Beyond Hit-and-Run: Stem Cells Leave a Lasting Memory

Mesenchymal stromal cells dampen trained immunity in house dust mite-primed macrophages expressing human macrophage migration inhibitory factor polymorphism

BACKGROUND

Trained immunity results in long-term immunological memory, provoking a faster and greater immune response when innate immune cells encounter a secondary, often heterologous, stimulus. We have previously shown that house dust mite (HDM)-induced innate training is amplified in mice expressing the human macrophage migration inhibitory factor (MIF) CATT7 functional polymorphism.

AIM

This study investigated the ability of mesenchymal stromal cells (MSCs) to modulate MIF-driven trained immunity both in vitro and in vivo.

METHODS

Compared with wild-type mice, in vivo HDM-primed bone marrow-derived macrophages (BMDMs) from CATT7 mice expressed significantly higher levels of M1-associated genes following lipopolysaccharide stimulation ex vivo. Co-cultures of CATT7 BMDMs with MSCs suppressed this HDM-primed effect, with tumor necrosis factor alpha (TNF-α) being significantly decreased in a cyclooxygenase 2 (COX-2)-dependent manner. Interestingly, interleukin 6 (IL-6) was suppressed by MSCs independently of COX-2. In an in vitro training assay, MSCs significantly abrogated the enhanced production of pro-inflammatory cytokines by HDM-trained CATT7 BMDMs when co-cultured at the time of HDM stimulus on day 0, displaying their therapeutic efficacy in modulating an overzealous human MIF-dependent immune response. Utilizing an in vivo model of HDM-induced trained immunity, MSCs administered systemically on day 10 and day 11 suppressed this trained phenomenon by significantly reducing TNF-α and reducing IL-6 and C-C motif chemokine ligand 17 (CCL17) production.

CONCLUSIONS

This novel study elucidates how MSCs can attenuate an MIF-driven, HDM-trained response in CATT7 mice in a model of allergic airway inflammation.

LNP-RNA-engineered adipose stem cells for accelerated diabetic wound healing

Adipose stem cells (ASCs) have attracted considerable attention as potential therapeutic agents due to their ability to promote tissue regeneration. However, their limited tissue repair capability has posed a challenge in achieving optimal therapeutic outcomes. Herein, we conceive a series of lipid nanoparticles to reprogram ASCs with durable protein secretion capacity for enhanced tissue engineering and regeneration. In vitro studies identify that the isomannide-derived lipid nanoparticles (DIM1T LNP) efficiently deliver RNAs to ASCs. Co-delivery of self-amplifying RNA (saRNA) and E3 mRNA complex (the combination of saRNA and E3 mRNA is named SEC) using DIM1T LNP modulates host immune responses against saRNAs and facilitates the durable production of proteins of interest in ASCs. The DIM1T LNP-SEC engineered ASCs (DS-ASCs) prolong expression of hepatocyte growth factor (HGF) and C-X-C motif chemokine ligand 12 (CXCL12), which show superior wound healing efficacy over their wild-type and DIM1T LNP-mRNA counterparts in the diabetic cutaneous wound model. Overall, this work suggests LNPs as an effective platform to engineer ASCs with enhanced protein generation ability, expediting the development of ASCs-based cell therapies.

Interactions of mesenchymal stromal/stem cells and immune cells following MSC-based therapeutic approaches in rheumatoid arthritis

Rheumatoid arthritis (RA) is considered to be a degenerative and progressive autoimmune disorder. Although several medicinal regimens are used to treat RA, potential adverse events such as metabolic disorders and increased risk of infection, as well as drug resistance in some patients, make it essential to find an effective and safe therapeutic approach. Mesenchymal stromal/stem cells (MSCs) are a group of non-hematopoietic stromal cells with immunomodulatory and inhibitory potential. These cells exert their regulatory properties through direct cell-to-cell interactions and paracrine effects on various immune and non-immune cells. As conventional therapeutic approaches for RA are limited due to their side effects, and some patients became refractory to the treatment, MSCs are considered as a promising alternative treatment for RA. In this review, we introduced various experimental and clinical studies conducted to evaluate the therapeutic effects of MSCs on animal models of arthritis and RA patients. Then, possible modulatory and suppressive effects of MSCs on different innate and adaptive immune cells, including dendritic cells, neutrophils, macrophages, natural killer cells, B lymphocytes, and various subtypes of T cells, were categorized and summarized. Finally, limitations and future considerations for the efficient application of MSCs as a therapeutic approach in RA patients were presented.

