Expression of Ten-m/Odz3 in the fibrous layer of mandibular condylar cartilage during postnatal growth in mice

Mesenchymal stem cells reversibly de-differentiate myofibroblasts to fibroblast-like cells by inhibiting the TGF-β-SMAD2/3 pathway

BACKGROUND

Myofibroblasts (MFB), one of the major effectors of pathologic fibrosis, mainly derived from the activation of fibroblast to myofibroblast transition (FMT). Although MFBs were historically considered terminally differentiated cells, their potential for de-differentiation was recently recognized and implied with therapeutic value in treating fibrotic diseases, for instance, idiopathic pulmonary fibrosis (IPF) and post allogeneic hematopoietic stem cell transplantation bronchiolitis obliterans (BO). During the past decade, several methods were reported to block or reverse MFB differentiation, among which mesenchymal stem cells (MSC) have demonstrated potential but undetermined therapeutic values. However, the MSC-mediated regulation of FMT and underlying mechanisms remained largely undefined.

METHOD

By identifying TGF-β1 hypertension as the pivotal landmark during the pro-fibrotic FMT, TGF-β1-induced MFB and MSC co-culture models were established and utilized to investigate regulations by MSC on FMT in vitro. Methods including RNA sequencing (RNA-seq), Western blot, qPCR and flow cytometry were used.

RESULT

Our data revealed that TGF-β1 readily induced invasive signatures identified in fibrotic tissues and initiated MFB differentiation in normal FB. MSC reversibly de-differentiated MFB into a group of FB-like cells by selectively inhibiting the TGF-β-SMAD2/3 signaling. Importantly, these proliferation-boosted FB-like cells remained sensitive to TGF-β1 and could be re-induced into MFB.

CONCLUSION

Our findings highlighted the reversibility of MSC-mediated de-differentiation of MFB through TGF-β-SMAD2/3 signaling, which may explain MSC's inconsistent clinical efficacies in treating BO and other fibrotic diseases. These de-differentiated FB-like cells are still sensitive to TGF-β1 and may further deteriorate MFB phenotypes unless the pro-fibrotic microenvironment is corrected.

Implications of zonal architecture on differential gene expression profiling and altered pathway expressions in mandibular condylar cartilage

Mandibular condylar cartilage (MCC) is a multi-zonal heterogeneous fibrocartilage containing different types of cells, but the factors/mechanisms governing the phenotypic transition across the zones have not been fully understood. The reliability of molecular studies heavily rely on the procurement of pure cell populations from the heterogeneous tissue. We used a combined laser-capture microdissection and microarray analysis approach which allowed identification of differential zone-specific gene expression profiling and altered pathways in the MCC of 5-week-old rats. The bioinformatics analysis demonstrated that the MCC cells clearly exhibited distinguishable phenotypes from the articular chondrocytes. Additionally, a set of genes has been determined as potential markers to identify each MCC zone individually; Crab1 gene showed the highest enrichment while Clec3a was the most downregulated gene at the superficial layer, which consists of fibrous (FZ) and proliferative zones (PZ). Ingenuity Pathway Analysis revealed numerous altered signaling pathways; Leukocyte extravasation signaling pathway was predicted to be activated at all MCC zones, in particular mature and hypertrophic chondrocytes zones (MZ&HZ), when compared with femoral condylar cartilage (FCC). Whereas Superpathway of Cholesterol Biosynthesis showed predicted activation in both FZ and PZ as compared with deep MCC zones and FCC. Determining novel zone-specific differences of large group of potential genes, upstream regulators and pathways in healthy MCC would improve our understanding of molecular mechanisms on regional (zonal) basis, and provide new insights for future therapeutic strategies.

Ten-m/Odz3 regulates migration and differentiation of chondrogenic ATDC5 cells via RhoA-mediated actin reorganization

Tenascin-like molecule major (Ten-m)/odd Oz (Odz), a type II transmembrane molecule, is well known to modulate neural development. We have reported that Ten-m/Odz3 is expressed in cartilaginous tissues and cells. Actin cytoskeleton and its regulator ras homolog gene family member A (RhoA) are closely associated with chondrogenesis. The present study aimed to evaluate the function and molecular mechanism of Ten-m/Odz3 during chondrogenesis, focusing on RhoA and the actin cytoskeleton. Ten-m/Odz3 was expressed in precartilaginous condensing mesenchyme in mouse limb buds. Ten-m/Odz3 knockdown in ATDC5 induced actin cytoskeleton reorganization and change of cell shape through modulation of RhoA activity and FGF2 expression. Ten-m/Odz3 knockdown suppressed ATDC5 migration and expression of genes associated with chondrogenesis, such as Sox9 and type II collagen, via RhoA. On the other hand, Ten-m/Odz3 knockdown inhibited proliferation of ATDC5 in a RhoA-independent manner. These findings suggest that Ten-m/Odz3 plays an important role in early chondrogenesis regulating RhoA-mediated actin reorganization.

