# Subchondral H-type blood vessel formation aggravates articular cartilage degeneration through LEP-LEPR axis

## TL;DR

This study shows that H-type blood vessels in subchondral bone worsen cartilage damage in osteoarthritis through a signaling pathway involving LEP and LEPR.

## Contribution

The study identifies a novel role of the LEP-LEPR-CD31 signaling pathway in subchondral H-type vessel formation and cartilage degeneration in osteoarthritis.

## Key findings

- Lipid metabolism is highly enriched in osteoarthritis lesion subchondral bone.
- LEP and LEPR are underexpressed in severe osteoarthritis lesions.
- The LEP-LEPR-CD31 pathway is causally linked to aging and osteoarthritis progression.

## Abstract

Osteoarthritis (OA) is a chronic degenerative joint disease characterized by cartilage deterioration that has resulted in severe physical and economic costs for society. Risk factors for osteoarthritis encompass genetic predisposition, mechanical influences, obesity, inflammation, and metabolic problems. Recent reports indicate that the morphological alterations of subchondral bone evolve dynamically with the advancement of osteoarthritis. A significant alteration in subchondral bone is the development of aberrant blood vessels, particularly H-type vessels. H-type arteries are essential for preserving subchondral bone homeostasis. They support nutrients and oxygen to bone tissue and eliminate waste, thereby supporting the metabolic activities of osteoblasts and osteoclasts. However, the upstream factors governing H-type arteries are yet unknown.

The whole transcriptome analysis was performed by informatics using the GSE51588 dataset, which includes subchondral bone samples from OA patients, comparing the OA lesion side with the non-lesion side, and was further verified in clinical samples. Using LEP and LEPR knockout mice, the correlation between abnormal subchondral bone metabolism and LEP, LEPR, and H-type vessel formation were uncovered.

This study reveals that the lipid metabolism pathway was highly enriched on the OA lesion, and LEP and LEPR were markedly underexpressed in the subchondral bone on the side with severe OA lesions. The causal relationship of the LEP-LEPR-CD31 signaling pathway in aging and osteoarthritis models is revealed at the overall and molecular levels. This project will provide a new theoretical basis for the pathogenesis of early OA and new ideas and targets for the clinical treatment of OA by exploring the LEP-LEPR-CD31 signaling in osteoarthritis.