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Suppression of cartilage matrix gene expression in upper zone chondrocytes of osteoarthritic cartilage.

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Vol. 40, No. 3, March 1997, pp 562-569
0 1997, American College of Rheumatology
Objective. To evaluate the anabolic activity of
osteoarthritic chondrocytes in situ by investigating the
messenger RNA (mRNA) expression of 3 major cartilage components, type I1 collagen, aggrecan, and link
Methods. In situ hybridization experiments and
histochemical analysis for proteoglycan content were
performed on parallel sections of normal and osteoarthritic (OA) cartilage specimens.
Results. Most chondrocytes in the deeper zones of
OA cartilage showed an increase in mRNA expression,
in particular, of type I1 collagen and to a lesser extent,
aggrecan, compared with normal specimens. However,
chondrocytes of the upper zone were largely negative for
aggrecan or type I1 collagen mRNA. The expression of
link protein mRNA was low in normal and OA
Conclusion. These observations suggest that suppression of the anabolic activity of chondrocytes in the
upper zones contributes to the metabolic imbalance
observed in OA cartilage. Stimulation of matrix anabolism in superficial chondrocytes might be a suitable
target for therapeutic intervention.
The unique biomechanical properties of articular
cartilage are provided by its extracellular matrix, and the
failure of cartilage in joint disease is a consequence of
the progressive destruction of this matrix. The extracelMar matrix of articular cartilage consists of 2 major
Supported by the Deutsche Forschungsgemeinschaft (DFG
Grant Ai 20/1-1).
T. Aigner, MD, S. I. Vornehm, BsC, K. von der Mark, PhD:
University of Erlangen-Nurnberg, Erlangen, Germany; G. Zeiler, MD:
Orthopedic Hospital Wichernhaus, Rummelsberg, Schwarzenbruck,
Germany; J. Dudhia, PhD, M. T. Bayliss, PhD: Kennedy Institute of
Rheumatology, London, UK.
Address reprint requests to T. Aigner, MD, Institute of
Pathology, University of Erlangen-Nurnberg, Krankenhausstrasse
8-10, D-91054 Erlangen, Germany.
Submitted for publication June 17, 1996; accepted in revised
form September 3, 1996.
components: the network of types 11, IX, and XI collagen (l), which provides the tensile strength and stiffness
of articular cartilage, and the large aggregating proteoglycan, aggrecan, which is responsible for the osmotic
swelling capacity, and thus the elasticity, of the cartilage
matrix (2,3). Aggrecan associates with hyaluronic acid,
and this interaction is stabilized by link protein (4),
which shares homology with the hyaluronan-binding
(Gl) domain of aggrecan. Other cartilage proteoglycans
such as decorin, biglycan, fibromodulin, and versican
may be present in the cartilage matrix in equimolar
amounts, but have other important functions, such as
control of collagen fibril diameter and binding of growth
factors (2,5,6). Similarly, type VI collagen, which is
specifically found in the pericellular matrix of articular
cartilage, presumably plays a crucial role in the establishment of the microenvironment of the chondrocytes (7).
In normal adult articular cartilage, the turnover
of collagen fibrils is very low (8-lo), whereas a relatively
high turnover rate for aggrecan has been measured
(11,12). In osteoarthritic (OA) cartilage, a number of
biochemical studies have demonstrated an enhanced
synthesis of collagen and proteoglycans (13-20). However, despite the increased biosynthetic activity, a net
loss of proteoglycan content is one of the hallmarks of all
stages of OA cartilage degeneration (21).
Our present study used in situ hybridization
techniques as a tool to analyze the messenger RNA
(mRNA) expression levels of the major cartilage matrix
components by cells in different regions of the tissue.
Probes for aggrecan, link protein, and type I1 collagen
were used to investigate normal and OA articular cartilage specimens. Our results suggest that despite an
overall increased expression of these matrix components
by O A chondrocytes, the suppression of synthetic activity in the zones with progressing matrix destruction is a
basic mechanism of the imbalanced matrix turnover
observed in O A cartilage.
