Age-Specific Changes of Mesenchymal Stem Cells Are Paralleled by Upregulation of CD106 Expression As a Response to an Inflammatory Environment

Hyaline Cartilage Microtissues Engineered from Adult Dedifferentiated Chondrocytes: Safety and Role of WNT Signaling

The repair of damaged articular cartilage is an unmet medical need. Chondrocyte-based cell therapy has been used to repair cartilage for over 20 years despite current limitations. Chondrocyte dedifferentiation upon expansion in monolayer is well known and is the main obstacle to their use as cell source for cartilage repair. Consequently, current approaches often lead to fibrocartilage, which is biomechanically different from hyaline cartilage and not effective as a long-lasting treatment. Here, we describe an innovative 3-step method to engineer hyaline-like cartilage microtissues, named Cartibeads, from high passage dedifferentiated chondrocytes. We show that WNT5A/5B/7B genes were highly expressed in dedifferentiated chondrocytes and that a decrease of the WNT signaling pathway was instrumental for full re-differentiation of chondrocytes, enabling production of hyaline matrix instead of fibrocartilage matrix. Cartibeads showed hyaline-like characteristics based on GAG quantity and type II collagen expression independently of donor age and cartilage quality. In vivo, Cartibeads were not tumorigenic when transplanted into SCID mice. This simple 3-step method allowed a standardized production of hyaline-like cartilage microtissues from a small cartilage sample, making Cartibeads a promising candidate for the treatment of cartilage lesions.

Patient Age and Cell Concentration Influence Prevalence and Concentration of Progenitors in Bone Marrow Aspirates: An Analysis of 436 Patients

BACKGROUND

Connective tissue progenitors (CTPs) resident in native tissues serve as biological building blocks in tissue repair and remodeling processes. Methods for analysis and reporting on CTP quantity and quality are essential for defining optimal cell sources and donor characteristics and the impact of cell processing methods for cell therapy applications. The present study examines the influence of donor characteristics and cell concentration (nucleated cells/mL) on CTP prevalence (CTPs/million nucleated cells) and CTP concentration (CTPs/mL) in bone marrow aspirates (BMAs).

METHODS

Iliac crest bone marrow was aspirated from 436 patients during elective total knee or hip arthroplasty. Bone marrow-derived nucleated cells were plated at a density of 1.19 × 105 cells/cm2. Colony-forming unit analysis was performed on day 6.

RESULTS

Large variation was seen between donors. Age (p < 0.05) and cell concentration (p < 0.001) significantly influenced CTP prevalence and CTP concentration. For every 1-year increase in age, the odds of having at least an average CTP prevalence and CTP concentration decreased by 1.5% and 1.6%, respectively. For every 1 million cells/mL increase in cell concentration, the odds of having at least an average CTP prevalence and CTP concentration increased by 2.2% and 7.9%, respectively. Sex, race, body mass index (BMI), and the presence of osteoporosis did not influence CTP prevalence or CTP concentration.

CONCLUSIONS

BMA-derived CTPs were obtained from all patient groups. CTP prevalence and CTP concentration decreased with age. Cell concentration decreased with age and positively correlated with total CTP prevalence and CTP concentration. The mean CTP concentration in patients >60 years of age was a third of the CTP concentration in patients <30 years of age.

CLINICAL RELEVANCE

Proper BMA techniques are necessary to obtain a high-quality yield and composition of cells and CTPs. The reduced CTP concentration and CTP prevalence in the elderly may be mitigated by the use of cell processing methods that increase CTP concentration and CTP prevalence (e.g., by removing red blood cells, serum, and non-CTPs or by increasing aspirate volumes). Cell concentration in the BMA can be measured at the point of care and is an appropriate initial assessment of the quality of BMA.

Systemic NF-κB-mediated inflammation promotes an aging phenotype in skeletal stem/progenitor cells

Aging tissues undergo a progressive decline in regenerative potential. This decline in regenerative responsiveness has been attributed to changes in tissue-specific stem cells and their niches. In bone, aged skeletal stem/progenitor cell dysfunction is characterized by decreased frequency and impaired osteogenic differentiation potential. This aging phenotype ultimately results in compromised regenerative responsiveness to injury. The age-associated increase of inflammatory mediators, known as inflamm-aging, has been identified as the main culprit driving skeletal stem cell dysfunction. Here, we utilized a mouse model of parabiosis to decouple aging from inflammation. Using the Nfkb1-/- mouse as a model of inflamm-aging, we demonstrate that a shared systemic circulation between a wild-type and Nfkb1-/- mouse results in an aging phenotype of the wild-type skeletal stem and progenitor cells, shown by CFU-fs and osteogenic and adipogenic differentiation assays. Our findings demonstrate that exposure to an inflammatory secretome results in a phenotype similar to the one observed in aging.

