A local application of mesenchymal stem cells and cyclosporine A attenuates immune response by a switch in macrophage phenotype

Transplantation of fibrin-thrombin encapsulated human induced neural stem cells promotes functional recovery of spinal cord injury rats through modulation of the microenvironment

Recent studies have mostly focused on engraftment of cells at the lesioned spinal cord, with the expectation that differentiated neurons facilitate recovery. Only a few studies have attempted to use transplanted cells and/or biomaterials as major modulators of the spinal cord injury microenvironment. Here, we aimed to investigate the role of microenvironment modulation by cell graft on functional recovery after spinal cord injury. Induced neural stem cells reprogrammed from human peripheral blood mononuclear cells, and/or thrombin plus fibrinogen, were transplanted into the lesion site of an immunosuppressed rat spinal cord injury model. Basso, Beattie and Bresnahan score, electrophysiological function, and immunofluorescence/histological analyses showed that transplantation facilitates motor and electrophysiological function, reduces lesion volume, and promotes axonal neurofilament expression at the lesion core. Examination of the graft and niche components revealed that although the graft only survived for a relatively short period (up to 15 days), it still had a crucial impact on the microenvironment. Altogether, induced neural stem cells and human fibrin reduced the number of infiltrated immune cells, biased microglia towards a regenerative M2 phenotype, and changed the cytokine expression profile at the lesion site. Graft-induced changes of the microenvironment during the acute and subacute stages might have disrupted the inflammatory cascade chain reactions, which may have exerted a long-term impact on the functional recovery of spinal cord injury rats.

Enhancing Immunomodulatory Function of Mesenchymal Stromal Cells by Hydrogel Encapsulation

Mesenchymal stromal cells (MSCs) showcase remarkable immunoregulatory capabilities in vitro, positioning them as promising candidates for cellular therapeutics. However, the process of administering MSCs and the dynamic in vivo environment may impact the cell-cell and cell-matrix interactions of MSCs, consequently influencing their survival, engraftment, and their immunomodulatory efficacy. Addressing these concerns, hydrogel encapsulation emerges as a promising solution to enhance the therapeutic effectiveness of MSCs in vivo. Hydrogel, a highly flexible crosslinked hydrophilic polymer with a substantial water content, serves as a versatile platform for MSC encapsulation. Demonstrating improved engraftment and heightened immunomodulatory functions in vivo, MSCs encapsulated by hydrogel are at the forefront of advancing therapeutic outcomes. This review delves into current advancements in the field, with a focus on tuning various hydrogel parameters to elucidate mechanistic insights and elevate functional outcomes. Explored parameters encompass hydrogel composition, involving monomer type, functional modification, and co-encapsulation, along with biomechanical and physical properties like stiffness, viscoelasticity, topology, and porosity. The impact of these parameters on MSC behaviors and immunomodulatory functions is examined. Additionally, we discuss potential future research directions, aiming to kindle sustained interest in the exploration of hydrogel-encapsulated MSCs in the realm of immunomodulation.

Mesenchymal stem cell-based therapy for autoimmune-related fibrotic skin diseases-systemic sclerosis and sclerodermatous graft-versus-host disease

BACKGROUND

Systemic sclerosis (SSc) and sclerodermatous graft-versus-host disease (Scl-GVHD)-characterized by similar developmental fibrosis, vascular abnormalities, and innate and adaptive immune response, resulting in severe skin fibrosis at the late stage-are chronic autoimmune diseases of connective tissue. The significant immune system dysfunction, distinguishing autoimmune-related fibrosis from mere skin fibrosis, should be a particular focus of treating autoimmune-related fibrosis. Recent research shows that innovative mesenchymal stem cell (MSC)-based therapy, with the capacities of immune regulation, inflammation suppression, oxidation inhibition, and fibrosis restraint, shows great promise in overcoming the disease.