Mesenchymal stem cells: Emerging concepts and recent advances in their roles in organismal homeostasis and therapy

Stem cells play a crucial role in re-establishing homeostasis in the body, and the search for mechanisms by which they interact with the host to exert their therapeutic effects remains a key question currently being addressed. Considering their significant regenerative/therapeutic potential, research on mesenchymal stem cells (MSCs) has experienced an unprecedented advance in recent years, becoming the focus of extensive works worldwide to develop cell-based approaches for a variety of diseases. Initial evidence for the effectiveness of MSCs therapy comes from the restoration of dynamic microenvironmental homeostasis and endogenous stem cell function in recipient tissues by systemically delivered MSCs. The specific mechanisms by which the effects are exerted remain to be investigated in depth. Importantly, the profound cell-host interplay leaves persistent therapeutic benefits that remain detectable long after the disappearance of transplanted MSCs. In this review, we summarize recent advances on the role of MSCs in multiple disease models, provide insights into the mechanisms by which MSCs interact with endogenous stem cells to exert therapeutic effects, and refine the interconnections between MSCs and cells fused to damaged sites or differentiated into functional cells early in therapy.

MiRNA-320a-5p contributes to the homeostasis of osteogenesis and adipogenesis in bone marrow mesenchymal stem cell

Objective

A number of miRNAs and their targets were dragged in the differentiation of bone marrow mesenchymal stem cells (BMSCs). We aimed to elaborate the underlying molecular mechanisms of miRNA-320a in the osteoblast and adipocyte differentiation.

Methods

Trauma-induced osteonecrosis of the femoral head (TIONFH) and normal control samples (n = 10 for each group) were collected, followed by miRNA chip analysis to identify the differentially expressed miRNAs. H&E staining was used to observe the pathological development of TIONFH. Lentiviral vector was used for overexpression and inhibition of miRNA-320a in vitro. Quantitative real-time PCR (qPCR), Western blotting and immunohistochemistry staining were employed to determine the expression of interested genes at mRNA or protein level. Luciferase report assay was employed to determine the binding of miRNA-320a and RUNX2. Alkaline phosphatase (ALP) and Alizarin red staining were performed to observe the osteogenesis and Oil red O staining were conducted to visualize the adipogenesis.

Results

Expression of miRNA-320a was up-regulated while RUNX2 expression was down-regulated in TIONFH than Normal control. Luciferase report assay confirmed that miRNA-320a directly targeted to the 3′UTR of RUNX2. miRNA-320a overexpression significantly declined the expressions of osteogenesis-related markers: RUNX2, OSTERIX, Collagen I, Osteocalcin and Osteopontin. ALP and Alizarin red staining confirmed the inhibition function of miRNA-320a in osteogenesis of BMSCs. miRNA-320a inhibition significantly decreased the expression of adipogenesis-related markers: AP2, C/EBPα, FABP4 and PPARγ. Oil Red O staining confirmed the miRNA-320a inhibition reduced adipogenesis of BMSCs.

Conclusions

miRNA-320a inhibits osteoblast differentiation via targeting RUNX2 and promotes adipocyte differentiation of BMSCs.

Bone marrow mononuclear cell transplant prevents rat depression and modulates inflammatory and neurogenic molecules

INTRODUCTION

Major depressive disorder is associated with chronic inflammation and deficient production of brain-derived neurotrophic factor (BDNF). Bone marrow mononuclear cell (BMMC) transplantation has an anti-inflammatory effect and has been proven effective in restoring non-depressive behavior. This study investigated whether BMMC transplantation can prevent the development of depression or anxiety in chronic mild stress (CMS), as well as its effect on inflammatory and neurogenic molecules.