Aging delays epimorphic regeneration in mice

Epimorphic regeneration is a multi-tissue regeneration process where amputation does not lead to scarring, but blastema formation and patterned morphogenesis for which cell plasticity and concerted cell-cell interactions are pivotal. Tissue regeneration declines with aging, yet if and how aging impairs epimorphic regeneration is unknown. Here we show for the first time that aging derails the spatiotemporal regulation of epimorphic regeneration in mammals, first, by exacerbating tissue histolysis and delaying wound closure, and second, by impairing blastema differentiation and skeletal regrowth. Surprisingly, aging did not limit stem cell availability in the blastema, but reduced osteoblast-dependent bone formation. Our data suggest that aging delays regeneration not by stem cell exhaustion, but functional defects of differentiated cells that may be driven by an aged wound environment and alterations in the spatiotemporal regulation of regeneration events. Our findings emphasize the importance of accurate timing of signaling events for regeneration, and highlight the need for carefully timed interventions in regenerative medicine.

Inflammation-mediated age-dependent effects of casein kinase 2-interacting protein-1 on osteogenesis in mesenchymal stem cells

BACKGROUND

The casein kinase 2-interacting protein-1 (CKIP-1) is important in the development of osteoblasts and cardiomyocytes. However, the effects of CKIP-1 on osteoblast precursor mesenchymal stem cells (MSCs) remain unclear. This study aimed to determine whether CKIP-1 affects osteogenic differentiation in MSCs and explore the relationship of CKIP-1 and inflammation.

METHODS

Bone marrow MSCs of CKIP-1 wild type (WT) and knockout (KO) mice were cultivated in vitro. Cell phenotype was analyzed by flow cytometry, colony formation was detected to study the proliferative ability. Osteogenic and adipogenic induction were performed. The osteogenic ability was explored by alizarin red staining, alkaline phosphatase (ALP) staining and ALP activity detection. Quantitative real-time polymerase chain reaction (qRT-PCR) was carried out to determine the mRNA expression levels of osteoblast marker genes. The adipogenic ability was detected by oil red O staining. Content of the bone was analyzed to observe the differences of bone imaging parameters including trabecular bone volume/tissue volume (BV/TV), bone surface area fraction/trabecular BV, trabecular number (Tb.N), and trabecular spacing (Tb.sp). Interleukin (IL)-1β was injected on WT mice of 2 months old and 18 months old, respectively. Difference in CKIP-1 expression was detected by RT-PCR and western blot. The relationship between CKIP-1 and inflammation was explored by RT-PCR and western blot.

RESULTS

ALP assays, alizarin red staining, and qRT-PCR showed that MSCs derived from CKIP-1 KO mice exhibited a stronger capability for osteogenesis. Micro-computed tomography detection showed that among 18-month-old mice, CKIP-1 KO mice presented significantly higher bone mass compared with WT mice (P = 0.02). No significant difference was observed in 2-month-old mice. In vivo data showed that expression of CKIP-1 was higher in the bone marrow of aging mice than in young mice (4.3-fold increase at the mRNA level, P = 0.04). Finally, the expression levels of CKIP-1 in bone marrow (3.2-fold increase at the mRNA level, P = 0.03) and cultured MSCs were up-regulated on chronic inflammatory stimulation by IL-1β.

CONCLUSIONS

CKIP-1 is responsible for negative regulation of MSC osteogenesis with age-dependent effects. Increasing levels of inflammation with aging may be the primary factor responsible for higher expression levels of CKIP-1 but may not necessarily affect MSC aging.

Multi-Parameter Analysis of Biobanked Human Bone Marrow Stromal Cells Shows Little Influence for Donor Age and Mild Comorbidities on Phenotypic and Functional Properties

Heterogeneous populations of human bone marrow-derived stromal cells (BMSC) are among the most frequently tested cellular therapeutics for treating degenerative and immune disorders, which occur predominantly in the aging population. Currently, it is unclear whether advanced donor age and commonly associated comorbidities affect the properties of ex vivo-expanded BMSCs. Thus, we stratified cells from adult and elderly donors from our biobank (n = 10 and n = 13, mean age 38 and 72 years, respectively) and compared their phenotypic and functional performance, using multiple assays typically employed as minimal criteria for defining multipotent mesenchymal stromal cells (MSCs). We found that BMSCs from both cohorts meet the standard criteria for MSC, exhibiting similar morphology, growth kinetics, gene expression profiles, and pro-angiogenic and immunosuppressive potential and the capacity to differentiate toward adipogenic, chondrogenic, and osteogenic lineages. We found no substantial differences between cells from the adult and elderly cohorts. As positive controls, we studied the impact of in vitro aging and inflammatory cytokine stimulation. Both conditions clearly affected the cellular properties, independent of donor age. We conclude that in vitro aging rather than in vivo donor aging influences BMSC characteristics.

