Gene expression profile in human induced pluripotent stem cells: Chondrogenic differentiation in vitro, part A

Differentiation of Human Induced Pluripotent Stem Cells (iPSCs)-derived Mesenchymal Progenitors into Chondrocytes

Induced pluripotent stem cells (iPSCs) generated from human sources are valuable tools for studying skeletal development and diseases, as well as for potential use in regenerative medicine for skeletal tissues such as articular cartilage. To successfully differentiate human iPSCs into functional chondrocytes, it is essential to establish efficient and reproducible strategies that closely mimic the physiological chondrogenic differentiation process. Here, we describe a simple and efficient protocol for differentiation of human iPSCs into chondrocytes via generation of an intermediate population of mesenchymal progenitors. These methodologies include step-by-step procedures for mesenchymal derivation, induction of chondrogenic differentiation, and evaluation of the chondrogenic marker gene expression. In this protocol, we describe the detailed procedure for successful derivation of mesenchymal progenitor population from human iPSCs, which are then differentiated into chondrocytes using high-density culture conditions by stimulating with bone morphogenetic protein-2 (BMP-2) or transforming growth factor beta-3 (TGFβ-3). The differentiated iPSCs exhibit temporal expression of cartilage genes and accumulation of a cartilaginous extracellular matrix in vitro, indicating successful chondrogenic differentiation. These detailed methodologies help effective differentiation of human iPSCs into the chondrogenic lineage to obtain functional chondrocytes, which hold great promise for modeling skeletal development and disease, as well as for potential use in regenerative medicine for cell-based therapy for cartilage regeneration. Key features • Differentiation of human iPSCs into chondrocytes using 3D culture methods. • Uses mesenchymal progenitors as an intermediate for differentiation into chondrocytes.

The Effects of Chronological Age on the Chondrogenic Potential of Mesenchymal Stromal Cells: A Systematic Review

Tissue engineering and cell therapy for regenerative medicine have great potential to treat chronic disorders. In musculoskeletal disorders, mesenchymal stromal cells (MSCs) have been identified as a relevant cell type in cell and regenerative strategies due to their multi-lineage potential, although this is likely to be a result of their trophic and immunomodulatory effects on other cells. This PRISMA systematic review aims to assess whether the age of the patient influences the chondrogenic potential of MSCs in regenerative therapy. We identified a total of 3027 studies after performing a search of four databases, including Cochrane, Web of Science, Medline, and PubMed. After applying inclusion and exclusion criteria, a total of 14 papers were identified that were reviewed, assessed, and reported. Cell surface characterization and proliferation, as well as the osteogenic, adipogenic, and chondrogenic differentiation, were investigated as part of the analysis of these studies. Most included studies suggest a clear link between aged donor MSCs and diminished clonogenic and proliferative potential. Our study reveals a heterogeneous and conflicting range of outcomes concerning the chondrogenic, osteogenic, and adipogenic potential of MSCs in relation to age. Further investigations on the in vitro effects of chronological age on the chondrogenic potential of MSCs should follow the outcomes of this systematic review, shedding more light on this complex relationship.

Insights into the present and future of cartilage regeneration and joint repair

Knee osteoarthritis is the most common joint disease. It causes pain and suffering for affected patients and is the source of major economic costs for healthcare systems. Despite ongoing research, there is a lack of knowledge regarding disease mechanisms, biomarkers, and possible cures. Current treatments do not fulfill patients' long-term needs, and it often requires invasive surgical procedures with subsequent long periods of rehabilitation. Researchers and companies worldwide are working to find a suitable cell source to engineer or regenerate a functional and healthy articular cartilage tissue to implant in the damaged area. Potential cell sources to accomplish this goal include embryonic stem cells, mesenchymal stem cells, or induced pluripotent stem cells. The differentiation of stem cells into different tissue types is complex, and a suitable concentration range of specific growth factors is vital. The cellular microenvironment during early embryonic development provides crucial information regarding concentrations of signaling molecules and morphogen gradients as these are essential inducers for tissue development. Thus, morphogen gradients implemented in developmental protocols aimed to engineer functional cartilage tissue can potentially generate cells comparable to those within native cartilage. In this review, we have summarized the problems with current treatments, potential cell sources for cell therapy, reviewed the progress of new treatments within the regenerative cartilage field, and highlighted the importance of cell quality, characterization assays, and chemically defined protocols.

