Tissue engineering strategies for annulus fibrosus repair: a scoping review of repair methods, animal models, and evaluation techniques

Abstract Background . intervertebral disc (IVD) degeneration is a common chronic disease and may lead to disc herniation. Microdiscectomy removes the herniated tissue, but cannot address altered IVD biomechanics or restore annulus fibrosus (AF) structural integrity. With the development of tissue engineering, AF repair has shown potential in preclinical studies. However, these studies have not been reviewed from a practical experimental perspective, particularly focusing on animal models and evaluation methods. Therefore, this review aims to summarise and compare tissue-engineered AF repair strategies from the past decade and propose guidance for more standardised AF repair assessment. Methods . This scoping review followed the preferred reporting items for systematic reviews and meta-analyses 2020 guidance covering studies from 2015 to 2025, a decade marked by rapid advancements in AF repair biomaterials. The search terms used were: (‘annulus-fibrosus-repair’ OR ‘intervertebral-disc-repair’ OR ‘annular closure’ OR ‘IVD regeneration’ OR ‘AF regeneration’) AND (‘ in vitro ’ OR ‘ in vivo ’ OR ‘comput*’ OR ‘animal model’ OR ‘biomechanic*’). Data were collected from Web of Science and PubMed databases. Results . Ninety-nine records were identified from PubMed and 155 from Web of Science in October 2025. After screening, 48 studies were included, demonstrating significant progress in biomaterial-driven AF repair. However, considerable variation was found in animal model selection, defect creation, and evaluation methods, limiting direct comparison across studies. In particular, AF defect sizes were often not consistently scaled to animal disc geometry. Accordingly, this review suggested geometrically scaled defect size ranges for common animal models. In addition, energy dissipation was identified as an important but rarely quantified marker of IVD viscoelastic restoration. Conclusion . This review provides practical guidance on animal model selection, AF defect size, and proposes an evaluation checklist for future AF repair studies. More standardised and physiologically relevant assessment is needed to improve cross-study comparison and support clinical translation.