# The 3D printed biphasic scaffolds incorporating epimedin C promotes osteochondral regeneration in osteoarthritis rats

## TL;DR

A 3D printed scaffold with epimedin C improves joint repair in rats with osteoarthritis by reducing inflammation and boosting tissue regeneration.

## Contribution

A novel biphasic scaffold incorporating epimedin C for enhanced osteochondral regeneration in osteoarthritis.

## Key findings

- The PTP@Epi C scaffold significantly promoted subchondral bone regeneration in a rat OA-OCD model.
- Epi C inhibited TNF-α expression in synovial tissue, reducing synovitis.
- Epi C suppresses NLRP3 mRNA and IL-1β secretion by inhibiting NF-κB activity.

## Abstract

The regeneration of osteochondral defect in osteoarthritis (OA-OCD) remains a significant clinical challenge, frequently accompanied by synovial inflammation and persistent joint pain. Tissue engineering scaffolds show promising application prospects; however, due to their lack of bioactive molecules, they often fail to effectively regulate extracellular matrix remodeling and inflammatory responses, resulting in poor repair outcomes. In our previous study, we identified epimedin C (Epi C) as one of the most bioactive compounds from Xianlinggubao (XLGB) through 3D human osteoarthritic chondrocyte pellet cultures, demonstrating significant anti-inflammatory and anabolic effects. In this study, we developed a novel biphasic scaffold incorporating Epi C to enhance osteochondral regeneration in an OA-like microenvironment. The biphasic scaffold consists of a cartilage phase [PLGA (50:50)] and a subchondral bone phase [PLGA (75:25)/β-TCP], both with biomimetic pore sizes, porosity and mechanical properties, while the incorporation of Epi C did not compromise the scaffold’s structural integrity. In vitro degradation experiments revealed that the cartilage phase degraded rapidly, facilitating the prompt release of Epi C, while the subchondral bone phase exhibited slower degradation, allowing for sustained drug release over an extended duration. In a rat OA-OCD model, PTP@Epi C scaffold significantly promoted subchondral bone regeneration compared to the OA-OCD group and PTP group. Additionally, the PTP@Epi C scaffold effectively inhibited the expression of TNF-α in the synovial tissue, thereby alleviating synovitis. Transcriptomic analysis and in vitro experiments demonstrate that Epi C downregulates NLRP3 mRNA expression by inhibiting the phosphorylation of IκBα and p65, thereby preventing p65 nuclear translocation and reducing NF-κB transcriptional activity. This ultimately suppresses NLRP3 mRNA levels and decreases downstream IL-1β secretion. In summary, the PTP@Epi C scaffold significantly enhances the osteochondral regeneration and improves the synovial microenvironment through a layered controlled release of Epi C, providing a novel approach for the OA-OCD treatment.

Graphical Abstract