Translating stem cell therapies: the role of companion animals in regenerative medicine

Generation of footprint-free, high-quality feline induced pluripotent stem cells using Sendai virus vector

Companion animals, such as felines and canines, could provide an excellent platform for translational research from veterinary to human medicine. However, the use of feline induced pluripotent stems (fiPSCs) of quality in basic or clinical research has not been reported. Here, we generated footprint-free fiPSCs derived from embryonic cells, as well as juvenile feline uterus-derived cells using Sendai virus vector harboring six feline-specific pluripotency-associated genes. The fiPSCs were confirmed to be of high quality with the potential to form teratomas including all three germ layers. Furthermore, our fiPSCs were maintained under feeder-free and chemically-defined conditions using StemFit® AK02N and recombinant laminin 511, iMatrix-511. Further research on fiPSCs could result in their widespread application in veterinary regenerative medicine, which could pave the way for their use in advanced regenerative medicine research for humans.

Adipose-derived stem cell exosomes act as delivery vehicles of microRNAs in a dog model of chronic hepatitis

Exosomes are nanosized extracellular vesicles secreted by all cell types, including canine adipose-derived stem cells (cADSCs). By mediating intercellular communication, exosomes modulate the biology of adjacent and distant cells by transferring their cargo. In the present work after isolation and characterization of exosomes derived from canine adipose tissue, we treated the same canine donors affected by hepatopathies with the previously isolated exosomes. We hypothesize that cADSC-sourced miRNAs are among the factors responsible for a regenerative and anti-inflammatory effect in the treatment of hepatopathies in dogs, providing the clinical veterinary field with an effective and innovative cell-free therapy. Exosomes were isolated and characterized for size, distribution, surface markers, and for their miRNomic cargo by microRNA sequencing. 295 dogs affected with hepatopathies were treated and followed up for 6 months to keep track of their biochemical marker levels. Results confirmed that exosomes derived from cADSCs exhibited an average diameter of 91 nm, and positivity to 8 known exosome markers. The administration of exosomes to dogs affected by liver-associated inflammatory pathologies resulted in the recovery of the animal alongside the normalization of biochemical parameters of kidney function. In conclusion, cADSCs-derived exosomes are a promising therapeutic tool for treating inflammatory disorders in animal companions.

Impact of multiple isolation procedures on the differentiation potential of adipose derived canine mesenchymal stem cells

OBJECTIVE

In regenerative biology, the most commonly used cells are adipose tissue-derived mesenchymal stem cells (AD-MSCs). This is due to the abundance and easy accessibility of AD-MSCs.

METHODS

In this study, canine AD-MSCs were harvested from different anatomical locations, i.e., subcutaneous (SC), omental (OM), and perirenal (PR). Various isolation techniques namely explants (TRT-I), collagenase-digestion (TRT-II), collagenase-digested explants (TRT-III), and trypsin-digested explants (TRT-IV) were used to segregate the MSCs to evaluate cell doubling time, viability, and adipogenic/osteogenic lineage differentiation potential.

RESULTS

The study showed that the SC stem cells had superior growth kinetics compared to other tissues, while the cells isolated through TRT-II performed better than the other cell isolation procedures. The metabolic status of cells isolated from dog adipose tissue indicated that all cells had adequate metabolic rates. However, SC-MSCs derived from TRT-III and TRT-IV outperformed those derived from TRT-I and TRT-II. The differentiation analysis revealed that cells differentiate into adipogenic and osteogenic lineage regardless of treatment, as demonstrated by positive oil red O (ORO) and Alizarin Red S (ALZ) stain. It is worth mentioning that cells derived from TRT-III had larger and more intracellular droplets compared to the other treatments. The TRT-I, -II, and -III showed greater osteogenic differentiation in cells isolated from PR and OM regions compared to SC-derived cells. However, the TRT-IV resulted in better osteogenic differentiation in cells from SC, followed by the OM and PR-derived cells.

CONCLUSION

It is concluded that all methods of MSCs isolation from adipose tissues are successful; however, the TRT-II had the highest rate of cell re-assortment from the SC, while, TRT-II and -IV are most suitable for isolating cells from PR and OM adipose tissue.

Generation of canine induced pluripotent stem cells under feeder-free conditions using Sendai virus vector encoding six canine reprogramming factors

Although it is in its early stages, canine induced pluripotent stem cells (ciPSCs) hold great potential for innovative translational research in regenerative medicine, developmental biology, drug screening, and disease modeling. However, almost all ciPSCs were generated from fibroblasts, and available canine cell sources for reprogramming are still limited. Furthermore, no report is available to generate ciPSCs under feeder-free conditions because of their low reprogramming efficiency. Here, we reanalyzed canine pluripotency-associated genes and designed canine LIN28A, NANOG, OCT3/4, SOX2, KLF4, and C-MYC encoding Sendai virus vector, called 159cf. and 162cf. We demonstrated that not only canine fibroblasts but also canine urine-derived cells, which can be isolated using a noninvasive and straightforward method, were successfully reprogrammed with or without feeder cells. ciPSCs existed in undifferentiated states, differentiating into the three germ layers in vitro and in vivo. We successfully generated ciPSCs under feeder-free conditions, which can promote studies in veterinary and consequently human regenerative medicines.

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

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

KY19382 Accelerates Cutaneous Wound Healing via Activation of the Wnt/β-Catenin Signaling Pathway

The Wnt/β-catenin signaling pathway plays important roles in the multi-phases of wound healing: homeostasis, inflammation, proliferative, and remodeling phases. However, there are no clinically available therapeutic agents targeting the Wnt/β-catenin pathway. In this study, we tested the effect of 5, 6-dichloroindirubin-3'-methoxime (KY19382), a small molecule that activates the Wnt/β-catenin pathway via interference with the function of the negative feedback regulator CXXC5, on cutaneous wound healing. KY19382 significantly enhanced cell migration of human keratinocytes and dermal fibroblasts with increased levels of β-catenin, phalloidin, Keratin 14, proliferating cell nuclear antigen (PCNA), Collagen I, and alpha-smooth muscle actin (α-SMA) by activating the Wnt/β-catenin signaling pathway without causing significant cytotoxicity. In addition, levels of Collagen I, Keratin 14, PCNA, and stem cell markers were significantly increased by KY19382 in a cutaneous murine wound healing model. Moreover, KY19382 treatment accelerated re-epithelialization and neo-epidermis formation with collagen deposition and stem cell activation at an early stage of cutaneous wound healing. Overall, KY19382 accelerates wound healing via activating the Wnt/β-catenin pathway, and may have the potential to be used for the development of a new wound healing agent.