METHOD

Three groups of animals were compared: BMMC-transplanted animals subjected to CMS for 45 days, CMS non-transplanted rats, and control animals. After the CMS period, the three groups underwent the following behavioral tests: sucrose preference test (SPT), eating-related depression test (ERDT), social avoidance test (SAT), social interaction test (SIT), and elevated plus maze test (EPMT). Transplanted cell tracking and measurement of the expression of high-mobility group box 1 (HMGB1), interleukin-1β (IL-1β), tumor necrosis factor (TNFα), and BDNF were performed on brain and spleen tissues.

RESULTS

BMMC transplantation prevented the effects of CMS in the SPT, ERDT, SAT, and SIT, while prevention was less pronounced in the EPMT. It was found to prevent increased HMGB-1 expression induced by CMS in the hippocampus and spleen, increase BDNF expression in both tissues, and prevent increased IL-1β expression in the hippocampus alone, while no effect of the transplant was observed in the TNFα expression. In addition, no transplanted cells were found in either the brain or spleen.

CONCLUSIONS

BMMC transplantation prevents the development of depression and anxiety-like behavior triggered by CMS. It could prevent increased HMGB-1 and IL-1β expression in the hippocampus and increased BDNF expression in the same tissue. Cell treatment represents a further perspective in the research and treatment of depression and possible mood disorders.

UBE2E3 regulates cellular senescence and osteogenic differentiation of BMSCs during aging

Background

Osteoporosis has gradually become a public health problem in the world. However, the exact molecular mechanism of osteoporosis still remains unclear. Senescence and osteogenic differentiation inhibition of bone marrow mesenchymal stem cells (BMSCs ) are supposed to play an important part in osteoporosis.

Methods

We used two gene expression profiles (GSE35956 and GSE35958) associated with osteoporosis and selected the promising gene Ubiquitin-conjugating enzyme E2 E3 (UBE2E3). We then verified its function and mechanism by in vitro experiments.

Results

UBE2E3 was highly expressed in the bone marrow and positively associated with osteogenesis related genes. Besides, UBE2E3 expression reduced in old BMSCs compared with that in young BMSCs. In in vitro experiments, knockdown of UBE2E3 accelerated cellular senescence and inhibited osteogenic differentiation of young BMSCs. On the other hand, overexpression of UBE2E3 attenuated cellular senescence as well as enhanced osteogenic differentiation of old BMSCs. Mechanistically, UBE2E3 might regulate the nuclear factor erythroid 2-related factor (Nrf2) and control its function, thus affecting the senescence and osteogenic differentiation of BMSCs.

Conclusion

UBE2E3 may be potentially involved in the pathogenesis of osteoporosis by regulating cellular senescence and osteogenic differentiation of BMSCs.

IL-1β-primed mesenchymal stromal cells exert enhanced therapeutic effects to alleviate Chronic Prostatitis/Chronic Pelvic Pain Syndrome through systemic immunity

BACKGROUND

Chronic prostatitis/chronic pelvic pain syndrome (CP/CPPS) seriously affects patient health. Despite the elusiveness of innate therapeutic effects, mesenchymal stromal cells (MSCs) hold great promise for inflammation-related diseases. Recent evidence indicates that disease-specific inflammatory cytokines could enhance the therapeutic effects of MSCs.

METHODS

By establishing a CP/CPPS mouse model and pretreating MSCs with the cytokine interleukin-1β (IL-1β), we studied the IL-1β-primed MSC immunoregulatory ability and targeted migration ability in vitro and in CP/CPPS mice.