Tissue preparation. The study was performed on a
series of 30 cartilage specimens from 16 patients undergoing
endoprosthetic joint surgery for severe OA lesions of the hip
or knee joints. All patients met the American College of
Rheumatology classification criteria for OA of the hip or knee
(22,23). Cases of rheumatoid origin were excluded from the
study. Seven macroscopically and histologically normalappearing samples were obtained from amputated knee joints
and from hip joints not later than 24 hours postmortem. The
age of the donors ranged from 45 to 79 years and from 52 to 78
years for OA and normal specimens, respectively.
Cartilage slices were fixed with 4% paraformaldehyde
immediately after removal, decalcified in 0.4M EDTA, dehydrated, and embedded in paraffin. Sections (5 pm thick)
were cut, mounted on slides pretreated with 4% 3triethoxysilylpropylamine acetone solution, and stored until
Histochemistry. For all samples, hernatoxylin and eosin, toluidine blue, and Safranin 0 stainings were performed
on serial sections. Toluidine blue- and Safranin 0-stained
slides were used to estimate the content of proteoglycans (24).
Fixation of cartilage samples in paraformaldehyde is known to
preserve the proteoglycan content well (25). Special care was
taken to distinguish newly formed cartilage at sites of osteophyte formation from original cartilage, and only the latter was
used for this study. The samples were graded according to the
method of Mankin et a1 (21).
Preparation of RNA probes. For specific RNA probes,
suitable fragments of human collagen chains al(l), al(II),
aggrecan core, and link protein mRNA were cloned into
pGEM and pBS vectors (Promega, Madison, WI; and Stratagene, Heidelberg, Germany). pHCG 1N contains a Sty I-Kpn
1 fragment (207 bp) of the N-propeptide of the collagen aI(I)
(26), pHCG 2 an Eco RI-Dru I fragment (435 bp) of the
C-propeptide and the C-terminal untranslated region of collagen al(II) (9), pKS H4 a 1.6-kb fragment of aggrecan core
protein (27), and pKS8.1D3 a 1.9-kb fragment of human link
protein (28).
pRNA 1 contains a 294-bp fragment of mouse 18s
ribosomal RNA (rRNA). This probe shows 100% homology to
human 18s rRNA (9) and was used as a positive control for
preservation of the RNA content in the samples during the
technical procedures.
The constructs were linearized and transcribed in vitro
using T7 and SP6 RNA polymerase (both from Promega) to
generate antisense and sense transcripts, res ectively. The
RNA probes were labeled with 150 pCi of a-3 S-UTP (1,200
Ciimmole; New England Nuclear, Dreireich, Germany) per
0.5-1 pg of template DNA to a specific activity of up to 1.2 X
10’ counts per minute per microgram, and non-incorporated
nucleotides were removed by ethanol precipitation.
In situ hybridization. In situ hybridization was performed as described in detail elsewhere (9). Briefly, deparaffinized and rehydrated sections were digested for 7 minutes
with proteinase K (20 pg/ml in 50 mM Tris HCI, pH 8, 5 mM
EDTA, at room temperature), postfixed for 5 minutes with 4%
paraformaldehyde in PBS, washed briefly in double-distilled
water, acetylated for 10 minutes in 0.25% acetic acid anhydride
(in 0.1M triethanolamine, pH 8), washed again in PBS and
Figure 1. Negative and positive control in situ hybridizations with
probes for a, type I collagen messenger RNA ( a , [ I ] )and b, 18s
ribosomal RNA in femoral condyles from a 79-year-old woman (dark
field examination; OA cartilage; original magnification X 140).
double-distilled water, and dehydrated. The sections were
hybridized for 12-16 hours at 43°C with riboprobes at a final
activity of 3-6 X lo7 disintegrations per minute per milliliter,
depending on their length. The hybridization buffer contained
50% formamide, 10% dextran sulfate, 20 mM dithiothreitol, 1
mg/ml transfer RNA, 300 mM NaCl, 10 mMTris HCl (pH 7.4),
10 mM NaH,PO, (pH 6.4), 5 m M EDTA, 0.02% Ficoll 400,
0.02% polyvinylpyrrolidone, and 0.02% bovine serum albumin.
