Kindlin-3 mutation in mesenchymal stem cells results in enhanced chondrogenesis.

Identifying patient mutations driving skeletal development disorders has driven our understanding of bone development. Integrin adhesion deficiency disease is caused by a Kindlin-3 (fermitin family member 3) mutation, and its inactivation results in bleeding disorders and osteopenia. In this study, we uncover a role for Kindlin-3 in the differentiation of bone marrow mesenchymal stem cells (BMSCs) down the chondrogenic lineage. Kindlin-3 expression increased with chondrogenic differentiation, similar to RUNX2. BMSCs isolated from a Kindlin-3 deficient patient expressed chondrocyte markers, including SOX9, under basal conditions, which were further enhanced with chondrogenic differentiation. Rescue of integrin activation by a constitutively activated ß3 integrin construct increased adhesion to multiple extracellular matrices and reduced SOX9 expression to basal levels. Growth plates from mice expressing a mutated Kindlin-3 with the integrin binding site ablated demonstrated alterations in chondrocyte maturation similar to that seen with the human Kindlin-3 deficient BMSCs. These findings suggest that Kindlin-3 expression mirrors RUNX2 during chondrogenesis.

Growth, differentiation capacity, and function of mesenchymal stem cells expanded in serum-free medium developed via combinatorial screening.

The presence of serum in cell culture medium presents an obstacle to safe and efficient production of hMSCs for therapeutic purposes. Availability of defined medium will be crucial to elucidating the mechanism of action of hMSCs in many indications as well as a prerequisite to consistently produce cells with predictable performance characteristics. Using a bioinformatics driven approach, which we call the BD Discovery Platform, we have developed a novel serum-free medium that supports highly efficient growth while maintaining the surface markers and functional characteristics defining hMSCs. In a comparison with serum-containing and other commercially available serum-free formulations, all conditions led to expansion of cells that meet the minimal criteria for hMSCs as set by the International Society for Cellular Therapy (ISCT). However, differences in growth characteristics and gene expression patterns suggest that expansion in serum-free growth conditions can provide greater yields in a shorter time. The mRNA expression profile observed in cells grown without serum suggests upregulation of several genes implicated in hMSC function as well as downregulation of the proinflammatory cytokine IL6.

Human mesenchymal stem cells suppress chronic airway inflammation in the murine ovalbumin asthma model.

Allogeneic human mesenchymal stem cells (hMSCs) introduced intravenously can have profound anti-inflammatory activity resulting in suppression of graft vs. host disease as well as regenerative events in the case of stroke, infarct, spinal cord injury, meniscus regeneration, tendinitis, acute renal failure, and heart disease in human and animal models of these diseases. hMSCs produce bioactive factors that provide molecular cuing for: 1) immunosuppression of T cells; 2) antiscarring; 3) angiogenesis; 4) antiapoptosis; and 5) regeneration (i.e., mitotic for host-derived progenitor cells). Studies have shown that hMSCs have profound effects on the immune system and are well-tolerated and therapeutically active in immunocompetent rodent models of multiple sclerosis and stroke. Furthermore, intravenous administration of MSCs results in pulmonary localization. Asthma is a major debilitating pulmonary disease that impacts in excess of 150 million people in the world with uncontrolled asthma potentially leading to death. In addition, the socioeconomic impact of asthma-associated illnesses at the pediatric and adult level are in the millions of dollars in healthcare costs and lost days of work. hMSCs may provide a viable multiaction therapeutic for this inflammatory lung disease by secreting bioactive factors or directing cellular activity. Our studies show the effectiveness and specificity of the hMSCs on decreasing chronic airway inflammation associated with the murine ovalbumin model of asthma. In addition, the results from these studies verify the in vivo immunoeffectiveness of hMSCs in rodents and support the potential therapeutic use of hMSCs for the treatment of airway inflammation associated with chronic asthma.

The Habitat Assay, a Platform to Study In Vivo Properties of Human Mesenchymal Stem Cells.