Synovium-derived stromal cell-induced osteoclastogenesis: a potential osteoarthritis trigger

Purpose: To shed light on the idea that mesenchymal stem/stromal cells (MSCs) recruited in synovium (SM) (i.e. Synovium-Derived Stromal Cells, SDSCs) could be involved in Osteoarthritis (OA) pathophysiology. Attention was also paid to a further stromal cell type with a peculiar ultrastructure called telocytes (TCs), whose role is far from clarified. Methods: In the present in vitro study, we compared SDSCs isolated from healthy and OA subjects in terms of phenotype, morphology and differentiation potential as well as in their capability to activate normal Peripheral Blood Mononuclear Cells (PBMCs). Histological, immunohistochemical and ultrastructural analyses were integrated by qRT-PCR and functional resorbing assays. Results: Our data demonstrated that both SDSC populations stimulated the formation of osteoclasts from PBMCs: the osteoclast-like cells generated by healthy-SDSCs via transwell co-cultures were inactive, while OA-derived SDSCs have a much greater effectiveness. Moreover, the presence of TCs was more evident in cultures obtained from OA subjects and suggests a possible involvement of these cells in OA. Conclusions: Osteoclastogenic differentiation capability of PBMCs from OA subjects, also induced by B synoviocytes has been already documented. Here we hypothesized that SDSCs, generally considered for their regenerative potential in cartilage lesions, have also a role in the onset/maintenance of OA. Clinical relevance: Our observations may represent an interesting opportunity for the development of a holistic approach for OA treatment, that considers the multifaceted capability of MSCs in relation to the environment.

The Analysis of In Vivo Aging in Human Bone Marrow Mesenchymal Stromal Cells Using Colony-Forming Unit-Fibroblast Assay and the CD45lowCD271+ Phenotype

Uncultured mesenchymal stromal cells (MSCs) are increasingly used in therapies; however, the effects of donor age on their biological characteristics and gene expression remain unclear. The aim of this study was to investigate age-related changes in bone marrow (BM) MSCs following minimal or no culture manipulation. Iliac crest BM was aspirated from 67 healthy donors (19-89 years old) and directly used for the colony-forming unit-fibroblast (CFU-F) assay or CD45^lowCD271⁺ cell enumeration. The colonies were analysed for colony area and integrated density (ID) when grown in standard MSC media or media supplemented with human serum from young (YS) or old (OS) donors. There was a notable age-related decline in the number of MSCs per millilitre of BM aspirate revealed by the CFU-F assay (r = −0.527, p < 0.0001) or flow cytometry (r = −0.307, p = 0.0116). Compared to young donors (19-40 years old), colony IDs were significantly lower in older donors (61-89 years old), particularly for smaller-sized colonies (42% lower, p < 0.01). When cultured in media supplemented with OS, young and old donor MSCs formed colonies with lower IDs, by 21%, p < 0.0001, and 27%, p < 0.05, respectively, indicating the formation of smaller sparser colonies. No significant differences in the expression of selected adipogenic, osteogenic, stromal, and bone remodelling genes as well as CD295, CD146, CD106, and connexin 43 surface molecules were found in sorted CD45^lowCD271⁺ MSCs from young and old donors (n = 8 donors each). Altogether, these results show similar trends for age-related decline in BM MSC numbers measured by the CFU-F assay and flow cytometry and reveal age-related effects of human serum on MSC colony formation. No significant differences in selected gene expression in uncultured CD45^lowCD271⁺ MSCs suggest that old donor MSCs may not be inferior in regard to their multipotential functions. Due to large donor-to-donor variation in all donor groups, our data indicate that an individual's chronological age is not a reliable predictor of their MSC number or potency.

Mesenchymal Stem Cells for Frailty?

Frailty is a medical syndrome associated with advancing age characterized by reduced functional reserve, strength, endurance, and susceptibility to infection associated with high morbidity, hospitalization, and death. Nonspecific interventions to improve the healthspan of affected patients include physical therapy, exercise, improved nutrition, etc. Among the hallmarks of aging, depletion of stem cells with resultant compromise of regeneration and repair of tissues informs a rational stem cell-based replacement strategy. This hypothesis has been evaluated in a randomized, double-blind, placebo-controlled clinical trial utilizing human allogeneic mesenchymal stem cells (allo-hMSCs), a facile, scalable stem cell replacement therapy. Intravenous infusion of 100 or 200 million allo-hMSCs was deemed safe in aged frail individuals. However, modest improvement outcomes were limited to the lower dose, a finding that remains difficult to explain. Future studies are definitely warranted given the magnitude of this increasingly important medical syndrome.

