impacting the lives of canine patients.

Microfluidic Separation of Canine Adipose-Derived Mesenchymal Stromal Cells

Mesenchymal stromal cells (MSCs) are potential treatments for a variety of veterinary medical conditions. However, clinical trials have often fallen short of expectations, due in part to heterogeneity and lack of characterization of the MSCs. Identification and characterization of subpopulations within MSC cultures may improve those outcomes. Therefore, the functional heterogeneity of different-sized subpopulations of MSCs was evaluated. A high-throughput, biophysical, label-free microfluidic sorting approach was used to separate subpopulations of canine adipose-derived MSCs (Ad-MSCs) based on size for subsequent characterization, as well as to evaluate the impact of culture conditions on their functional heterogeneity. We found that culture-expanded canine Ad-MSCs comprise distinct subpopulations: larger MSCs (mean diameter of 18.6 ± 0.2 μm), smaller MSCs (mean diameter of 15.3 ± 0.2 μm), and intermediate MSCs (mean diameter of 16.9 ± 0.1 μm). In addition, proliferation characteristics, senescence, and differentiation potential of canine Ad-MSCs are also dependent on cell size. We observed that larger MSCs proliferate more slowly, senesce at earlier passages, and are inclined to differentiate into adipocytes compared with smaller MSCs. Most importantly, these size-dependent functions are also affected by the presence of serum in the culture medium, as well as time in culture. Cell surface staining for MSC-specific CD44 and CD90 antigens showed that all subpopulations of MSCs are indistinguishable, suggesting that this criterion is not relevant to define subpopulations of MSCs. Finally, transcriptome analysis showed differential gene expression between larger and smaller subpopulations of MSCs. Larger MSCs expressed genes involved in cellular senescence such as cyclin-dependent kinase inhibitor 1A and smaller MSCs expressed genes that promote cell growth [mechanistic target of rapamycin 1 (mTORC1) pathway] and cell proliferation [myelocytomatosis (myc), e2f targets]. These results suggest that different subpopulations of MSCs have specific properties. Impact statement Clinical trials of mesenchymal stromal cells (MSCs) from veterinary species have often fallen short of expectations, due in part to heterogeneity and lack of characterization of the MSCs. A high-throughput, biophysical, label-free microfluidic sorting approach was used to separate subpopulations of canine adipose-derived MSCs (Ad-MSCs) based on size for subsequent characterization. Proliferation characteristics, senescence, and differentiation potential of canine Ad-MSCs are also dependent on cell size. Cell surface staining for MSC-specific cell surface markers showed that all subpopulations of MSCs are indistinguishable, suggesting that this criterion is not relevant to define subpopulations of MSCs.

Viability, yield and expansion capability of feline MSCs obtained from subcutaneous and reproductive organ adipose depots

BACKGROUND

The source of multipotent stromal cells (MSC) can have a significant influence on the health and expansion capacity of the cells. As the applications for allogeneic MSCs in the treatment of feline diseases increase, the location of the initial donor tissue must be analyzed. To date, comparisons have only been made between feline MSCs collected from bone marrow or abdominal fat. This is the first report to compare cells obtained from different adipose depots in the cat with a focus on clinically relevant donor tissues. The tissue was collected from 34 healthy cats undergoing spaying (fat around the ovaries and uterine horn) or subcutaneous fat collected during surgical procedures.

RESULTS

The amount of starting material is essential to isolate sufficient MSCs. The total tissue yield from the subcutaneous fat was significantly greater than could be obtained from around the reproductive organs, leading to 3 times more MSCs per donor. However, the concentration of MSCs obtained from reproductive fat was higher than from subcutaneous fat. In addition, the viability of the MSCs from the reproductive fat was significantly higher than the subcutaneous fat. Since most spaying occurs in young cats (under 18 months) reproductive fat was collected from adult cats during spaying, illustrating that age did not alter the yield or viability of the MSCs. When sufficient tissue was collected, it was digested either mechanically or enzymatically. Mechanical digestion further decreased the viability and yield of MSCs from subcutaneous fat compared to enzymatic digestion. Biomarkers of stem cell characterization, expansion capacity and function were detected using qPCR. CD70, CD90 and CD105 were all expressed in high levels in the 3 groups. However, the reproductive fat had higher levels of CD73 with the mechanically digested subcutaneous fat having the least. Gata6 was detected in all samples while Sox2 and Sox17 were also detected with higher quantities found in the enzymatically digested subcutaneous fat. Negative control genes of Gata4 and Pdx1 showed no detection prior to 50 cycles. During the first three passages, age of the donor, location of the donor tissue, or digestion protocol had no effect on cell culture doubling times or cell viability.

CONCLUSIONS

While MSCs from reproductive fat had superior cells/tissue weight and initial viability, there were still dramatically fewer cells obtained compared to subcutaneous fat due to the limited amount of tissue surrounding the reproductive organs. Further, in P1-P3 cultures there were no differences noted in doubling time or cell viability between tissue obtained from reproductive or subcutaneous fat depots.

[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.

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.

