ABSTRACT: Cellular differentiation and lineage commitment are considered to be robust and irreversible processes during development. Recent work has shown that mouse and human fibroblasts can be reprogrammed to a pluripotent state with a combination of four transcription factors. This raised the question of whether transcription factors could directly specify somatic cell fates in cells such as pancreatic β cells, contractile cardiomyocytes and neurons. We hypothesized that combinatorial expression of chondrocyte-specific transcription factors could directly convert human amnion cells into chondrosarcoma. Starting from a pool of candidate genes, we identified a combination of only five genes (5F pool), BCL6, T (also called BRACHYURY), c-MYC, MITF and BAF60C (also called SMARCD3) that rapidly and efficiently convert postnatal human amnion into chondrosarcoma. The cells generated expressed multiple cartilage-specific genes such as collagen type II α1, link protein-1 and aggrecan, and exhibited characteristics of cartilage both in vivo and in vitro. Expression of the endogenous genes for T and MITF was initiated, implying that the cell conversion is due to not only the forced expression of the transgenes, but also the cellular reprogramming by the transgenes. The same set of genes converted human placental artery-derived endothelial (hPAE) cells and menstrual blood-derived cells into chondrosarcoma cells, implying that this conversion is independent of cell types. Direct conversion system from non-cartilage tissue to cartilaginous tissue contributes substantially to a major advance toward cartilage development, oncogenesis of chondrocytes, and cell-based therapy. We hypothesized that combinatorial expression of chondrocyte-specific transcription factors could directly convert human amnion cells into chondrosarcoma. Starting from a pool of candidate genes, we identified a combination of only five genes that rapidly efficiently convert postnatal human amnion into chondrosarcoma.
Project description:Hydrostatic pressure is one of the main mechanical stimuli cartilage cells are submitted to during joint loading. If moderate hydrostatic pressure is known to be beneficial to cartilage differentiation, excessive pressure, on the other hand, induces changes in cartilage similar to those observed in osteoarthritic cartilage. Therefore, the purpose of the experiment is to identify new target genes of high hydrostatic pressure in chondrocyte precursor cells.
Project description:Long non-coding RNAs (lncRNAs) are expressed in a highly tissue-specific manner where they function in various aspects of cell biology, often as key regulators of gene expression. In this study we established a role for lncRNAs in chondrocyte differentiation. Using RNA sequencing we identified a human articular chondrocyte repertoire of lncRNAs from normal hip cartilage donated by neck of femur fracture patients. Of particular interest are lncRNAs upstream of the master chondrocyte transcription factor SOX9 locus. SOX9 is an HMG-box transcription factor which is essential for chondrocyte development by directing the expression of chondrocyte specific genes. Two of these lncRNAs are upregulated during chondrogenic differentiation of MSCs. Depletion of one of these lncRNA, LOC102723505, which we termed ROCR (regulator of chondrogenesis RNA), by RNAi disrupted MSC chondrogenesis, concomitant with reduced cartilage-specific gene expression and incomplete matrix component production, indicating an important role in chondrocyte biology. Specifically, SOX9 induction was significantly ablated in the absence of ROCR, and overexpression of SOX9 rescued the differentiation of MSCs into chondrocytes. Our work sheds further light on chondrocyte specific SOX9 expression and highlights a novel method of chondrocyte gene regulation involving a lncRNA. Overall design: Human neck of femure fracture hip cartilage chondrocyte mRNA profile generated by RNA-seq
Project description:These libraries represent instances of Swarm rat chondrosarcoma tumors taken from different transplantation experiments. This series also contains one non-cancerous cartilage library made from rat normal growing femoral head cartilage as a comparative data point. Keywords: other
Project description:In this study we explore the gene set that is selectively expressed in chondrocytes and therefore determines the unique properties and functions of cartilage tissue. Through identification of cartilage-selective transcription factors, lncRNAs, enhancers and protein-coding genes, we address the determinants of cartilage-selective gene expression, including interactions among the regulatory molecules and selectively active promoters, which define the pattern of gene expression and ultimately chondrocyte biology. Among 34 previously undescribed cartilage selective lncRNAs, one particular lncRNA was found to be co-expressed with and reciprocally regulated by SOX9, the master transcriptional regulator of chondrogenesis, revealing a new aspect of the regulation of the gene for this critical determinant of chondrocyte function. Finally, we relate cartilage-selective gene expression to the human and mouse skeletal disorders that result from mutations in many of the selectively regulated genes, providing clinical context to the basic biological discoveries. Overall design: Identification of cartilage-selective genes in human fetal cartilage by RNA-seq
Project description:Bone morphogenetic proteins (BMPs) regulate many aspects of skeletal development, including osteoblast and chondrocyte differentiation, cartilage and bone formation, and cranial and limb development. Among them, BMP2, one of the most potent osteogenic signaling molecules, stimulates osteoblast differentiation. We used cDNA microarrays to elucidate regulators of BMP-2-induced osteoblast differentiation.
