Functional Nanofiber Scaffolds Enabling Local Immunomodulation and Inhibition of Ectopic Bone Formation

Area of Science:

• Biomaterials Science
• Regenerative Medicine
• Orthopedics

Background:

• Heterotopic ossification (HO) involves abnormal bone formation in soft tissues, driven by inflammation and osteogenic pathways.
• Current treatments for HO face challenges like surgical recurrence and systemic toxicity.
• Effective, localized therapies are needed to manage HO progression and improve patient outcomes.

Purpose of the Study:

• To investigate the potential of a multifunctional electrospun nanofiber scaffold for sustained local delivery of ritonavir.
• To explore the role of ritonavir in regulating mesenchymal lineage fate, osteogenesis, osteoclast activity, and immune signaling in HO.
• To evaluate the efficacy of ritonavir-eluting scaffolds in preventing ectopic bone formation and promoting tendon healing in an HO model.

Main Methods:

• Fabrication of an electrospun nanofiber scaffold for sustained ritonavir release over 28 days.
• In vitro assessment of ritonavir's effects on cell viability, lineage differentiation (chondrogenesis, fibroblastic phenotype), osteogenic differentiation, and osteoclast activity.
• In vivo evaluation of the ritonavir-eluting scaffold in a tendon injury-associated HO model.
• Analysis of inflammatory markers (TNF-α, IL-6) and macrophage polarization.

Main Results:

• The scaffold demonstrated sustained ritonavir release, maintaining cell viability and mechanical integrity.
• Local ritonavir delivery suppressed chondrogenic differentiation (downregulating SOX9, COL2A1) and promoted a fibroblastic phenotype (upregulating COL1A1, α-SMA).
• Ritonavir inhibited osteogenic differentiation, enhanced osteoclast resorption, and induced anti-inflammatory macrophage polarization.
• In vivo, the scaffold significantly reduced ectopic bone formation and improved tendon functional recovery.

Conclusions:

• Localized ritonavir delivery via a nanofiber scaffold is a multifunctional strategy for HO prevention.
• This approach integrates control of cell lineage, bone remodeling, and immunomodulation.
• The ritonavir-eluting scaffold presents a clinically translatable solution for preventing aberrant bone formation in at-risk patients.