Treatment of cranial cruciate ligament injuries in dogs using a combination of tibial tuberosity advancement procedure and autologous mesenchymal stem cells/multipotent mesenchymal stromal cells - A pilot study

In the present pilot study, we evaluated different supplemental therapies using autologous multipotent mesenchymal stromal cells (MMSCs) for the treatment of cranial cruciate ligament defects in dogs. We used tibial tuberosity advancement (TTA) and augmented it by supportive therapy with MMSCs in three patient groups. In the first patient group, the dogs were injected with MMSCs directly into the treated stifle one month after surgery. In the second group, MMSCs were delivered in a silk fibroin scaffold which was placed in the osteotomy gap during surgery. In the third group, MMSCs were first mixed with bone tissue and blood from the patient and delivered into the osteotomy gap during surgery. In the control group, patients underwent the TTA procedure but did not receive MMSC treatment. In the group of patients who received cells in the silk fibroin scaffold during surgery, the osteotomy gap did not heal, presumably due to the low absorption of silk fibroin. Patients who received MMSCs mixed with bone tissue and blood during surgery into the osteotomy gap recovered clinically faster and had better healing of the osteotomy gap than dogs from the other two treated groups and from the control group, as assessed by clinical examination and quantification of radiographs. In conclusion, dogs that received stem cells directly into the osteotomy gap (Group 3) recovered faster compared to dogs from Groups 1 (MMSCs injected into the joint one month after surgery), 2 (cells implanted into the osteotomy gap in a silk fibroin scaffold), and the control group that did not receive additional MMSCs treatment.

Tissue Harvesting Site Effect on the Canine Adipose Stromal Vascular Fraction Quantity and Quality

Simple Summary

Adipose stromal vascular fraction (SVF) cells are freshly isolated non-cultured mesenchymal stem cells, which have been recently applied in the treatment of several musculoskeletal inflammatory conditions in dogs. However, the best adipose tissue (AT) sampling site is still challenging. This study first addressed the ideal AT harvesting site in canines ranging between middle and old age, the most susceptible age to chronic musculoskeletal problems. Our results showed that the peri-ovarian region is the best AT harvesting site, which yields high amounts of SVF cells with enough adipose-derived stem cells. These data may help the further set-up of cell-based regenerative therapies at the preclinical and experimental level in canines.

Abstract

Mesenchymal stem cells (MSCs) constitute a great promise for regenerative therapy, but these cells are difficultly recovered in large amounts. A potent alternative is the stromal vascular fraction (SVF), non-cultured MSCs, separated from adipose tissue (AT). We aim to evaluate AT harvesting site effect on the SVF cells’ quantity and quality in dogs. Subcutaneous abdominal fat, falciform ligament and peri-ovarian fat were sampled. After SVF isolation, the trypan blue exclusion test and a hemocytometer were used to assess the cell viability and cellular yield. SVF cells were labeled for four surface antigenic markers, clusters of differentiation CD90, CD44, CD29, and CD45, and then examined by flow cytometry. Semi-quantitative RT-PCR was used to evaluate the gene expression of the former markers in addition to OCT-4 and CD34. SVF cells in the peri-ovarian AT recorded the highest viability% (99.63 ± 0.2%), as well as a significantly higher cellular yield (36.87 ± 19.6 × 10⁶ viable cells/gm fat, p < 0.001) and a higher expression of adipose-derived mesenchymal stem cells AD-MSCs surface markers than that of other sites. SVF cells from the peri-ovarian site revealed a higher expression of MSC markers (CD90, CD44, and CD29) and OCT-4 compared to the other sites, with weak CD45 and CD34 expressions. The positive OCT-4 expression demonstrated the pluripotency of SVF cells isolated from different sites. To conclude, the harvesting site is a strong determinant of SVF cells’ quantity and quality, and the peri-ovarian site could be the best AT sampling site in dogs.

Challenges of stem cell therapies in companion animal practice

Regenerative medicine using stem cells from various sources are emerging treatment modality in several refractory diseases in veterinary medicine. It is well-known that stem cells can differentiate into specific cell types, self-renew, and regenerate. In addition, the unique immunomodulatory effects of stem cells have made stem cell transplantation a promising option for treating a wide range of disease and injuries. Recently, the medical demands for companion animals have been rapidly increasing, and certain disease conditions require alternative treatment options. In this review, we focused on stem cell application research in companion animals including experimental models, case reports and clinical trials in dogs and cats. The clinical studies and therapeutic protocols were categorized, evaluated and summarized according to the organ systems involved. The results indicate that evidence for the effectiveness of cell-based treatment in specific diseases or organ systems is not yet conclusive. Nonetheless, stem cell therapy may be a realistic treatment option in the near future, therefore, considerable efforts are needed to find optimized cell sources, cell numbers and delivery methods in order to standardize treatment methods and evaluation processes.

Adipose-Derived Stromal/Stem Cells from Large Animal Models: from Basic to Applied Science

Adipose-derived stem cells (ASCs) isolated from domestic animals fulfill the qualitative criteria of mesenchymal stem cells, including the capacity to differentiate along multiple lineage pathways and to self-renew, as well as immunomodulatory capacities. Recent findings on human diseases derived from studying large animal models, have provided evidence that administration of autologous or allogenic ASCs can improve the process of healing. In a narrow group of large animals used in bioresearch studies, pigs and horses have been shown to be the best suited models for study of the wound healing process, cardiovascular and musculoskeletal disorders. To this end, current literature demonstrates that ASC-based therapies bring considerable benefits to animal health in both spontaneously occurring and experimentally induced clinical cases. The purpose of this review is to provide an overview of the diversity, isolation, and characterization of ASCs from livestock. Particular attention has been paid to the functional characteristics of the cells that facilitate their therapeutic application in large animal models of human disease. In this regard, we describe outcomes of ASCs utilization in translational research with pig and horse models of disease. Furthermore, we evaluate the current status of ASC-based therapy in veterinary practice, particularly in the rapidly developing field of equine regenerative medicine. In conclusion, this review presents arguments that support the relevance of animal ASCs in the field of regenerative medicine and it provides insights into the future perspectives of ASC utilization in animal husbandry.

Canine atopic dermatitis attenuated by mesenchymal stem cells

Objective:

To evaluate the use of mesenchymal stem cells (MSCs) in the attenuation of canine atopic dermatitis (AD).