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.

The role of embryonic stem cells, transcription and growth factors in mammals: A review

Mammals represent a relevant species in worldwide cultures with significant commercial value. These animals are considered an attractive large animal model for biomedical and biotechnology research. The development of large animal experimental models may open alternative strategies for investigating stem cells (SCs) physiology and potential application in the veterinary field. The embryonic stem cells (ESCs) are known to possess natural pluripotency that confers the ability to differentiate into various tissues in vivo and in vitro. These notable characteristics can be useful for research and innovative applications, including biomedicine, agriculture and industry. Transcription factors play a crucial role in preserving stem cell self-renewal, whereas growth factors are involved in both growth and differentiation. However, to date, many questions concerning pluripotency, cellular differentiation regulator genes, and other molecules such as growth factors and their interactions in many mammalian species remain unresolved. The purpose of this review is to provide an overall review regarding the study of ESCs in mammals and briefly discuss the role of transcription and growth factors.

An Update on Applications of Cattle Mesenchymal Stromal Cells

Simple Summary

Among livestock species, cattle are crucially important for the meat and milk production industry. Cows can be affected by different pathologies, such as mastitis, endometritis and lameness, which can negatively affect either food production or reproductive efficiency. The use of mesenchymal stromal cells (MSCs) is a valuable tool both in the treatment of various medical conditions and in the application of reproductive biotechnologies. This review provides an update on state-of-the-art applications of bovine MSCs to clinical treatments and reproductive biotechnologies.

Abstract

Attention on mesenchymal stromal cells (MSCs) research has increased in the last decade mainly due to the promising results about their plasticity, self-renewal, differentiation potential, immune modulatory and anti-inflammatory properties that have made stem cell therapy more clinically attractive. Furthermore, MSCs can be easily isolated and expanded to be used for autologous or allogenic therapy following the administration of either freshly isolated or previously cryopreserved cells. The scientific literature on the use of stromal cells in the treatment of several animal health conditions is currently available. Although MSCs are not as widely used for clinical treatments in cows as for companion and sport animals, they have the potential to be employed to improve productivity in the cattle industry. This review provides an update on state-of-the-art applications of bovine MSCs to clinical treatments and reproductive biotechnologies.

Peptide Mediated Adhesion to Beta-Lactam Ring of Equine Mesenchymal Stem Cells: A Pilot Study

Simple Summary

In recent years, stem cell therapy has emerged as a promising potential treatment for chronic wounds in both human and veterinary medicine. Particularly, mesenchymal stem cells (MSCs) may be an attractive therapeutic tool for regenerative medicine and tissue engineering because these cells play a critical role in wound repair and tissue regeneration due to their immunosuppressive properties and multipotency. The use of biomaterials with integrin agonists could promote cell adhesion increasing tissue repair processes. This pilot study focuses on the adhesion ability of equine adult (adipose tissue) and fetal adnexa (Wharton’s jelly) derived MSCs mediated by GM18, an α4β1 integrin agonist, alone and combined with a biodegradable polymeric scaffold. Results show that a 24 h exposition to soluble GM18 affects equine MSCs adhesion ability with a donor-related variability and might suggest that WJ-MSCs more easily adhere to poly L-lactic acid (PLLA) nanofibers combined with GM18. These preliminary results need to be confirmed by further studies on the interactions between the different types of equine MSCs and GM18 incorporated PLLA scaffolds before drawing definitive conclusions on which cells and scaffolds could be successfully used for the treatment of decubitus ulcers.

Abstract

Regenerative medicine applied to skin lesions is a field in constant improvement. The use of biomaterials with integrin agonists could promote cell adhesion increasing tissue repair processes. The aim of this pilot study was to analyze the effect of an α4β1 integrin agonist on cell adhesion of equine adipose tissue (AT) and Wharton’s jelly (WJ) derived MSCs and to investigate their adhesion ability to GM18 incorporated poly L-lactic acid (PLLA) scaffolds. Adhesion assays were performed after culturing AT- and WJ-MSCs with GM18 coating or soluble GM18. Cell adhesion on GM18 containing PLLA scaffolds after 20 min co-incubation was assessed by HCS. Soluble GM18 affects the adhesion of equine AT- and WJ-MSCs, even if its effect is variable between donors. Adhesion to PLLA scaffolds containing GM18 is not significantly influenced by GM18 for AT-MSCs after 20 min or 24 h of culture and for WJ-MSCs after 20 min, but increased cell adhesion by 15% GM18 after 24 h. In conclusion, the α4β1 integrin agonist GM18 affects equine AT- and WJ-MSCs adhesion ability with a donor-related variability. These preliminary results represent a first step in the study of equine MSCs adhesion to PLLA scaffolds containing GM18, suggesting that WJ-MSCs might be more suitable than AT-MSCs. However, the results need to be confirmed by increasing the number of samples before drawing definite conclusions.

The effect of hypoxia on myogenic differentiation and multipotency of the skeletal muscle-derived stem cells in mice

Background

Skeletal muscle-derived stem cells (SC) have become a promising approach for investigating myogenic differentiation and optimizing tissue regeneration. Muscle regeneration is performed by SC, a self-renewal cell population underlying the basal lamina of muscle fibers. Here, we examined the impact of hypoxia condition on the regenerative capacity of SC either in their native microenvironment or via isolation in a monolayer culture using ectopic differentiation inductions. Furthermore, the effect of low oxygen tension on myogenic differentiation protocols of the myoblasts cell line C2C12 was examined.

Methods

Hind limb muscles of wild type mice were processed for both SC/fiber isolation and myoblast extraction using magnetic beads. SC were induced for myogenic, adipogenic and osteogenic commitments under normoxic (21% O2) and hypoxic (3% O2) conditions. SC proliferation and differentiation were evaluated using histological staining, immunohistochemistry, morphometric analysis and RT-qPCR. The data were statistically analyzed using ANOVA.

Results

The data revealed enhanced SC proliferation and motility following differentiation induction after 48 h under hypoxia. Following myogenic induction, the number of undifferentiated cells positive for Pax7 were increased at 72 h under hypoxia. Hypoxia upregulated MyoD and downregulated Myogenin expression at day-7 post-myogenic induction. Hypoxia promoted both SC adipogenesis and osteogenesis under respective induction as shown by using Oil Red O and Alizarin Red S staining. The expression of adipogenic markers; peroxisome proliferator activated receptor gamma (PPARγ) and fatty acid-binding protein 4 (FABP4) were upregulated under hypoxia up to day 14 compared to normoxic condition. Enhanced osteogenic differentiation was detected under hypoxic condition via upregulation of osteocalcin and osteopontin expression up to day 14 as well as, increased calcium deposition at day 21. Hypoxia exposure increases the number of adipocytes and the size of fat vacuoles per adipocyte compared to normoxic culture. Combining the differentiation medium with dexamethasone under hypoxia improves the efficiency of the myogenic differentiation protocol of C2C12 by increasing the length of the myotubes.