Optimizing Laser Capture Microdissection Protocol for Isolating Zone-Specific Cell Populations from Mandibular Condylar Cartilage

Mandibular condylar cartilage (MCC) is a multizonal heterogeneous fibrocartilage consisting of fibrous (FZ), proliferative (PZ), mature (MZ), and hypertrophic (HZ) zones. Gross sampling of the whole tissue may conceal some important information and compromise the validity of the molecular analysis. Laser capture microdissection (LCM) technology allows isolating zonal (homogenous) cell populations and consequently generating more accurate molecular and genetic data, but the challenges during tissue preparation and microdissection procedures are to obtain acceptable tissue section morphology that allows histological identification of the desirable cell type and to minimize RNA degradation. Therefore, our aim is to optimize an LCM protocol for isolating four homogenous zone-specific cell populations from their respective MCC zones while preserving the quality of RNA recovered. MCC and FCC (femoral condylar cartilage) specimens were harvested from 5-week-old Sprague-Dawley male rats. Formalin-fixed and frozen unfixed tissue sections were prepared and compared histologically. Additional specimens were microdissected to prepare LCM samples from FCC and each MCC zone individually. Then, to evaluate LCM-RNA integrity, 3'/m ratios of glyceraldehyde 3-phosphate dehydrogenase (GAPDH) and beta-actin (β-Actin) using quantitative reverse transcription-polymerase chain reaction (qRT-PCR) were calculated. Both fixed and unfixed tissue sections allowed reliable identification of MCC zones. The improved morphology of the frozen sections of our protocol has extended the range of cell types to be isolated. Under the empirically set LCM parameters, four homogeneous cell populations were efficiently isolated from their respective zones. The 3'/m ratio means of GAPDH and β-Actin ranged between 1.11-1.56 and 1.41-2.12, respectively. These values are in line with the reported quality control requirements. The present study shows that the optimized LCM protocol could allow isolation of four homogenous zone-specific cell populations from MCC, meanwhile preserving RNA integrity to meet the high quality requirements for subsequent molecular analyses. Thereby, accurate molecular and genetic data could be generated.

Ancient Function of Teneurins in Tissue Organization and Neuronal Guidance in the Nematode Caenorhabditis elegans

The nematode Caenorhabditis elegans expresses the ten-1 gene that encodes teneurin. TEN-1 protein is expressed throughout the life of C. elegans. The loss of ten-1 function results in embryonic and larval lethality, highlighting its importance for fundamental processes during development. TEN-1 is expressed in the epidermis and neurons. Defects in neuronal pathfinding and epidermal closure are characteristic of ten-1 loss-of-function mutations. The molecular mechanisms of TEN-1 function in neurite outgrowth, neuronal pathfinding, and dendritic morphology in C. elegans are largely unknown. Its genetic redundancy with the extracellular matrix receptors integrin and dystroglycan and genetic interactions with several basement membrane components suggest a role for TEN-1 in the maintenance of basement membrane integrity, which is essential for neuronal guidance. Identification of the lat-1 gene in C. elegans, which encodes latrophilin, as an interaction partner of ten-1 provides further mechanistic insights into TEN-1 function in neuronal development. However, receptor-ligand interactions between LAT-1 and TEN-1 remain to be experimentally proven. The present review discusses the function of teneurin in C. elegans, with a focus on its involvement in the formation of receptor signaling complexes and neuronal networks.