Materials and methods:

Sixteen dogs were selected and divided into three groups, mild, moderate, and severe, according to the Canine Atopic Dermatitis Extent and Severity Index (CADESI-4). They were evaluated for 82 days. The protocol recommended in this experiment was to inject 2 × 10⁶/kg bodyweight of MSC’s in all groups by the intravenous route with intervals of applications of 21 days. The degree of pruritus was evaluated by examining the visual analog scale, the CADESI-4, the histopathology of the skin, hematological and biochemical parameters, the pyogenic effect of MSCs, and the thickness of the epidermis.

Results:

There was a significant difference in the reduction of epidermal thickness in the moderate and severe groups. Hematological, biochemical, and body temperature parameters remained within normal limits for the species with no side effects

Conclusion:

MSCs attenuated the clinical signs of AD.

Study of bilateral elbow joint osteoarthritis treatment using conditioned medium from allogeneic adipose tissue-derived MSCs in Labrador retrievers

Canine elbow dysplasia is a common cause of forelimb lameness in dogs and can lead to development of osteoarthritis (OA). A potential alternative to pain management is the use of a safe cell-free based therapy through trophic and paracrine factors of mesenchymal stem cells (MSCs). The aim of study was to identify the profile of selected mediators of potential clinical relevance in synovial fluid (SF) samples of dogs with elbow OA and analyse the range of motion (ROM) before and after cell-free MSCs-based treatment. In this study, conditioned medium from allogeneic canine adipose tissue - derived MSC (CM-AD-MSC) was prepared and administered into both elbow joints with OA in six Labrador retriever dogs (n = 6) on day 0 and 14 without creating a control group with a placebo. The SF of the elbow joints was analysed for the presence of several biomolecules (IL-6, IL-10, IL-8, IL-2, IL-12, TNF-αIFN-γ, MMP-3TIMP-1) before and after intraarticular applications of CM-AD-MSC. Kinematic analysis was used to assess the clinical effect of CM-AD-MSC. Analyses of SF and ROM were performed on days 0, 14 and 42. Concentration levels of MMP-3, TIMP-1, IL-6 and TNF-α in SF showed significant differences before and after the treatment (P < .05). There was a significant improvement in ROM between day 0 and 42 (P < .001). No severe adverse events were observed during the study. Results support the potential supportive effect of CM-AD-MSC as a noninvasive therapeutic tool for pain management of OA elbow joints in dogs.

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.

Intraovarian injection of mesenchymal stem cells improves oocyte yield and in vitro embryo production in a bovine model of fertility loss

Valuable female cattle are continuously subject to follicular puncture (ovum pick-up - OPU). This technique is commonly used for in-vitro embryo production, but may result in ovarian lesion. Mesenchymal stem cells (MSC) ameliorate the function of injured tissues, but their use to treat ovarian lesions in cattle has not been established. We investigated whether a local injection of MSC would reduce the negative effects of repeated OPU under acute and chronic scenarios in bovines. First, we performed four OPU sessions and injected 2.5 × 106 MSCs immediately after the 4th OPU procedure (n = 5). The treated organs (right ovary) were compared to their saline-treated counterparts (left), and presented superior production of oocytes and embryos in the three following OPU sessions (P < 0.05). Then, cows with progressive fertility loss went through three OPU sessions. Animals received MSC, saline, or MSC + FSH in both ovaries after the first OPU. In the two following OPU sessions, the MSC and MSC + FSH - treated groups failed to present any significant alteration in the number of oocytes and embryos compared to saline-treated animals. Thus, MSC have beneficial effects on the fertility of OPU-lesioned cows, but not in cows with cystic ovarian disease and chronic ovarian lesions.

In vitro differentiation of rhesus macaque bone marrow- and adipose tissue-derived MSCs into hepatocyte-like cells

Orthotopic liver or hepatocyte transplantation is effective for the treatment of acute liver injury and end-stage chronic liver disease. However, both of these therapies are hampered by the extreme shortage of organ donors. The clinical application of cell therapy through the substitution of hepatocytes with mesenchymal stem cells (MSCs) that have been differentiated into hepatocyte-like cells (HLCs) for liver disease treatment is expected to overcome this shortage. Bone marrow and adipose tissue are two major sources of MSCs [bone marrow-derived MSCs (BM-MSCs) and adipose tissue-derived MSCs (AT-MSCs), respectively]. However, knowledge about the variability in the differentiation potential between BM-MSCs and AT-MSCs is lacking. In the present study, the hepatogenic differentiation potential of rhesus macaque BM-MSCs and AT-MSCs was compared with the evaluation of morphology, immunophenotyping profiles, differentiation potential, glycogen deposition, urea secretion and hepatocyte-specific gene expression. The results indicated that BM-MSCs and AT-MSCs shared similar characteristics in terms of primary morphology, surface markers and trilineage differentiation potential (adipogenesis, osteogenesis and chondrogenesis). Subsequently, the hepatogenic differentiation potential of BM-MSCs and AT-MSCs was evaluated by morphology, glycogen accumulation, urea synthesis and expression of hepatocyte marker genes. The results indicated that rhesus BM-MSCs and AT-MSCs had hepatogenic differentiation ability. To the best of our knowledge, this is the first report to detect the hepatogenic differentiation potential of rhesus macaque BM-MSCs and AT-MSCs. The present study provides the basis for the selection of seed cells that can trans-differentiate into HLCs for cytotherapy of acute or chronic liver injuries in either clinical or veterinary practice.

