Fibroblast Growth Factor Ligand Dependent Proliferation and Chondrogenic Differentiation of Synovium-Derived Stem Cells and Concomitant Adaptation of Wnt/Mitogen-Activated Protein Kinase Signals

Converse modulation of Wnt/β-catenin signaling during expansion and differentiation phases of Infrapatellar fat pad-derived MSCs for improved engineering of hyaline cartilage

Mesenchymal stem cells (MSCs) are potential candidates in cell-based therapy for cartilage repair and regeneration. However, during chondrogenic differentiation, MSCs undergo undesirable hypertrophic maturation. This poses a risk of ossification in the neo-tissue formed that eventually impedes the clinical use of MSCs for cartilage repair. TGF-β is a potent growth factor used for chondrogenic differentiation of MSCs, however, its role in hypertrophy remains ambiguous. In the present work, we decipher that TGF-β activates Wnt/β-catenin signaling through SMAD3 and increases the propensity of Infrapatellar fat pad derived MSCs (IFP-MSCs) towards hypertrophy. Notably, inhibiting TGF-β induced Wnt/β-catenin signaling suppresses hypertrophic progression and enhances chondrogenic ability of IFP-MSCs in plasma hydrogels. Additionally, we demonstrate that activating Wnt signaling during expansion phase, promotes proliferation and reduces senescence, while improving stemness of IFP-MSCs. Thus, conversely modulating Wnt signaling in vitro during expansion and differentiation phases generates hyaline-like cartilage with minimal hypertrophy. Importantly, pre-treatment of IFP-MSCs encapsulated in plasma hydrogel with Wnt modulators followed by subcutaneous implantation in nude mice resulted in formation of a cartilage tissue with negligible calcification. Overall, this study provides technological advancement on targeting Wnt/β-catenin pathway in a 3D scaffold, while maintaining the standard chondro-induction protocol to overcome the challenges associated with the clinical use of MSCs to engineer hyaline cartilage.

Cartilage Tissue Engineering in Practice: Preclinical Trials, Clinical Applications, and Prospects

Articular cartilage defects significantly compromise the quality of life in the global population. Although many strategies are needed to repair articular cartilage, including microfracture, autologous osteochondral transplantation, and osteochondral allograft, the therapeutic effects remain suboptimal. In recent years, with the development of cartilage tissue engineering, scientists have continuously improved the formulations of therapeutic cells, biomaterial-based scaffolds, and biological factors, which have opened new avenues for better therapeutics of cartilage lesions. This review focuses on advances in cartilage tissue engineering, particularly in preclinical trials and clinical applications, prospects, and challenges.

Growth Factor Immobilization to Synthetic Hydrogels: Bioactive bFGF-Functionalized Polyisocyanide Hydrogels

With its involvement in cell proliferation, migration and differentiation basic fibroblast growth factor (bFGF) has great potential for tissue engineering purposes. So far, however, clinical translation of soluble bFGF-based therapies is unsuccessful, because the required effective doses are often supraphysiological, which may cause adverse effects. An effective solution is growth factor immobilization, whereby bFGF retains its bioactivity at increased efficacy. Studied carriers include films, solid scaffolds, and particles, as well as natural and synthetic hydrogels. However, these synthetic hydrogels poorly resemble the characteristics of the native extracellular matrix (ECM). In this work, bFGF is covalently conjugated to the synthetic, but highly biocompatible, polyisocyanide-based hydrogel (PIC-bFGF), which closely mimics the architecture and mechanical properties of the ECM. The growth factor conjugation protocol is straightforward and readily extrapolated to other growth factors or proteins. The PIC-bFGF hydrogel shows a prolonged bioactivity up to 4 weeks although no clear effects on the ECM metabolism are observed. Beyond the future potential of the PIC-bFGF hydrogel toward various tissue engineering applications, this work underlines that simple biological conjugation procedures are a powerful strategy to induce additional bioactivity in 3D synthetic cell culture matrices.