Platelet-derived growth factor receptor beta identifies mesenchymal stem cells with enhanced engraftment to tissue injury and pro-angiogenic property

Mesenchymal stem cells (MSCs) are heterogeneous likely consisting of subpopulations with various therapeutic potentials. Here we attempted to acquire a subset of MSCs with enhanced effect in wound healing. We found that human placental MSCs expressing platelet-derived growth factor (PDGF) receptor (PDGFR)-β exhibited greater proliferation rates and generated more colony-forming unit-fibroblast (CFU-F), compared to PDGFR-β- MSCs. Notably, PDGFR-β+ MSCs expressed higher levels of pro-angiogenic factors such as Ang1, Ang2, VEGF, bFGF and PDGF. When 106 GFP-expressing MSCs were topically applied into excisional wounds in mice, PDGFR-β+ MSCs actively incorporated into the wound tissue, resulting in enhanced engraftment (3.92 ± 0.31 × 105 remained in wound by 7 days) and accelerated wound closure; meanwhile, PDGFR-β- MSCs tended to remain on the top of the wound bed with significantly fewer cells (2.46 ± 0.26 × 105) engrafted into the wound, suggesting enhanced chemotactic migration and engraftment of PDGFR-β+ MSCs into the wound. Real-Time PCR and immunostain analyses revealed that the expression of PDGF-B was upregulated after wounding; transwell migration assay showed that PDGFR-β+ MSCs migrated eightfold more than PDGFR-β- MSCs toward PDGF-BB. Intriguingly, PDGFR-β+ MSC-treated wounds showed significantly enhanced angiogenesis compared to PDGFR-β- MSC- or vehicle-treated wounds. Thus, our results indicate that PDGFR-β identifies a subset of MSCs with enhanced chemotactic migration to wound injury and effect in promoting angiogenesis and wound healing, implying a greater therapeutic potential for certain diseases.

Allogeneic Human Mesenchymal Stem Cell Infusions for Aging Frailty

Background

Impaired endogenous stem cell repair capacity is hypothesized to be a biologic basis of frailty. Therapies that restore regenerative capacity may therefore be beneficial. This Phase 1 study evaluated the safety and potential efficacy of intravenous, allogeneic, human mesenchymal stem cell (allo-hMSC)-based therapy in patients with aging frailty.

Methods

In this nonrandomized, dose-escalation study, patients received a single intravenous infusion of allo-hMSCs: 20-million (n = 5), 100-million (n = 5), or 200-million cells (n = 5). The primary endpoint was incidence of any treatment-emergent serious adverse events measured at 1 month postinfusion. The secondary endpoints were functional efficacy domains and inflammatory biomarkers, measured at 3 and 6 months, respectively.

Results

There were no treatment-emergent serious adverse events at 1-month postinfusion or significant donor-specific immune reactions during the first 6 months. There was one death at 258 days postinfusion in the 200-million group. In all treatment groups, 6-minute walk distance increased at 3 months (p = .02) and 6 months (p = .001) and TNF-α levels decreased at 6 months (p < .0001). Overall, the 100-million dose showed the best improvement in all parameters, with the exception of TNF-α, which showed an improvement in both the 100- and 200-million groups (p = .0001 and p = .0001, respectively). The 100-million cell-dose group also showed significant improvements in the physical component of the SF-36 quality of life assessment at all time points relative to baseline.

Conclusions

Allo-hMSCs are safe and immunologically tolerated in aging frailty patients. Improvements in functional and immunologic status suggest that ongoing clinical development of cell-based therapy is warranted for frailty.

Microenvironmental factors that regulate mesenchymal stem cells: lessons learned from the study of heterotopic ossification

Bone marrow contains a non-hematopoietic, clonogenic, multipotent population of stromal cells that are later called mesenchymal stem cells (MSC). Similar cells that share many common features with MSC are also found in other organs, which are thought to contribute both to normal tissue regeneration and to pathological processes such as heterotopic ossification (HO), the formation of ectopic bone in soft tissue. Understanding the microenvironmental factors that regulate MSC in vivo is essential both for understanding the biology of the stem cells and for effective translational applications of MSC. Unfortunately, this important aspect has been largely underappreciated. This review tries to raise the attention and highlight this critical issue by updating the relevant literature along with discussions of the key issues in the area.

Interferon‑γ alters the microRNA profile of umbilical cord‑derived mesenchymal stem cells

Numerous studies have demonstrated that interferon-γ (IFN-γ) is an important inflammatory cytokine, which may activate the immunomodulatory abilities of mesenchymal stem cells (MSCs), and may influence certain other functions of these cells. MicroRNAs are small non-coding RNAs that regulate the majority of the biological functions of cells and are important in a variety of biological processes. However, few studies have been performed to investigate whether IFN-γ affects the microRNA profile of MSCs. The aim of the present study was to analyze the microRNA profile of MSCs derived from the umbilical cord (UC-MSCs) cultured in the presence or absence of IFN-γ (IFN-UC-MSCs). An array that detects 754 microRNAs was used to determine the expression profiles. Statistical analysis of the array data revealed that 8 microRNAs were significantly differentially expressed in UC-MSCs and IFN-UC-MSCs. Reverse transcription-quantitative polymerase chain reaction validated the differential expression of the 8 identified microRNAs. The target genes of the 8 microRNAs were predicted through two online databases, TargetScan and miRanda, and the predicted results were screened by bioinformatics analysis. The majority of the target genes were involved in the regulation of transcription, signal transduction, proliferation, differentiation and migration. These results may provide insight into the mechanism underlying the regulation of the biological functions of MSCs by IFN-γ, in particular the immunomodulatory activity.

