Scleraxis is required for the growth of adult tendons in response to mechanical loading

AbstractScleraxis is a basic helix-loop-helix transcription factor that plays a central role in promoting tenocyte proliferation and matrix synthesis during embryonic tendon development. However, the role of scleraxis in the growth and adaptation of adult tendons is not known. We hypothesized that scleraxis is required for tendon growth in response to mechanical loading, and that scleraxis promotes the specification of progenitor cells into tenocytes. We conditionally deleted scleraxis in adult mice using a tamoxifen-inducible Cre-recombinase expressed from the Rosa26 locus (ScxΔ), and then induced tendon growth in Scx+ and ScxΔ adult mice via plantaris tendon mechanical overload. Compared to the wild type Scx+ group, ScxΔ mice demonstrated blunted tendon growth. Transcriptional and proteomic analyses revealed significant reductions in cell proliferation, protein synthesis, and extracellular matrix genes and proteins. Our results indicate that scleraxis is required for mechanically-stimulated adult tendon growth by causing the commitment of CD146+ pericytes into the tenogenic lineage, and by promoting the initial expansion of newly committed tenocytes and the production of extracellular matrix proteins.

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Mechanical loading and TGF-β change the expression of multiple miRNAs in tendon fibroblasts

Journal of Applied Physiology ◽

10.1152/japplphysiol.00301.2012 ◽

2012 ◽

Vol 113 (1) ◽

pp. 56-62 ◽

Cited By ~ 41

Author(s):

Christopher L. Mendias ◽

Jonathan P. Gumucio ◽

Evan B. Lynch

Keyword(s):

Extracellular Matrix ◽

Cell Proliferation ◽

Mechanical Loading ◽

Transforming Growth Factor ◽

Transforming Growth Factor Β ◽

Matrix Synthesis ◽

Adult Rats ◽

Helix Loop Helix ◽

Musculoskeletal Tissues ◽

Important Regulator

Tendons link skeletal muscles to bones and are important components of the musculoskeletal system. There has been much interest in the role of microRNA (miRNA) in the regulation of musculoskeletal tissues to mechanical loading, inactivity, and disease, but it was unknown whether miRNA is involved in the adaptation of tendons to mechanical loading. We hypothesized that mechanical loading and transforming growth factor-β (TGF-β) treatment would regulate the expression of several miRNA molecules with known roles in cell proliferation and extracellular matrix synthesis. To test our hypothesis, we subjected untrained adult rats to a single session of mechanical loading and measured the expression of several miRNA transcripts in Achilles tendons. Additionally, as TGF-β is known to be an important regulator of tendon growth and adaptation, we treated primary tendon fibroblasts with TGF-β and measured miRNA expression. Both mechanical loading and TGF-β treatment modulated the expression of several miRNAs that regulate cell proliferation and extracellular matrix synthesis. We also identified mechanosensitive miRNAs that may bind to the 3′-untranslated region of the basic helix-loop-helix transcription factor scleraxis, which is a master regulator of limb tendon development. The results from this study provide novel insight into the mechanobiology of tendons and indicate that miRNA could play an important role in the adaptation of tendons to growth stimuli.

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An analysis of culmination in Dictyostelium using prestalk and stalk-specific cell autonomous markers

Development ◽

10.1242/dev.111.3.779 ◽

1991 ◽

Vol 111 (3) ◽

pp. 779-787 ◽

Cited By ~ 19

Author(s):

K.A. Jermyn ◽

J.G. Williams

Keyword(s):

Gene Expression ◽

Extracellular Matrix ◽

Dictyostelium Discoideum ◽

Tube Formation ◽

Matrix Proteins ◽

Specific Cell ◽

Primary Role ◽

Fusion Genes ◽

Spore Mass

The ecmA (pDd63) and ecmB (pDd56) genes encode extracellular matrix proteins of the slime sheath and stalk tube of Dictyostelium discoideum. Using fusion genes containing the promoter of one or other gene coupled to an immunologically detectable reporter, we previously identified two classes of prestalk cells in the tip of the migrating slug; a central core of pstB cells, which express the ecmB gene, surrounded by pstA cells, which express the ecmA gene. PstB cells lie at the position where stalk tube formation is initiated at culmination and we show that they act as its founders. As culmination proceeds, pstA cells transform into pstB cells by activating the ecmB gene as they enter the stalk tube. The prespore region of the slug contains a population of cells, termed anterior-like cells (ALC), which have the characteristics of prestalk cells. We show that the ecmA and ecmB genes are expressed at a low level in ALC during slug migration and that their expression in these cells is greatly elevated during culmination. Previous observations have shown that ALC sort to surround the prespore cells during culmination (Sternfeld and David, 1982 Devl Biol. 93, 111–118) and we find just such a distribution for pstB cells. We believe that the ecmB protein plays a structural role in the stalk tube and its presence, as a cradle around the spore head, suggests that it may play a further function, perhaps in ensuring integrity of the spore mass during elevation. If this interpretation is correct, then a primary role of anterior-like cells may be to form these structures at culmination. We previously identified a third class of prestalk cells, pstO cells, which lie behind pstA cells in the slug anterior and which appeared to express neither the ecmA nor the ecmB gene. Using B-galactosidase fusion constructs, which give more sensitive detection of gene expression, we now find that these cells express the ecmA gene but at a much lower level than pstA cells. We also show that expression of the ecmA gene becomes uniformly high throughout the prestalk zone when slugs are allowed to migrate in the light. Overhead light favours culmination and it may be that increased expression of the ecmA gene in the pst ‘O’ region is a preparatory step in the process.