MAIN BODY

This review of recent studies aims to summarize the therapeutic effect and theoretical mechanisms of MSC-based therapy in treating autoimmune-related fibrotic skin diseases, SSc and Scl-GVHD, providing novel insights and references for further clinical applications. It is noteworthy that the efficacy of MSCs is not reliant on their migration into the skin. Working on the immune system, MSCs can inhibit the chemotaxis and infiltration of immune cells to the skin by down-regulating the expression of skin chemokines and chemokine receptors and reducing the inflammatory and pro-fibrotic mediators. ​Furthermore, to reduce levels of oxidative stress, MSCs may improve vascular abnormalities, and enhance the antioxidant defenses through inducible nitric oxide synthase, thioredoxin 1, as well as other mediators. The oxidative stress environment does not weaken MSCs and may even strengthen certain functions. Regarding fibrosis, MSCs primarily target the transforming growth factor-β signaling pathway to inhibit fibroblast activation. Here, miRNAs may play a critical role in ECM remodeling. Clinical studies have demonstrated the safety of these approaches, though outcomes have varied, possibly owing to the heterogeneity of MSCs, the disorders themselves, and other factors. Nevertheless, the research clearly reveals the immense potential of MSCs in treating autoimmune-related fibrotic skin diseases.

CONCLUSION

The application of MSCs presents a promising approach for treating autoimmune-related fibrotic skin diseases: SSc and Scl-GVHD. Therapies involving MSCs and MSC extracellular vesicles have been found to operate through three primary mechanisms: rebalancing the immune and inflammatory disorders, resisting oxidant stress, and inhibiting overactivated fibrosis (including fibroblast activation and ECM remodeling). However, the effectiveness of these interventions requires further validation through extensive clinical investigations, particularly randomized control trials and phase III/IV clinical trials. Additionally, the hypothetical mechanism underlying these therapies could be elucidated through further research.

Multiple Shades of Gray-Macrophages in Acute Allograft Rejection

Long-term results following solid organ transplantation do not mirror the excellent short-term results achieved in recent decades. It is therefore clear that current immunosuppressive maintenance protocols primarily addressing the adaptive immune system no longer meet the required clinical need. Identification of novel targets addressing this shortcoming is urgently needed. There is a growing interest in better understanding the role of the innate immune system in this context. In this review, we focus on macrophages, which are known to prominently infiltrate allografts and, during allograft rejection, to be involved in the surge of the adaptive immune response by expression of pro-inflammatory cytokines and direct cytotoxicity. However, this active participation is janus-faced and unspecific targeting of macrophages may not consider the different subtypes involved. Under this premise, we give an overview on macrophages, including their origins, plasticity, and important markers. We then briefly describe their role in acute allograft rejection, which ranges from sustaining injury to promoting tolerance, as well as the impact of maintenance immunosuppressants on macrophages. Finally, we discuss the observed immunosuppressive role of the vitamin-like compound tetrahydrobiopterin and the recent findings that suggest the innate immune system, particularly macrophages, as its target.

The Impact of Metal Nanoparticles on the Immunoregulatory and Therapeutic Properties of Mesenchymal Stem Cells

Negative impacts of nanomaterials on stem cells and cells of the immune system are one of the main causes of an impaired or slowed tissue healing. Therefore, we tested effects of four selected types of metal nanoparticles (NPs): zinc oxide (ZnO), copper oxide (CuO), silver (Ag), and titanium dioxide (TiO₂) on the metabolic activity and secretory potential of mouse mesenchymal stem cells (MSCs), and on the ability of MSCs to stimulate production of cytokines and growth factors by macrophages. Individual types of nanoparticles differed in the ability to inhibit metabolic activity, and significantly decreased the production of cytokines and growth factors (interleukin-6, vascular endothelial growth factor, hepatocyte growth factor, insulin-like growth factor-1) by MSCs, with the strongest inhibitory effect of CuO NPs and the least effect of TiO₂ NPs. The recent studies indicate that immunomodulatory and therapeutic effects of transplanted MSCs are mediated by macrophages engulfing apoptotic MSCs. We co-cultivated macrophages with heat-inactivated MSCs which were untreated or were preincubated with the highest nontoxic concentrations of metal NPs, and the secretory activity of macrophages was determined. Macrophages cultivated in the presence of both untreated MSCs or MSCs preincubated with NPs produced significantly enhanced and comparable levels of various cytokines and growth factors. These results suggest that metal nanoparticles inhibit therapeutic properties of MSCs by a direct negative effect on their secretory activity, but MSCs cultivated in the presence of metal NPs have preserved the ability to stimulate cytokine and growth factor production by macrophages.