Novel mutation in Teneurin 3 found to co-segregate in all affecteds in a multi-generation family with developmental dysplasia of the hip

DDH is a debilitating condition characterized by incomplete formation of the acetabulum leading to dislocation of the hip, suboptimal joint function and accelerated wear of the articular cartilage resulting in early onset crippling arthritis of the hip in 20-40 year olds. Current diagnostic tests in newborns using physical manipulation of the femur or ultrasound either under or over-diagnose this condition. Developing an accurate, cost effective diagnostic test is a goal of this study. To better understand the biologic pathways involved in acetabular development, DNA from severely affected individuals in a four generation family that showed inter-generational transmission of the disorder was isolated and whole exome sequenced. A novel A to C transversion at position 183721398 on human chromosome four was found to co-segregate with the affected phenotype in this family. This mutation encodes a glutamine to proline change at position 2665 in the Teneurin 3 (TENM3) gene and was judged damaging by four prediction programs. Eight week old knock-in mutant mice show delayed development of the left acetabulum and the left glenoid fossa as shown by the presence of more Alcian blue staining on the socket rims of both the hip and the shoulder. We hypothesize that mutated TENM3 will slow chondrogenesis. MMP13 has been shown to impair extracellular matrix remodeling and suppress differentiation. Bone marrow cells from the knock-in mouse were found to overexpress MMP13 with or without BMP2 stimulation. This variant may elucidate pathways responsible for normal hip development and become part of an accurate test for DDH. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res.

Teneurin-2 presence in rat and human odontoblasts

Teneurins are transmembrane proteins consisting of four paralogues (Ten-1-4), notably expressed in the central nervous system during development. All teneurins contain a bioactive peptide in their carboxyl terminal named teneurin C-terminal associated peptide (TCAP). The present study analyzed the detailed distribution of teneurin-2-like immunoreactive (Ten-2-LI) cells in developing and mature rat molar teeth, as well as in mature human dental pulps. Ten-2 and TCAP-2 genic expressions were also evaluated in rat and human dental pulps. Finally, Ten-2-LI cells were analyzed during the repair process after dentin-pulp complex injury in rat lower molar teeth. For this, histological sections of rat molar teeth and human dental pulps were submitted to immunohistochemical techniques, while total RNA from developing rat teeth and mature human dental pulps were submitted to conventional RT-PCR. Ten-2-LI cells were evident in the initial bell stage of rat molar teeth development, especially in ectomesenchymal cells of the dental papilla. Ten-2-LI odontoblasts showed strong immunoreactivity in rat and human mature teeth. Ten-2 and TCAP-2 genic expressions were confirmed in rat and human dental pulps. Dentin-pulp complex injury resulted in a decrease of Ten-2-LI odontoblasts after traumatic injury. Interestingly, Ten-2-LI cells were also evident in the pulp cell-rich zone in all postoperative days. In conclusion, Ten-2-LI presence in rat and human odontoblasts was demonstrated for the first time and Ten-2/TCAP-2 genic expressions were confirmed in rat and human dental pulps. Furthermore, it was revealed that Ten-2-LI rat odontoblasts can be modulated during the regenerative process.

The intracellular domain of teneurin-1 induces the activity of microphthalmia-associated transcription factor (MITF) by binding to transcriptional repressor HINT1

Teneurins are large type II transmembrane proteins that are necessary for the normal development of the CNS. Although many studies highlight the significance of teneurins, especially during development, there is only limited information known about the molecular mechanisms of function. Previous studies have shown that the N-terminal intracellular domain (ICD) of teneurins can be cleaved at the membrane and subsequently translocates to the nucleus, where it can influence gene transcription. Because teneurin ICDs do not contain any intrinsic DNA binding sequences, interaction partners are required to affect transcription. Here, we identified histidine triad nucleotide binding protein 1 (HINT1) as a human teneurin-1 ICD interaction partner in a yeast two-hybrid screen. This interaction was confirmed in human cells, where HINT1 is known to inhibit the transcription of target genes by directly binding to transcription factors at the promoter. In a whole transcriptome analysis of BS149 glioblastoma cells overexpressing the teneurin-1 ICD, several microphthalmia-associated transcription factor (MITF) target genes were found to be up-regulated. Directly comparing the transcriptomes of MITF versus TEN1-ICD-overexpressing BS149 cells revealed 42 co-regulated genes, including glycoprotein non-metastatic b (GPNMB). Using real-time quantitative PCR to detect endogenous GPNMB expression upon overexpression of MITF and HINT1 as well as promoter reporter assays using GPNMB promoter constructs, we could demonstrate that the teneurin-1 ICD binds HINT1, thus switching on MITF-dependent transcription of GPNMB.

