The chemokines CXCL12 and CXCL14 differentially regulate connective tissue markers during limb development

Sonya Nassari,Delphine Duprez,Marie-Ange Bonnin,Sigmar Stricker,Claire Fournier-Thibault,Cédrine Blavet

doi:10.1038/s41598-017-17490-z

Abstract

Connective tissues (CT) support and connect organs together. Understanding the formation of CT is important, as CT deregulation leads to fibrosis. The identification of CT specific markers has contributed to a better understanding of CT function during development. In developing limbs, Osr1 transcription factor is involved in the differentiation of irregular CT while the transcription factor Scx labels tendon. In this study, we show that the CXCL12 and CXCL14 chemokines display distinct expression pattern in limb CT during chick development. CXCL12 positively regulates the expression of OSR1 and COL3A1, a collagen subtype of irregular CT, while CXCL14 activates the expression of the tendon marker SCX. We provide evidence that the CXCL12 effect on irregular CT involves CXCR4 receptor and vessels. In addition, the expression of CXCL12, CXCL14 and OSR genes is suppressed by the anti-fibrotic BMP signal. Finally, mechanical forces, known to be involved in adult fibrosis, control the expression of chemokines, CT-associated transcription factors and collagens during limb development. Such unexpected roles of CXCL12 and CXCL14 chemokines during CT differentiation can contribute to a better understanding of the fibrosis mechanisms in adult pathological conditions.

Highlights

In the body, the main role of connective tissues (CT) is to support organs and to connect cells and tissues
We provide evidence that CXCL12 positively regulates the expression of OSR1 and COL3A1, a major collagen subtype of the irregular CT (ICT), in chick embryonic limbs and fibroblasts, while CXCL14 activates the expression of the tendon marker SCX in chick fibroblasts
At E7, CXCL12 expression was still observed in ICT and muscle connective tissue (MCT), overlapping with OSR1 expression in ICT and both OSR1 and OSR2 expression in MCT (Fig. 2A–F)

Summary

Introduction

The main role of connective tissues (CT) is to support organs and to connect cells and tissues. Most studies designed to identify CT-specific genes during development have been conducted on the vertebrate limb musculoskeletal system as a model This multicomponent structure formed by skeletal muscle, bone and cartilage (specialized CT), tendon and ligament (regular CT) and irregular CT (ICT), surrounding and connecting the different elements of the musculoskeletal system, is suitable to investigate CT differentiation in the embryo. Tcf[4] and Tbx[5] are considered as MCT-associated markers, Tcf[4] is expressed in myogenic cells[16] and Tbx[5] is observed in cartilage, tendon and muscle progenitors of mouse limbs[20], showing that both factors are not specific to ICT and MCT. Specific receptors for CXCL14 have not yet been identified but it is proposed that CXCL14 is a natural inhibitor of the CXCL12/CXCR4 axis[42]

Methods

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Conclusion