Mesenchymal stem cells (MSCs) are at the forefront as therapeutic tools for an extensive number of tissue engineering and regenerative medicine applications. MSC differentiation properties have been extensively studied in vitro by this laboratory and many others. The generation and validation of in vivo potency assays would be a valuable tool for the study of cellular properties relevant for in vivo applications. We have developed a unique system, we call the Habitat assay, in which porous ceramic cube carrier loaded with human bone marrow (BM)-MSCs (hMSCs) is subcutaneously implanted into immune-compromised mice. These cells have the capacity to create bone tissue and reconstitute the hematopoietic microenvironment within the "Habitat." These donor-derived hMSCs form bone structures by 3-4 weeks and associate as perivascular MSCs. In this study, we have extensively analyzed data generated with the habitat (ceramic cube in vivo assay) using cells derived from 117 hMSC-donors (iliac aspiration); this analysis provides a validation of the platform as a way to study the in vivo effect of several variables involved in the generation of the bony Habitat. These studies show that passage number and the age of the hMSC donor influence the sequence of in vivo bone formation within the Habitat. These variables have been shown to have an effect on in vitro properties of MSCs; in this study, for the first time, we show these effects to be important on an in vivo setting.

Human bone marrow-derived mesenchymal stem cells induce Th2-polarized immune response and promote endogenous repair in animal models of multiple sclerosis.

Cell-based therapies are attractive approaches to promote myelin repair. Recent studies demonstrated a reduction in disease burden in mice with experimental allergic encephalomyelitis (EAE) treated with mouse mesenchymal stem cells (MSCs). Here, we demonstrated human bone marrow-derived MSCs (BM-hMSCs) promote functional recovery in both chronic and relapsing-remitting models of mouse EAE, traced their migration into the injured CNS and assayed their ability to modulate disease progression and the host immune response. Injected BM-hMSCs accumulated in the CNS, reduced the extent of damage and increased oligodendrocyte lineage cells in lesion areas. The increase in oligodendrocytes in lesions may reflect BM-hMSC-induced changes in neural fate determination, since neurospheres from treated animals gave rise to more oligodendrocytes and less astrocytes than nontreated neurospheres. Host immune responses were also influenced by BM-hMSCs. Inflammatory T-cells including interferon gamma producing Th1 cells and IL-17 producing Th17 inflammatory cells and their associated cytokines were reduced along with concomitant increases in IL-4 producing Th2 cells and anti-inflammatory cytokines. Together, these data suggest that the BM-hMSCs represent a viable option for therapeutic approaches.

Mesenchymal Stem Cell Soluble Mediators and Cystic Fibrosis.

Human Mesenchymal stem cells (hMSCs) secrete products (supernatants) that are anti-inflammatory and antimicrobial. We have previously shown that hMSCs decrease inflammation and Pseudomonas aeruginosa infection in the in vivo murine model of Cystic Fibrosis (CF). Cystic Fibrosis (CF) is a genetic disease in which pulmonary infection and inflammation becomes the major cause of morbidity and mortality. Our studies focus on determining how MSCs contribute to improved outcomes in the CF mouse model centering on how the MSCs impact the inflammatory response to pathogenic organisms. We hypothesize that MSCs secrete products that are anti-inflammatory in scenarios of chronic pulmonary infections using the murine model of infection and inflammation with a specific interest in Pseudomonas aeruginosa (gram negative). Further, our studies will identify whether the MSCs are impacting this inflammatory response through the regulation of peroxisome proliferator activator receptor gamma (PPARγ) which aides in decreasing inflammation.

Antimicrobial Properties of Mesenchymal Stem Cells: Therapeutic Potential for Cystic Fibrosis Infection, and Treatment.

