Bioactive scaffolds for osteochondral regeneration

Abstract

Treatment for osteochondral defects remains a great challenge. Although several clinical strategies have been developed for management of osteochondral defects, the reconstruction of both cartilage and subchondral bone has proved to be difficult due to their different physiological structures and functions. Considering the restriction of cartilage to self-healing and the different biological properties in osteochondral tissue, new therapy strategies are essential to be developed. This review will focus on the latest developments of bioactive scaffolds, which facilitate the osteogenic and chondrogenic differentiation for the regeneration of bone and cartilage. Besides, the topic will also review the basic anatomy, strategies and challenges for osteochondral reconstruction, the selection of cells, biochemical factors and bioactive materials, as well as the design and preparation of bioactive scaffolds. Specifically, we summarize the most recent developments of single-type bioactive scaffolds for simultaneously regenerating cartilage and subchondral bone. Moreover, the future outlook of bioactive scaffolds in osteochondral tissue engineering will be discussed. This review offers a comprehensive summary of the most recent trend in osteochondral defect reconstruction, paving the way for the bioactive scaffolds in clinical therapy.

The translational potential of this article: This review summaries the latest developments of single-type bioactive scaffolds for regeneration of osteochondral defects. We also highlight a new possible translational direction for cartilage formation by harnessing bioactive ions and propose novel paradigms for subchondral bone regeneration in application of bioceramic scaffolds.

Keywords: Bioactive scaffolds; Bioceramics; Cartilage repair; Osteochondral regeneration; Subchondral bone regeneration.

Figure 1

Osteochondral defect category. Visual representation for cartilage defects by using an Outerbridge classification system: (A) Grade 0, normal cartilage; (B) Grade II, partial thickness defect; (C) Grade III, full-thickness defect; (D) Grade IV, osteochondral defect.

Figure 2

Developments of clinical methods for treatment of osteochondral defects. Current strategies for osteochondral treatment can be categorized as palliative treatment methods, reparative treatment methods and restorative treatment methods. The future strategies for treatment of osteochondral defects will be intelligent methods, which may involve nanobots, 3D printing, artificial intelligence and structural and biological functionalization materials. Structural and biological functionalization strategies, which apply 3D printing technique and artificial intelligence, are promising methods for regeneration of osteochondral defects. 3D = three-dimensional.

Figure 3

The category of bioceramic materials applied in bone tissue engineering. Based on the ability to bond with living tissue after surgery, bioceramics can be divided into three different categories: bioinert ceramics, bioactive ceramics and bioresorbable ceramics , , , , . TCP = tricalcium phosphate.

Figure 4

The LCS scaffolds significantly promoted osteochondral regeneration. (A) Abstract graphic; (B) knee samples at 12 weeks; (C) micro-CT analysis; (D) Safranin O staining; (E) HE staining . CT = computed tomography; HE = haematoxylin and eosin; LCS = lithium-calcium-silicate.