RESULTS

IL-1β levels significantly increased in the prostate tissue and serum of experimental autoimmune prostatitis (EAP) mice. Pretreatment with IL-1β enhanced the immunomodulatory potential and targeted migration of MSCs in vitro. Furthermore, intravenous infusion of IL-1β-primed MSCs dampened inflammation in prostate tissues and alleviated hyperalgesia in EAP mice. The infused MSCs inhibited monocyte infiltration and promoted regulatory T lymphocyte formation in prostate tissue, thus remodeling the local environment. Surprisingly, IL-1β-primed MSCs exhibited improved accumulation in the spleen but not in prostate tissue. Accordingly, infused MSCs reshaped systemic immunity by reducing the proportion of Ly6C^highCD11b⁺ monocytes and boosting the proportion of CD4⁺Foxp3⁺ regulatory T lymphocytes in the spleen and lung. Inflammatory chemokine (C-C motif) ligand 2 (CCL2) decreased through the downregulation of the NF-κB and JNK/MAPK pathways by inflammatory resolution via MSCs infusion to alleviate pain.

CONCLUSION

In summary, IL-1β-primed MSCs restored systemic immunologic homeostasis to alleviate CP/CPPS by modulating systemic immunity. These findings provide a novel strategy to boost the therapeutic effects of MSC-based therapy for CP/CPPS and reveal the essential role of systematic immunity in the treatment of CP/CPPS with MSC infusion.

Autologous BMAC Therapy Improves Spinal Degenerative Joint Disease in Lower Back Pain Patients

Spinal degenerative joint disease (DJD) is associated with lower back pain (LBP) arising from the degeneration of intervertebral discs (IVD), facet joints, intertransversarii muscles, and interspinous ligaments among other anatomical structures. To circumvent the socioeconomic burdens and often-problematic surgical options imposed by DJD therapy, cell-based biologic modalities like bone marrow aspirate concentrate (BMAC) have been investigated in pre-clinical and clinical settings, mostly for IVD degeneration (IDD), with encouraging outcomes. In this study, we evaluated the differences in therapeutic benefits of BMAC between IVD- and facet joint-originating chronic LBP. Eighteen patients diagnosed with chronic LBP met the selection criteria. Following discography and provocation testing, 13 patients tested positive and were assigned into IDD-associated LBP (1st arm), while the remaining 5 tested negative and were assigned into facetogenic LBP (2nd arm). Autologous BMAC was injected intradiscally in the 1st arm, while the 2nd arm received posterior spinal chain injections. No procedure-related serious events ensued. Clinical improvement was evaluated over 12 months based on pain and functionality questionnaires (VAS, BPI, RAND-36), opioid use, and changes in disc parameters assessed by magnetic resonance imaging (MRI). Ameliorated VAS and BPI scores differed significantly between both arms in favor of IDD patients who also took significantly less opioids. Average RAND-36 scores showed no significant difference between groups albeit a trend suggesting improvement was observed in IDD patients. MRI scans conducted on IDD patients demonstrated marked elevation in disc height and spinal canal space size without worsening disc quality. Overall, this is the first study investigating the potency of BMAC as an IDD treatment in Canada and the first globally for addressing facetogenic pain using cellular therapy.

Promising Opportunities for Treating Neurodegenerative Diseases with Mesenchymal Stem Cell-Derived Exosomes

Neurodegenerative disease refers to any pathological condition in which there is a progressive decline in neuronal function resulting from brain atrophy. Despite the immense efforts invested over recent decades in developing treatments for neurodegenerative diseases, effective therapy for these conditions is still an unmet need. One of the promising options for promoting brain recovery and regeneration is mesenchymal stem cell (MSC) transplantation. The therapeutic effect of MSCs is thought to be mediated by their secretome, and specifically, by their exosomes. Research shows that MSC-derived exosomes retain some of the characteristics of their parent MSCs, such as immune system modulation, regulation of neurite outgrowth, promotion of angiogenesis, and the ability to repair damaged tissue. Here, we summarize the functional outcomes observed in animal models of neurodegenerative diseases following MSC-derived exosome treatment. We will examine the proposed mechanisms of action through which MSC-derived exosomes mediate their therapeutic effects and review advanced studies that attempt to enhance the improvement achieved using MSC-derived exosome treatment, with a view towards future clinical use.

