Fibronectin isoforms promote postnatal skeletal development

• Published in: Matrix biology 2024-11, Vol.133, p.86-102
• Main Authors: Dinesh, Neha E.H., Baratang, Nissan, Rosseau, Justine, Mohapatra, Ronit, Li, Ling, Mahalingam, Ramshaa, Tiedemann, Kerstin, Campeau, Philippe M., Reinhardt, Dieter P.
• Format: Article
• Language: English
• Subjects: Chondrocytes; Chondrogenesis; Differentiation; Fibronectin; Growth Plate; Skeletal development
• ISSN: 0945-053X; 1569-1802; 1569-1802
• DOI: 10.1016/j.matbio.2024.08.002

•FN is expressed early during mouse limb development at distinct regions within the growth plate and bone.•Cartilage-specific cFN and circulating pFN are distributed distinctly during embryonic and postnatal bone development.•Deletion of cFN and pFN leads to reduced bone growth and bone formation during early and adult postnatal development.•Absence of both FN isoforms in FN double knockout mice leads to altered chondrogenesis.•Ablation of both FN isoforms in developing long bones is associated with reduced TGFβ1 and phospho-AKT. Fibronectin (FN) is a ubiquitous extracellular matrix glycoprotein essential for the development of various tissues. Mutations in FN cause a unique form of spondylometaphyseal dysplasia, emphasizing its importance in cartilage and bone development. However, the relevance and functional role of FN during skeletal development has remained elusive. To address these aspects, we have generated conditional knockout mouse models targeting the cellular FN isoform in cartilage (cFNKO), the plasma FN isoform in hepatocytes (pFNKO), and both isoforms together in a double knockout (FNdKO). We used these mice to determine the relevance of the two principal FN isoforms in skeletal development from postnatal day one to the adult stage at two months. We identified a distinct topological FN deposition pattern in the mouse limb during different gestational and postnatal skeletal development phases, with prominent levels at the resting and hypertrophic chondrocyte zones and in the trabecular bone. Cartilage-specific cFN emerged as the predominant isoform in the growth plate, whereas circulating pFN remained excluded from the growth plate and confined to the primary and secondary ossification centers. Deleting either isoform independently (cFNKO or pFNKO) yielded only relatively subtle changes in the analyzed skeletal parameters. However, the double knockout of cFN in the growth plate and pFN in the circulation of the FNdKO mice significantly reduced postnatal body weight, body length, and bone length. Micro-CT analysis of the adult bone microarchitecture in FNdKO mice exposed substantial reductions in trabecular bone parameters and bone mineral density. The mice also showed elevated bone marrow adiposity. Analysis of chondrogenesis in FNdKO mice demonstrated changes in the resting, proliferating and hypertrophic growth plate zones, consistent alterations in chondrogenic markers such as collagen type II and X, decreased apoptosis of hypertrophic chon