After hybridization, the tissue sections were washed
at 40°C with 2 X saline sodium citrate (SSC)/O.S% Dmercaptoethanol and at 40°C with 0.5X SSC/O.5% Dmercaptoethanol, treated with RNase A (20 pg/ml) and RNase
T, (50 units/ml), and washed again for 2 hours at 45°C with 2X
SSC/SO% formamide/0.5% B-mercaptoethanol. After 3 final
washes in 0.1X SSC at room temperature, the slides were
Autoradiography was performed (Kodak NTB-2 nuclear track emulsion) and sections counterstained in 5%
Giemsa dye. Exposure times for aggrecan core and link protein
mRNA detection were 3 weeks. For types I1 and I collagen, the
best results were obtained with exposure times of 3-4 days.
Longer exposure times did not improve signal-to-noise ratios
or reveal more positive cells.
Control experiments. The specificity of the complementary DNA probes was ascertained by computerized homology search and in situ hybridization experiments of the fetal
growth plate (data not shown). Additionally, within the tissue
sections, no hybridization signals were obtained for aggrecan
and link protein and type I1 collagen mRNA in noncartilagenous areas such as bone, bone marrow, and fibrous tissue.
The al(I) probe served as the negative control in
cartilage specimens since no signals were seen for type I
collagen in normal and OA chondrocytes (Figure la). Focally,
subchondral osteoblasts showed strong positive signals for
Figure 3. Enhanced expression of aggrecan core (b), link protein (c), and type I1 collagen (d) messenger RNA (mRNA) in
chondrocytes of the middle zone of moderately damaged cartilage (Mankin grade 5). The upper zone chondrocytes did not show
expression of these matrix components. Corresponding to the suppression of aggrecan mRNA expression, depletion of proteoglycans
of the extracellular matrix in these upper areas was observed (a). a, Toluidine blue stained; b-d, dark fields (femoral head of a
69-year-old woman; exposure time b and c, 3 weeks; d, 4 days). Original magnification X100.
.,(I) collagen mRNA in OA specimens, thus proving the
functioning of the control probe. Sense transcripts were used
as nonspecific negative controls, and they did not show more
than background signals. The probe for 18s rRNA was used as
a positive control for preservation of RNA during the technical
procedure and showed strong positive signals in all samples
(also in cells, which were negative for all other probes used)
(Figure lb).
Normal cartilage. Normal articular cartilage samples (Mankin grade 0-1) showed a smooth surface.
Histochemical staining was intense for proteoglycan in
all regions, except the very superficial zone of the tissue
(results not shown). The signal intensity for aggrecan
and link protein mRNA varied between specimens, and
in some cases, their expression was below the detection
level. However, in the majority of specimens, moderate
signals were found for aggrecan and rather weak signals
for link protein mRNA in chondrocytes of all zones,
except the very superficial and calcified regions of
cartilage (Figures 2a,_, and cl-,). In contrast, no or only
very weak signals for al(II) mRNA were detected, even
after an exposure time of 3 weeks (Figures 2b,-,).
Although only a semiquantative evaluation can
be made of in situ mRNA expression, because of the
differences in the affinity of probes for their ligand,
aggrecan mRNA appeared to be more strongly expressed than link protein mRNA (Figures 2a,-, and
Moderately damaged OA cartilage. In moderately damaged OA cartilage (Mankin grades 2-6), the
surface of the tissue showed macroscopic signs of fibrillation and softening. Clustering of cells and proteoglycan loss was also evident histologically, but the overall
thickness of the cartilage was largely preserved.
