Fibronectin matrix assembly is essential for cell condensation during chondrogenesis

Abstract

Mesenchymal cell condensation is the initiating event in endochondral bone formation. Cell condensation is followed by differentiation into chondrocytes, which is accompanied by induction of chondrogenic gene expression. Gene mutations involved in chondrogenesis cause chondrodysplasias and other skeletal defects. Using mesenchymal stem cells (MSCs) in an in vitro chondrogenesis assay, we found that knockdown of the diastrophic dysplasia (DTD) sulfate transporter (DTDST, also known as SLC26A2), which is required for normal cartilage development, blocked cell condensation and caused a significant reduction in fibronectin matrix. Knockdown of fibronectin with small interfering RNAs (siRNAs) also blocked condensation. Fibrillar fibronectin matrix was detected prior to cell condensation, and its levels increased during and after condensation. Inhibition of fibronectin matrix assembly by use of the functional upstream domain (FUD) of adhesin F1 from Streptococcus pyogenes prevented cell condensation by MSCs and also by the chondrogenic cell line ATDC5. Our data show that cell condensation and induction of chondrogenesis depend on fibronectin matrix assembly and DTDST, and indicate that this transporter is required earlier in chondrogenesis than previously appreciated. They also raise the possibility that certain of the skeletal defects in DTD patients might derive from the link between DTDST, fibronectin matrix and condensation.

miR-27 regulates chondrogenesis by suppressing focal adhesion kinase during pharyngeal arch development

“…PNA staining of the fli1a:eGFP + PCCs showed that mesenchymal condensations were equally detectable in miR-27 morphants and control embryos at 48 hpf (data not shown). Next, we analyzed the distribution of the extracellular matrix (ECM) protein fibronectin which is highly expressed during mesenchymal condensation (Hall and Miyake, 2000; Singh and Schwarzbauer, 2014). PCCs in both morphants and control embryos had equal fibronectin matrix distribution at 48 hpf (Fig.…”

Cooperative effects of fibronectin matrix assembly and initial cell–substrate adhesion strength in cellular self-assembly

“…Fibronectin-dependent cellular self-assembly is emerging as a common morphological process, as it has been observed in several cell types, including primary fibroblasts [16], a variety of cell lines [5, 54], as well as mixed cell populations [57]. Recent studies have demonstrated a role for fibronectin matrix assembly in mesenchymal stem cell condensation [58], while other studies suggest that disruption of fibronectin-mediated cohesion may play a role in tumor metastasis [59]. As such, understanding how cell-substrate adhesion parameters cooperate with fibronectin matrix assembly to dynamically regulate the level of tissue or tumor cohesion or dyscohesion has implications in a variety of physiological and pathological processes, and may provide new avenues for therapeutic intervention.…”

Collaboration of fibronectin matrix with other extracellular signals in morphogenesis and differentiation

“…The early events in chondrogenic differentiation such as cell condensation and changes in gene expression are recapitulated in a micromass culture system using mesenchymal stem cells [24]. We showed that cell aggregation depends on FN matrix assembly [25]. As mesenchymal stem cells condense, FN and N-cadherin levels are up-regulated and matrix assembly increases.…”

“…During this period, cells proliferate and initiate the differentiation program, which requires induction of the Sox9 transcription factor, which is essential for cartilage-specific gene expression. Either the blockade of FN polymerization [25] or the knockdown of N-cadherin [26] in micromass cultures prevents cell condensation. Incomplete condensation prevents up-regulation of Sox9 expression and cell differentiation into chondrocytes.…”