Abstract
Objective
To investigate the histological and immunohistochemical characteristics of revised and failed MACI repair tissues.
Methods
We examined the matrix profiles of repair biopsies taken from revised and clinically failed MACI cases by semi-quantitative immunohistochemical study using antibodies specific to aggrecan, collagens I, II, III, VI, and IX, Sox-9, Ki-67 and MMP-13. We also stiffness tested an intact clinically failed repair site.
Results
Histologically, the majority of these biopsies (n=39) were hyaline-like (HLC) and fibrocartilage (FC) in both the revised (30% and 38% respectively) and failed (34% and 22% respectively) cases. Compositionally, more revised cases were positive for aggrecan, collagens VI and IX, and Ki67 compared to failed cases, but not quantitatively different (P>0.05). More HLC biopsies were positive for aggrecan and collagen II (compared to the FC group), with diffuse and often colocalized matrix distribution. The majority of HLC biopsies stained positive for Sox-9, whereas FC cases were negative. Most (75%) FC biopsies were positive for Ki-67, compared to the HLC group with 25%. MMP-13 was negative in all biopsies. Qualitatively, reduced collagen II and IX, and increased Ki67 production was noted in FC biopsies (P<0.05). An intact repair site showed FC with 30% greater stiffness in the inferior portion compared to the superior, with an associated proteoglycan content increase.
Conclusions
Revised and failed biopsies display predominantly fibrocartilage and hyaline-like cartilage and are histologically dissimilar to healthy cartilage, but do not differ in composition. Hyaline-like repairs show lower proliferation but improved matrix to fibrocartilage repairs. Our study furthers knowledge into failed and revised cartilage repair by MACI.