Project description:Although regeneration of human cartilage is inherently inefficient, age is an important risk factor for Osteoarthritis (OA). Recent reports have provided compelling evidence that juvenile chondrocytes (from donors below 13 years of age) are more efficient at generating articular cartilage as compared to adult chondrocytes. However, the molecular basis for such a superior regenerative capability is not understood. In order to identify the cell-intrinsic differences between juvenile and adult cartilage, we have systematically profiled global gene expression changes between a small cohort of human neonatal/juvenile and adult chondrocytes. No such study is available for human chondrocytes although ‘young’ and ‘old’ bovine and equine cartilage have been recently profiled. Overall design: 3 juvenile chondrocyte samples and 2 adult chondrocyte samples were profiled. Bone-marrow derived mesenchymal cells (MSC) from 2 donors were profiled. We analyzed the changes in gene expression; genes with a fold-change ≥ or ≤1.5, with a difference in intensity of >100 and within the lower 90% confidence bound were selected.
Project description:Chondrocyte gene expression was analyzed to study mechanisms involved in the structural and functional adaptation of articular cartilage during postnatal maturation. Transcriptional profiling was used to compare articular chondrocytes between four neonatal and four adult horses. Expressional differences featured matrix proteins and matrix-modifying enzymes reflecting the transition from cartilage growth to cartilage homeostasis. Keywords: articular cartilage, maturation, horse, cDNA microarray Overall design: This is a direct comparison between full-thickness neonatal and adult articular cartilage transcriptomes. Cartilage from four neonatal horses were compared to cartilage from four adults. For each comparison and its dye-swap, one neonate was randomly compared to one adult.
Project description:Pigment Epithelium-Derived Factor (PEDF) has recently been identified as a factor that is significantly upregulated in late-stage osteoarthritic cartilage in which chondrocytes are confronted with terminal differentiation and cell death. Since PEDF is known to induce cell death of endothelial cells, it may also be responsible for terminal differentiation and cell death in cartilage. Using cDNA microarray analysis, we found PEDF among the factors with the strongest differential expression and significant higher levels (118.5-fold) in osteophytic cartilage compared with articular cartilage. This study explored if PEDF interferes with the stable chondrocyte phenotype by promoting terminal differentiation or cell death.
Project description:Joint injury and osteoarthritis affect millions of people worldwide, but attempts to generate articular cartilage using adult stem/progenitor cells have been unsuccessful. We hypothesized that recapitulation of the human developmental chondrogenic program using pluripotent stem cells (PSCs) may represent a superior approach for cartilage restoration. Using laser capture microdissection followed by microarray analysis, we first defined a surface phenotype (CD146low/negCD166low/negCD73+CD44lowBMPR1B+) distinguishing the earliest cartilage committed cells (pre-chondrocytes) at 5-6 weeks of development; pellet assays confirmed these cells as functional, chondrocyte-restricted progenitors. Flow cytometry, qPCR and immunohistochemistry at 17 weeks revealed that the superficial layer of peri-articular chondrocytes was enriched in cells with this surface phenotype. Isolation of cells with a similar immunophenotype from differentiating human PSCs revealed a population of CD166negBMPR1B+ putative pre-chondrocytes. Functional characterization confirmed these cells as cartilage-committed, chondrocyte progenitors. The identification of a specific molecular signature for primary cartilagecommitted progenitors may provide essential knowledge for the generation of purified, clinically relevant cartilage cells from PSCs. A total of 15 samples were analyzed. In the first comparison, there were 6 biological replicates for both the chondrogenic condensations and total limb cells. In the second comparison, three biological replicates of chondrocytes from the articular region were compared to the 6 replicates of the condensations.