Conclusions

Hypoxia exposure increases cell resources for clinical applications and promotes SC multipotency and thus beneficial for tissue regeneration.

Clinical application of both amniotic membranes and adipose derived mesenchymal stem cells in a cat with a large skin defect

Surgical procedures on large skin defects can be challenging in the short term due to the size of the lesion, infection, and tissue defect. A regenerative therapy for skin wounds has been applied to promote the healing process. An 8-month-old, Korean domestic short-haired female cat, weighing 3 kg, was rescued with extensive defects on the right flank to right inguinal region caused by bite wounds. In this case, amniotic membranes and adipose-derived mesenchymal stem cells were used as the regenerative therapy to treat the large skin defect rather than a surgical intervention alone. To the best of our knowledge, this is the first report of a case with of a large skin defect treated by applying allogeneic amniotic membranes and allogeneic mesenchymal stem cells to a cat.

Approaches for Regenerative Healing of Cutaneous Wound with an Emphasis on Strategies Activating the Wnt/β-Catenin Pathway

Significance: In adult mammals, spontaneous repair of a cutaneous wound occurs slowly and leaves a scar with skin adnexa deficiencies. To accelerate cutaneous wound-healing rates and avoid scar formation, current studies have focused on regenerative therapies. Recent Advances: Emerging therapeutics for regenerative wound healing often focus on the use of growth factors and stem cells. However, these therapeutic approaches have limited routine clinical use due to high costs and technical requirements. Critical Issue: Understanding the molecular mechanisms involved in the signaling pathways for cutaneous wound healing and neogenic synthesis of the skin components is important for identification of novel targets for the development of regenerative wound-healing agents. Future Directions: The Wnt/β-catenin pathway is a well-known key player for enhancement of the overall healing process involving tissue regeneration via crosstalk with other signaling pathways. Strategies that activate the Wnt/β-catenin pathway via modulation of the pathway-controlling regulatory factors could provide effective therapeutic approaches for regenerative wound healing.

Cell Therapy in Veterinary Medicine as a Proof-of-Concept for Human Therapies: Perspectives From the North American Veterinary Regenerative Medicine Association

In the past decade, the potential to translate scientific discoveries in the area of regenerative therapeutics in veterinary species to novel, effective human therapies has gained interest from the scientific and public domains. Translational research using a One Health approach provides a fundamental link between basic biomedical research and medical clinical practice, with the goal of developing strategies for curing or preventing disease and ameliorating pain and suffering in companion animals and humans alike. Veterinary clinical trials in client-owned companion animals affected with naturally occurring, spontaneous disease can inform human clinical trials and significantly improve their outcomes. Innovative cell therapies are an area of rapid development that can benefit from non-traditional and clinically relevant animal models of disease. This manuscript outlines cell types and therapeutic applications that are currently being investigated in companion animals that are affected by naturally occurring diseases. We further discuss how such investigations impact translational efforts into the human medical field, including a critical evaluation of their benefits and shortcomings. Here, leaders in the field of veterinary regenerative medicine argue that experience gained through the use of cell therapies in companion animals with naturally occurring diseases represent a unique and under-utilized resource that could serve as a critical bridge between laboratory/preclinical models and successful human clinical trials through a One-Health approach.

Canine dental pulp and umbilical cord-derived mesenchymal stem cells as alternative sources for cell therapy in dogs

The use of regenerative medicine for pets has been growing in recent years, and an increasing number of studies have contributed to the widespread use of cell therapies in clinical veterinary medicine. Mesenchymal stem cells (MSCs) can be isolated from different sources such as dental pulp and umbilical cord. Aiming safety and reproducibility of cell therapy in clinical practice by using sources easily obtained that are usually discarded, this study isolated, characterized, and evaluated the proliferation and colony formation potential of canine dental pulp-derived mesenchymal stem cells (cDPSCs) and canine umbilical cord tissue (cUCSCs). Three samples from each source were collected, isolated, and cultured. MSCs were differentiated into three lineages and quantified by spectrophotometry. For immunophenotypic characterization, antibodies were used to analyze the expression of cell surface markers, and 7-AAD and Annexin-V were used to analyze cell viability and apoptosis, respectively. For the clonogenic assay, cells were cultured, the colonies were stained, and counted. For the proliferation assay, the cells were plated in flasks for three days and added EdU nucleoside. cDPSCs and cUCSCs showed plastic adherence and fibroblastic morphology after cultivation. Both sources showed differentiation potential and showed CD29 and CD44 positivity and CD14, CD45, CD34 and HLA-DR negativity, and low mortality and apoptosis rates. There was no difference in proliferation rates between sources. Overall, although cUCSCs had a higher number of colony-forming units than cDPSCs, both sources presented MSCs characteristics and can be used safely as alternative sources in cell therapy.

The One Medicine concept: its emergence from history as a systematic approach to re-integrate human and veterinary medicine

The COVID-19 pandemic has resulted in the global recognition for greater inter-disciplinary and multi-disciplinary working, and the need for systematic approaches which recognise the interconnectedness and interactions between human, animal and environmental health. The notion of such a One Team/One science approach is perhaps best exemplified by the One Health concept, a systematic approach which is rapidly entering into the mainstream. However, the concept of One Health, as we presently know it, originated from One Medicine, a notion which is much older and which emerged to promote collaboration between the human and veterinary medicine professions and the allied health/scientific disciplines. Whilst One Medicine is perhaps better known by the veterinary community, some misconceptions of what One Medicine is have arisen. Therefore, this review introduces this emerging concept and how it can help to address overlapping (communicable and non-communicable disease) health challenges faced by both human and veterinary medicine.