An Effect of Cyclosporin A in a Treatment of Temporal Bone Defect Using hBM-MSCs

Background. The treatment of middle ear cholesteatoma requires surgical treatment and the reconstruction of the temporal bone, which represents an ongoing problem. Otologists have focused on the research of materials allowing an airy middle ear and the preservation of hearing function to reconstruct the temporal bone. Methods. This study evaluated the effect of cyclosporin A (CsA) and a combined biomaterial in the healing process of postoperative temporal bone defects in an animal model. Cultured human Bone Marrow Mesenchymal Stromal Cells (hBM-MSCs) were mixed with hydroxyapatite (Cem-Ostetic^®), and subsequently applied as a bone substitute after middle ear surgery, showing that the therapeutic potential of hBM-MSCs associated with bone regeneration and replacement is directly influenced by CsA, confirming that it promotes the survival of MSCs in vivo. Results. The therapeutic efficacy of the combination of MSCs with CsA is greater than the sole application of MSCs in a hydroxyapatite carrier. Conclusion. The reconstruction of a temporal bone defect using hBM-MSCs requires an immunosuppressant to improve the results of treatment.

Cyclosporine A Regulates Influenza A Virus-induced Macrophages Polarization and Inflammatory Responses by Targeting Cyclophilin A

Cyclosporine A (CsA) is an immunosuppressive drug that suppresses T cell responses and is broadly used in transplantation. Its immunosuppressive action is closely linked to its binding of cyclophilin A (CypA), which widely distributed in different cell types. CsA also regulates the functions of innate immune cells, but the mechanism remains elusive. Here, we investigate the role of CsA in regulating macrophages polarization in influenza A virus-infected mice and mouse bone marrow-derived macrophages. CsA downregulates pro-inflammatory cytokines expression and upregulates anti-inflammatory cytokines expression. Mechanically, CsA decreases the polarization of macrophages into pro-inflammatory M1 phenotype and increases the polarization of macrophages into anti-inflammatory M2 phenotype. Further studies show that CsA regulates macrophages polarization-associated IFN-γ/STAT1 and IL-4/STAT6 signaling pathways. Meanwhile, all these roles of CsA are eliminated when CypA is absent, suggesting that CsA regulates macrophages polarization and inflammatory responses depend on its binding to CypA. Collectively, these results reveal a crucial mechanism of CsA in attenuating IAV-induced inflammatory responses by a switch in macrophages polarization.

The Inability of Ex Vivo Expanded Mesenchymal Stem/Stromal Cells to Survive in Newborn Mice and to Induce Transplantation Tolerance

An encounter of the developing immune system with an antigen results in the induction of immunological areactivity to this antigen. In the case of transplantation antigens, the application of allogeneic hematopoietic cells induces a state of neonatal transplantation tolerance. This tolerance depends on the establishment of cellular chimerism, when allogeneic cells survive in the neonatally treated recipient. Since mesenchymal stem/stromal cells (MSCs) have been shown to have low immunogenicity and often survive in allogeneic recipients, we attempted to use these cells for induction of transplantation tolerance. Newborn (less than 24 h old) C57BL/6 mice were injected intraperitoneally with 5 × 10⁶ adipose tissue-derived MSCs isolated from allogeneic donors and the fate and survival of these cells were monitored. The impact of MSC application on the proportion of cell populations of the immune system and immunological reactivity was assessed. In addition, the survival of skin allografts in neonatally treated recipients was tested. We found that in vitro expanded MSCs did not survive in neonatal recipients, and the living MSCs were not detected few days after their application. Furthermore, there were no significant changes in the proportion of individual immune cell populations including CD4⁺ cell lineages, but we detected an apparent shift to the production of Th1 cytokines IL-2 and IFN-γ in neonatally treated mice. However, skin allografts in the MSC-treated recipients were promptly rejected. These results therefore show that in vitro expanded MSCs do not survive in neonatal recipients, but induce a cytokine imbalance without induction of transplantation tolerance.