Combining canine mesenchymal stromal cells and hyaluronic acid for cartilage repair

Cell therapy and tissue engineering have been intensively researched for repair of articular cartilage. In this study, we investigated the chondrogenic potential of canine adipose-derived mesenchymal stromal cells (ASCs) combined to high molecular weight hyaluronic acid (HA) in vitro, and their therapeutic effect in dogs with chronic osteoarthritis (OA) associated with bilateral hip dysplasia. Canine ASCs were characterized after conventional 2D culture or 3D culture in HA, showing adequate immunophenotype, proliferation and trilineage differentiation, as well as chondrogenesis after cultivation in HA. ASC/HA constructs were used to treat 12 dogs with OA, sequentially assigned to control, ASC and ASC/HA groups. Animals were examined for clinical, orthopedic and radiological parameters. Lameness at walk and pain on manipulation were reduced in the ASC group and mainly in the ASC/HA group. Range of motion and detection of crepitus on hip rotation and abduction improved similarly in all groups. For articular edema, muscle atrophy, Norberg angle values and radiographic analyses, there were no variations throughout the period. These results indicate that ASC/HA constructs are safe and may be an effective therapeutic tool in treating canine chronic osteoarthritis, which should be confirmed with larger studies and additional clinical parameters.

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.

Comparison of Properties of Stem Cells Isolated from Adipose Tissue and Lipomas in Dogs

Adipose-derived mesenchymal stem cells (ADSCs) have been suggested their benefits in regenerative medicine for various diseases. Lipomas, benign neoplasms in adipose tissue, have been reported as a potential source of stem cells. These lipoma-derived mesenchymal stem cells (LDSCs) may be useful for regenerative medicine. However, the detailed characteristics of LDSCs have not been fully elucidated. This study investigated the cellular proteomics and secretomes of canine LDSCs in addition to morphology and proliferation and differentiation capacities. Some LDSCs isolated from canine subcutaneous lipomas were morphologically different from ADSCs and showed a rounded shape instead of fibroblast-like morphology. The phenotype of cell surface markers in LDSCs was similar to those in ADSCs, but CD29 and CD90 stem cell markers were more highly expressed compared with those of ADSCs. LDSCs had noticeably high proliferation ability, but no significant differences were observed compared with ADSCs. In regard to differentiation capacity compared to ADSCs, LDSCs showed higher adipogenesis, but no differences were observed with osteogenesis. Cellular proteomic analysis using two-dimensional gel electrophoresis revealed that over 95% of protein spots showed similar expression levels between LDSCs and ADSCs. Secretome analysis was performed using iTRAQ and quantitative cytokine arrays. Over 1900 proteins were detected in conditioned medium (CM) of LDSCs and ADSCs, and 94.0% of detected proteins showed similar expression levels between CM of both cell types. Results from cytokine arrays including 20 cytokines showed no significant differences between CM of LDSCs and that of ADSCs. Our results indicate that canine LDSCs had variability in characteristics among individuals in contrast with those of ADSCs. Cellular proteomics and secretomes were similar in both LDSCs and ADSCs. These findings suggest that LDSCs may be suitable for application in regenerative medicine.

Isolation of canine adipose-derived mesenchymal stem cells from falciform tissue obtained via laparoscopic morcellation: A pilot study

OBJECTIVE

To evaluate the feasibility of stem cell isolation from falciform fat harvested via laparoscopic morcellation.

STUDY DESIGN

Pilot study.

ANIMALS

Eleven client-owned dogs.

METHODS

Falciform was harvested traditionally via laparotomy and laparoscopically via tissue morcellation. Harvested tissue was processed with a commercially available adipose tissue dissociation kit to obtain a stromal vascular fraction (SVF). Cells were subsequently labeled for CD90, CD45, and CD44 cell surface antigens by using magnetic-activated cell sorting (MACS) and fluorescence-activated cell sorting flow cytometry. CD90⁺ cells were quantitated, and their viability was assessed with a hemocytometer and a trypan blue exclusion test of cell viability.

RESULTS

No perioperative complications occurred in dogs undergoing laparoscopic morcellation. Laparoscopically and traditionally harvested samples yielded an average of 0.39 (±0.1) × 10⁶ and 0.33 (±0.1) × 10⁶ CD90⁺ cells, respectively, per 10 million SVF cells. CD90⁺ cell viability after MACS was 89% (±11%) for morcellated and 86% (±7%) for traditionally harvested samples. Neither CD90⁺ cell quantity nor viability was different between samples obtained via traditional laparotomy vs laparoscopic morcellation (P = .38 and P = .63, respectively). Populations of CD90⁺ cells isolated with each harvest technique had similar CD44 and CD45 expression profiles.

CONCLUSION

Viable populations of CD90⁺ cells with similar CD44/CD45 expression profiles were isolated from laparoscopically morcellated and traditionally harvested falciform tissue. No appreciable morbidity was associated with laparoscopic falciform morcellation.

CLINICAL SIGNIFICANCE

Laparoscopic morcellation is a safe and effective minimally invasive approach to falciform tissue harvest for adipose-derived mesenchymal stem cell isolation.

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.

Bone marrow mononuclear cells versus mesenchymal stem cells from adipose tissue on bone healing in an Old World primate: can this be extrapolated to humans?

ABSTRACT In veterinary medicine, the cell therapy is still unexplored and there are many unanswered questions that researchers tend to extrapolate to humans in an attempt to treat certain injuries. Investigating this subject in nonhuman primates turns out to be an unparalleled opportunity to better understand the dynamics of stem cells against some diseases. Thus, we aimed to compare the efficiency of bone marrow mononuclear cells (BMMCs) and mesenchymal stem cells (MSCs) from adipose tissue of Chlorocebus aethiops in induced bone injury. Ten animals were used, male adults subjected, to bone injury the iliac crests. The MSCs were isolated by and cultured. In an autologous manner, the BMMCs were infused in the right iliac crest, and MSCs from adipose tissue in the left iliac crest. After 4.8 months, the right iliac crests fully reconstructed, while left iliac crest continued to have obvious bone defects for up to 5.8 months after cell infusion. The best option for treatment of injuries with bone tissue loss in old world primates is to use autologous MSCs from adipose tissue, suggesting we can extrapolate the results to humans, since there is phylogenetic proximity between species.