A proteomic analysis of chondrogenic, osteogenic and tenogenic constructs from ageing mesenchymal stem cells

Background

Mesenchymal stem cells (MSCs) have prospective applications in regenerative medicine and tissue engineering but to what extent phenotype and differentiation capacity alter with ageing is uncertain. Consequently, any loss in functionality with age would have profound consequences for the maintenance of tissue viability and the quality of tissues. Proteomics enables the set of proteins responsible for a particular cell phenotype to be identified, as well as enabling insights into mechanisms responsible for age-related alterations in musculoskeletal tissues. Few proteomic studies have been undertaken regarding age-related effects on tissue engineered into cartilage and bone, and none for tendon. This study provides a proteome inventory for chondrogenic, osteogenic and tenogenic constructs synthesised from human MSCs, and elucidates proteomic alterations as a consequence of donor age.

Methods

Human bone-marrow derived MSCs from young (n = 4, 21.8 years ± 2.4SD) and old (n = 4, 65.5 years ± 8.3SD) donors were used to make chondrogenic, osteogenic and tenogenic tissue-engineered constructs. We utilised an analytical method relying on extracted peptide intensities as a label-free approach for peptide quantitation by liquid chromatography–mass spectrometry. Results were validated using western blotting.

Results

We identified proteins that were differentially expressed with ageing; 128 proteins in chondrogenic constructs, 207 in tenogenic constructs and four in osteogenic constructs. Differentially regulated proteins were subjected to bioinformatic analysis to ascertain their molecular functions and the signalling pathways. For all construct types, age-affected proteins were involved in altered cell survival and death, and antioxidant and cytoskeletal changes. Energy and protein metabolism were the principle pathways affected in tenogenic constructs, whereas lipid metabolism was strongly affected in chondrogenic constructs and mitochondrial dysfunction in osteogenic constructs.

Conclusions

Our results imply that further work on MSC-based therapeutics for the older population needs to focus on oxidative stress protection. The differentially regulated proteome characterised by this study can potentially guide translational research specifically aimed at effective clinical interventions.

Electronic supplementary material

The online version of this article (doi:10.1186/s13287-016-0384-2) contains supplementary material, which is available to authorized users.

Clinical Outcomes After Autologous Chondrocyte Implantation in Adolescents' Knees: A Systematic Review

PURPOSE

To perform a systematic review of the use of autologous chondrocyte implantation (ACI) in the adolescent knee.

SPECIFIC AIMS

(1) quantify clinical outcomes of ACI in adolescent knees, (2) identify lesion and patient factors that correlate with clinical outcome, and (3) determine the incidence of complications of ACI in adolescents.

METHODS

PubMed, MEDLINE, SCOPUS, CINAHL, and Cochrane Collaboration Library databases were searched systematically. Outcome scores recorded included the International Knee Documentation Committee score, the International Cartilage Repair Society score, the Knee Injury and Osteoarthritis Outcome Score, the visual analog scale, the Bentley Functional Rating Score, the Modified Cincinnati Rating System, Tegner activity Lysholm scores, and return athletics. Outcome scores were compared among studies based on proportion of adolescents achieving specific outcome quartiles at a minimum 1-year follow-up. Methodologic quality of studies was evaluated by Coleman Methodology Scores (CMSs).

RESULTS

Five studies reported on 115 subjects who underwent ACI with periosteal cover (ACI-P; 95, 83%), ACI with type I/type III collagen cover (ACI-C; 6, 5%), or matrix-induced ACI (MACI; 14, 12%). Mean patient age was 16.2 years (range, 11 to 21 years). All studies were case series. Follow-up ranged from 12 to 74 months (mean, 52.3 months). Mean defect size was 5.3 cm(2) (range, 0.96 to 14 cm(2)). All studies reported improvement in clinical outcomes scores. Graft hypertrophy was the most common complication (7.0%). The mean preoperative clinical outcome percentage (based on percentage of outcome scale used) was 37% (standard deviation [SD], 18.9%) and the mean postoperative clinical outcome percentage was 72.7% (SD, 16.9%). The overall percentage increase in clinical outcome scores was 35.7% (SD, 14.2%). Mean CMS was 47.8 (SD, 8.3).

CONCLUSIONS

Cartilage repair in adolescent knees using ACI provides success across different clinical outcomes measures. The only patient- or lesion-specific factor that influenced clinical outcome was the shorter duration of preoperative symptoms.

LEVEL OF EVIDENCE

Level IV, systemic review of Level I-IV studies.