Exosomes derived from mesenchymal stem cells improved core symptoms of genetically modified mouse model of autism Shank3B

BACKGROUND

Partial or an entire deletion of SHANK3 are considered as major drivers in the Phelan-McDermid syndrome, in which 75% of patients are diagnosed with autism spectrum disorder (ASD). During the recent years, there was an increasing interest in stem cell therapy in ASD, and specifically, mesenchymal stem cells (MSC). Moreover, it has been suggested that the therapeutic effect of the MSC is mediated mainly via the secretion of small extracellular vesicle that contains important molecular information of the cell and are used for cell-to-cell communication. Within the fraction of the extracellular vesicles, exosomes were highlighted as the most effective ones to convey the therapeutic effect.

METHODS

Exosomes derived from MSC (MSC-exo) were purified, characterized, and given via intranasal administration to Shank3B KO mice (in the concentration of 10⁷ particles/ml). Three weeks post treatment, the mice were tested for behavioral scoring, and their results were compared with saline-treated control and their wild-type littermates.

RESULTS

Intranasal treatment with MSC-exo improves the social behavior deficit in multiple paradigms, increases vocalization, and reduces repetitive behaviors. We also observed an increase of GABARB1 in the prefrontal cortex.

CONCLUSIONS

Herein, we hypothesized that MSC-exo would have a direct beneficial effect on the behavioral autistic-like phenotype of the genetically modified Shank3B KO mouse model of autism. Taken together, our data indicate that intranasal treatment with MSC-exo improves the core ASD-like deficits of this mouse model of autism and therefore has the potential to treat ASD patients carrying the Shank3 mutation.

Relationship between GDF15 level and bone metabolism in postmenopausal Chinese women

Background: Growth differentiation factor 15 (GDF15), is a newly identified member of the transforming growth factor-beta (TGF-β) family. It circulates as a 24.5-kDa homodimer. However, the function of GDF15 in bone metabolism remains unclear. In this study, we investigated the function of GDF15 in postmenopausal Chinese women.Methods: We measured serum GDF15 levels, bone mineral density (BMD), and bone turnover markers in 201 postmenopausal Chinese women ranging in age from 47 to 80 years.Results: The concentration of serum GDF15 increased with age. Growth differentiation factor 15 levels displayed a negative correlation with lumbar spine, femoral neck, and total hip BMD. After adjusting for age, this association still existed and was significant. We identified age, GDF15, body mass index (BMI), and estradiol to be associated with BMD. Furthermore, we found that GDF15 levels had a significant negative relationship with bone alkaline phosphatase (BAP) levels; this relationship remained significant after adjustment. However, there was no significant correlation between levels of GDF15 and N-terminal telopeptide of type I collagen (NTX).Conclusions: For postmenopausal Chinese women, GDF15 is a negative predictor of BMD and has a negative correlation with bone formation biomarker BAP. In other words, GDF15 exerts negative regulation on bone mass by inhibiting bone formation.

Positive Effect of Gushukang on Type-H Vessel and Bone Formation

Gushukang (GSK) is a traditional herbal compound used in Chinese medicine for the treatment of osteoporosis. Numerous studies have been conducted to elucidate the effects of GSK, but the mechanisms underlying these effects remain unclear. In the present study, we cultured osteoblasts and osteoclasts with low and high doses of GSK, and also administered 3-month-old mice with 4 and 8 g/kg/day of GSK solution. Gushukang was found to promote osteoblast differentiation and inhibit osteoclast differentiation in vitro. In vivo, mice in the GSK treatment groups showed an increase in bone mass, as measured by micro-computed tomography (Micro-CT). Tartrate resistant acid phosphatase (TRAP) staining and osteocalcin (OCN) staining experiments revealed decreased bone resorption and increased bone formation in the GSK treatment groups. In addition, we found a novel effect of GSK—it could induce type-H vessel formation in mice. The underlying mechanisms of these actions were further explored at the molecular level to investigate whether these effects were due to an overexpression of the hypoxia inducible factor-1 (HIF-1α). Our findings indicate the utility of GSK as a therapeutic for the prevention of osteoporosis.

