Development of migrating tendon-bone attachments involves replacement of progenitor populations

Felsenthal, Neta; Rubin, Sarah; Stern, Tomer; Krief, Sharon; Pal, Deepanwita; Pryce, Brian A.; Schweitzer, Ronen; Zelzer, Elazar

doi:10.1242/dev.165381

Cited by 43 publications

(59 citation statements)

References 32 publications

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“…For example, our bioinformatic analysis identified other TF families such as GLI's, RUNX's and NFI's as regulators of the attachment sites. Gli1 was previously reported as a marker for enthesis cells [9,11,17,55]. Since gene expression by attachment cells is regulated by sharing enhancers with chondrocytes or tenocytes, it is reasonable to assume that some regulators of these cells might be part of the network that regulates the attachment cells.…”

Section: Discussionmentioning

confidence: 99%

“…5Dc',d'). To gain a molecular understanding, we studied the expression of several genes that were previously shown to be expressed at these stages in the attachment site [11] (Fig. 2).…”

Section: Krüppel-like Factors Are Regulators Of Attachment Cell Develmentioning

confidence: 99%

“…The patterning of the Sox9 + /Scx + progenitors along the skeleton is regulated by a genetic program that includes several transcription factors [8]. Later, the Sox9 + /Scx + cells differentiate into Gli1 + cells [9][10][11]. Furthermore, both molecular and mechanical signals regulate the AU.…”

Section: Introductionmentioning

confidence: 99%

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Bi-fated tendon-to-bone attachment cells are regulated by shared enhancers and KLF transcription factors

Kult

Zelzer

Olender

et al. 2020

Preprint

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The connection between different tissues is vital for the development and function of any organs and systems. In the musculoskeletal system, the attachment of elastic tendons to stiff bones poses a mechanical challenge that is solved by the formation of a transitional tissue, which allows the transfer of muscle forces to the skeleton without tearing. Here, we show that tendon-to-bone attachment cells are bi-fated, activating a mixture of chondrocyte and tenocyte transcriptomes, which is regulated by sharing regulatory elements with these cells and by Krüppel-like factors transcription factors (KLF).To uncover the molecular identity of attachment cells, we first applied high-throughput RNA sequencing to murine humeral attachment cells. The results, which were validated by in situ hybridization and single-molecule in situ hybridization, reveal that attachment cells express hundreds of chondrogenic and tenogenic genes. In search for the underlying mechanism allowing these cells to express these genes, we performed ATAC sequencing and found that attachment cells share a significant fraction of accessible intergenic chromatin areas with either tenocytes or chondrocytes. Epigenomic analysis further revealed transcriptional enhancer signatures for the majority of these regions. We then examined a subset of these regions using transgenic mouse enhancer reporter. Results verified the shared activity of some of these enhancers, supporting the possibility that the transcriptome of attachment cells is regulated by enhancers with shared activities in tenocytes or chondrocytes. Finally, integrative chromatin and motif analyses, as well as the transcriptome data, indicated that KLFs are regulators of attachment cells. Indeed, blocking the expression of Klf2 and Klf4 in the developing limb mesenchyme led to abnormal differentiation of attachment cells, establishing these factors as key regulators of the fate of these cells.In summary, our findings show how the molecular identity of bi-fated attachment cells enables the formation of the unique transitional tissue that connect tendon to bone. More broadly, we show how mixing the transcriptomes of two cell types through shared enhancers and a dedicated set of transcription factors can lead to the formation of a new cell fate that connects them.

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Section: Discussionmentioning

confidence: 99%

“…5Dc',d'). To gain a molecular understanding, we studied the expression of several genes that were previously shown to be expressed at these stages in the attachment site [11] (Fig. 2).…”

Section: Krüppel-like Factors Are Regulators Of Attachment Cell Develmentioning

confidence: 99%

See 1 more Smart Citation

Bi-fated tendon-to-bone attachment cells are regulated by shared enhancers and KLF transcription factors

Kult

Zelzer

Olender

et al. 2020

Preprint

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“…While the cellular components and genetic program that are responsible for the initial embryonic formation and elongation of tendons are well understood (20)(21)(22)(23), less is known about growth of tendon tissue in adult animals. Using the synergist ablation model, we previously identified the formation of a neotendon matrix that develops around the original tendon matrix, and that this new matrix was populated with proliferative, scleraxis-expressing cells (14).…”

Section: Discussionmentioning

confidence: 99%

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

Gumucio

Schonk

Kharaz

et al. 2020

Preprint

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Scleraxis 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 (Scx Δ ), and then induced tendon growth in Scx + and Scx Δ adult mice via plantaris tendon mechanical overload. Compared to the wild type Scx + group, Scx Δ 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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“…The mechanisms that drive maturation of the enthesis during postnatal growth may be similar to the maturation process that occurs in the tunnel attachments, especially since these attachments have mineralized fibrocartilage with an organized tidemark. The hedgehog pathway is one of the key signaling pathways that drives maturation and mineralization of the enthesis during development 17,[25][26][27][28][29] , as ablation of this pathway resulted in severe reductions in mineralized fibrocartilage formation. Indian hedgehog (IHH) is the ligand expressed during mineralization of the enthesis 17 , more so than sonic or desert hedgehog, so this isoform likely regulates the maturation process.…”

Section: Discussionmentioning

confidence: 99%

Bone marrow stromal cells from a GDF5 origin produce zonal tendon-to-bone attachments following anterior cruciate ligament reconstruction

Hagiwara¹,

Dyrna

Kuntz

et al. 2019

Preprint

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Following anterior cruciate ligament (ACL) reconstruction surgery, a staged repair response occurs where cells from outside the tendon graft participate in tunnel integration. The mechanisms that regulate this process, including the specific cellular origin, are poorly understood. Embryonic cells expressing growth and differentiation factor 5 (GDF5) give rise to several mesenchymal tissues in the joint and epiphyses. We hypothesized that cells from a GDF5 origin, even in the adult tissue, would give rise to cells that contribute to the stages of repair. ACLs were reconstructed in Gdf5‐Cre;R26R‐tdTomato lineage tracing mice to monitor the contribution of Gdf5‐Cre;tdTom+ cells to the tunnel integration process. Anterior−posterior drawer tests demonstrated 58% restoration in anterior−posterior stability. Gdf5‐Cre;tdTom+ cells within the epiphyseal bone marrow adjacent to tunnels expanded in response to the injury by 135‐fold compared with intact controls to initiate tendon‐to‐bone attachments. They continued to mature the attachments yielding zonal insertion sites at 4 weeks with collagen fibers spanning across unmineralized and mineralized fibrocartilage and anchored to the adjacent bone. The zonal attachments possessed tidemarks with concentrated alkaline phosphatase activity similar to native entheses. This study established that mesenchymal cells from a GDF5 origin can contribute to zonal tendon‐to‐bone attachments within bone tunnels following ACL reconstruction.

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Development of migrating tendon-bone attachments involves replacement of progenitor populations

Cited by 43 publications

References 32 publications

Bi-fated tendon-to-bone attachment cells are regulated by shared enhancers and KLF transcription factors

Bi-fated tendon-to-bone attachment cells are regulated by shared enhancers and KLF transcription factors

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

Bone marrow stromal cells from a GDF5 origin produce zonal tendon-to-bone attachments following anterior cruciate ligament reconstruction

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