Tissue Engineering of Cartilage Using Collagen Scaffold Enriched with Plant Polysaccharides

Degenerative diseases associated with articular cartilage pose a huge burden on health care economics. The nature of the tissue involved and the changes therein do not allow self-healing; and most of these problems are progressive. Tissue engineering offers some solutions provided we focus on the right kind of cells and the appropriate surrounding niches created for a particular tissue. The present study deals with the formation of polysaccharide rich stable scaffold of collagen after cross-linking with oxidized gum arabic. The scaffold was tested for its biocompatibility and ability to support cells. The in vitro cytotoxicity of the scaffolds toward induced pluripotent stem cells and chondrocytes was evaluated. Evaluation of expression of lineage specific markers indicates differentiation of induced pluripotent stem cells to chondrogenic lineage and maintenance of chondrocytes per se when grown in the scaffold. Animal studies were carried out to study the efficacy of the scaffold to repair the knee injuries. Cells along with the scaffold appeared to be the best filling, in repair of injured cartilage. These studies show that these scaffolds are potential candidates in applications such as tissue engineering of cartilage.

Paracrine Interactions Involved in Human Induced Pluripotent Stem Cells Differentiation into Chondrocytes

Osteoarthritis (OA), as a degenerative joint disease, is the most common form of joint disorder that causes pain, stiffness, and other symptoms associated with OA. Various genetic, biomechanical, and environmental factors have a relevant role in the development of OA. To date, extensive efforts are currently being made to overcome the poor self-healing capacity of articular cartilage. Despite the pivotal role of chondrocytes, their proliferation and repair capacity after tissue injury are limited. Therefore, the development of new strategies to overcome these constraints is urgently needed. Recent advances in regenerative medicine suggest that pluripotent stem cells are promising stem cell sources for cartilage repair. Pluripotent stem cells are undifferentiated cells that have the capacity to differentiate into different types of cells and can self-renew indefinitely. In the past few decades, numerous attempts have been made to regenerate articular cartilage by using induced pluripotent stem cells (iPSCs). The potential applications of patient-specific iPSCs hold great promise for regenerative medicine and OA treatment. However, there are different culture conditions for the preparation and characterization of human iPSCs-derived chondrocytes (hiChondrocytes). Recent biochemical analyses reported that several paracrine factors such as TGFb, BMPs, WNT, Ihh, and Runx have been shown to be involved in cartilage cell proliferation and differentiation from human iPSCs. In this review, we summarize and discuss the paracrine interactions involved in human iPSCs differentiation into chondrocytes in different cell culture media.

MicroRNA-30a regulates chondrogenic differentiation of human bone marrow-derived mesenchymal stem cells through targeting Sox9

Cartilage injury is difficult to repair since the cartilage tissue lacks self-restoration ability. Improved formation of chondrocytes differentiated from the mesenchymal stem cells (MSC) by genetic regulation is a potentially promising therapeutic option. SOX9 is a critical transcription factor for mesenchymal condensation prior to chondrogenesis. Previous studies demonstrated that several microRNAs (miRNAs or miRs) play a critical role in the chondrogenic differentiation of MSCs. However, the interactional relations between miR-30a and SOX9 during chondrogenic differentiation of MSCs need to be further elucidated. In the present study, human bone marrow-derived mesenchymal stem cells have been isolated and induced into chondrogenic differentiation to imitate the cartilage formation in vitro. Additionally, the expression levels of several miRNAs that were reported to interact with the SOX9 3'untranslated region (UTR) were examined by using reverse transcription-quantitative PCR. The interactional relations between candidate miRNAs and SOX9 were verified with the transfection of a miRNA mimic or inhibitor and a luciferase reporter gene assay. The results indicate that miR-30a and miR-195 were consistently increased during MSC chondrogenic differentiation. Additionally, the binding of miR-30a to the SOX9 3UTR was verified. Then, the authors upregulated the expression of miR-30a and found that MSC chondrogenic differentiation was inhibited. Taken together, the results of the present study demonstrate that miR-30a has a negative regulatory effect on MSC chondrogenic differentiation by targeting SOX9. Advances in epigenetic regulating methods will likely be the future of systemic treatment of cartilage injury.

Gene expression markers in horse articular chondrocytes: Chondrogenic differentiaton IN VITRO depends on the proliferative potential and ageing. Implication for tissue engineering of cartilage

Chondrocyte dedifferentiation is a key limitation in therapies based on autologous chondrocyte implantation for cartilage repair. Articular chondrocytes, obtained from (metacarpophalangeal and metatarsophalangeal) joints of different aged horses, were cultured in monolayer for several passages (P0 to P8). Cumulative Populations Doublings Levels (PDL) and gene expression of relevant chondrocyte phenotypic markers were analysed during culturing. Overall data confirmed that, during proliferation in vitro, horse chondrocytes undergo marked morphological and phenotypic alterations of their differentiation status. Particularly, the dedifferentiation started early in culture (P0-P1) and was very marked at P3 subculture (PDL 4-6): proliferative phase after P3 could be critical for maintenance/loss of differentiation potential. In elderly animals, chondrocytes showed aspects of dedifferentiation shortly after their isolation, associated with reduced proliferative capacity. Regarding the gene expression of major cartilage markers (Col2, Aggrecan, SOX9) there was a very early reduction (P1) in proliferating chondrocytes independent of age. The chondrocytes from adult donors showed a more stable expression (up to P3) of some (Col6, Fibromodulin, SOX6, TGβ1) markers of mature cartilage; these markers could be tested as parameter to determine the dedifferentiation level. This study can provide parameters to identify up to which "culture step" chondrocytes for implantation with a conserved phenotypic potential can be obtained, and to test the efficiency of biomaterial scaffold or chondroinductive media/signals to maintain/recover the chondrocyte phenotype. Moreover, the determination of levels and time related expression of these markers can be useful during the chondroinduction of mesenchymal stem cells.