The Role of Bone-Derived Exosomes in Regulating Skeletal Metabolism and Extraosseous Diseases

Bone-derived exosomes are naturally existing nano-sized extracellular vesicles secreted by various cells, such as bone marrow stromal cells, osteoclasts, osteoblasts, and osteocytes, containing multifarious proteins, lipids, and nucleic acids. Accumulating evidence indicates that bone-derived exosomes are involved in the regulation of skeletal metabolism and extraosseous diseases through modulating intercellular communication and the transfer of materials. Following the development of research, we found that exosomes can be considered as a potential candidate as a drug delivery carrier thanks to its ability to transport molecules into targeted cells with high stability, safety, and efficiency. This review aims to discuss the emerging role of bone-derived exosomes in skeletal metabolism and extraosseous diseases as well as their potential role as candidate biomarkers or for developing new therapeutic strategies.

MicroRNA-130a controls bone marrow mesenchymal stem cell differentiation towards the osteoblastic and adipogenic fate

Objectives

With age, bone marrow mesenchymal stem cells (BMSC) have reduced ability of differentiating into osteoblasts but have increased ability of differentiating into adipocytes which leads to age‐related bone loss. MicroRNAs (miRNAs) play major roles in regulating BMSC differentiation. This paper explored the role of miRNAs in regulating BMSC differentiation swift fate in age‐related osteoporosis.

Material and methods

Mice and human BMSC were isolated from bone marrow, whose miR‐130a level was measured. The abilities of BMSC differentiate into osteoblast or fat cell under the transfected with agomiR‐130a or antagomiR‐130a were analysed by the level of ALP, osteocalcin, Runx2, osterix or peroxisome proliferator‐activated receptorγ (PPARγ), Fabp4. Related mechanism was verified via qT‐PCR, Western blotting (WB) and siRNA transfection. Animal phenotype intravenous injection with agomiR‐130a or agomiR‐NC was explored by Micro‐CT, immunochemistry and calcein double‐labelling.

Results

MiR‐130a was dramatically decreased in BMSC of advanced subjects. Overexpression of miR‐130a increased osteogenic differentiation of BMSC and attenuated adipogenic differentiation in BMSC, conversely, Inhibition of miR‐130a reduced osteogenic differentiation and facilitated lipid droplet formation. Consistently, overexpression of miR‐130a in elderly mice dropped off the bone loss. Furthermore, the protein levels of Smad regulatory factors 2 (Smurf2) and PPARγ were regulated by miR‐130a with an negative effect through directly combining the 3'UTR of Smurf2 and PPARγ.

Conclusions

The results indicated that miR‐130a promotes osteoblastic differentiation of BMSC by negatively regulating Smurf2 expression and suppresses adipogenic differentiation of BMSC by targeting the PPARγ, and supply a new target for clinical therapy of age‐related bone loss.

Intranasal administration of exosomes derived from mesenchymal stem cells ameliorates autistic-like behaviors of BTBR mice

Autism spectrum disorders (ASD) are neurodevelopmental disorders characterized by three core symptoms that include social interaction deficits, cognitive inflexibility, and communication disorders. They have been steadily increasing in children over the past several years, with no effective treatment. BTBR T+tf/J (BTBR) mice are an accepted model of evaluating autistic-like behaviors as they present all core symptoms of ASD. We have previously shown that transplantation of human bone marrow mesenchymal stem cells (MSC) to the lateral ventricles of BTBR mice results in long lasting improvement in their autistic behavioral phenotypes. Recent studies point exosomes as the main mediators of the therapeutic effect of MSC. Here, we tested whether treatment with the exosomes secreted from MSC (MSC-exo) will show similar beneficial effects. We found that intranasal administration of MSC-exo increased male to male social interaction and reduced repetitive behaviors. Moreover, the treatment led to increases of male to female ultrasonic vocalizations and significant improvement in maternal behaviors of pup retrieval. No negative symptoms were detected following MSC-exo intranasal treatments in BTBR or healthy C57BL mice. The marked beneficial effects of the exosomes in BTBR mice may translate to a novel, non-invasive, and therapeutic strategy to reduce the symptoms of ASD.

