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Research: J. H. Lee, K. V. B. Prakash, Y. H. Pengatteeri, S. E. Park, H. S. Koh, and C. W. Han Chondrocyte apoptosis in the regenerated articular cartilage after allogenic chondrocyte transplantation in the rabbit knee J Bone Joint Surg Br 2007; 89-B: 977-983 [Abstract] [Full text] [PDF]

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Chondrocyte apoptosis in the regenerated articular cartilage

Benedict A Rogers   (5 September 2007)

Chondrocyte apoptosis in the regenerated articular cartilage 5 September 2007
Benedict A Rogers, Specialist Registrar The Princess Royal Hospital, Haywards Heath, UK Send letter to journal: Re: Chondrocyte apoptosis in the regenerated articular cartilage benedictrogers{at}hotmail.com Benedict A Rogers	Sir, I read this paper with interest and would like to make the following points: 1. Chondrocytes were harvested from the knee, hip and shoulder, and implanted into chondral defects created in the trochlear of the distal femur. Since significant inter-species variations exist in the intrinsic mechanical properties of distal femoral cartilage,1 a load-sensitive tissue, care must be taken when extrapolating the results of cartilage healing to other species. Specifically, the implications of the apoptotic response observed should be guarded since the sources of the implanted chondrocytes differ in their anatomical location and previous weight-bearing status. Correlating these results with human autologous chondrocyte implantation (ACI) is difficult since chondrocytes for ACI are harvested from non-weight-bearing regions of the affected knee.2 2. Apoptosis was quantified by counting cell nuclei labelled with diaminobenzidine chromagen substrate in a high-power field microscopy. Fluorometric DNA assay using a bisbenzimidazole dye has previously been shown to provide a validated, reproducible and accurate measure of cellular density within cartilage explants.3 How accurate is the measurement of apoptosis by diaminobenzidine chromagen labelling, as employed in this study, in comparison to fluorometric analysis? 3. The cultured chondrocytes used in this study were embedded in bovine type I collagen. Articular cartilage consists of type II collagen4 and previous scaffolds have utilised a collegen I – II bilayer membrane Does evidence exist demonstrating no difference in the chondrocyte apoptotic response when embedded in type I bovine collagen compared with type II rabbit collagen? 4. The cellular density of articular cartilage is not as critical as biochemical composition in determining the mechanical properties of the tissue. Was any quantitative or qualitative analysis made of the products of chondrocyte metabolism, namely collagen II, glycosaminoglycans, matrix metalloproteins (MMPs) or tissue inhibitors of matrix metalloproteins (TIMPS)? B.A. Rogers, MA, MSc, MRCGP, MRCS, Specialist Registrar, Princess Royal Hospital, Haywards Heath, UK. 1. Athanasiou KA, Rosenwasser MP, Buckwalter JA, Malinin TI, Mow VC. Interspecies comparisons of in situ intrinsic mechanical properties of distal femoral cartilage. J Orthop Res 1991;9:330-40. 2. Brittberg M, Lindahl A, Nilsson A, et al. Treatment of deep cartilage defects in the knee with autologous chondrocyte transplantation. N Engl J Med 1994;331:889-95. 3. Kim YJ, Sah RL, Doong JY, Grodzinsky AJ. Fluorometric assay of DNA in cartilage explants using Hoechst 33258. Anal Biochem 1988;174:168-76. 4. Mankin HJ, Mow VC, Buckwalter JA. Articular Cartilage Structure, Composition and Function. In: Buckwalter JA, Einhorn TA, Simon WH, eds. Illinois: AAOS, 2005:444-67.