Systemic impact molds mesenchymal stromal/stem cell aging

Aging is associated with an accruing emergence of non-functional tissues. Mesenchymal stem cells (MSC) bring forth progenitors with multi-lineage differentiation potential, yet, they also exhibit anti-inflammatory and tissue-protective properties. Due to aging, altered tissue microenvironments constrict controlled stem cell proliferation and progenitor differentiation, thus diminishing the fitness of MSC. Therefore, deepening our understanding of metabolic, molecular and environmental factors impacting on MSC during human aging as well as providing new vistas on their role in promoting healthy aging and preventing age-associated disease is pivot. It is anticipated that integrative quantification of systemic parameters dominantly impacting on MSC will also enable effective personalized prognosis and provision of effective early medical interventions. Working along this line, it can be envisaged that standards in medical therapies can be individually adjusted by accounting not solely for the patient's chronological age or other physical parameters rather than specific physiological parameters which are believed to functionally shape stem cell niches within the bone marrow.

Biological differences between native and cultured mesenchymal stem cells: implications for therapies

We describe the current knowledge of the surface marker phenotype of native bone marrow mesenchymal stem/stromal cells (MSCs) in humans and in mouse models, highlighting similarities in the MSC marker "signature" between the two species. The chapter proceeds to discuss the published literature pertaining to native MSC topography and their interactions with hematopoietic stem cells and their progeny, as well as with blood vessels and nerve endings. Additionally, the chapter describes phenotypic and functional "drifts" that occur in MSC preparations as they are taken out of their native bone marrow microenvironment and induced to proliferate in vitro (in the presence of animal or human serum). We propose that the understanding of the biology of MSCs in their native niches in the bone marrow could lead to future developments in the treatment of hematological diseases such as multiple myeloma. Additionally, this knowledge would assist in the development of more "natural" MSC culture conditions, best preserving MSC functionality including their homing potential in order to optimize MSC transplantation in the context of graft-versus-host and other diseases.

Comparison of biological properties of umbilical cord-derived mesenchymal stem cells from early and late passages: immunomodulatory ability is enhanced in aged cells

Mesenchymal stem cells (MSCs) are a potential source of adult stem cells for cell-based therapeutics due to their substantial multilineage differentiation capacity and secretory functions. No information is presently available regarding the maintenance of immunosuppressive properties of this cell type with repeated passages. It was therefore the aim of the present study to analyze the biological properties, particularly the immunoregulatory effect, of MSCs from late passages. The differences between young and old MSCs in morphology, cell surface antigen phenotype, proliferation, gene expression and immunomodulatory ability were investigated. The results of the current study demonstrated that with the passage of cells, senescent MSCs displayed a characteristically enlarged and flattened morphology, different gene expression profiles and stronger immunosuppressive activities. Increased interleukin-6 production may be a possible underlying mechanism for this enhanced immunomodulatory ability of MSCs. These findings suggest that aged MSCs may provide a treatment option for patients with graft versus host disease and other diseases associated with dysregulation of the immune system.

TNFα and IL-1β influence the differentiation and migration of murine MSCs independently of the NF-κB pathway

INTRODUCTION

Mesenchymal stem cells (MSCs) have the ability to repair and regenerate tissue, home to sites of inflammation, and evade the host immune system. As such, they represent an attractive therapy for the treatment of autoimmune inflammatory diseases. However, results from in vivo murine studies in inflammatory arthritis have been conflicting, and this may be due to the genetic background of the MSCs used. It is known that the inflammatory milieu may influence properties of MSCs and that, in the case of human bone marrow-derived MSCs, this may be mediated by the nuclear factor-kappa-B (NF-κB) pathway. We sought to determine whether pro-inflammatory cytokines altered the differentiation and migration capacity of murine MSCs from different mouse strains and whether this was mediated by NF-κB.

METHODS

The differentiation and migration of FVB and BALB/c MSCs were carried out in the presence of varying concentrations of tumor necrosis factor-alpha (TNFα) and interleukin (IL)-1β, and the NF-κB pathway was inhibited in one of two ways: either by transduction of MSCs with an adenoviral vector expressing a super-repressor of NF-κB or by the addition of curcumin to culture media.

RESULTS

Both BALB/c and FVB MSCs were sensitive to the effect of pro-inflammatory cytokines in vitro. TNFα and IL-1β suppressed BALB/c osteogenesis and adipogenesis and FVB osteogenesis. The migration of both cell types toward media containing fetal bovine serum was augmented by pre-stimulation with either cytokine. In neither cell type were the cytokine effects reversed by abrogation of the NF-κB pathway.

CONCLUSIONS

These data show that murine MSCs from different genetic backgrounds may be influenced by an inflammatory milieu in a manner that is not mediated by NF-κB, as is the case for human MSCs. This is not mediated by NF-κB. These findings are important and should influence how in vivo trials of murine MSCs are interpreted and the future development of pre-clinical studies in inflammatory diseases.