Macrophage Polarization and Plasticity in Systemic Lupus Erythematosus

Systemic lupus erythematosus (SLE) is an autoimmune disease that attacks almost every organ. The condition mostly happens to adults but is also found in children, and the latter have the most severe manifestations. Among adults, females, especially non-Caucasian, are mostly affected. Even if the etiology of SLE remains unclear, studies show a close relation between this disease and both genetics and environment. Despite the large number of published articles about SLE, we still do not have a clear picture of its pathogenesis, and no specific drug has been found to treat this condition effectively. The implication of macrophages in SLE development is gaining ground, and studying it could answer these gaps. Indeed, both in vivo and in vitro studies increasingly report a strong link between this disease and macrophages. Hence, this review aims to explore the role of macrophages polarization and plasticity in SLE development. Understanding this role is of paramount importance because in-depth knowledge of the connection between macrophages and this systemic disease could clarify its pathogenesis and provide a foundation for macrophage-centered therapeutic approaches.

Macrophages in Transplantation: A Matter of Plasticity, Polarization, and Diversity

Macrophages have emerged at the forefront of research in immunology and transplantation because of recent advances in basic science. New findings have illuminated macrophage populations not identified previously, expanded upon traditional macrophage phenotypes, and overhauled macrophage ontogeny. These advances have major implications for the field of transplant immunology. Macrophages are known to prime adaptive immune responses, perpetuate T-cell-mediated rejection and antibody-mediated rejection, and promote allograft fibrosis. In this review, macrophage phenotypes and their role in allograft injury of solid organ transplants will be discussed with an emphasis on kidney transplantation. Additionally, consideration will be given to the prospect of manipulating macrophage phenotypes as cell-based therapy. Innate immunity and macrophages represent important players in allograft injury and a promising target to improve transplant outcomes.

Sertoli Cells Possess Immunomodulatory Properties and the Ability of Mitochondrial Transfer Similar to Mesenchymal Stromal Cells

It is becoming increasingly evident that selecting an optimal source of mesenchymal stromal cells (MSCs) is crucial for the successful outcome of MSC-based therapies. During the search for cells with potent regenerative properties, Sertoli cells (SCs) have been proven to modulate immune response in both in vitro and in vivo models. Based on morphological properties and expression of surface markers, it has been suggested that SCs could be a kind of MSCs, however, this hypothesis has not been fully confirmed. Therefore, we compared several parameters of MSCs and SCs, with the aim to evaluate the therapeutic potential of SCs in regenerative medicine. We showed that SCs successfully underwent osteogenic, chondrogenic and adipogenic differentiation and determined the expression profile of canonical MSC markers on the SC surface. Besides, SCs rescued T helper (Th) cells from undergoing apoptosis, promoted the anti-inflammatory phenotype of these cells, but did not regulate Th cell proliferation. MSCs impaired the Th17-mediated response; on the other hand, SCs suppressed the inflammatory polarisation in general. SCs induced M2 macrophage polarisation more effectively than MSCs. For the first time, we demonstrated here the ability of SCs to transfer mitochondria to immune cells. Our results indicate that SCs are a type of MSCs and modulate the reactivity of the immune system. Therefore, we suggest that SCs are promising candidates for application in regenerative medicine due to their anti-inflammatory and protective effects, especially in the therapies for diseases associated with testicular tissue inflammation.