As found for normal cartilage, there was considerable variation in the expression of aggrecan mRNA
between individual specimens of OA cartilage. However,
a moderate increase in expression was observed in a
subset of chondrocytes (Figures 2d, and and 3b). There
was no obvious difference in the expression of single
chondrocytes and cells in clusters, but a distinct zonal
distribution was observed. Cells in the lower middle and
deep zones of OA cartilage showed significant expression of aggrecan mRNA, but no detectable expression
was observed in the chondrocytes in the upper,
proteoglycan-depleted zones of the tissue (Figures 2d2
Figure 4. Osteoarthritic chondrocytes principally retain their anabolic capacity even in severely damaged cartilage (Mankin grade
8-12), as demonstrated by the messenger RNA expression of aggrecan core protein (a and b), link protein (c), and type I1 collagen
(d). a-d, dark fields (a, c, and d, femoral heads of a 60-year-old man; b, femoral head of a 52-year-old woman). Original magnification
X 140.
and 3a and b). Furthermore, the weak or absent pericellular staining of proteoglycans in the upper zones of
the tissue (Figure 3a) contrasted with the high concentration of these components in the pericellular regions in
the lower middle and deep zones in most samples. Thus,
a distinct correlation between the expression of aggrecan
mRNA and the tissue distribution of glycosaminoglycans
could be established.
In all OA cartilage specimens, the most intense
expression of mRNA was seen for type I1 collagen
(Figures 2e, and 3d). However, as was observed for
aggrecan and link protein mRNA, the upper zone
chondrocytes were negative for ~ ~ ~ ( collagen
(Figure 2eJ. In contrast to aggrecan, which also showed
activation in the deep zone of cartilage, signals for type
I1 collagen mRNA were most intense in the lower
middle zone chondrocytes (Figures 2e, and J. The signals
for type I1 collagen mRNA in the lower middle zone
chondrocytes were considerably stronger than for aggrecan and link protein mRNA: they could be clearly
detected even after a short exposure time (3 days,
compared with 21 days for aggrecan and link protein)
(Figures 3b-d). This was in striking contrast to normal
articular cartilage, where mRNA expression was greater
for aggrecan than for type I1 collagen (Figures 2a and b).
The probe for link protein showed the weakest hybridization signals of the three cartilage matrix proteins
investigated, and its distribution was similar to that of
aggrecan (Figures 2fZp4).
Severely damaged OA cartilage. Samples of severely damaged articular cartilage (Mankin grade 7-13)
showed extensive fissuring, advanced destruction of the
extracellular matrix, loss of proteoglycans, and in many
cases, clustering of chondrocytes. Even in specimens
with a very high Mankin grade (>8), some chondrocytes
expressing aggrecan (Figures 4a and b), link protein
(Figure 4c), and collagen type I1 (Figure 4d) mRNA
were observed. However, in the majority of samples, the
cells did not express any of these mRNAs. This was also
true for cells from the calcified zone.
The maintenance of the extracellular matrix is
crucial for the functioning of articular cartilage. In
articular cartilage, a high turnover of aggrecan is found
(11,12), whereas little remodeling of the collagen network is observed (8-10). Consistent with these observa-
tions, a very low expression of type I1 collagen, but a
significant expression of aggrecan mRNA was detected
in samples of healthy articular cartilage. Whether the
high variability of expression of aggrecan mRNA observed in the present study and the similar wide range of
proteoglycan synthesis rates measured by others (20)
reflect true individual variation between normal articular cartilage samples or is a site-specific difference within
the joints (29), or is even an indication that proteoglycan synthesis occurs as a phasic event, remains to be
While aggrecan is subject to a rather high turnover due to mechanisms such as metalloproteinase degradation, link protein seems to be more stable (30),
suggesting that less new synthesis of this component may
be required. This may explain why only low levels of
expression of link mRNA are found in normal and OA
articular cartilage.
In OA cartilage, damage to the collagen network
and loss of aggrecan are functionally deleterious (31,32).