Cystic fibrosis (CF) is a genetic disease in which the battle between pulmonary infection and inflammation becomes the major cause of morbidity and mortality. We have previously shown that human MSCs (hMSCs) decrease inflammation and infection in the in vivo murine model of CF. The studies in this paper focus on the specificity of the hMSC antimicrobial effectiveness using Pseudomonas aeruginosa (gram negative bacteria) and Staphylococcus aureus (gram positive bacteria). Our studies show that hMSCs secrete bioactive molecules which are antimicrobial in vitro against Pseudomonas aeruginosa, Staphylococcus aureus, and Streptococcus pneumonia, impacting the rate of bacterial growth and transition into colony forming units regardless of the pathogen. Further, we show that the hMSCs have the capacity to enhance antibiotic sensitivity, improving the capacity to kill bacteria. We present data which suggests that the antimicrobial effectiveness is associated with the capacity to slow bacterial growth and the ability of the hMSCs to secrete the antimicrobial peptide LL-37. Lastly, our studies demonstrate that the tissue origin of the hMSCs (bone marrow or adipose tissue derived), the presence of functional cystic fibrosis transmembrane conductance regulator (CFTR: human, Cftr: mouse) activity, and response to effector cytokines can impact both hMSC phenotype and antimicrobial potency and efficacy. These studies demonstrate, the unique capacity of the hMSCs to manage different pathogens and the significance of their phenotype in both the antimicrobial and antibiotic enhancing activities.

Effect of transforming growth factor beta 2 on marrow-infused foam poly(propylene fumarate) tissue-engineered constructs for the repair of critical-size cranial defects in rabbits.

This study investigates the osseointegration of poly(propylene fumarate) (PPF) with beta-tricalcium phosphate (beta-TCP) scaffolds in a critical-size (diameter, 1.6 cm), cranial defect in 4-month-old rabbits (n = 51), killed at 6 or 12 weeks. Two molecular weights of PPF were used to produce bilayer scaffolds with 0.5-mm solid external and 2.0-mm porous internal layers. The porous layer was infused with bone marrow aspirate, with half the animals receiving 0.8 microg of transforming growth factor beta2 (TGF-beta2). No foreign body or inflammatory response was observed externally or on histological examination of explants. Statistical analysis of histological areal and linear measures of new bone formation found significantly more bone at the later sacrifice time, followed by implants receiving TGF-beta2, followed by low molecular weight PPF implants. Approximately 40% of the explants were tested for incorporation strength with a one-point "push-in" test. Because no permanent fixation was used, implant strength (28.37-129.03 N; range, 6.4 to 29.0 lb of resistance) was due entirely to new bone formation. The strongest bone was seen in implants receiving TGF-beta2-infused marrow in animals killed at 12 weeks. These results support the use of PPF as an osteogenic substrate and future research into preoperative fabrication of critical size and supercritical-size cranial prosthetic implants.

Generation of pluripotent stem cells and their differentiation to the chondrocytic phenotype.

It is well documented that adult cartilage has minimal self-repair ability. Current methods for treatment of cartilage injury focus on the relief of pain and inflammation and have met with limited long-term success. In the forefront of new therapeutic approaches, autologous chondrocyte transplantation is still only applied to a very small percentage of the patient population. Our laboratory has focused on cartilage repair using progenitor cells and studied their differentiation into cartilage. Adult mesenchymal stem cells are an attractive candidate as progenitor cells for cartilage repair because of their documented osteogenic and chondrogenic potential, ease of harvest, and ease of expansion in culture; furthermore, their use will obviate the need for harvesting precious healthy cartilage from a patient to obtain autologous chondrocytes for transplantation. However, the need to induce chondrogenic differentiation in the mesenchymal stem cells is superposed on other technical issues associated with cartilage repair; this adds a level of complexity over using mature chondrocytes. This chapter focuses on the methods involved in the isolation of human mesenchymal stem cells and their differentiation along the chondrogenic lineage. Although we have the technology to accomplish chondrogenic differentiation of stem cells, much is still to be learned regarding the regulatory mechanisms controlling the lineage transitions and maturation of the cartilaginous tissue.

Validating continuous digital light processing (cDLP) additive manufacturing accuracy and tissue engineering utility of a dye-initiator package.