The Altered Migration and Distribution of Systemically Administered Mesenchymal Stem Cells in Morphine-Treated Recipients

Mesenchymal stem cells (MSCs) have the ability to migrate to the site of injury or inflammation, and to contribute to the healing process. Since patients treated with MSCs are often users of analgesic drugs, to relieve their uncomfortable pain associated with the tissue disorder, there is a possibility of negative effects of these drugs on the migration of endogenous and exogenous MSCs. Therefore, we tested the impact of acute and chronic treatment with morphine on the migration and organ distribution of exogenous adipose tissue-derived MSCs in mouse models. Firstly, we showed that the incubation of MSCs with morphine significantly reduced the expression of adhesive molecules CD44 (HCAM), CD54 (ICAM-1) and CD106 (VCAM-1) on MSCs. Using a model of systemic administration of MSCs labeled with vital dye PKH26 and by the application of flow cytometry to detect living CD45^-PKH26⁺ cells, we found a decreased number of labeled MSCs in the lung, spleen and bone marrow, and a significantly increased number of MSCs in the liver of morphine-treated recipients. A skin allograft model was used to study the effects of morphine on the migration of exogenous MSCs to the superficial wound. Intraperitoneally administered MSCs migrated preferentially to the wound site, and this migration was significantly decreased in the morphine-treated recipients. The present results showed that morphine significantly influences the distribution of exogenous MSCs in the body, and decreases their migration to the site of injury.

Giant cell tumor stromal cells: osteoblast lineage-derived cells secrete IL-6 and IL-10 for M2 macrophages polarization

Background

The giant cell tumor (GCT) is a benign tumor which consists of three types cells: mononuclear histiocytic cells (MNHCs), multinuclear giant cells (MNGCs), and GCT stromal cells (GCTSCs). Numerous studies claim that GCTSCs have mesenchymal stem cells (MSCs) characters and play an important role in osteoclastogenesis; however, there are no research studies concerning macrophage polarization among GCT, which can be regarded as an ingredient for tumor aggression.

Method

We tested the effect of GCTSCs from three GCT samples which were collected from patients on proliferation, apoptosis and polarization of macrophage.

Result

In this article, we verified that GCTSCs expressed MSCs markers and had higher proliferation and relative lower differentiation abilities compared with BMMSCs. What's more, we found a higher proportion of M2 macrophages among neoplasm. Co-culturing GCTSCs with macrophages resulted in prominent macrophage M2 polarization and increased the release of IL-6 (Interleukin-6) and IL-10 (Interleukin-10)from GCTSCs. In conclusion, GCTSCs, as originating from MSCs, can secret IL-6 and IL-10, which may play a significant role in macrophage M2 polarization.

Mesenchymal Stem Cells: A Potential Therapeutic Strategy for Neurodegenerative Diseases

Neurodegenerative disease is a kind of chronic, progressive nervous system disease characterized by neuron degeneration or apoptosis. Current treatments cannot prevent the development of the disease. Possible alternative treatments include cell therapy, especially with the use of mesenchymal stem cells (MSCs). MSCs are pluripotent stem cells with capacities for self-renewal and multidirectional differentiation. MSCs may serve as a reliable source of neural cells for potential cell replacement therapy or regenerative medicine treatment. Here, we summarized the therapeutic mechanisms of MSCs and how they can contribute to the development of treatments for neurodegenerative diseases.

Cyclosporine A promotes the therapeutic effect of mesenchymal stem cells on transplantation reaction

The successful application of mesenchymal stem cells (MSCs) remains a major challenge in stem cell therapy. Currently, several in vitro studies have indicated potentially beneficial interactions of MSCs with immunosuppressive drugs. These interactions can be even more complex in vivo, and it is in this setting that we investigate the effect of MSCs in combination with Cyclosporine A (CsA) on transplantation reaction and allogeneic cell survival. Using an in vivo mouse model, we found that CsA significantly promoted the survival of MSCs in various organs and tissues of the recipients. In addition, compared to treatment with CsA or MSCs alone, the survival of transplanted allogeneic cells was significantly improved after the combined application of MSCs with CsA. We further observed that the combinatory treatment suppressed immune response to the alloantigen challenge and modulated the immune balance by harnessing proinflammatory CD4+T-bet+ and CD4+RORγt+ cell subsets. These changes were accompanied by a significant decrease in IL-17 production along with an elevated level of IL-10. Co-cultivation of purified naive CD4+ cells with peritoneal macrophages isolated from mice treated with MSCs and CsA revealed that MSC-educated macrophages play an important role in the immunomodulatory effect observed on distinct T-cell subpopulations. Taken together, our findings suggest that CsA promotes MSC survival in vivo and that the therapeutic efficacy of the combination of MSCs with CsA is superior to each monotherapy. This combinatory treatment thus represents a promising approach to reducing immunosuppressant dosage while maintaining or even improving the outcome of therapy.