Effect of allogeneic mesenchymal stem cells (MSCs) on corneal wound healing in dogs

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Allogeneic MSCs are safety to be transplanted by subconjunctival route.

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Allogeneic MSCs therapy seems to be efficient in improving corneal healing in dogs.

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Allogeneic MSCs therapy applied to depth corneal ulcers promoted healing in 14 days.

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The paracrine effect of MSCs must provide a rapid corneal wound healing.

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.

Effects of enzyme and cryoprotectant concentrations on yield of equine adipose-derived multipotent stromal cells

OBJECTIVE To evaluate effects of various concentrations of collagenase and dimethyl sulfoxide (DMSO) on yield of equine adipose-derived multipotent stromal cells (ASCs) before and after cryopreservation. SAMPLE Supragluteal subcutaneous adipose tissue from 7 Thoroughbreds. PROCEDURES Tissues were incubated with digests containing 0.1%, 0.05%, or 0.025% type I collagenase. Part of each resulting stromal vascular fraction was cryopreserved in 80% fetal bovine serum (FBS), 10% DMSO, and 10% Dulbecco modified Eagle medium F-12 and in 95% FBS and 5% DMSO. Half of each fresh and cryopreserved heterogeneous cell population was not immunophenotyped (unsorted) or was immunophenotyped for CD44⁺, CD105⁺, and major histocompatability complex class II (MHCII; CD44⁺-CD105⁺-MHCII⁺ cells and CD44⁺-CD105⁺-MHCII^- cells). Cell proliferation (cell viability assay), plasticity (CFU frequency), and lineage-specific target gene and oncogene expression (reverse transcriptase PCR assays) were determined in passage 1 cells before and after culture in induction media. RESULTS Digestion with 0.1% collagenase yielded the highest number of nucleated cells. Cell surface marker expression and proliferation rate were not affected by collagenase concentration. Cryopreservation reduced cell expansion rate and CD44⁺-CD105⁺-MHCII^- CFUs; it also reduced osteogenic plasticity of unsorted cells. However, effects appeared to be unrelated to DMSO concentrations. There were also variable effects on primordial gene expression among cell isolates. CONCLUSIONS AND CLINICAL RELEVANCE Results supported the use of 0.1% collagenase in an adipose tissue digest and 5% DMSO in cryopreservation medium for isolation and cryopreservation, respectively, of equine ASCs. These results may be used as guidelines for standardization of isolation and cryopreservation procedures for equine ASCs.

Canine mesenchymal stem cells treated with TNF-α and IFN-γ enhance anti-inflammatory effects through the COX-2/PGE2 pathway

Mesenchymal stem cells (MSCs) have been used in studies on treatment of various diseases, and their application to immune-mediated diseases has garnered interest. Various methods for enhancing the immunomodulation effect of human MSCs have been used; however, similar approaches for canine MSCs are relatively unexplored. Accordingly, we evaluated immunomodulatory effects and mechanisms in canine MSCs treated with TNF-α and IFN-γ. Lipopolysaccharide (LPS)-stimulated RAW 264.7 cells were incubated with the conditioned media (CM) from canine MSCs for 48 h. Expression of RNA was assessed by quantitative reverse transcription PCR (qRT-PCR), and protein levels were assessed by western blot. Expression of inducible nitric oxide synthase (iNOS), IL-6 and IL-1β was significantly (one-way ANOVA) decreased in LPS-stimulated RAW 264.7 cells incubated with CM from canine MSCs compared to that in LPS-stimulated RAW 264.7 cells alone. Furthermore, anti-inflammatory effects of TNF-α- and IFN-γ-primed canine MSCs were significantly increased compared with those of naïve canine MSCs. Expression of cyclooxygenase 2 (COX-2) and prostaglandin E₂ (PGE₂) were likewise significantly increased in primed canine MSCs. The level of iNOS protein in LPS-stimulated RAW 264.7 cells incubated with CM from the primed canine MSCs was decreased, but it increased when the cells were treated with NS-398(PGE₂ inhibitor). In conclusion, compared with naïve canine MSCs, cells primed with TNF-α and IFN-γ cause a greater reduction in release of anti-inflammatory cytokines from LPS-stimulated RAW 264.7 cells; the mechanism is upregulation of the COX-2/PGE₂ pathway.

Altered properties of feline adipose-derived mesenchymal stem cells during continuous in vitro cultivation

Cytotherapy with mesenchymal stem cells (MSCs) has been studied in many species, and often requires in vitro cell expansion to obtain therapeutic doses of stem cells. Because the characteristics of MSCs, such as self-renewal and multi-lineage differentiation, can be altered by long-term culture, it is important to maintain stemness during cultivation. This study assessed the changes in the characteristics of feline adipose tissue-derived (fAT)-MSCs during in vitro passaging. Stem cells isolated from the adipose tissue of donor cats were cultured for seven sub-passages. Proliferation capacity was analyzed by calculating the cell doubling time and by colorimetric assay. Expression of stem cell-specific markers was evaluated by quantitative reverse transcription (qRT)-PCR and immunophenotyping. Expression of adipogenic and osteogenic differentiation markers was also measured by qRT-PCR. Histochemical staining and measurement of β-galactosidase activity were conducted to detect cellular senescence. The cell proliferation rate decreased significantly at passage 5 (P5). Gene expression levels of pluripotency markers (Sox2, Nanog and Klf4) and stem cell surface markers (CD9, CD44, CD90 and CD105) decreased during continuous culture; in most assays, statistically significant changes were observed at P5. The ability of cells to undergo adipogenic or osteogenic differentiation was inversely proportional to the number of passages. The proportion of senescent cells increased with the number of passages. These results suggest that repeated passages alter the proliferation and multipotency of fAT-MSCs. In clinical trials, early-passage cells should be used to achieve the maximum therapeutic effect.