New developments in the biology of fibroblast growth factors

The fibroblast growth factor (FGF) family is composed of 18 secreted signaling proteins consisting of canonical FGFs and endocrine FGFs that activate four receptor tyrosine kinases (FGFRs 1-4) and four intracellular proteins (intracellular FGFs or iFGFs) that primarily function to regulate the activity of voltage-gated sodium channels and other molecules. The canonical FGFs, endocrine FGFs, and iFGFs have been reviewed extensively by us and others. In this review, we briefly summarize past reviews and then focus on new developments in the FGF field since our last review in 2015. Some of the highlights in the past 6 years include the use of optogenetic tools, viral vectors, and inducible transgenes to experimentally modulate FGF signaling, the clinical use of small molecule FGFR inhibitors, an expanded understanding of endocrine FGF signaling, functions for FGF signaling in stem cell pluripotency and differentiation, roles for FGF signaling in tissue homeostasis and regeneration, a continuing elaboration of mechanisms of FGF signaling in development, and an expanding appreciation of roles for FGF signaling in neuropsychiatric diseases. This article is categorized under: Cardiovascular Diseases > Molecular and Cellular Physiology Neurological Diseases > Molecular and Cellular Physiology Congenital Diseases > Stem Cells and Development Cancer > Stem Cells and Development.

Preparation and Application of Decellularized ECM-Based Biological Scaffolds for Articular Cartilage Repair: A Review

Cartilage regeneration is dependent on cellular-extracellular matrix (ECM) interactions. Natural ECM plays a role in mechanical and chemical cell signaling and promotes stem cell recruitment, differentiation and tissue regeneration in the absence of biological additives, including growth factors and peptides. To date, traditional tissue engineering methods by using natural and synthetic materials have not been able to replicate the physiological structure (biochemical composition and biomechanical properties) of natural cartilage. Techniques facilitating the repair and/or regeneration of articular cartilage pose a significant challenge for orthopedic surgeons. Whereas, little progress has been made in this field. In recent years, with advances in medicine, biochemistry and materials science, to meet the regenerative requirements of the heterogeneous and layered structure of native articular cartilage (AC) tissue, a series of tissue engineering scaffolds based on ECM materials have been developed. These scaffolds mimic the versatility of the native ECM in function, composition and dynamic properties and some of which are designed to improve cartilage regeneration. This review systematically investigates the following: the characteristics of cartilage ECM, repair mechanisms, decellularization method, source of ECM, and various ECM-based cartilage repair methods. In addition, the future development of ECM-based biomaterials is hypothesized.

Integrated regulation of chondrogenic differentiation in mesenchymal stem cells and differentiation of cancer cells

Chondrogenesis is the formation of chondrocytes and cartilage tissues and starts with mesenchymal stem cell (MSC) recruitment and migration, condensation of progenitors, chondrocyte differentiation, and maturation. The chondrogenic differentiation of MSCs depends on co-regulation of many exogenous and endogenous factors including specific microenvironmental signals, non-coding RNAs, physical factors existed in culture condition, etc. Cancer stem cells (CSCs) exhibit self-renewal capacity, pluripotency and cellular plasticity, which have the potential to differentiate into post-mitotic and benign cells. Accumulating evidence has shown that CSCs can be induced to differentiate into various benign cells including adipocytes, fibrocytes, osteoblast, and so on. Retinoic acid has been widely used in the treatment of acute promyelocytic leukemia. Previous study confirmed that polyploid giant cancer cells, a type of cancer stem-like cells, could differentiate into adipocytes, osteocytes, and chondrocytes. In this review, we will summarize signaling pathways and cytokines in chondrogenic differentiation of MSCs. Understanding the molecular mechanism of chondrogenic differentiation of CSCs and cancer cells may provide new strategies for cancer treatment.

Regulating the fate of stem cells for regenerating the intervertebral disc degeneration

Lower back pain is a leading cause of disability and is one of the reasons for the substantial socioeconomic burden. The etiology of intervertebral disc (IVD) degeneration is complicated, and its mechanism is still not completely understood. Factors such as aging, systemic inflammation, biochemical mediators, toxic environmental factors, physical injuries, and genetic factors are involved in the progression of its pathophysiology. Currently, no therapy for restoring degenerated IVD is available except pain management, reduced physical activities, and surgical intervention. Therefore, it is imperative to establish regenerative medicine-based approaches to heal and repair the injured disc, repopulate the cell types to retain water content, synthesize extracellular matrix, and strengthen the disc to restore normal spine flexion. Cellular therapy has gained attention for IVD management as an alternative therapeutic option. In this review, we present an overview of the anatomical and molecular structure and the surrounding pathophysiology of the IVD. Modern therapeutic approaches, including proteins and growth factors, cellular and gene therapy, and cell fate regulators are reviewed. Similarly, small molecules that modulate the fate of stem cells for their differentiation into chondrocytes and notochordal cell types are highlighted.