The equine navicular apparatus as a premier enthesis organ: Functional implications

Navicular syndrome has been traditionally characterized by progressive lameness with chronic degeneration of the navicular bone. Advances in imaging techniques have revealed that its associated soft tissue structures are also affected. This distribution of lesions is explained by conceptualizing the equine navicular apparatus as an enthesis organ that facilitates the dissemination of mechanical stress throughout the tissues of the foot. The navicular apparatus has the same structural adaptations to mechanical stress as the human Achilles tendon complex. These adaptations efficiently dissipate mechanical force away from the tendon's bony attachment site, thereby protecting it from failure. The comparison of these two anatomically distinct structural systems demonstrates their similar adaptations to mechanical forces, and illustrates that important functional insights can be gained from studying anatomic convergences and cross-species comparisons of function. Such a functional conceptualization of the equine navicular apparatus resolves confusion about the diagnosis of navicular syndrome and offers insights for the development of mechanically based therapies. Through comparison with the human Achilles complex, this review (1) re-conceptualizes the equine navicular apparatus as an enthesis organ in which mechanical forces are distributed throughout the structures of the organ; (2) describes the relationship between failure of the navicular enthesis organ and lesions of navicular syndrome; (3) considers the therapeutic implications of navicular enthesis organ degeneration as a form of chronic osteoarthritis; and based upon these implications (4) proposes a focus on whole body posture/motion for the development of prehabilitative and rehabilitative therapies similar to those that have already proven effective in humans.

A Cell-Based Approach to Dental Pulp Regeneration Using Mesenchymal Stem Cells: A Scoping Review

Despite the recent explosion of investigations on dental pulp regeneration using various tissue engineering strategies, the translation of the findings from such studies into therapeutic applications has not been properly achieved. The purpose of this scoping review was to systematically review the efficacy of mesenchymal stem cell transplantation for dental pulp regeneration. A literature search was conducted using five electronic databases from their inception to January 2021 and supplemented by hand searches. A total of 17 studies, including two clinical trials and 15 animal studies using orthotopic pulp regeneration models, were included for the review. The risk of bias for the individual studies was assessed. This scoping review demonstrated that the regeneration of vascularized pulp-like tissue was achieved using the stem cell transplantation strategy in animal models. Autologous cell transplantation in two clinical studies also successfully regenerated vascularized vital tissue. Dental pulp stem cell subpopulations, such as mobilized dental pulp stem cells, injectable scaffolds such as atelocollagen, and a granulocyte-colony forming factor, were the most commonly used for pulp regeneration. The overall risk of bias was unclear for animal studies and was moderate or judged to raise some concerns for clinical studies. More high-quality clinical studies are needed to further determine the safety and efficacy of the stem cell transplantation strategy for dental pulp regeneration.

Perspectives of pluripotent stem cells in livestock

The recent progress in derivation of pluripotent stem cells (PSCs) from farm animals opens new approaches not only for reproduction, genetic engineering, treatment and conservation of these species, but also for screening novel drugs for their efficacy and toxicity, and modelling of human diseases. Initial attempts to derive PSCs from the inner cell mass of blastocyst stages in farm animals were largely unsuccessful as either the cells survived for only a few passages, or lost their cellular potency; indicating that the protocols which allowed the derivation of murine or human embryonic stem (ES) cells were not sufficient to support the maintenance of ES cells from farm animals. This scenario changed by the innovation of induced pluripotency and by the development of the 3 inhibitor culture conditions to support naïve pluripotency in ES cells from livestock species. However, the long-term culture of livestock PSCs while maintaining the full pluripotency is still challenging, and requires further refinements. Here, we review the current achievements in the derivation of PSCs from farm animals, and discuss the potential application areas.

In Vitro Induction of Pluripotency from Equine Fibroblasts in 20% or 5% Oxygen

The cellular reprogramming into pluripotency is influenced by external and internal cellular factors, such as in vitro culture conditions (e.g., environmental oxygen concentration), and the aging process. Herein, we aimed to generate and maintain equine iPSCs (eiPSCs) derived from fibroblasts of a horse older than 20 years and to evaluate the effect of different levels of oxygen tension (atmospheric 20% O₂, 5% O₂, or 20% to 5% O₂) on these cells. Fibroblasts were reprogrammed, and putative eiPSCs were positive for positive alkaline phosphatase detection; they were positive for pluripotency-related genes OCT4, REX1, and NANOG; immunofluorescence-positive staining was presented for OCT4 and NANOG (all groups), SOX2 (groups 5% O₂ and 20% to 5% O₂), and TRA-1-60, TRA-1-81, and SSEA-1 (only in 20% O₂); they formed embryoid bodies; and there is spontaneous differentiation in mesoderm, endoderm, and ectoderm embryonic germ layers. In addition to the differences in immunofluorescence analysis results, the eiPSC colonies generated at 20% O₂ presented a more compact morphology with a well-defined border than cells cultured in 5% O₂ and 20% to 5% O₂. Significant differences were also observed in the expression of genes related to glucose metabolism, mitochondrial fission, and hypoxia (GAPDH, GLUT3, MFN1, HIF1α, and HIF2α), after reprogramming. Our results show that the derivation of eiPSCs was not impaired by aging. Additionally, this study is the first to compare high and low oxygen cultures of eiPSCs, showing the generation of pluripotent cells with different profiles. Under the tested conditions, the lower oxygen tension did not favor the pluripotency of eiPSCs. This study shows that the impact of oxygen atmosphere has to be considered when culturing eiPSCs, as this condition influences the pluripotency characteristics.

Injectable Gel Form of a Decellularized Bladder Induces Adipose-Derived Stem Cell Differentiation into Smooth Muscle Cells In Vitro

Biologic scaffolds composed of extracellular matrix components have been proposed to repair and reconstruct a variety of tissues in clinical and pre-clinical studies. Injectable gels can fill and conform any three-dimensional shape and can be delivered to sites of interest by minimally invasive techniques. In this study, a biological gel was produced from a decellularized porcine urinary bladder by enzymatic digestion with pepsin. The enzymatic digestion was confirmed by visual inspection after dissolution in phosphate-buffered saline solution and Fourier-transform infrared spectroscopy. The rheological and biological properties of the gel were characterized and compared to those of the MatrigelTM chosen as a reference material. The storage modulus G' reached 19.4 ± 3.7 Pa for the 30 mg/mL digested decellularized bladder gels after ca. 3 h at 37 °C. The results show that the gel formed of the porcine urinary bladder favored the spontaneous differentiation of human and rabbit adipose-derived stem cells in vitro into smooth muscle cells to the detriment of cell proliferation. The results support the potential of the developed injectable gel for tissue engineering applications to reconstruct for instance the detrusor muscle part of the human urinary bladder.

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.

Adult mesenchymal stem cells: is there a role for purine receptors in their osteogenic differentiation?