Extensive characterization of feline intra-abdominal adipose-derived mesenchymal stem cells

Mesenchymal stem cells (MSCs) isolated from various tissues have been well characterized for therapeutic application to clinical diseases. However, in contrast to MSCs from other animal species, the characteristics of feline MSCs have not been fully documented. In this study, we conducted extensive characterization of feline adipose tissue-derived MSCs (fAD-MSCs). Study fAD-MSCs were individually isolated from the intra-abdominal adipose tissues of six felines. The expression levels of cell surface markers and pluripotent markers were evaluated. Next, proliferation capacity was analyzed by performing cumulative population doubling level (CPDL) and doubling time (DT) calculation assays. Differentiation potentials of fAD-MSCs into mesodermal cell lineages were analyzed by examining specific staining and molecular markers. All fAD-MSCs positively expressed cell surface markers such as CD29, CD44, CD90, CD105, CD166, and MHC-I, while CD14, CD34, CD45, and CD73 were negatively expressed. The CPDL of the fAD-MSCs was maintained until passage 5 to 6 (P5 to P6), whereas DT increased after P3 to P4. Also, stem cell-specific pluripotent markers (Oct3/4, Nanog, and SSEA-4) were detected. Importantly, all fAD-MSCs demonstrated mesodermal differentiation capacity. These results suggest that fully characterized fAD-MSCs could be beneficial when considering the use of these cells in feline disease research.

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.

Soluble factors from adipose tissue-derived mesenchymal stem cells promote canine hepatocellular carcinoma cell proliferation and invasion

The potential effects of adipose tissue-derived mesenchymal stem cells (AT-MSCs) on the growth and invasion of canine tumours including hepatocellular carcinoma (HCC) are not yet understood. Moreover in humans, the functional contribution of AT-MSCs to malignancies remains controversial. The purpose of this study was to investigate the effects of AT-MSCs on the proliferation and invasion of canine HCC cells in vitro. The effect of AT-MSCs on mRNA levels of factors related to HCC progression were also evaluated. Conditioned medium from AT-MSCs (AT-MSC-CM) significantly enhanced canine HCC cell proliferation and invasion. Moreover, mRNA expression levels of transforming growth factor-beta 1, epidermal growth factor A, hepatocyte growth factor, platelet-derived growth factor-beta, vascular endothelial growth factor, and insulin-like growth factor 2 were 2.3 ± 0.4, 2.0 ± 0.5, 5.7 ± 1.9, 1.7 ± 0.2, 2.1 ± 0.4, and 1.4 ± 0.3 times higher, respectively (P < 0.05). The mRNA expression level of MMP-2 also increased (to 4.0 ± 1.2 times control levels) in canine HCC cells co-cultured with AT-MSCs, but MMP-9 mRNA significantly decreased (to 0.5 ± 0.1 times control levels). These findings suggest that soluble factors from AT-MSCs promote the proliferation and invasion of canine HCC cells.

Stem cell factor supports migration in canine mesenchymal stem cells

Adult Mesenchymal Stem Cells (MSC) are cells that can be defined as multipotent cells able to differentiate into diverse lineages, under appropriate conditions. These cells have been widely used in regenerative medicine, both in preclinical and clinical settings. Initially discovered in bone marrow, MSC can now be isolated from a wide spectrum of adult and foetal tissues. Studies to evaluate the therapeutic potential of these cells are based on their ability to arrive to damaged tissues. In this paper we have done a comparative study analyzing proliferation, surface markers and OCT4, SOX9, RUNX2, PPARG genes expression in MSC cells from Bone marrow (BMMSC) and Adipose tissue (ASC). We also analyzed the role of Stem Cell Factor (SCF) on MSC proliferation and on ASCs metalloproteinases MMP-2, MMP-9 secretion. Healthy dogs were used as BMMSC donors, and ASC were collected from omentum during elective ovariohysterectomy surgery. Both cell types were cultured in IMDM medium with or without SCF, 10% Dog Serum (DS), and incubated at 38 °C with 5% CO2. Growth of BMMSCs and ASCs was exponential until 25-30 days. Flow citometry of MSCs revealed positive results for CD90 and negative for CD34, CD45 and MCH-II. Genes were evaluated by RT-PCR and metalloproteinases by zymografy. Our findings indicate morphological and immunological similarities as well as expression of genes from both origins on analyzed cells. Furthermore, SCF did not affect proliferation of MSCs, however it up-regulated MMP-2 and MMP-9 secretion in ASCs. These results suggest that metalloproteinases are possibly essential molecules pivoting migration.

Adult multipotent stromal cell cryopreservation: Pluses and pitfalls

Study and clinical testing of adult multipotent stromal cells (MSCs) are central to progressive improvements in veterinary regenerative medicine. Inherent limitations to long-term culture preclude use for storage. Until cell line creation from primary isolates becomes routine, MSC stasis at cryogenic temperatures is required for this purpose. Many protocols and reagents, including cryoprotectants, used for veterinary MSCs are derived from those for human and rodent cells. Dissimilarities in cryopreservation strategies play a role in variable MSC behaviors. Familiarity with contemporary cryopreservation reagents and processes is essential to an appreciation of their impact on MSC survival and post-cryopreservation behavior. In addition to these points, this review includes a brief history and description of current veterinary stem cell regulation.