MiRNAs and Cancer: Key Link in Diagnosis and Therapy

Since the discovery of the first microRNA (miRNA), the exploration of miRNA biology has come to a new era in recent decades. Monumental studies have proven that miRNAs can be dysregulated in different types of cancers and the roles of miRNAs turn out to function to either tumor promoters or tumor suppressors. The interplay between miRNAs and the development of cancers has grabbed attention of miRNAs as novel tools and targets for therapeutic attempts. Moreover, the development of miRNA delivery system accelerates miRNA preclinical implications. In this review, we depict recent advances of miRNAs in cancer and discuss the potential diagnostic or therapeutic approaches of miRNAs.

Enhanced proliferative capacity of human preadipocytes achieved by an optimized cultivating method that induces transient activity of hTERT

Human mesenchymal stromal cells (MSC) are an important tool for basic and translational research. Large amounts of MSC are required for in vitro and in vivo studies, however, the limited life-span and differentiation ability in vitro hamper their optimal use. Here we report that 1:1 mixture of L15 and mTeSR1 culture media increased the life-span of IPI-SA3-C4, a normal non-immortalized human subcutaneous preadipocyte strain by 20% while retaining their adipogenic capacity and stable karyotype. The increased proliferative capacity was accompanied by increased expression of the stem markers POU5F1, SOX2, MYC and hTERT, and inhibition of hTERT activity abolished the growth advantage of L15-mTeSR1. Consequently, the described MSC culture would considerably enhance the utility of MSC for in vitro studies.

Commentary on 'Surface markers associated with chondrogenic potential of human mesenchymal stromal/stem cells'

In the last decade, researchers have searched for predictive surface markers of multipotent mesenchymal stromal/stem cells (MSCs) for ensuring improved therapeutic outcomes following cartilage damage in humans. However, we have achieved only limited progress because of the challenge presented by conflicting data. This commentary provides some evidence to prove a lack of success with current efforts, including an inconsistency in accepted surface markers and chondrogenic potential of MSCs as well as the tissue source-dependent MSC surface markers that correlate with chondrogenic potential. A brief discussion on these disputed topics and perspective about functionally predictive surface markers and standardization of analytic procedures are also highlighted.

Role of lineage-specific matrix in stem cell chondrogenesis

Cartilage repair in clinics is a challenge owing to the limited regenerative capacities of cartilage. Synovium-derived stem cells (SDSCs) are suggested as tissue-specific stem cells for chondrogenesis. In this study, we hypothesize that decellularized extracellular matrix (dECM) deposited by SDSCs could provide a superior tissue-specific matrix microenvironment for optimal rejuvenation of adult SDSCs for cartilage regeneration. dECMs were deposited by adult stem cells with varying chondrogenic capacities; SDSCs (strong) (SECM), adipose-derived stem cells (weak) (AECM) and dermal fibroblasts (weak) (DECM), and urine-derived stem cells (none) (UECM). Plastic flasks (Plastic) were used as a control substrate. Human SDSCs were expanded on the above substrates for one passage and examined for chondrogenic capacities. We found that each dECM consisted of unique matrix proteins and exhibited varied stiffnesses, which affected cell morphology and elasticity. Human SDSCs grown on dECMs displayed a significant increase in cell proliferation and unique surface phenotypes. Under induction media, dECM expanded cells yielded pellets with a dramatically increased number of chondrogenic markers. Interestingly, SECM expanded cells had less potential for hypertrophy compared to those grown on other dECMs, indicating that a tissue-specific matrix might provide a superior microenvironment for stem cell chondrogenic differentiation.

Fibroblast growth factor-2 stimulates proliferation of human adipose-derived stem cells via Src activation

Background

Human adipose-derived stem cells (hASCs) are a subset of mesenchymal stem cells (MSCs); it has been regarded as one of the most promising stem cells. We previously found that fibroblast growth factor-2 (FGF-2) enhanced the proliferation and differentiation of hASC. However, the mechanisms involved in the growth of hASCs by FGF-2 have not been investigated.

Methods

Human adipose-derived stem cells (hASCs) were cultured with FGF-2, and cell growth was assessed. Effects of FGF Receptor (FGFR) inhibitor (NVP-BGJ398), ERK1/2 inhibitor (PD98059), PI3K/Akt inhibitor (LY294002), JNK inhibitor (SP600125), and p38 MAPK inhibitor (SB203580) and Src inhibitor (PP1) on the proliferation were investigated. At the same time, we assessed the effect of FGFR inhibitor on several signaling enzymes such as ERK1/2, JNK, p38, and Akt, in protein level. The involvement of Src activation by FGF-2 was also examined.