The role played by mesenchymal stem cells (MSCs) in contributing to adult tissue homeostasis and damage repair thanks to their differentiation capabilities has raised a great interest, mainly in bone regenerative medicine. The growth/function of these undifferentiated cells of mesodermal origin, located in specialized structures (niches) of differentiated organs is influenced by substances present in this microenvironment. Among them, ancestral and ubiquitous molecules such as adenine-based purines, i.e., ATP and adenosine, may be included. Notably, extracellular purine concentrations greatly increase during tissue injury; thus, MSCs are exposed to effects mediated by these agents interacting with their own receptors when they act/migrate in vivo or are transplanted into a damaged tissue. Here, we reported that ATP modulates MSC osteogenic differentiation via different P2Y and P2X receptors, but data are often inconclusive/contradictory so that the ATP receptor importance for MSC physiology/differentiation into osteoblasts is yet undetermined. An exception is represented by P2X7 receptors, whose expression was shown at various differentiation stages of bone cells resulting essential for differentiation/survival of both osteoclasts and osteoblasts. As well, adenosine, usually derived from extracellular ATP metabolism, can promote osteogenesis, likely via A2B receptors, even though findings from human MSCs should be implemented and confirmed in preclinical models. Therefore, although many data have revealed possible effects caused by extracellular purines in bone healing/remodeling, further studies, hopefully performed in in vivo models, are necessary to identify defined roles for these compounds in favoring/increasing the pro-osteogenic properties of MSCs and thereby their usefulness in bone regenerative medicine.

Design and fabrication of electrospun SBA-15-incorporated PVA with curcumin: a biomimetic nanoscaffold for skin tissue engineering

Fabricating and designing a scaffold is a complex and highly challenging process in the current scenario. The present study deals with the design and fabrication of electrospun Santa Barbara Amorphous (SBA)-15-incorporated polyvinyl alcohol (PVA) with curcumin, which can be used as a biomimetic nanoscaffold for skin tissue engineering. Curcumin was selected due to its effective anti-microbial and anti-inflammatory properties. SBA-15 was selected for its characteristic drug-carrying potential. Fourier transform infrared spectroscopy and x-ray diffraction characterizations of the fabricated nanofiber demonstrated the interaction of PVA, SBA-15 and curcumin. The scanning electron microscopy results depicted that the nanofiber was highly interconnected with a porous structure mimicking the extracellular matrix. The nanofibrous scaffold showed a higher percentage of cell migration, proliferation, cytocompatibility and biocompatibility with absence of cytotoxicity which was evidenced from the results of MTT assay, cell adhesion and live/dead assay using HaCaT cells. The results of the anti-bacterial test depicted that the synthesized nanofiber forms a potent material for skin wound-healing therapeutics. The in vitro drug release study performed over a period of 80 h revealed a sustained release pattern of curcumin from the SBA-15-incorporated PVA nanofiber. Finally, the in vivo results confirmed that SBA-15-incorporated PVA nanofiber with curcumin showed efficient wound-healing activities.

Long-Term Survival of Transplanted Autologous Canine Liver Organoids in a COMMD1-Deficient Dog Model of Metabolic Liver Disease

The shortage of liver organ donors is increasing and the need for viable alternatives is urgent. Liver cell (hepatocyte) transplantation may be a less invasive treatment compared with liver transplantation. Unfortunately, hepatocytes cannot be expanded in vitro, and allogenic cell transplantation requires long-term immunosuppression. Organoid-derived adult liver stem cells can be cultured indefinitely to create sufficient cell numbers for transplantation, and they are amenable to gene correction. This study provides preclinical proof of concept of the potential of cell transplantation in a large animal model of inherited copper toxicosis, such as Wilson’s disease, a Mendelian disorder that causes toxic copper accumulation in the liver. Hepatic progenitors from five COMMD1-deficient dogs were isolated and cultured using the 3D organoid culture system. After genetic restoration of COMMD1 expression, the organoid-derived hepatocyte-like cells were safely delivered as repeated autologous transplantations via the portal vein. Although engraftment and repopulation percentages were low, the cells survived in the liver for up to two years post-transplantation. The low engraftment was in line with a lack of functional recovery regarding copper excretion. This preclinical study confirms the survival of genetically corrected autologous organoid-derived hepatocyte-like cells in vivo and warrants further optimization of organoid engraftment and functional recovery in a large animal model of human liver disease.

Human adipose-derived mesenchymal stem cells accelerate decellularized neobladder regeneration

Decellularized natural bladder matrices (neobladders) represent an exciting means to regenerate the bladder following bladder cancer-associated cystectomy. In this study, we compare the evolution of decellularized matrices with recellularized matrices by seeding it with human adipose-derived mesenchymal stem cells (ADSC) after implantation following partial cystectomy in rats. We discovered significant anatomical differences since 10 days after neobladder implantation with the ADSC-containing matrices promoting a significant recovery of mature p63- and cytokeratin 7-positive urothelium. We also discovered significantly induced expression of the vimentin mesoderm marker in the submucosal layer in ADSC-seeded matrices. Interestingly, we found a higher expression of smooth muscle actin in transversal and longitudinal smooth muscle layers with ADSC-seeded matrices. Furthermore, ADSC also showed increased vascularization and nerve innervation of the neobladder as determined by the distribution of CD31 and S100β reactivity, respectively. We believe that ADSC and their paracrine-acting pro-regenerative secretome within decellularized matrices represent an efficient bladder substitution strategy; however, we require a fuller understanding of the mechanisms involved before clinical studies can begin.

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.

Characterization of canine adipose tissue-derived mesenchymal stem cells immortalized by SV40-T retrovirus for therapeutic use

Canine mesenchymal stem cells (cMSCs) are gaining popularity in the veterinary field as a regenerative therapy. But, their limited culture lifespan makes it an obstacle for preclinical investigation and therapeutic use. In this study, primary canine adipose tissue-derived MSCs (PCAT-MSCs) were isolated from adipose tissue and were transfected with the SV40-T retrovirus resulting in a life-extended immortalized canine adipose tissue-derived MSCs (ICAT-MSCs). A comparison was made through the characterization of both PCAT-MSCs and ICAT-MSCs. Both showed a fibroblastic morphology; ICAT-MSCs showed a higher potential of colony formation compared with PCAT-MSCs and a reduced population doubling time; stem cell markers SOX2 and NANOG were expressed in both cell lines; karyotyping analysis showed no abnormalities in both PCAT-MSCs and ICAT-MSCs; both cell lines were CD90⁺ , CD44 ⁺ , and CD45 ^- ; both generated chondrogenic pellet; in osteogenic differentiation both showed upregulation of Osterix, a master transcriptome of osteogenesis, but in PCAT-MSCs, an upregulation of SOX2 was also observed. In conclusion, ICAT-MSCs showed similar characteristics with PCAT-MSCs, thus established as an easy to access platform for studies on better understanding about cMSCs nature.