Allogenic Adipose Tissue-Derived Mesenchymal Stem Cells Ameliorate Acute Hepatic Injury in Dogs

Adipose tissue-derived mesenchymal stem cells (AT-MSCs) are an attractive source for cell-based therapy of some diseases, including acute and chronic liver failure, in not only human medicine but also veterinary medicine. However, in veterinary medicine, no studies have reported the effects of AT-MSCs on liver injury in dogs. The purpose of this study was to investigate the effects of allogenic AT-MSCs on acute liver injury by carbon tetrachloride in dogs and to compare the therapeutic effects of AT-MSCs transplanted via the peripheral vein (PV) or splenic vein (SV). After transplantation of AT-MSCs through the PV or SV, serum liver enzymes were decreased significantly, and SV injection was more effective compared with PV injection. By comparing the number of engrafted AT-MSCs in the liver, SV injection was significantly more effective than PV injection. mRNA expression levels of proinflammatory cytokines, such as IL-1, IL-6, IL-8, and IFNγ, in the liver were decreased significantly, but those of anti-inflammatory cytokines, such as IL-4 and IL-10, HGF, and VEGFA, were significantly increased after the first AT-MSC injection. These findings suggest that allogenic AT-MSCs injected via the PV or SV ameliorate acute hepatic injury in dogs, and AT-MSCs injected via the SV provide more effective improvement.

Effect of single intralesional treatment of surgically induced equine superficial digital flexor tendon core lesions with adipose-derived mesenchymal stromal cells: a controlled experimental trial

Background

Adipose tissue is a promising source of mesenchymal stromal cells (MSCs) for the treatment of tendon disease. The goal of this study was to assess the effect of a single intralesional implantation of adipose tissue-derived mesenchymal stromal cells (AT-MSCs) on artificial lesions in equine superficial digital flexor tendons (SDFTs).

Methods

During this randomized, controlled, blinded experimental study, either autologous cultured AT-MSCs suspended in autologous inactivated serum (AT-MSC-serum) or autologous inactivated serum (serum) were injected intralesionally 2 weeks after surgical creation of centrally located SDFT lesions in both forelimbs of nine horses. Healing was assessed clinically and with ultrasound (standard B-mode and ultrasound tissue characterization) at regular intervals over 24 weeks. After euthanasia of the horses the SDFTs were examined histologically, biochemically and by means of biomechanical testing.

Results

AT-MSC implantation did not substantially influence clinical and ultrasonographic parameters. Histology, biochemical and biomechanical characteristics of the repair tissue did not differ significantly between treatment modalities after 24 weeks. Compared with macroscopically normal tendon tissue, the content of the mature collagen crosslink hydroxylysylpyridinoline did not differ after AT-MSC-serum treatment (p = 0.074) while it was significantly lower (p = 0.027) in lesions treated with serum alone. Stress at failure (p = 0.048) and the modulus of elasticity (p = 0.001) were significantly lower after AT-MSC-serum treatment than in normal tendon tissue.

Conclusions

The effect of a single intralesional injection of cultured AT-MSCs suspended in autologous inactivated serum was not superior to treatment of surgically created SDFT lesions with autologous inactivated serum alone in a surgical model of tendinopathy over an observation period of 22 weeks. AT-MSC treatment might have a positive influence on collagen crosslinking of remodelling scar tissue. Controlled long-term studies including naturally occurring tendinopathies are necessary to verify the effects of AT-MSCs on tendon disease.

Electronic supplementary material

The online version of this article (doi:10.1186/s13287-017-0564-8) contains supplementary material, which is available to authorized users.

Effect of canine mesenchymal stromal cells loaded with paclitaxel on growth of canine glioma and human glioblastoma cell lines

This study investigated whether canine mesenchymal stromal cells (cMSCs) are able to take up and release paclitaxel (PTX) in active form, and therefore whether they have potential as a tool for therapeutic delivery of this drug. cMSCs from bone marrow and adipose tissue were isolated, expanded and characterised phenotypically. cMSCs were loaded with PTX (cMSCs-PTX) and their capacity for release of PTX was determined by their effect on proliferation of cancer cells. cMSCs-PTX derived from bone marrow and adipose tissue were able to take up and then release active PTX. cMSCs-PTC inhibited proliferation of the canine glioma cell line J3T, and the human glioblastoma cell lines T98G and U87MG. The potential of canine cMSCs-PTX for treatment of canine gliomas should be investigated further.

Immunophenotypical characterization of canine mesenchymal stem cells from perivisceral and subcutaneous adipose tissue by a species-specific panel of antibodies

Immunophenotypical characterization of mesenchymal stem cells is fundamental for the design and execution of sound experimental and clinical studies. The scarce availability of species-specific antibodies for canine antigens has hampered the immunophenotypical characterization of canine mesenchymal stem cells (MSC). The aim of this study was to select a panel of species-specific direct antibodies readily useful for canine mesenchymal stem cells characterization. They were isolated from perivisceral and subcutaneous adipose tissue samples collected during regular surgeries from 8 dogs. Single color flow cytometric analysis of mesenchymal stem cells (P3) deriving from subcutaneous and perivisceral adipose tissue with a panel of 7 direct anti-canine antibodies revealed two largely homogenous cell populations with a similar pattern: CD29⁺, CD44⁺, CD73⁺, CD90⁺, CD34^-, CD45^- and MHC-II^- with no statistically significant differences among them. Antibody reactivity was demonstrated on canine peripheral blood mononuclear cells. The similarities are reinforced by their in vitro cell morphology, trilineage differentiation ability and RT-PCR analysis (CD90⁺, CD73⁺, CD105⁺, CD44⁺, CD13⁺, CD29⁺, Oct-4⁺ gene and CD31^- and CD45^- expression). Our results report for the first time a comparison between the immunophenotypic profile of canine MSC deriving from perivisceral and subcutaneous adipose tissue. The substantial equivalence between the two populations has practical implication on clinical applications, giving the opportunity to choose the source depending on the patient needs. The results contribute to routine characterization of MSC populations grown in vitro, a mandatory process for the definition of solid and reproducible laboratory and therapeutic procedures.