Therapeutic potential of allogeneic mesenchymal stromal cells transplantation for lupus nephritis

Animal and human studies have suggested the potential of mesenchymal stromal cells (MSCs) to treat systemic lupus erythematosus (SLE). Here, we present the results of compassionate MSC treatments for three SLE patients to provide the proof of concept for a randomized and controlled clinical trial. Three patients of different ethnicities who suffer from chronic SLE, and who presented with class IV active proliferative nephritis confirmed by biopsy, were treated with allogeneic MSCs from healthy donors. Ninety million cells were infused intravenously into each patient during high and very high activity disease flare-ups and follow-up was continued for 9 months. Multi-organic affectation was quantified by the SLE disease activity index (SLEDAI), and indicators of lupus nephritis activity, such as proteinuria, as well as lymphocyte and monocyte antigens and anti-HLA antibodies were measured at 1, 3, 6, and 9 months after treatment. Proteinuria levels improved dramatically during the 1st month after treatment and the ameliorations were sustained throughout the follow-up period. SLEDAI scores revealed early, durable, and substantial remissions that were complete for two patients and partial for the third patient and that permitted medication doses to be reduced 50-90%. These favourable outcomes support completion of the randomized and controlled MSC trial for SLE.

Peak MSC-Are We There Yet?

Human mesenchymal stem cells (hMSCs) are a critical raw material for many regenerative medicine products, including cell-based therapies, engineered tissues, or combination products, and are on the brink of radically changing how the world of medicine operates. Their unique characteristics, potential to treat many indications, and established safety profile in more than 800 clinical trials have contributed to their current consumption and will only fuel future demand. Given the large target patient populations with typical dose sizes of 10's to 100's of millions of cells per patient, and engineered tissues being constructed with 100's of millions to billions of cells, an unprecedented demand has been created for hMSCs. The fulfillment of this demand faces an uphill challenge in the limited availability of large quantities of pharmaceutical grade hMSCs for the industry—fueling the need for parallel rapid advancements in the biomanufacturing of this living critical raw material. Simply put, hMSCs are no different than technologies like transistors, as they are a highly technical and modular product that requires stringent control over manufacturing that can allow for high quality and consistent performance. As hMSC manufacturing processes are optimized, it predicts a future time of abundance for hMSCs, where scientists and researchers around the world will have access to a consistent and readily available supply of high quality, standardized, and economical pharmaceutical grade product to buy off the shelf for their applications and drive product development—this is “Peak MSC.”

Dual IFN-γ/hypoxia priming enhances immunosuppression of mesenchymal stromal cells through regulatory proteins and metabolic mechanisms

The immunosuppressive capacity of human mesenchymal stromal cells (MSCs) renders them promising candidates for treating diverse immune disorders. However, after hundreds of clinical trials, there are still no MSC therapies approved in the United States. MSCs require specific cues to adopt their immunosuppressive phenotype, and yet most clinical trials use cells expanded in basic culture medium and growth conditions. We propose that priming MSCs prior to administration will improve their therapeutic efficacy. Interferon-gamma (IFN-γ) priming are cues common to situations of immune escape that have individually shown promise as MSC priming cues but have not been systematically compared. Using mixed lymphocyte reactions, we show that priming MSCs with either cue alone improves T-cell inhibition. However, combining the two cues results in additive effects and markedly enhances the immunosuppressive phenotype of MSCs. We demonstrate that IFN-γ induces expression of numerous immunosuppressive proteins (IDO, PD-L1, HLA-E, HLA-G), whereas hypoxia switches MSCs to glycolysis, causing rapid glucose consumption and production of T-cell inhibitory lactate levels. Dual IFN-γ/hypoxia primed MSCs display both attributes and have even higher induction of immunosuppressive proteins over IFN-γ priming alone (IDO and HLA-G), which may reflect another benefit of metabolic reconfiguration.