Results

FGF-2 markedly promoted proliferation of hASCs at concentrations lower than 10 ng/ml and stimulated cell progression to the S and G2/M phases. Proliferation was blocked by the FGFR inhibitor (NVP-BGJ398) and various signaling pathway inhibitors, such as Erk1/2 inhibitor (PD98059), PI3K/Akt inhibitor (LY294002), JNK inhibitor (SP600125), and p38MAPK inhibitor (SB203580). The FGFR inhibitor reduced the activation of protein kinases, such as AKT, Erk1/2, JNK, and p38, in several signaling pathways. The downstream kinase of FGFR, Src, was activated by FGF-2, and its activation was canceled by the FGFR inhibitor. MEK1/2, a downstream kinase of Src, was parallelly regulated by FGF-2. The Src inhibitor (PP1) markedly blocked the proliferation of hASCs via inhibition of Src and MEK1/2.

Conclusion

Src activation is indispensable for FGF-2-mediated proliferation of ASCs, as well as the subsequent activation of multi-signaling pathways.

Comparison of the effect of growth factors on chondrogenesis of canine mesenchymal stem cells

Mesenchymal stem cells (MSCs) are proposed to be useful in cartilage regenerative medicine, however, canine MSCs have been reported to show poor chondrogenic capacity. Therefore, optimal conditions for chondrogenic differentiation should be determined by mimicking the developmental process. We have previously established novel and superior canine MSCs named bone marrow peri-adipocyte cells (BM-PACs) and the objective of this study was to evaluate the effects of growth factors required for in vivo chondrogenesis using canine BM-PACs. Spheroids of BM-PACs were cultured in chondrogenic medium containing 10 ng/ml transforming growth factor-β1 (TGF-β1) with or without 100 ng/ml bone morphogenetic protein-2 (BMP-2), 100 ng/ml growth differentiation factor-5 (GDF-5) or 100 ng/ml insulin-like growth factor-1 (IGF-1). Chondrogenic differentiation was evaluated by the quantification of glycosaminoglycan and Safranin O staining for proteoglycan production. The expression of cartilage matrix or hypertrophic gene/protein was also evaluated by qPCR and immunohistochemistry. Spheroids in all groups were strongly stained with Safranin O. Although BMP-2 significantly increased glycosaminoglycan production, Safranin O-negative outer layer was formed and the mRNA expression of COL10 relating to cartilage hypertrophy was also significantly upregulated (P<0.05). GDF-5 promoted the production of glycosaminoglycan and type II collagen without increasing COL10 mRNA expression. The supplementation of IGF-1 did not significantly affect cartilaginous and hypertrophic differentiation. Our results indicate that GDF-5 is a useful growth factor for the generation of articular cartilage from canine MSCs.

Effect of Fibroblast Growth Factor-2 and Serum on Canine Mesenchymal Stem Cell Chondrogenesis

IMPACT STATEMENT

Tissue engineering using the chondrogenic potential of mesenchymal stem cells (MSCs) is a promising approach for cartilage regenerative therapy. Although dogs are widely used as an animal model for cartilage regeneration, chondrogenic differentiation of canine MSCs is still challenging. In this study, we aimed at establishing the optimal conditions for canine MSC chondrogenesis. Our results demonstrated that preconditioning with fibroblast growth factor-2 and serum-free induction medium enabled robust chondrogenesis of canine MSCs. These findings will allow effective generation of cartilage tissue from canine MSCs and advance research of cartilage regeneration in both dogs and humans.

Determinants of stem cell lineage differentiation toward chondrogenesis versus adipogenesis

Adult stem cells, also termed as somatic stem cells, are undifferentiated cells, detected among differentiated cells in a tissue or an organ. Adult stem cells can differentiate toward lineage specific cell types of the tissue or organ in which they reside. They also have the ability to differentiate into mature cells of mesenchymal tissues, such as cartilage, fat and bone. Despite the fact that the balance has been comprehensively scrutinized between adipogenesis and osteogenesis and between chondrogenesis and osteogenesis, few reviews discuss the relationship between chondrogenesis and adipogenesis. In this review, the developmental and transcriptional crosstalk of chondrogenic and adipogenic lineages are briefly explored, followed by elucidation of signaling pathways and external factors guiding lineage determination between chondrogenic and adipogenic differentiation. An in-depth understanding of overlap and discrepancy between these two mesenchymal tissues in lineage differentiation would benefit regeneration of high-quality cartilage tissues and adipose tissues for clinical applications.

