Glycosaminoglycan profiles of repair tissue formed following autologous chondrocyte implantation differ from control cartilage

Abstract

Currently, autologous chondrocyte implantation (ACI) is the most commonly used cell-based therapy for the treatment of isolated femoral condyle lesions of the knee. A small number of centres performing ACI have reported encouraging long-term clinical results, but there is currently a lack of quantitative and qualitative biochemical data regarding the nature of the repair tissue. Glycosaminoglycan (GAG) structure influences physiological function and is likely to be important in the longterm stability of the repair tissue. The objective of this study was to use fluorophore-assisted carbohydrate electrophoresis (FACE) to both quantitatively and qualitatively analyse the GAG composition of repair tissue biopsies and compare them with age-matched cadaveric controls. We used immunohistochemistry to provide a baseline reference for comparison. Biopsies were taken from eight patients (22 to 52 years old) 1 year after ACI treatment and from four cadavers (20 to 50 years old). FACE quantitatively profiled the GAGs in as little as 5 μg of cartilage. The pattern and intensity of immunostaining were generally comparable with the data obtained with FACE. In the ACI repair tissue, there was a twofold reduction in chondroitin sulphate and keratan sulphate compared with age-matched control cartilage. By contrast, there was an increase in hyaluronan with significantly shorter chondroitin sulphate chains and less chondroitin 6-sulphate in repair tissue than control cartilage. The composition of the repair tissue thus is not identical to mature articular cartilage.

A case study: Glycosaminoglycan profiles of autologous chondrocyte implantation (ACI) tissue improve as the tissue matures

“…KS chains also demonstrate an age-related increase in chain length 20 . HA has been reported to account for 1-10% of GAGs in articular cartilage although higher values have been reported 8,[21][22][23] .…”

“…In this age range, CS chains are ~25kD and almost entirely terminated with a 4-sulphated N-acetylgalactosamine 18 . During adulthood, CS chains tend to have more C6S than C4S, the chains are shorter at ~16kD, and they are terminated with a 4-or 6-sulphated N-acetylgalactosamine 8,22 , or a 4,6-sulphated N-acetylgalactosamine 18 19 . KS chains also demonstrate an age-related increase in chain length 20 .…”

“…Immunological assessment of ACI biopsies 20,24 have defined the distribution of GAGs but these approaches are limited in characterising sulphation pattern or the real quantitation of GAGs. Fluorophore-Assisted Carbohydrate Electrophoresis (FACE) has evolved over the last decade to be a highly sensitive technique for profiling GAGs 8,22,[25][26][27] . Our lab has used FACE in a range of applications 7 including describing age-related changes in GAGs in a limited number of ACI biopsies 8 and through the zones of normal, healthy cartilage 22 .…”

“…Histology: Core biopsies of the cadaveric and repair tissue formed were obtained and processed as previously described 8 . These were snap-frozen in liquid nitrogen-cooled hexane prior to sectioning and 7-µm thick cryosections were collected onto poly-L-lysine-coated slides.…”

“…The majority of failures occur within the first year. Only a small number of centres, including our own, have investigated the long-term stability of the repair tissue using outcome measures such as mechanical testing, clinical scores, MRI and histology [6][7][8] .…”