Mesenchymal stem cells: a promising way in therapies of graft-versus-host disease

It is well acknowledged that allogeneic hematopoietic stem cell transplantation (allo-HSCT) is an effective treatment for numerous malignant blood diseases, which has also been applied to autoimmune diseases for more than a decade. Whereas graft-versus-host disease (GVHD) occurs after allogeneic hematopoietic stem cell transplantation (allo-HSCT) as a common serious complication, seriously affecting the efficacy of transplantation. Mesenchymal stem cells (MSCs) derived from a wealth of sources can easily isolate and expand with low immunogenicity. MSCs also have paracrine and immune regulatory functions, leading to a broad application prospect in treatment and tissue engineering. This review focuses on immunoregulatory function of MSCs, factors affecting mesenchymal stem cells to exert immunosuppressive effects, clinical application of MSCs in GVHD and researches on MSC-derived extracellular vesicles (EVs). The latest research progress on MSC in related fields is reviewed as well. The relevant literature from PubMed databases is reviewed in this article.

The Use of Human Mesenchymal Stem Cells as Therapeutic Agents for the in vivo Treatment of Immune-Related Diseases: A Systematic Review

Background: One of the greatest challenges for medicine is to find a safe and effective treatment for immune-related diseases. However, due to the low efficacy of the treatment available and the occurrence of serious adverse effects, many groups are currently searching for alternatives to the traditional therapy. In this regard, the use of human mesenchymal stem cells (hMSCs) represents a great promise for the treatment of a variety of immune-related diseases due to their potent immunomodulatory properties. The main objective of this study is, therefore, to present and summarize, through a systematic review of the literature, in vivo studies in which the efficacy of the administration of hMSCs for the treatment of immune-related diseases was evaluated. Methods: The article search was conducted in PubMed/MEDLINE, Scopus and Web of Science databases. Original research articles assessing the therapeutic potential of hMSCs administration for the in vivo treatment immune-related diseases, published from 1984 to December 2017, were selected and evaluated. Results: A total of 132 manuscripts formed the basis of this systematic review. Most of the studies analyzed reported positive results after hMSCs administration. Clinical effects commonly observed include an increase in the survival rates and a reduction in the severity and incidence of the immune-related diseases studied. In addition, hMSCs administration resulted in an inhibition in the proliferation and activation of CD19⁺ B cells, CD4⁺ Th1 and Th17 cells, CD8⁺ T cells, NK cells, macrophages, monocytes, and neutrophils. The clonal expansion of both Bregs and Tregs cells, however, was stimulated. Administration of hMSCs also resulted in a reduction in the levels of pro-inflammatory cytokines such as IFN-γ, TNF-α, IL-1, IL-2, IL-12, and IL-17 and in an increase in the levels of immunoregulatory cytokines such as IL-4, IL-10, and IL-13. Conclusions: The results obtained in this study open new avenues for the treatment of immune-related diseases through the administration of hMSCs and emphasize the importance of the conduction of further studies in this area.