Impact of Wnt signals on human intervertebral disc cell regeneration

Although preconditioning strategies are growing areas of interest for therapies targeting intervertebral discs (IVDs), it is unknown whether the Wnt signals previously implicated in chondrogenesis, Wnt3A, Wnt5A, and Wnt11, play key roles in the promotion of human nucleus pulposus (NP) cell redifferentiation. In this study, NP cells isolated from herniated disc patients were transduced with lentiviral vectors to overexpress the WNT3A, WNT5A, or WNT11 genes, or CRISPR associated protein 9 (Cas9)/single-guide RNA (sgRNA) vectors to knock out these genes. Following expansion, transduced NP cells were induced for redifferentiation toward the NP phenotype. The overexpression of specific WNT factors led to increases in both glycosaminoglycan (GAG) deposition and expression of redifferentiation genes. These effects were attenuated by knockout of the same WNT genes. These results indicate that specific WNT signals can regulate the expression of redifferentiation genes, unequally impact GAG deposition, and contribute to the redifferentiation of human NP cells. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:3196-3207, 2018.

Functionality of decellularized matrix in cartilage regeneration: A comparison of tissue versus cell sources

Increasing evidence indicates that decellularized extracellular matrices (dECMs) derived from cartilage tissues (T-dECMs) or chondrocytes/stem cells (C-dECMs) can support proliferation and chondrogenic differentiation of cartilage-forming cells. However, few review papers compare the differences between these dECMs when they serve as substrates for cartilage regeneration. In this review, after an introduction of cartilage immunogenicity and decellularization methods to prepare T-dECMs and C-dECMs, a comprehensive comparison focuses on the effects of T-dECMs and C-dECMs on proliferation and chondrogenic differentiation of chondrocytes/stem cells in vitro and in vivo. Key factors within dECMs, consisting of microarchitecture characteristics and micromechanical properties as well as retained insoluble and soluble matrix components, are discussed in-depth for potential mechanisms underlying the functionality of these dECMs in regulating chondrogenesis. With this information, we hope to benefit dECM based cartilage engineering and tissue regeneration for future clinical application.

STATEMENT OF SIGNIFICANCE

The use of decellularized extracellular matrix (dECM) is becoming a promising approach for tissue engineering and regeneration. Compared to dECM derived from cartilage tissue, recently reported dECM from cell sources exhibits a distinct role in cell based cartilage regeneration. In this review paper, for the first time, tissue and cell based dECMs are comprehensively compared for their functionality in cartilage regeneration. This information is expected to provide an update for dECM based cartilage regeneration.

The role of laminins in cartilaginous tissues: from development to regeneration

As a key molecule of the extracellular matrix, laminin provides a delicate microenvironment for cell functions. Recent findings suggest that laminins expressed by cartilage-forming cells (chondrocytes, progenitor cells and stem cells) could promote chondrogenesis. However, few papers outline the effect of laminins on providing a favorable matrix microenvironment for cartilage regeneration. In this review, we delineated the expression of laminins in hyaline cartilage, fibrocartilage and cartilage-like tissue (nucleus pulposus) throughout several developmental stages. We also examined the effect of laminins on the biological activities of chondrocytes, including adhesion, migration and survival. Furthermore, we scrutinized the potential influence of various laminin isoforms on cartilage-forming cells' proliferation and chondrogenic differentiation. With this information, we hope to facilitate the understanding of the spatial and temporal interactions between cartilage-forming cells and laminin microenvironment to eventually advance cell-based cartilage engineering and regeneration.

Environmental preconditioning rejuvenates adult stem cells' proliferation and chondrogenic potential

Adult stem cells are a promising cell source for cartilage regeneration. Unfortunately, due to donor age and ex vivo expansion, stem cell senescence becomes a huge hurdle for these cells to be used clinically. Increasing evidence indicates that environmental preconditioning is a powerful approach in promoting stem cells' ability to resist a harsh environment post-engraftment, such as hypoxia and inflammation. However, few reports organize and evaluate the literature regarding the rejuvenation effect of environmental preconditioning on stem cell proliferation and chondrogenic differentiation capacity, which are important variables for stem cell based tissue regeneration. This report aims to identify several critical environmental factors such as oxygen concentration, growth factors, and extracellular matrix and to discuss their preconditioning influence on stem cells' rejuvenation including proliferation and chondrogenic potential as well as underlying molecular mechanisms. We believe that environmental preconditioning based rejuvenation is a simpler and safer strategy to program pre-engraftment stem cells for better survival and enhanced proliferation and differentiation capacity without the undesired effects of some treatments, such as genetic manipulation.