CellSaic, A Cell Aggregate-Like Technology Using Recombinant Peptide Pieces for MSC Transplantation

In the field of stem cell therapy, research on the application of Mesenchymal Stem Cells (MSCs) has flourished because of the various functions. On the other hand, research on the method of cell transplantation has developed from the administration of cell suspensions to cell-sheet engineering and 3D technology. In the trend, a cell transplantation platform named CellSaic, which is a combination of xeno-free recombinant scaffolds in a cell aggregate-like shape, was developed. CellSaic is the cell trans-plantation platform that can prevent the central necrosis within cell aggregates by arranging the cells and petaloid pieces of Recombinant Peptide (RCP) in a mosaic. The prevention of central necrosis is the most significant advantage over other 3D culture systems. This review details the unique characteristics of CellSaic including safety examination results and describes its future application for MSC transplantation. Particularly, in the application of MSCs, it has been reported that the MSC CellSaics increased the effect on improving various symptoms compared with MSCs only in the application of the therapy to Inflamma-tory Bowel Disease (IBD), cerebral infarction, bone cartilage regeneration in joints, and islet transplanta-tion. In accordance with the “One Health” concept, it is anticipated that this technology is expected to con-tribute to companion animal therapy and human therapy in the future.

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.

Stem cells on regenerative and reproductive science in domestic animals

Stem cells are undifferentiated and self-renewable cells that present new possibilities for both regenerative medicine and the understanding of early mammalian development. Adult multipotent stem cells are already widely used worldwide in human and veterinary medicine, and their therapeutic signalling, particularly with respect to immunomodulation, and their trophic properties have been intensively studied. The derivation of embryonic stem cells (ESCs) from domestic species, however, has been challenging, and the poor results do not reflect the successes obtained in mouse and human experiments. More recently, the generation of induced pluripotent stem cells (iPSCs) via the forced expression of specific transcription factors has been demonstrated in domestic species and has introduced new potentials in regenerative medicine and reproductive science based upon the ability of these cells to differentiate into a variety of cells types in vitro. For example, iPSCs have been differentiated into primordial germ-like cells (PGC-like cells, PGCLs) and functional gametes in mice. The possibility of using iPSCs from domestic species for this purpose would contribute significantly to reproductive technologies, offering unprecedented opportunities to restore fertility, to preserve endangered species and to generate transgenic animals for biomedical applications. Therefore, this review aims to provide an updated overview of adult multipotent stem cells and to discuss new possibilities introduced by the generation of iPSCs in domestic animals, highlighting the possibility of generating gametes in vitro via PGCL induction.

Roles of Mesenchymal Stem Cells in Tissue Regeneration and Immunomodulation

Mesenchymal stem cells are classified as multipotent stem cells, due to their capability to transdifferentiate into various lineages that develop from mesoderm. Their popular appeal as cell-based therapy was initially based on the idea of their ability to restore tissue because of their differentiation potential in vitro; however, the lack of evidence of their differentiation to target cells in vivo led researchers to focus on their secreted trophic factors and their role as potential powerhouses on regulation of factors under different immunological environments and recover homeostasis. To date there are more than 800 clinical trials on humans related to MSCs as therapy, not to mention that in animals is actively being applied as therapeutic resource, though it has not been officially approved as one. But just as how results from clinical trials are important, so is to reveal the biological mechanisms involved on how these cells exert their healing properties to further enhance the application of MSCs on potential patients. In this review, we describe characteristics of MSCs, evaluate their benefits as tissue regenerative therapy and combination therapy, as well as their immunological properties, activation of MSCs that dictate their secreted factors, interactions with other immune cells, such as T cells and possible mechanisms and pathways involved in these interactions.

Therapeutic Potential of Autologous Adipose-Derived Stem Cells for the Treatment of Liver Disease

Currently, the most effective therapy for liver diseases is liver transplantation, but its use is limited by organ donor shortage, economic reasons, and the requirement for lifelong immunosuppression. Mesenchymal stem cell (MSC) transplantation represents a promising alternative for treating liver pathologies in both human and veterinary medicine. Interestingly, these pathologies appear with a common clinical and pathological profile in the human and canine species; as a consequence, dogs may be a spontaneous model for clinical investigations in humans. The aim of this work was to characterize canine adipose-derived MSCs (cADSCs) and compare them to their human counterpart (hADSCs) in order to support the application of the canine model in cell-based therapy of liver diseases. Both cADSCs and hADSCs were successfully isolated from adipose tissue samples. The two cell populations shared a common fibroblast-like morphology, expression of stemness surface markers, and proliferation rate. When examining multilineage differentiation abilities, cADSCs showed lower adipogenic potential and higher osteogenic differentiation than human cells. Both cell populations retained high viability when kept in PBS at controlled temperature and up to 72 h, indicating the possibility of short-term storage and transportation. In addition, we evaluated the efficacy of autologous ADSCs transplantation in dogs with liver diseases. All animals exhibited significantly improved liver function, as evidenced by lower liver biomarkers levels measured after cells transplantation and evaluation of cytological specimens. These beneficial effects seem to be related to the immunomodulatory properties of stem cells. We therefore believe that such an approach could be a starting point for translating the results to the human clinical practice in future.

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.

Comparison of the characteristics of canine adipose tissue-derived mesenchymal stem cells extracted from different sites and at different passage numbers

Mesenchymal stem cells (MSCs) have desirable characteristics for use in therapy in animal models and veterinary medicine, due to their capacity of inducing tissue regeneration and immunomodulation. The objective of this study was to evaluate the differences between canine adipose tissue-derived MSCs (AD-MSCs) extracted from subcutaneous (Sc) and visceral (Vs) sites. Surface antigenic markers, in vitro differentiation, and mineralized matrix quantification of AD-MSCs at different passages (P₄, P₆, and P₈) were studied. Immunophenotypic analysis showed that AD-MSCs from both sites were CD44+, CD90+, and CD45-. Moreover, they were able, in vitro, to differentiate into fat, cartilage, and bone. Sc-AD-MSCs preserve in vitro multipotentiality up to P₈, but Vs-AD-MSCs only tri-differentiated up to P₄. In addition, compared to Vs-AD-MSCs, Sc-AD-MSCs had greater capacity for in vitro mineralized matrix synthesis. In conclusion, Sc-AD-MSCs have advantages over Vs-AD-MSCs, as Sc AD-MSCs preserve multipotentiality during a greater number of passages, have more osteogenic potential, and require less invasive extraction.

