Localization and expression of chondromodulin-I in the rat cornea

A Narrative Review of the Roles of Chondromodulin-I (Cnmd) in Adult Cartilage Tissue

Articular cartilage is crucial for joint function but its avascularity limits intrinsic repair, leading to conditions like osteoarthritis (OA). Chondromodulin-I (Cnmd) has emerged as a key molecule in cartilage biology, with potential implications for OA therapy. Cnmd is primarily expressed in cartilage and plays an important role in chondrocyte proliferation, cartilage homeostasis, and the blocking of angiogenesis. In vivo and in vitro studies on Cnmd, also suggest an involvement in bone repair and in delaying OA progression. Its downregulation correlates with OA severity, indicating its potential as a therapeutic target. Further research is needed to fully understand the mode of action of Cnmd and its beneficial implications for managing OA. This comprehensive review aims to elucidate the molecular characteristics of Cnmd, from its expression pattern, role in cartilage maintenance, callus formation during bone repair and association with OA.

Chondromodulin-1 in health, osteoarthritis, cancer, and heart disease

The human chondromodulin-1 (Chm-1, Chm-I, CNMD, or Lect1) gene encodes a 334 amino acid type II transmembrane glycoprotein protein with characteristics of a furin cleavage site and a putative glycosylation site. Chm-1 is expressed most predominantly in healthy and developing avascular cartilage, and healthy cardiac valves. Chm-1 plays a vital role during endochondral ossification by the regulation of angiogenesis. The anti-angiogenic and chondrogenic properties of Chm-1 are attributed to its role in tissue development, homeostasis, repair and regeneration, and disease prevention. Chm-1 promotes chondrocyte differentiation, and is regulated by versatile transcription factors, such as Sox9, Sp3, YY1, p300, Pax1, and Nkx3.2. Decreased expression of Chm-1 is implicated in the onset and progression of osteoarthritis and infective endocarditis. Chm-1 appears to attenuate osteoarthritis progression by inhibiting catabolic activity, and to mediate anti-inflammatory effects. In this review, we present the molecular structure and expression profiling of Chm-1. In addition, we bring a summary to the potential role of Chm-1 in cartilage development and homeostasis, osteoarthritis onset and progression, and to the pathogenic role of Chm-1 in infective endocarditis and cancers. To date, knowledge of the Chm-1 receptor, cellular signalling, and the molecular mechanisms of Chm-1 is rudimentary. Advancing our understanding the role of Chm-1 and its mechanisms of action will pave the way for the development of Chm-1 as a therapeutic target for the treatment of diseases, such as osteoarthritis, infective endocarditis, and cancer, and for potential tissue regenerative bioengineering applications.

Synthetic disulfide-bridged cyclic peptides mimic the anti-angiogenic actions of chondromodulin-I

Chondromodulin-I (ChM-I) is a 25-kDa glycoprotein in cartilage matrix that inhibits angiogenesis. It contains two distinctive structural domains: the N-terminal third of the molecule is a hydrophilic domain that contains O-linked and N-linked oligosaccharide chains, and the C-terminal two-thirds is a hydrophobic domain that contains all of the cysteine residues. In the present study, we have attempted to further uncover the structural requirements for ChM-I to exert anti-angiogenic activity by monitoring its inhibition of the vascular endothelial growth factor (VEGF)-A-induced migration of HUVEC in vitro. Site-directed mutagenesis experiments revealed that the cyclic structure formed by the disulfide bridge between Cys⁸³ and Cys⁹⁹ in human ChM-I is indispensable for its anti-angiogenic function. Moreover, the C-terminal hydrophobic tail (from Trp¹¹¹ to Val¹²⁰) was found to play an important role in ensuring the effectiveness of ChM-I activity on HUVEC. A synthetic cyclic peptide corresponding to the ChM-I region between Ile⁸² to Arg¹⁰⁰ also inhibited the migration of HUVEC, while replacing the Cys⁸³ and Cys⁹⁹ residues in this peptide with Ser completely negated this inhibitory activity. An additional synthetic cyclic peptide harboring the hydrophobic C-terminal tail of ChM-I clearly mimicked the inhibitory action of this protein on the migration of HUVEC and successfully inhibited tumor angiogenesis and growth in a xenograft mouse model of human chondrosarcoma.

A role for chromosomal protein HMGN1 in corneal maturation

Corneal differentiation and maturation are associated with major changes in the expression levels of numerous genes, including those coding for the chromatin-binding high-mobility group (HMG) proteins. Here we report that HMGN1, a nucleosome-binding protein that alters the structure and activity of chromatin, affects the development of the corneal epithelium in mice. The corneal epithelium of Hmgn1(-/-) mice is thin, has a reduced number of cells, is poorly stratified, is depleted of suprabasal wing cells, and its most superficial cell layer blisters. In mature Hmgn1(-/-)mice, the basal cells retain the ovoid shape of immature cells, and rest directly on the basal membrane which is disorganized. Gene expression was modified in Hmgn1(-/-) corneas: glutathione-S-transferase (GST)alpha 4 and GST omega 1, epithelial layer-specific markers, were selectively reduced while E-cadherin and alpha-, beta-, and gamma-catenin, components of adherens junctions, were increased. Immunofluorescence analysis reveals a complete co-localization of HMGN1 and p 63 in small clusters of basal corneal epithelial cells of wild-type mice, and an absence of p 63 expressing cells in the central region of the Hmgn1(-/-) cornea. We suggest that interaction of HMGN1 with chromatin modulates the fidelity of gene expression and affects corneal development and maturation.