Teneurin-4, a transmembrane protein, is a novel regulator that suppresses chondrogenic differentiation

Teneurin-4 (Ten-4), a transmembrane protein, is expressed in the nervous systems and the mesenchymal tissues, including the cartilage. However, the Ten-4 function in cartilage development remains unknown. Here, we showed that Ten-4 is a novel regulator of chondrogenesis. In situ hybridization analysis revealed that Ten-4 was highly expressed in the mesenchymal condensation area of the mouse femur at embryonic day (E) 13.5, while its expression was decreased in the growth plate of the femur at E18.5. Using the cartilage-like pellet culture of human synovial mesenchymal cells, Ten-4 expression was induced and peaked 7 days after induction of differentiation, while a production of type II and X collagens was increased after Day 14. In the cartilage-like pellet, Ten-4 was highly expressed in the less differentiated region. In the chondrogenic cell line ATDC5, knockdown of Ten-4 expression significantly increased the alcian blue staining and expression levels of aggrecan and type II and X collagens. Further, an elevated expression of Sox6, Sox9, and Runx2 and an attenuation of the ERK activation were observed in the Ten-4-knockdown ATDC5 cells. These results suggested that Ten-4 suppresses chondrogenic differentiation and regulates the expression and activation of the key molecules for chondrogenesis.

Acute Rejection of Knee Joint Articular Cartilage in a Rat Composite Tissue Allotransplantation Model

BACKGROUND

Osteochondral allograft transplantation is used to treat severe cartilage injury or chondral defects, with good outcomes in clinical studies. However, allograft chondrocyte death due to apoptosis may occur during storage or as a result of implantation stress. We investigated a third possible cause, chondrocyte apoptosis resulting from an immune response, by means of composite tissue allografting, thus eliminating the role of storage and implantation stresses on osteochondral grafts.

METHODS

Vascularized composite tissue allotransplantation (from Fisher 344 to Lewis rat strains) and isotransplantation (from Lewis to Lewis strains) of rat hind limbs were performed. Immunohistochemistry was performed with use of caspase-3 and TUNEL (terminal deoxynucleotidyl transferase mediated dUTP nick end labeling) assays. Analyses were performed immediately after perfusion (day zero) and on postoperative days one, three, seven, twelve, and eighteen (n = 5 for immunohistochemistry). Transmission electron microscopy was used for detection of chondrocyte apoptosis. Laser capture microdissection followed by quantitative real-time polymerase chain reaction assays was used for analysis of postoperative caspase-3 gene expression.

RESULTS

Caspase-3 immunochemistry was increasingly positive in allograft chondrocytes from postoperative day seven onward. In contrast, caspase-3 gene expression decreased in all allografts. TUNEL assays showed increasing apoptosis of allograft chondrocytes, and electron microscopy also revealed evidence supporting the development of apoptosis.

CONCLUSIONS

Immunorejection of chondrocytes in transplanted cartilage has been thought to be unlikely, but our data reveal that chondrocytes can undergo apoptosis in allotransplantation. This apoptosis involves the caspase-3 cascade and indicates that chondrocytes may induce acute rejection.

Genetic interaction between Caenorhabditis elegans teneurin ten-1 and prolyl 4-hydroxylase phy-1 and their function in collagen IV-mediated basement membrane integrity during late elongation of the embryo

A whole-genome RNAi screen identified phy-1 as a novel interaction partner of the Caenorhabditis elegans gene ten-1. It is shown that the catalytic subunit of prolyl 4-hydroxylase, which is coded for by phy-1, is important for type IV collagen secretion and that the transmembrane protein TEN-1 links the epidermis to muscle cells through the basement membrane.

Teneurins are a family of phylogenetically conserved proteins implicated in pattern formation and morphogenesis. The sole orthologue in Caenorhabditis elegans, ten-1, is important for hypodermal cell migration, neuronal migration, path finding and fasciculation, gonad development, and basement membrane integrity of some tissues. However, the mechanisms of TEN-1 action remain to be elucidated. Using a genome-wide RNA interference approach, we identified phy-1 as a novel interaction partner of ten-1. phy-1 codes for the catalytic domain of collagen prolyl 4-hydroxylase. Loss of phy-1 significantly enhanced the embryonic lethality of ten-1 null mutants. Double-mutant embryos arrested during late elongation with epidermal defects, disruption of basement membranes, and detachment of body wall muscles. We found that deletion of phy-1 caused aggregation of collagen IV in body wall muscles in elongated embryos and triggered the loss of tissue integrity in ten-1 mutants. In addition, phy-1 and ten-1 each genetically interact with genes encoding collagen IV. These findings support a functional mechanism in which loss of ten-1, together with a reduction of assembled and secreted basement membrane collagen IV protein, leads to detachment of the epidermis from muscle cells during late elongation of the embryo when mechanical stress is generated by muscle contractions.