Current Status of Canine Umbilical Cord Blood-Derived Mesenchymal Stem Cells in Veterinary Medicine

Stem cell therapy has prompted the expansion of veterinary medicine both experimentally and clinically, with the potential to contribute to contemporary treatment strategies for various diseases and conditions for which limited or no therapeutic options are presently available. Although the application of various types of stem cells, such as bone marrow-derived mesenchymal stem cells (BM-MSCs), adipose tissue-derived mesenchymal stem cells (AT-MSCs), and umbilical cord blood-derived mesenchymal stem cells (UCB-MSCs), has promising potential to improve the health of different species, it is crucial that the benefits and drawbacks are completely evaluated before use. Umbilical cord blood (UCB) is a rich source of stem cells; nonetheless, isolation of mesenchymal stem cells (MSCs) from UCB presents technical challenges. Although MSCs have been isolated from UCB of diverse species such as human, equine, sheep, goat, and canine, there are inherent limitations of using UCB from these species for the expansion of MSCs. In this review, we investigated canine UCB (cUCB) and compared it with UCB from other species by reviewing recent articles published from February 2003 to June 2017 to gain an understanding of the limitations of cUCB in the acquisition of MSCs and to determine other suitable sources for the isolation of MSCs from canine. Our review indicates that cUCB is not an ideal source of MSCs because of insufficient volume and ethical issues. However, canine reproductive organs discarded during neutering may help broaden our understanding of effective isolation of MSCs. We recommend exploring canine reproductive and adipose tissue rather than UCB to fulfill the current need in veterinary medicine for the well-designed and ethically approved source of MSCs.

The Therapeutic Effects of Adipose-Derived Stem Cells and Recombinant Peptide Pieces on Mouse Model of DSS Colitis

Cell therapies using adipose-derived stem cells (ADSCs) have been used to treat inflammatory bowel disease (IBD) in human and dog. We previously reported the CellSaic technique, which uses a recombinant scaffold to enhance the efficacy of cell therapy. To examine whether this technique can be applied to cell therapy for colitis, we evaluated the efficacy of CellSaic in colitis mouse models. Colitis mouse models were developed by administering dextran sulfate sodium (DSS) to C57BL/6 mice for 7 days. Then CellSaic comprising human/canine ADSCs (1.2 × 10⁶ cells) or human/canine ADSCs only (1.2 × 10⁶ cells) were administered to the mice. The body weights were measured, and the colon length measurements and histological evaluations were conducted at 7 days after administration. After in vitro culture of human ADSC (hADSC) CellSaic and hADSC spheroids in medium containing TNFα, the levels of the anti-inflammatory protein TSG-6 in each supernatant were measured. Furthermore, we conducted tumorigenicity and general toxicity tests of canine ADSC (cADSC) CellSaic in NOG mice for 8 weeks. In the colitis mouse models, the ADSC CellSaic group presented recovery of body weight and colon length compared with the ADSC-only group. Histological analysis showed that ADSC CellSaic decreased the number of inflammatory cells and repaired ulceration. In vitro, hADSC CellSaic secreted 3.1-fold more TSG-6 than the hADSCs. In addition, tumorigenicity and general toxicity of cADSC CellSaic were not observed. This study suggests that human and canine ADSC CellSaic has a therapeutic effect of colitis in human and dogs.

Preclinical Development of Cell-Based Products: a European Regulatory Science Perspective

PURPOSE

This article describes preclinical development of cell-based medicinal products for European markets and discusses European regulatory mechanisms open to developers to aid successful product development. Cell-based medicinal products are diverse, including cells that are autologous or allogeneic, have been genetically modified, or not, or expanded ex vivo, and applied systemically or to an anatomical site different to that of their origin; comments applicable to one product may not be applicable to others, so bespoke development is needed, for all elements - quality, preclinical and clinical.

METHODS

After establishing how the product is produced, proof of potential for therapeutic efficacy, and then safety, of the product need to be determined. This includes understanding biodistribution, persistence and toxicity, including potential for malignant transformation. These elements need to be considered in the context of the intended clinical development.

RESULTS

This article describes regulatory mechanisms available to developers to support product development that aim to resolve scientific issues prior to marketing authorization application, to enable patients to have faster access to the product than would otherwise be the case.

CONCLUSIONS

Developers are encouraged to be aware of both the scientific issues and regulatory mechanisms to ensure patients can be supplied with these products.

Allogeneic transplantation of mobilized dental pulp stem cells with the mismatched dog leukocyte antigen type is safe and efficacious for total pulp regeneration

Background

We recently demonstrated that autologous transplantation of mobilized dental pulp stem cells (MDPSCs) was a safe and efficacious potential therapy for total pulp regeneration in a clinical study. The autologous MDPSCs, however, have some limitations to overcome, such as limited availability of discarded teeth from older patients. In the present study, we investigated whether MDPSCs can be used for allogeneic applications to expand their therapeutic use.

Methods

Analysis of dog leukocyte antigen (DLA) was performed using polymerase chain reaction from blood. Canine allogeneic MDPSCs with the matched and mismatched DLA were transplanted with granulocyte-colony stimulating factor in collagen into pulpectomized teeth respectively (n = 7, each). Results were evaluated by hematoxylin and eosin staining, Masson trichrome staining, PGP9.5 immunostaining, and BS-1 lectin immunostaining performed 12 weeks after transplantation. The MDPSCs of the same DLA used in the first transplantation were further transplanted into another pulpectomized tooth and evaluated 12 weeks after transplantation.

Results

There was no evidence of toxicity or adverse events of the allogeneic transplantation of the MDPSCs with the mismatched DLA. No adverse event of dual transplantation of the MDPSCs with the matched and mismatched DLA was observed. Regenerated pulp tissues including neovascularization and neuronal extension were quantitatively and qualitatively similar at 12 weeks in both matched and mismatched DLA transplants. Regenerated pulp tissue was similarly observed in the dual transplantation as in the single transplantation of MDPSCs both with the matched and mismatched DLA.

Conclusions

Dual allogeneic transplantation of MDPSCs with the mismatched DLA is a safe and efficacious method for total pulp regeneration.

Electronic supplementary material

The online version of this article (10.1186/s13287-018-0855-8) contains supplementary material, which is available to authorized users.

Isolation and Flow Cytometric Analysis of the Stromal Vascular Fraction Isolated from Mouse Adipose Tissue

Evidence from preclinical research and clinical trials demonstrates the use of the stromal vascular fraction (SVF) as therapy for numerous indications. These results demonstrate that autologous SVF is not only safe and effective but provides robust anti-inflammatory, immunomodulatory, and reparative effects in vivo. The potency of the SVF is attributed to the cellular composition which includes adipose-derived stem cells (ASCs), adipocytes, endothelial cells, and various immune cells. As the name would suggest, these SVF cells are derived from the stromal compartment of adipose, or fat. Once digested, the cells that constitute adipose are released and collected as the SVF. The cellular frequencies within the SVF can then be assessed using a fluorescent antibody-based technique known as flow cytometry. The following chapter provides a standard operating protocol that describes the procedures from harvesting the fat tissue from experimental mice to isolating and characterizing the SVF.