Implications of multipotent mesenchymal stromal cell aging

Aging is defined as the progressive and generalized impairment of function, resulting in an increasing vulnerability to environmental challenges and a growing risk of disease and death. The decline in the regenerative capacity of resident stem cells across different tissues is a central mediator of aging. In this paper we review the evidence implicating multipotent mesenchymal stromal cells as being subject to and causes of tissue and organismal aging. We specifically discuss the nuclear changes that occur in the context of Hutchinson-Gilford progeria syndrome, a premature aging syndrome that preferentially affects tissues of mesenchymal origin.

Long-chain polyunsaturated fatty acids may mutually benefit both obesity and osteoporosis

The overconsumption of n-6 polyunsaturated fatty acids (PUFA), resulting in a high ratio of n-6 to n-3 PUFA, may contribute to the increased pathogenesis of obesity and osteoporosis by promoting low-grade chronic inflammation (LGCI). As evidence suggests, both obesity and osteoporosis are linked on a cellular and systemic basis. This review will analyze if a relationship exists between LGCI, fat, bone, and n-3 PUFA. During the life cycle, inflammation increases, fat mass accumulates, and bone mass declines, thus suggesting that a connection exists. This review will begin by examining how the current American diet and dietary guidelines may fall short of providing an anti-inflammatory dose of the n-3 PUFA eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). It will then define LGCI and outline the evidence for a relationship between fat and bone. Inflammation as it pertains to obesity and osteoporosis and how EPA and DHA can alleviate the associated inflammation will be discussed, followed by some preliminary evidence to show how mesenchymal stem cell (MSC) lineage commitment may be altered by inflammation to favor adipogenesis. Our hypothesis is that n-3 PUFA positively influence obesity and osteoporosis by reducing LGCI, ultimately leading to a beneficial shift in MSC lineage commitment. This hypothesis essentially relates the need for more focused research in several areas such as determining age and lifestyle factors that promote the shift in MSC commitment and if current intakes of EPA and DHA are optimal for fat and bone.

Autologous chondrocyte implantation in children and adolescents

PURPOSE

Autologous chondrocyte implantation (ACI) is a well-established treatment method for cartilage defects in knees. Age-related grouping was based on expression data of cartilage-specific markers. Specificities of ACI in the different populations were analysed.

METHODS

Two hundred and sixty-seven patients undergoing ACI in the knee between 2006 and 2010 were included in this analysis. Cell characteristics and expression data of cartilage-specific surface markers as CD44, aggrecan and collagen type II were statistically analysed for age association. Epidemiological data of the defined groups were compared. Course of treatment was evaluated using MRI.

RESULTS

A correlation analysis showed statistically significant associations between age and aggrecan or collagen type II expression in all patients <30 years. A cluster analysis could predict age-dependent expression of these markers separating groups with an average age of 18.1 ± 2.3 and 23.6 ± 4.2 years, respectively (p < 0.02). Discriminance analysis suggested the age border between adults and juveniles at about 20 years. There was no influence of age on cell characteristics or CD44 expression. In the 19 of 267 patients with an age ≤18 years, gender distribution was not different compared to adults, but patella was significantly more affected. Cartilage lesions were mainly caused by osteochondritis dissecans (OCD) and trauma. The Knee Osteoarthritis Scoring System in MRI reached 4.8 ± 2.3 points before, declining to 3.3 ± 2.3 points 6 and 12 months after the operation.

CONCLUSIONS

Age-related expression of cartilage-specific markers allows definition of adolescents in cartilage regenerating surgery. Chondromalacia in these patients is mainly caused by OCD or trauma.

LEVEL OF EVIDENCE

Case series, Level IV.

From cellular senescence to age-associated diseases: the miRNA connection

Cellular senescence has evolved from an in-vitro model system to study aging in vitro to a multifaceted phenomenon of in-vivo importance as senescent cells in vivo have been identified and their removal delays the onset of age-associated diseases in a mouse model system. From the large emerging class of non-coding RNAs, miRNAs have only recently been functionally implied in the regulatory networks that are modified during the aging process. Here we summarize examples of similarities between the differential expression of miRNAs during senescence and age-associated diseases and suggest that these similarities might emphasize the importance of senescence for the pathogenesis of age-associated diseases. Understanding such a connection on the level of miRNAs might offer valuable opportunities for designing novel diagnostic and therapeutic strategies.

Developmental programs are kept alive during adulthood by stem cells: the aging aspect

Stem cells are fundamental for life-long preservation of cellular somatic maintenance. Tissue-borne stem cells replenish worn-out critical elements. Provided they remain fit over lifetime, enduring stem cell activities avert the emergence of age-associated chronic degenerative diseases and pathologies. Although experimentally still unclear, it is assumed that stem cells reside in protected niches. Freshly isolated mesenchymal stem cells exhibit donor-specific aberrations, which cannot solely be ascribed to differences in genetic background. Besides inevitably accumulating intrinsic modifications, the systemic environment also impacts on basic properties of mesenchymal stem cells such as their inherent multi-lineage differentiation potential. Chronic systemic aberrations over time comprise unwholesome influences, in particular in terms of regeneration and repair when stem cells recapitulate distinct developmental programs. During or thereafter, stem cells can diversify either because of insufficiently silencing activated building cycles, or by acquiring epigenetic deviations.