Chondrocytes attempt to repair the damaged matrix by
increasing the synthesis of both of these main components (9,13,14,20,33,34).The net increase in the mRNA
level of the components (in particular, the high increase
in type I1 collagen mRNA) correlates well with previous
biochemical studies of isotope incorporation rates
(14,20). This suggests that the control of the synthesis of
these matrix molecules occurs largely at the transcriptional level and that changes in the expression of specific
mRNAs represent a reasonable estimation of the actual
synthetic activity of these cells. Our data are consistent
with the considerably higher activation of type I1 collagen mRNA expression compared with aggrecan mRNA
measured in canine OA cartilage (34). In this respect,
OA cartilage resembles fetal cartilage (35,36) and osteophytic cartilage (37). In both of these tissues, chondrocytes have to synthesize and assemble a new extracellular matrix consisting largely of type I1 collagen whereas
in normal articular cartilage, the chondrocytes control
tissue homeostasis by maintaining a stable matrix composition, which mainly involves the control of proteoglycan turnover.
Since OA chondrocytes are considered to be
metabolically hyperactive (18-20,38-40), the loss of
proteoglycans in OA cartilage (17,32,40) has been attributed to an increased proteoglycan catabolism or has
been explained as a secondary effect of the weakening of
the collagen network (41). Our in situ analysis provides
a different model to explain these changes: the activation of synthetic activity is restricted to the OA chondrocytes in the middle and deeper zones. However, a
suppression of proteoglycan mRNA expression is found
in the upper zone, where most of the proteoglycan loss
occurs. Correspondingly, the major sulfate incorporation activity in other studies has been found in the
middle and deep zone, but not in the upper zone, OA
chondrocytes (29,42). The cells of the upper zones in
O A cartilage, which do not express aggrecan and type I1
collagen mRNA, are, however, not necrotic, since they
show strong signals for 18s rRNA and poly-dT RNA
(Aigner et al: unpublished results).
The continuous active synthesis of aggrecan is
crucial to maintaining matrix balance, given the high
turnover and degradation rate of aggrecan, which is also
seen in normal articular cartilage (11,12). Thus, a decrease in proteoglycan synthesis in the upper zones has
a direct impact on the matrix composition and is at least
partly responsible for the loss of proteoglycan content
from this zone. The loss of aggrecan results in an
increase in the stress applied to the collagen network
(41), and thus promotes its destruction, which itself leads
to an even more enhanced loss of proteoglycans (41).
Our findings do not preclude the importance of
proteolytic degradation events involved in OA cartilage
degeneration, but rather, focus them on the damage to
the collagen network (31). In contrast to aggrecan, the
type I1 collagen synthesized in OA cartilage might not be
efficiently incorporated into the matrix network since
collagen fibers are rigid structures.
The general expression pattern presented in this
study cannot reflect the entire complex variety of alterations found in OA cartilage. However, by applying
techniques of high local resolution, we are able to
establish patterns in OA cartilage degeneration. Our
studies delineate a 4-step evolution of cellular events
during the OA cartilage destruction process: 1) an
increase in type I1 collagen and aggrecan core protein
synthesis by the chondrocytes; 2) modulation of the
chondrocytic phenotype with the expression of atypical
gene products, such as type I11 collagen (26); 3 ) suppression of aggrecan core protein and type I1 collagen
mRNA expression with subsequent quantitative loss of
proteoglycans from the extracellular matrix, and 4)
physical damage to the collagen network, and fissuring
and complete destruction of the cartilage matrix and
cells in mechanically stressed areas (41).
It will be a major future goal to develop approaches to delay, stop, or even reverse the process
described. This may be possible since according to our
findings, chondrocytes even in severely damaged areas
maintain the capacity to synthesize the necessary cartilage matrix components (17). Our results further corrob-
orate the notion that there is no constitutive drop of
synthetic activity in more advanced cartilage lesions
(17,18,29,33), although other reports have suggested
otherwise (15,21). Several studies have shown that
changes in the expression pattern in chondrocytes are
essentially reversible (43-45). Therefore, one can assume, that if further damage to the collagen network can
be prevented, cartilage could repair itself due to its high
renewal capacity (17,33).
The authors thank Ms. G. Herbig for expert photographical assistance and Ms. M. Mauser and Ms. M. Schaller
for expert technical assistance.