Characterization of companion animal pluripotent stem cells

Pluripotent stem cells have the capacity to grow indefinitely in culture and differentiate into derivatives of the three germ layers. These properties underpin their potential to be used in regenerative medicine. Originally derived from early embryos, pluripotent stem cells can now be derived by reprogramming an adult cell back to a pluripotent state. Companion animals such as horses, dogs, and cats suffer from many injuries and diseases for which regenerative medicine may offer new treatments. As many of the injuries and diseases are similar to conditions in humans the use of companion animals for the experimental and clinical testing of stem cell and regenerative medicine products would provide relevant animal models for the translation of therapies to the human field. In order to fully utilize companion animal pluripotent stem cells robust, standardized methods of characterization must be developed to ensure that safe and effective treatments can be delivered. In this review we discuss the methods that are available for characterizing pluripotent stem cells and the techniques that have been applied in cells from companion animals. We describe characteristics which have been described consistently across reports as well as highlighting discrepant results. Significant steps have been made to define the in vitro culture requirements and drive lineage specific differentiation of pluripotent stem cells in companion animal species. However, additional basic research to compare pluripotent stem cell types and define characteristics of pluripotency in companion animal species is still required. © 2017 International Society for Advancement of Cytometry.

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.

Canine articular cartilage regeneration using mesenchymal stem cells seeded on platelet rich fibrin: Macroscopic and histological assessments

Objectives

Mesenchymal stem cells have the ability to differentiate into various cell types, and thus have emerged as promising alternatives to chondrocytes in cell-based cartilage repair methods. The aim of this experimental study was to investigate the effect of bone marrow derived mesenchymal stem cells combined with platelet rich fibrin on osteochondral defect repair and articular cartilage regeneration in a canine model.

Methods

Osteochondral defects were created on the medial femoral condyles of 12 adult male mixed breed dogs. They were either treated with stem cells seeded on platelet rich fibrin or left empty. Macroscopic and histological evaluation of the repair tissue was conducted after four, 16 and 24 weeks using the International Cartilage Repair Society macroscopic and the O’Driscoll histological grading systems. Results were reported as mean and standard deviation (sd) and compared at different time points between the two groups using the Mann-Whitney U test, with a value < 0.05 considered statistically significant.

Results

Higher cumulative macroscopic and histological scores were observed in stem cell treated defects throughout the study period with significant differences noted at four and 24 weeks (9.25, sd 0.5 vs 7.25, sd 0.95, and 10, sd 0.81 vs 7.5, sd 0.57; p < 0.05) and 16 weeks (16.5, sd 4.04 vs 11, sd 1.15; p < 0.05), respectively. Superior gross and histological characteristics were also observed in stem cell treated defects.

Conclusion

The use of autologous culture expanded bone marrow derived mesenchymal stem cells on platelet rich fibrin is a novel method for articular cartilage regeneration. It is postulated that platelet rich fibrin creates a suitable environment for proliferation and differentiation of stem cells by releasing endogenous growth factors resulting in creation of a hyaline-like reparative tissue.

Cite this article: D. Kazemi, K. Shams Asenjan, N. Dehdilani, H. Parsa. Canine articular cartilage regeneration using mesenchymal stem cells seeded on platelet rich fibrin: Macroscopic and histological assessments. Bone Joint Res 2017;6:98–107. DOI: 10.1302/2046-3758.62.BJR-2016-0188.R1.

Injectable alginate-microencapsulated canine adipose tissue-derived mesenchymal stem cells for enhanced viable cell retention

The purpose of this study was to establish an optimized protocol for the production of alginate-encapsulated canine adipose-derived mesenchymal stem cells (cASCs) and evaluate their suitability for clinical use, including viability, proliferation and in vivo cell retention. Alginate microbeads were formed by vibrational technology and the production of injectable microbeads was performed using various parameters with standard methodology. Microbead toxicity was tested in an animal model. Encapsulated cASCs were evaluated for viability and proliferation in vitro. HEK-293 cells, with or without microencapsulation, were injected into the subcutaneous tissue of mice and were tracked using in vivo bioluminescent imaging to evaluate the retention of transplanted cells. The optimized injectable microbeads were of uniform size and approximately 250 µm in diameter. There was no strong evidence of in vivo toxicity for the alginate beads. The cells remained viable after encapsulation, and there was evidence of in vitro proliferation within the microcapsules. In vivo bioluminescent imaging showed that alginate encapsulation improved the retention of transplanted cells and the encapsulated cells remained viable in vivo for 7 days. Encapsulation enhances the retention of viable cells in vivo and might represent a potential strategy to increase the therapeutic potency and efficacy of stem cells.

Allogeneic Mesenchymal Stem Cell Transplantation in Dogs With Keratoconjunctivitis Sicca

Keratoconjunctivitis sicca (KCS) is a dysfunction in tear production associated with clinical signs, which include conjunctival hyperemia, ocular discharge, discomfort, pain, and, eventually, corneal vascularization and pigmentation. Immunosuppressive drugs are routinely administrated for long periods to treat KCS but with side effects and limited results. Evaluation of the clinical benefits of intralacrimal transplantation of allogeneic mesenchymal stem cells (MSCs) in dogs with mild-moderate and severe KCS was done. A total of 24 eyes with KCS from 15 dogs of different breeds were enrolled in the present study. A single transplantation of MSCs (1 × 10⁶) directly into lacrimal glands (dorsal and third eyelid) was performed. The Schirmer tear tests (STTs) and ocular surface improvements were used to assess short- and long-term effects of these cells. The STTs were carried out on day 0 (before MSCs transplantation) and on days 7, 14, 21, and 28, as well as 6 and 12 months after MSC transplantation. Our data demonstrate that allogeneic MSC transplantation in KCS dogs is safe since no adverse effects were observed immediately after transplantation and in short- and long-term follow-ups. A statistically significant increase in the STT and ocular surface improvements was found in all eyes studied. In all the eyes with mild-moderate KCS, STT values reverted to those of healthy eyes, while in eyes with severe KCS, although complete reversion was not found, there was improvement in tear production and in other clinical signs. Our study shows that a single dose of a low number of MSCs can be used to treat KCS in dogs. In contrast to immunosuppressive drug use, MSC transplantation has an effect over a long period (up to 12 months), even after a single administration, and does not require daily drug administration.