Immunomodulatory plasticity of mesenchymal stem cells: a potential key to successful solid organ transplantation

Organ transplantation remains to be a treatment of choice for patients suffering from irreversible organ failure. Immunosuppressive (IS) drugs employed to maintain the allograft have shown excellent short-term graft survival, but, their long-term use could contribute to immunological and non-immunological risk factors, resulting in graft dysfunctionalities. Upcoming IS regimes have highlighted the use of cell-based therapies, which can eliminate the risk of drug-borne toxicities while maintaining efficacy of the treatment. Mesenchymal stem cells (MSCs) have been considered as an invaluable cell type, owing to their unique immunomodulatory properties, which makes them desirable for application in transplant settings, where hyper-activation of the immune system is evident. The immunoregulatory potential of MSCs holds true for preclinical studies while achieving it in clinical studies continues to be a challenge. Understanding the biological factors responsible for subdued responses of MSCs in vivo would allow uninhibited use of this therapy for countless conditions. In this review, we summarize the variations in the preclinical and clinical studies utilizing MSCs, discuss the factors which might be responsible for variability in outcome and propose the advancements likely to occur in future for using this as a "boutique/personalised therapy" for patient care.

Therapeutic Benefit for Late, but Not Early, Passage Mesenchymal Stem Cells on Pain Behaviour in an Animal Model of Osteoarthritis

Background

Mesenchymal stem cells (MSCs) have a therapeutic potential for the treatment of osteoarthritic (OA) joint pathology and pain. The aims of this study were to determine the influence of a passage number on the effects of MSCs on pain behaviour and cartilage and bone features in a rodent model of OA.

Methods

Rats underwent either medial meniscal transection (MNX) or sham surgery under anaesthesia. Rats received intra-articular injection of either 1.5 × 10⁶ late passage MSCs labelled with 10 μg/ml SiMAG, 1.5 × 10⁶ late passage mesenchymal stem cells, the steroid Kenalog (200 μg/20 μL), 1.5 × 10⁶ early passage MSCs, or serum-free media (SFM). Sham-operated rats received intra-articular injection of SFM. Pain behaviour was quantified until day 42 postmodel induction. Magnetic resonance imaging (MRI) was used to localise the labelled cells within the knee joint.

Results

Late passage MSCs and Kenalog attenuated established pain behaviour in MNX rats, but did not alter MNX-induced joint pathology at the end of the study period. Early passage MSCs exacerbated MNX-induced pain behaviour for up to one week postinjection and did not alter joint pathology.

Conclusion

Our data demonstrate for the first time the role of a passage number in influencing the therapeutic effects of MSCs in a model of OA pain.

Influences of age-related changes in mesenchymal stem cells on macrophages during in-vitro culture

BACKGROUND

Mesenchymal stem cells (MSCs) have been widely used in cytotherapy and tissue engineering due to their immunosuppressive ability and regenerative potential. Recently, the immunomodulatory influence of MSCs has been gaining increasing attention because their functional roles in modulating immune responses likely have high clinical significance.

METHODS

In this study, we investigated the influence of MSCs on macrophages (Mφs) in in-vitro cell culture systems. Given evidence that aged MSCs are functionally compromised, bone marrow-derived MSCs (BMSCs) isolated from both young and aged mice (YMSCs and AMSCs) were evaluated and contrasted.

RESULTS

We found that YMSCs exhibited greater proliferative and osteo-differentiation potential compared to AMSCs. When cocultured with RAW264.7 cells (an Mφ cell line), both YMSCs and AMSCs coaxed polarization of Mφs toward an M2 phenotype and induced secretion of anti-inflammatory and immunomodulatory cytokines. Compared to AMSCs, YMSCs exhibited a more potent immunomodulatory effect. While Mφs cocultured with either YMSCs or AMSCs displayed similar phagocytic ability, AMSC coculture was found to enhance Mφ migration in Transwell systems. When BMSCs were prestimulated with interferon gamma before coculture with RAW264.7 cells, their regulatory effects on Mφs appeared to be modified. Here, compared to stimulated AMSCs, stimulated YMSCs also exhibited enhanced cellular influence on cocultured RAW264.7 cells.

CONCLUSIONS

Our data suggest that BMSCs exert an age-related regulatory effect on Mφs with respect to their phenotype and functions but an optimized stimulation to enhance MSC immunomodulation is in need of further investigation.