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Exploring the role of extracellular matrix proteins to develop biomarkers of plaque vulnerability and outcome

Journal of Internal Medicine ◽

10.1111/joim.13034 ◽

2020 ◽

Vol 287 (5) ◽

pp. 493-513 ◽

Cited By ~ 4

Author(s):

S. Holm Nielsen ◽

L. Jonasson ◽

K. Kalogeropoulos ◽

M. A. Karsdal ◽

A. L. Reese‐Petersen ◽

...

Keyword(s):

Extracellular Matrix ◽

Extracellular Matrix Proteins ◽

Matrix Proteins ◽

Plaque Vulnerability

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The Role of Structural Extracellular Matrix Proteins in Urothelial Bladder Cancer (Review)

Biomarker Insights ◽

10.4137/bmi.s294 ◽

2007 ◽

Vol 2 ◽

pp. BMI.S294 ◽

Cited By ~ 14

Author(s):

Andrea Brunner ◽

Alexandar Tzankov

Keyword(s):

Extracellular Matrix ◽

Cancer Cells ◽

Cell Invasion ◽

Matrix Proteins ◽

Urothelial Bladder Cancer ◽

Ecm Proteins ◽

Cancer Review ◽

Urothelial Bladder ◽

Carcinoma Of The Bladder

The extracellular matrix (ECM) plays a key role in the modulation of cancer cell invasion. In urothelial carcinoma of the bladder (UC) the role of ECM proteins has been widely studied. The mechanisms, which are involved in the development of invasion, progression and generalization, are complex, depending on the interaction of ECM proteins with each other as well as with cancer cells. The following review will focus on the pathogenetic role and prognostic value of structural proteins, such as laminins, collagens, fibronectin (FN), tenascin (Tn-C) and thrombospondin 1 (TSP1) in UC. In addition the role of integrins mediating the interaction of ECM molecules and cancer cells will be addressed, since integrin-mediated FN, Tn-C and TSP1 interactions seem to play an important role during tumor cell invasion and angiogenesis.

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Extracellular-matrix synthesis by skeletal muscle in culture. Major secreted collagenous proteins of clonal myoblasts

Biochemical Journal ◽

10.1042/bj2250619 ◽

1985 ◽

Vol 225 (3) ◽

pp. 619-627 ◽

Cited By ~ 12

Author(s):

R L Beach ◽

J S Rao ◽

B W Festoff

Keyword(s):

Skeletal Muscle ◽

Extracellular Matrix ◽

Muscle Cells ◽

Skeletal Muscle Cell ◽

Matrix Proteins ◽

Type I ◽

Matrix Synthesis ◽

Genetic Types ◽

Skeletal Muscle Cell Line ◽

Muscle Cell Line

We have previously shown that G8-1, a murine clonal skeletal-muscle cell line, produces a substrate-attached extracellular matrix [Beach, Burton, Hendricks & Festoff (1982) J. Biol. Chem. 257, 11437-11442]. To examine further the expression of extracellular-matrix proteins by muscle cells, we have analysed the collagenous proteins secreted by G8-1 myoblasts. We have found that collagens and/or procollagens, corresponding to genetic types I, III and IV (and possibly V), are produced and secreted by G8-1 myoblasts. The major secreted collagenous polypeptides were identified as alpha 1 type I and its precursors by using pulse-chase studies, pepsin and collagenase digestions and CNBr fragmentation. The presence of lesser amounts of the other collagens was determined by immunoprecipitation. These results demonstrate that clonal skeletal-muscle cells, in the absence of fibroblasts and an exogenous collagen substrate, are able to synthesize and secrete several extracellular-matrix collagenous proteins in proportions similar to those which are commonly found in muscle tissue and mixed cultures of muscle cells and fibroblasts.

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