This study tested the accuracy of tissue engineering scaffold rendering via the continuous digital light processing (cDLP) light-based additive manufacturing technology. High accuracy (i.e., <50 µm) allows the designed performance of features relevant to three scale spaces: cell-scaffold, scaffold-tissue, and tissue-organ interactions. The biodegradable polymer poly (propylene fumarate) was used to render highly accurate scaffolds through the use of a dye-initiator package, TiO2 and bis (2,4,6-trimethylbenzoyl)phenylphosphine oxide. This dye-initiator package facilitates high accuracy in the Z dimension. Linear, round, and right-angle features were measured to gauge accuracy. Most features showed accuracies between 5.4-15% of the design. However, one feature, an 800 µm diameter circular pore, exhibited a 35.7% average reduction of patency. Light scattered in the x, y directions by the dye may have reduced this feature's accuracy. Our new fine-grained understanding of accuracy could be used to make further improvements by including corrections in the scaffold design software. Successful cell attachment occurred with both canine and human mesenchymal stem cells (MSCs). Highly accurate cDLP scaffold rendering is critical to the design of scaffolds that both guide bone regeneration and that fully resorb. Scaffold resorption must occur for regenerated bone to be remodeled and, thereby, achieve optimal strength.

The effects of crosslinking of scaffolds engineered from cartilage ECM on the chondrogenic differentiation of MSCs.

Scaffolds fabricated from cartilage extracellular matrix provide a chondroinductive environment that stimulates cartilaginous matrix synthesis in a variety of cell types. A limitation of these cartilage-derived matrix (CDM) scaffolds is that they contract during in vitro culture, which unpredictably alters their shape. The current study examined the hypothesis that collagen crosslinking techniques could inhibit cell-mediated contraction of CDM scaffolds. We analyzed the effects of dehydrothermal (DHT) treatment, ultraviolet light irradiation (UV), and the chemical crosslinker carbodiimide (CAR) on scaffold contraction and chondrogenic differentiation of adult human bone marrow-derived stem cells (MSCs). Both physical and chemical crosslinking treatments retained the original scaffold dimensions. DHT and UV treatments produced significantly higher glycosaminoglycan and collagen contents than CAR crosslinked and non-crosslinked constructs. Crosslinking treatments influenced the composition of newly synthesized matrix, and DHT treatment best matched the composition of native cartilage. DHT, UV, and non-crosslinked CDM films supported cell attachment, while CAR crosslinking inhibited cell adhesion. These results affirm that collagen crosslinking treatments can prevent cell-mediated contraction of CDM scaffolds. Interestingly, crosslinking treatments influence chondrogenic differentiation. These effects seem to be mediated by modifications to cell-matrix interactions between MSCs and the CDM; however, further work is necessary to elucidate the specific mechanisms involved in this process.

The effect of extended first passage culture on the proliferation and differentiation of human marrow-derived mesenchymal stem cells.

Human marrow-derived mesenchymal stem cells (hMSCs) have been investigated for more than 20 years. They have been shown to be therapeutic in a number of animal models and are currently in use in more than 200 clinical trials, thus documenting their importance in the field of translational medicine. Standard protocols for the passage and collection of hMSCs involve trypsinization of preconfluent cultures. This practice is based, at least in part, on concerns that the multipotency of these cells would be diminished if the cultures became confluent. To test this concern, hMSCs were isolated and maintained in standard culture conditions in primary culture and were then subcultured after 2 weeks. The resulting first passage cultures were divided into two groups: those that were subcultured at the normal frequency, usually at 7 days for each passage (referred to as standard conditions [SC]), and those that were maintained for up to 53 days without being further subcultured (extended first passage [EFP]). At the end of the second passage and each of five subsequent subcultures for cells in SC (i.e., through passage 7), complementary EFP cultures were also trypsinized. Cells from each group were counted, resuspended in serum-free medium, and assayed to determine the ability of the cells to differentiate along osteogenic, chondrogenic, and adipogenic lineages. Cells in SC experienced an average of 27 population doublings through seven passages, whereas hMSCs in EFP achieved approximately 16 population doublings after 34 days but demonstrated very little increase in cell number after that time. The ability of hMSCs in EFP to produce bone in ceramic cubes implanted subcutaneously in immunocompromised mice and to differentiate into cartilage in pellet or aggregate culture was at least equivalent to that of the cells in SC through seven passages, whereas the capacity of the EFP hMSCs to produce lipid droplets in adipogenic conditions was maintained but was diminished relative to that of SC cells.