Cyclosporine A Loaded Electrospun Poly(D,L-Lactic Acid)/Poly(Ethylene Glycol) Nanofibers: Drug Carriers Utilizable in Local Immunosuppression

PURPOSE

The present study aims to prepare poly(D,L-lactic acid) (PLA) nanofibers loaded by the immunosuppressant cyclosporine A (CsA, 10 wt%). Amphiphilic poly(ethylene glycol)s (PEG) additives were used to modify the hydrophobic drug release kinetics.

METHODS

Four types of CsA-loaded PLA nanofibrous carriers varying in the presence and molecular weight (MW) of PEG (6, 20 and 35 kDa) were prepared by needleless electrospinning. The samples were extracted for 144 h in phosphate buffer saline or tissue culture medium. A newly developed and validated LC-MS/MS method was utilized to quantify the amount of released CsA from the carriers. In vitro cell experiments were used to evaluate biological activity.

RESULTS

Nanofibers containing 15 wt% of PEG showed improved drug release characteristics; significantly higher release rates were achieved in initial part of experiment (24 h). The highest released doses of CsA were obtained from the nanofibers with PEG of the lowest MW (6 kDa). In vitro experiments on ConA-stimulated spleen cells revealed the biological activity of the released CsA for the whole study period of 144 h and nanofibers containing PEG with the lowest MW exhibited the highest impact (inhibition).

CONCLUSIONS

The addition of PEG of a particular MW enables to control CsA release from PLA nanofibrous carriers. The biological activity of CsA-loaded PLA nanofibers with PEG persists even after 144 h of previous extraction. Prepared materials are promising for local immunosuppression in various medical applications.

Macrophages as Effectors of Acute and Chronic Allograft Injury

Organ transplants give a second chance of life to patients with end-stage organ failure. However, the immuno-logical barriers prove to be very challenging to overcome and graft rejection remains a major hurdle to long-term transplant survival. For decades, adaptive immunity has been the focus of studies, primarily based on the belief that T cells are necessary and sufficient for rejection. With better-developed immunosuppressive drugs and protocols that effectively control adaptive cells, innate immune cells have emerged as key effector cells in triggering graft injury and have therefore attracted much recent attention. In this review, we discuss current understanding of macrophages and their role in transplant rejection, their dynamics, distinct phenotypes, locations, and functions. We also discuss novel therapeutic approaches under development to target macrophages in transplant recipients.

Improved Mobilization of Exogenous Mesenchymal Stem Cells to Bone for Fracture Healing and Sex Difference

Mesenchymal stem cell (MSC) transplantation has been tested in animal and clinical fracture studies. We have developed a bone-seeking compound, LLP2A-Alendronate (LLP2A-Ale) that augments MSC homing to bone. The purpose of this study was to determine whether treatment with LLP2A-Ale or a combination of LLP2A-Ale and MSCs would accelerate bone healing in a mouse closed fracture model and if the effects are sex dependent. A right mid-femur fracture was induced in two-month-old osterix-mCherry (Osx-mCherry) male and female reporter mice. The mice were subsequently treated with placebo, LLP2A-Ale (500 μg/kg, IV), MSCs derived from wild-type female Osx-mCherry adipose tissue (ADSC, 3 x 10⁵ , IV) or ADSC + LLP2A-Ale. In phosphate buffered saline-treated mice, females had higher systemic and surface-based bone formation than males. However, male mice formed a larger callus and had higher volumetric bone mineral density and bone strength than females. LLP2A-Ale treatment increased exogenous MSC homing to the fracture gaps, enhanced incorporation of these cells into callus formation, and stimulated endochondral bone formation. Additionally, higher engraftment of exogenous MSCs in fracture gaps seemed to contribute to overall fracture healing and improved bone strength. These effects were sex-independent. There was a sex-difference in the rate of fracture healing. ADSC and LLP2A-Ale combination treatment was superior to on callus formation, which was independent of sex. Increased mobilization of exogenous MSCs to fracture sites accelerated endochondral bone formation and enhanced bone tissue regeneration. Stem Cells 2016;34:2587-2600.