From tendon to nerve: an MSC for all seasons

The potential of mesenchymal stem cells (MSCs) to regenerate damaged tissue is well documented, as this specialized progenitor cell type exhibits superior cellular properties, and would allow medical as well as ethical limitations to be overcome. By now, MSCs have been successfully introduced in manifold experimental approaches within the newly defined realm of Regenerative Medicine. Advanced methods for in vitro cell expansion, defined induction of distinct differentiation processes, 3-dimensional culture on specific scaffold material, and tissue engineering approaches have been designed, and many clinical trials not only have been launched, but recently could be completed. To date, most of the MSC-based therapeutic approaches have been executed to address bone, cartilage, or heart regeneration; further, prominent studies have shown the efficacy of ex vivo expanded and infused MSCs to countervail graft-versus-host disease. Yet more fields of application emerge in which MSCs unfold beneficial effects, and presently, therapies that effectively ameliorate nonhealing conditions after tendon or spinal cord injury are, courtesy of scientific research, forging ahead to the clinical trial stage.

In situ guided tissue regeneration in musculoskeletal diseases and aging : Implementing pathology into tailored tissue engineering strategies

In situ guided tissue regeneration, also addressed as in situ tissue engineering or endogenous regeneration, has a great potential for population-wide "minimal invasive" applications. During the last two decades, tissue engineering has been developed with remarkable in vitro and preclinical success but still the number of applications in clinical routine is extremely small. Moreover, the vision of population-wide applications of ex vivo tissue engineered constructs based on cells, growth and differentiation factors and scaffolds, must probably be deemed unrealistic for economic and regulation-related issues. Hence, the progress made in this respect will be mostly applicable to a fraction of post-traumatic or post-surgery situations such as big tissue defects due to tumor manifestation. Minimally invasive procedures would probably qualify for a broader application and ideally would only require off the shelf standardized products without cells. Such products should mimic the microenvironment of regenerating tissues and make use of the endogenous tissue regeneration capacities. Functionally, the chemotaxis of regenerative cells, their amplification as a transient amplifying pool and their concerted differentiation and remodeling should be addressed. This is especially important because the main target populations for such applications are the elderly and diseased. The quality of regenerative cells is impaired in such organisms and high levels of inhibitors also interfere with regeneration and healing. In metabolic bone diseases like osteoporosis, it is already known that antagonists for inhibitors such as activin and sclerostin enhance bone formation. Implementing such strategies into applications for in situ guided tissue regeneration should greatly enhance the efficacy of tailored procedures in the future.

The suppressive effect of mesenchymal stromal cells on T cell proliferation is conserved in old age

Mesenchymal stromal cells (MSC) have become a useful tool in curing graft versus host disease (GVHD) after transplantation. No information is presently available whether the immunosuppressive properties of this cell type are maintained in old age. It was therefore the aim of our study to analyze the immunoregulatory effect of MSC on peripheral blood mononuclear cells (PBMC) in old age. We studied the proliferation, activation and cytokine production of PBMC following co-culture with MSC from young (<30 years) and old (>61 years) donors. Our results demonstrate that MSC from elderly donors exhibit the same suppressive effects on T cell proliferation as their young counterparts. In both age groups T cell activation was not influenced by co-culture with MSC from young and elderly donors. With the exception of IL-6, cytokine production by unstimulated or stimulated PBMC was also not affected by MSC from either age group. IL-6 production was increased during co-culture of PBMC and MSC and was higher when MSC from elderly donors were used. After PHA stimulation, however, this age-specific difference was balanced and appeared even. As high IL-6 production is a prerequisite for an effective suppression of T cell proliferation, MSC can be considered a powerful tool for immunoregulatory therapies in old age.

Inflammation and mesenchymal stem cell aging

In adults, mesenchymal stromal cells contain tissue-specific multipotent stem cells, MSC, which can be found throughout the body. With advancing age, tight controls of regulatory networks, which guide MSC biology, gradually deteriorate. Aberrations within the MSC microenvironment such as chronic inflammation eventually lead to adverse manifestations, such as the accumulation of fat deposits in bone and muscles, impaired healing and fibrosis after severe injury, or altered hematopoiesis and autoimmunity. MSC can also specifically interact with a large variety of immune cells, and in doing so, they secrete cytoprotective and immunoregulatory molecules, which together with intercellular contacts mediate immune modulatory processes. This review comprehends the current knowledge regarding molecular mechanisms and cellular interactions that occur in stem cell niches, which are jointly shared between MSC and hematopoietic stem and progenitor cells, as well as those intracellular interdependences taking place between mesenchymal and a wide variety of hematopoietic progeny in particular T lymphocytes, which eventually perturb tissue homeostasis and immunology at advanced age.