Efficient lentiviral transduction of human mesenchymal stem cells that preserves proliferation and differentiation capabilities.

Long-term lentiviral transduction of human mesenchymal stem cells (hMSCs) greatly enhances the usefulness of these cells. However, such transduction currently requires the use of polybrene, which severely inhibits hMSC proliferation. In contrast, protamine sulfate at 100 µg/ml doubled transduction efficiencies without affecting proliferation or differentiation potential. Expression levels improved 2.2-fold with the addition of a woodchuck hepatitis post-transcriptional regulatory element. Further improvements in transduction efficiencies could be obtained by a modest increase in viral concentrations through increased viral titers or decreased transduction volumes without changing multiplicity of infection, by transducing over multiple days, or by culturing the cells in fibroblast growth factor-2. Centrifugation improved expression but had no effect on efficiency. Transgene expression was stable over 6 weeks in vitro and in vivo. Donor-to-donor and intradonor variability were observed in primary passage through passage 2 cultures, but not at passage 3. These results provide a better optimized approach for expanded use of hMSCs through genetic manipulation.

The inhibition by interleukin 1 of MSC chondrogenesis and the development of biomechanical properties in biomimetic 3D woven PCL scaffolds.

Tissue-engineered constructs designed to treat large cartilage defects or osteoarthritic lesions may be exposed to significant mechanical loading as well as an inflammatory environment upon implantation in an injured or diseased joint. We hypothesized that a three-dimensionally (3D) woven poly(ε-caprolactone) (PCL) scaffold seeded with bone marrow-derived mesenchymal stem cells (MSCs) would provide biomimetic mechanical properties in early stages of in vitro culture as the MSCs assembled a functional, cartilaginous extracellular matrix (ECM). We also hypothesized that these properties would be maintained even in the presence of the pro-inflammatory cytokine interleukin-1 (IL-1), which is found at high levels in injured or diseased joints. MSC-seeded 3D woven scaffolds cultured in chondrogenic conditions synthesized a functional ECM rich in collagen and proteoglycan content, reaching an aggregate modulus of ~0.75 MPa within 14 days of culture. However, the presence of pathophysiologically relevant levels of IL-1 limited matrix accumulation and inhibited any increase in mechanical properties over baseline values. On the other hand, the mechanical properties of constructs cultured in chondrogenic conditions for 4 weeks prior to IL-1 exposure were protected from deleterious effects of the cytokine. These findings demonstrate that IL-1 significantly inhibits the chondrogenic development and maturation of MSC-seeded constructs; however, the overall mechanical functionality of the engineered tissue can be preserved through the use of a 3D woven scaffold designed to recreate the mechanical properties of native articular cartilage.

Hepatocyte growth factor mediates mesenchymal stem cell­induced recovery in multiple sclerosis models.

Mesenchymal stem cells (MSCs) have emerged as a potential therapy for a range of neural insults. In animal models of multiple sclerosis, an autoimmune disease that targets oligodendrocytes and myelin, treatment with human MSCs results in functional improvement that reflects both modulation of the immune response and myelin repair. Here we demonstrate that conditioned medium from human MSCs (MSC-CM) reduces functional deficits in mouse MOG35­55-induced experimental autoimmune encephalomyelitis (EAE) and promotes the development of oligodendrocytes and neurons. Functional assays identified hepatocyte growth factor (HGF) and its primary receptor cMet as critical in MSC-stimulated recovery in EAE, neural cell development and remyelination. Active MSC-CM contained HGF, and exogenously supplied HGF promoted recovery in EAE, whereas cMet and antibodies to HGF blocked the functional recovery mediated by HGF and MSC-CM. Systemic treatment with HGF markedly accelerated remyelination in lysolecithin-induced rat dorsal spinal cord lesions and in slice cultures. Together these data strongly implicate HGF in mediating MSC-stimulated functional recovery in animal models of multiple sclerosis.