Suppression of Canine Dendritic Cell Activation/Maturation and Inflammatory Cytokine Release by Mesenchymal Stem Cells Occurs Through Multiple Distinct Biochemical Pathways

Mesenchymal stem cells (MSC) represent a readily accessible source of cells with potent immune modulatory activity. MSC can suppress ongoing inflammatory responses by suppressing T cell function, while fewer studies have examined the impact of MSC on dendritic cell (DC) function. The dog spontaneous disease model represents an important animal model with which to evaluate the safety and effectiveness of cellular therapy with MSC. This study evaluated the effects of canine MSC on the activation and maturation of canine monocyte-derived DC, as well as mechanisms underlying these effects. Adipose-derived canine MSC were cocultured with canine DC, and the MSC effects on DC maturation and activation were assessed by flow cytometry, cytokine ELISA, and confocal microscopy. We found that canine MSC significantly suppressed lipopolysaccharide (LPS)-stimulated upregulation of DC activation markers such as major histocompatibility class II (MHCII), CD86, and CD40. Furthermore, pretreatment of MSC with interferon gamma (IFNγ) augmented this suppressive activity. IFNγ-activated MSC also significantly reduced LPS-elicited DC secretion of tumor necrosis factor alpha without reducing secretion of interleukin-10. The suppressive effect of IFNγ-treated MSC on LPS-induced DC activation was mediated by soluble factors secreted by both MSC and DC. Pathways of DC functional suppression included programmed death ligand-1 expression and secretion of nitrous oxide, prostaglandin E2, and adenosine by activated MSC. Coculture of DC with IFNγ-treated MSC maintained DC in an immature state and prolonged DC antigen uptake during LPS maturation stimulus. Taken together, canine MSC are capable of potently suppressing DC function in a potentially inflammatory microenvironment through several separate immunological pathways and confirm the potential for immune therapy with MSC in canine immune-mediated disease models.

Immunomodulatory effects of OX40Ig gene-modified adipose tissue-derived mesenchymal stem cells on rat kidney transplantation

Recent studies have suggested that adipose tissue-derived mesenchymal stem cell (ADSC) therapy and OX40 costimulation blockade are two immunomodulatory strategies used to suppress the immune response to alloantigens. However, relatively little has been reported regarding the immunomodulatory potential of the abilityof these two strategies to synergize. Thus, in the present study, we aimed to investigate OX40-Ig fusion protein (OX40Ig) expression in ADSCs and to validate their more potent immunosuppressive activity in preventing renal allograft rejection. For this purpose, ADSCs from Lewis rats were transfected with the recombinant plasmid, pcDNA3.1(-)OX40Ig, by nucleofection. The ADSCs transduced with the plasmid (termed ADSCsOX40Ig) or untransduced ADSCs (termed ADSCsnative) were added to allostimulated mixed lymphocyte reaction (MLR) in vitro. In vivo, ADSCsOX40Ig, ADSCsnative, or PBS were administered to an allogeneic renal transplantation model, and the therapeutic effects, as well as the underlying mechanisms were examined. The results revealed that both the ADSCsnative and ADSCsOX40Ig significantly suppressed T cell proliferation and increased the percentage of CD4+CD25+ regulatory T cells in allogeneic MLR assays, with the ADSCsOX40Ig being more effective. Furthermore, the results from our in vivo experiments revealed that compared with the ADSCsnative or PBS group, the administration of autologous ADSCsOX40Ig markedly prolonged the mean survival time of renal grafts, reduced allograft rejection, and significantly downregulated the mRNA expression of intragraft interferon-γ (IFN-γ) , and upregulated the mRNA expression of interleukin (IL)‑10, transforming growth factor-β (TGF-β) and forkhead box protein 3 (Foxp3). The findings of our study indicate that the use of ADSCsOX40Ig is a promising strategy for preventing renal allograft rejection. This strategy provides the synergistic benefits of ADSC immune modulation and OX40-OX40L pathway blockade, and may therefore have therapeutic potential in clinical renal transplantation.

Molecular Characterization of Equine APRIL and its Expression Analysis During the Adipogenic Differentiation of Equine Adipose-Derived Stem Cell In Vitro

A proliferation inducing ligand (APRIL) is a member of the TNF superfamily. It shares two receptors with B-cell activating factor (BAFF), B-cell maturation antigen (BCMA), and transmembrane activator and CAML interactor (TACI). Herein, the equine APRIL was identified from equine adipose-derived stem cell (ASC), and the protein expression of APRIL and its related molecules were detected during the adipogenic differentiation of equine ASC in vitro. The equine APRIL gene was located on chromosome 11, spans 1852 base pairs (bp). Its open reading frame covers 753 bp, encoding a 250-amino acid protein with the typical TNF structure domain. During the two weeks' adipogenic differentiation of equine ASC, although the protein expression of APRIL and TACI had an insignificant change, that of BCMA increased significantly. Moreover, with the addition of recombinant protein His6-sAPRIL, a reduced differentiation of equine ASC toward adipocyte was detected. These results may provide the basis for investigating the role of APRIL in ASC adipogenic differentiation.