Chondral Differentiation of Induced Pluripotent Stem Cells Without Progression Into the Endochondral Pathway

A major problem with chondrocytes derived in vitro from stem cells is undesired hypertrophic degeneration, to which articular chondrocytes (ACs) are resistant. As progenitors of all adult tissues, induced pluripotent stem cells (iPSCs) are in theory able to form stable articular cartilage. In vitro differentiation of iPSCs into chondrocytes with an AC-phenotype and resistance to hypertrophy has not been demonstrated so far. Here, we present a novel protocol that succeeded in deriving chondrocytes from human iPSCs without using pro-hypertrophic bone-morphogenetic-proteins. IPSC-chondrocytes had a high cartilage formation capacity and deposited two-fold more proteoglycans per cell than adult ACs. Importantly, cartilage engineered from iPSC-chondrocytes had similar marginal expression of hypertrophic markers (COL10A1, PTH1R, IBSP, ALPL mRNAs) like cartilage from ACs. Collagen X was barely detectable in iPSC-cartilage and 30-fold lower than in hypertrophic cartilage derived from mesenchymal stromal cells (MSCs). Moreover, alkaline phosphatase (ALP) activity remained at basal AC-like levels throughout iPSC chondrogenesis, in contrast to a well-known significant upregulation in hypertrophic MSCs. In line, iPSC-cartilage subjected to mineralizing conditions in vitro showed barely any mineralization, while MSC-derived hypertrophic cartilage mineralized strongly. Low expression of Indian hedgehog (IHH) like in ACs but rising BMP7 expression like in MSCs suggested that phenotype stability was linked to the hedgehog rather than the bone morphogenetic protein (BMP) pathway. Taken together, unlimited amounts of AC-like chondrocytes with a high proteoglycan production reminiscent of juvenile chondrocytes and resistance to hypertrophy and mineralization can now be produced from human iPSCs in vitro. This opens new strategies for cartilage regeneration, disease modeling and pharmacological studies.

Gene expression profile in human induced pluripotent stem cells: Chondrogenic differentiation in vitro, part B

The development of human induced pluripotent stem cells (hiPSCs) is considered a turning point in tissue engineering. However, more data are required to improve understanding of key aspects of the cell differentiation process, including how specific chondrogenic processes affect the gene expression profile of chondrocyte‑like cells and the relative value of cell differentiation markers. The main aims of the present study were as follows: To determine the gene expression profile of chondrogenic‑like cells derived from hiPSCs cultured in mediums conditioned with HC‑402‑05a cells or supplemented with transforming growth factor β3 (TGF‑β3), and to assess the relative utility of the most commonly‑used chondrogenic markers as indicators of cell differentiation. These issues are relevant with regard to the use of human fibroblasts in the reprogramming process to obtain hiPSCs. Human fibroblasts are derived from mesoderm and thus share a wide range of properties with chondrocytes, which originate from the mesenchyme. The hiPSCs were obtained from human primary dermal fibroblasts during a reprogramming process. Two methods, both involving embryoid bodies (EB), were used to obtain chondrocytes from the hiPSCs: EBs formed in the presence of a chondrogenic medium with TGF‑β3 (10 ng/ml) and EBs formed in a medium conditioned with growth factors from HC‑402‑05a cells. Based on reverse transcription-quantitative polymerase chain reaction analysis, the results demonstrated that hiPSCs are capable of effective chondrogenic differentiation, with the cells obtained in the HC‑402‑05a medium presenting with morphological features and markers characteristic of mature human chondrocytes. In contrast, cells differentiated in the presence of TGF‑β3 presented with certain undesirable hypertrophic characteristics. Several genes, most notably runt‑related transcription factor 2, transforming growth factor β2 and transforming growth factor β3, were good markers of advanced and late hiPSC chondrogenic differentiation, whereas transforming growth factor β3I, II, III receptors and bone morphogenetic protein-2, bone morphogenetic protein-4 and growth differentiation factor 5 were less valuable. These findings provide valuable data on the use of stem cells in cartilage tissue regeneration.