The potential of mesenchymal stem cells for neural repair.

Developing effective therapies for serious neurological insults remains a major challenge for biomedical research. Despite intense efforts, the ability to promote functional recovery after contusion injuries, ischemic insults, or the onset of neurodegenerative diseases in the brain and spinal cord remains very limited even while the need for such therapies is increasing with an aging population. Recent studies suggest that cellular therapies utilizing mesenchymal stem cells (MSCs) may provide a functional benefit in a wide range of neurological insults. MSCs derived from a variety of tissue sources have been therapeutically evaluated in animal models of stroke, spinal cord injury, and multiple sclerosis. In each situation, treatment with MSCs results in substantial functional benefit and these pre-clinical studies have led to the initiation of a number of clinical trials worldwide in neural repair.

Chondrogenesis of adult stem cells from adipose tissue and bone marrow: induction by growth factors and cartilage-derived matrix.

OBJECTIVES: Adipose-derived stem cells (ASCs) and bone marrow-derived mesenchymal stem cells (MSCs) are multipotent adult stem cells with potential for use in cartilage tissue engineering. We hypothesized that these cells show distinct responses to different chondrogenic culture conditions and extracellular matrices, illustrating important differences between cell types. METHODS: Human ASCs and MSCs were chondrogenically differentiated in alginate beads or a novel scaffold of reconstituted native cartilage-derived matrix with a range of growth factors, including dexamethasone, transforming growth factor beta3, and bone morphogenetic protein 6. Constructs were analyzed for gene expression and matrix synthesis. RESULTS: Chondrogenic growth factors induced a chondrocytic phenotype in both ASCs and MSCs in alginate beads or cartilage-derived matrix. MSCs demonstrated enhanced type II collagen gene expression and matrix synthesis as well as a greater propensity for the hypertrophic chondrocyte phenotype. ASCs had higher upregulation of aggrecan gene expression in response to bone morphogenetic protein 6 (857-fold), while MSCs responded more favorably to transforming growth factor beta3 (573-fold increase). CONCLUSIONS: ASCs and MSCs are distinct cell types as illustrated by their unique responses to growth factor-based chondrogenic induction. This chondrogenic induction is affected by the composition of the scaffold and the presence of serum.

Defining human mesenchymal stem cell efficacy in vivo.

Allogeneic human mesenchymal stem cells (hMSCs) can suppress graft versus host disease (GvHD) and have profound anti-inflammatory and regenerative capacity in stroke, infarct, spinal cord injury, meniscus regeneration, tendinitis, acute renal failure, and heart disease in human and animal models of disease. There is significant clinical hMSC variability in efficacy and the ultimate response in vivo. The challenge in hMSC based therapy is defining the efficacy of hMSC in vivo. Models which may provide insight into hMSC bioactivity in vivo would provide a means to distinguish hMSCs for clinical utility. hMSC function has been described as both regenerative and trophic through the production of bioactive factors. The regenerative component involves the multi-potentiality of hMSC progenitor differentiation. The secreted factors generated by the hMSCs are milieu and injury specific providing unique niches for responses in vivo. These bioactive factors are anti-scarring, angiogenic, anti-apoptotic as well as regenerative. Further, from an immunological standpoint, hMSC's can avoid host immune response, providing xenographic applications. To study the in vivo immuno-regulatory effectiveness of hMSCs, we used the ovalbumin challenge model of acute asthma. This is a quick 3 week in vivo pulmonary inflammation model with readily accessible ways of measuring effectiveness of hMSCs. Our data show that there is a direct correlation between the traditional ceramic cube score to hMSCs attenuation of cellular recruitment due to ovalbumin challenge. The results from these studies verify the in vivo immuno-modulator effectiveness of hMSCs and support the potential use of the ovalbumin model as an in vivo model of hMSC potency and efficacy. Our data also support future directions toward exploring hMSCs as an alternative therapeutic for the treatment of airway inflammation associated with asthma.