1. Bruckner P, van der Rest M: Structure and function of cartilage
collagens. Microsc Res Technol 28:378-384, 1994
2. Roughley PJ, Lee ER: Cartilage proteoglycans: structure and
potential functions. Microsc Res Technol 28:385-397, 1994
3. Poole AR, Pidoux I, Reiner A, Rosenberg LC: An immunoelectron microscope study of the organization of proteoglycan monomer, link protein, and collagen in the matrix of articular cartilage.
J Cell Biol 93:921-937, 1982
4. Hardingham TE: The role of link-protein in the structure of
cartilage proteoglycan aggregates. Biochem J 177:237-247, 1979
5. Heinegard DK, Pimentel ER: Cartilage matrix proteins. In, Articular Cartilage and Osteoarthritis. Edited by K Kuettner, R Schleyerbach, JG Peyron, VC Hascall. New York, Raven Press, 1992
6. Yamaguchi Y, Mann DM, Ruoslathi E: Negative regulation of
transforming growth factor-b by the proteoglycan decorin. Nature
346:281-284, 1990
7. Poole C A Chondrons-the chondrocyte and its pericellular microenvironment. In, Articular Cartilage and Osteoarthritis. Edited
by K Kuettner, R Schleyerbach, JG Peyron, VC Hascall. New
York, Raven Press, 1992
8. Rep0 RU, Mitchell NS: Collagen synthesis in mature articular
cartilage of the rabbit. J Bone Joint Surg Br 53541-548, 1971
9. Aigner T, StoR H, Weseloh G, Zeiler G, von der Mark K
Activation of collagen type I1 expression in osteoarthritic and
rheumatoid cartilage. Virchows Arch 62:337-345, 1992
10. Maroudas A. Physicochemical properties of articular cartilage. In,
Adult Articular Cartilage. Edited by MAR Freeman. Tunbridge
Wells, Pitman Medical Publishing, 1980
11. Hardingham TE, Fosang AJ,Dudhia J: Aggrecan, the chondroitin
sulfate/keratan sulfate proteoglycan from cartilage. In, Articular
Cartilage and Osteoarthritis. Edited by K Kuettner, R Schleyerbach, JG Peyron, VC Hascall. New York, Raven Press, 1992
12. Van Kampen GPJ, van de Stadt RJ, van de Laar AFJ, van der
Korst J K Two distinct metabolic pools of proteoglycans in articular cartilage. In, Articular Cartilage and Osteoarthritis. Edited by
K Kuettner, R Schleyerbach, JG Peyron, V Hascall. New York,
Raven Press, 1992
13. Lippiello L, Hall MD, Mankin HJ: Collagen synthesis in normal
and osteoarthrotic human cartilage. J Clin Invest 59593-600, 1977
14. Eyre DR, McDevitt CA, Billingham MEJ, Muir H: Biosynthesis of
collagen and other matrix proteins by articular cartilage in experimental osteoarthrosis. Biochem J 188:823-837, 1980
15. Collins DH, McElligott TF: Sulphate (35S0,) uptake by chondro-
cytes in relation to histological changes in osteoarthritic human
articular cartilage. Ann Rheum Dis 19:318-330, 1960
16. McDevitt CA, Muir H: Biochemical changes in the cartilage of the
knee in experimental and natural osteoarthritis in the dog. J Bone
Joint Surg Br 58:94-101, 1976
17. Mankin HJ, Johnson ME, Lippiello L Biochemical and metabolic
abnormalities in articular cartilage from osteoarthritic human hips.
J Bone Joint Surg Am 63:131-139, 1981
18. Mitrovic D, Gruson M, Demignon J, Mercier P, Aprile F, de Seze
S: Metabolism of human femoral head cartilage in osteoarthrosis
and subcapital fracture. Ann Rheum Dis 40:18-26, 1981
19. Ryu J, Treadwell BV, Mankin HJ: Biochemical and metabolic
abnormalities in normal and osteoarthritic human articular cartilage. Arthritis Rheum 27:49-57, 1984
20. Sandy JD, Adams ME, Billingham MEJ, Plaas A, Muir H: In vivo
and in vitro stimulation of chondrocyte biosynthetic activity in
early experimental osteoarthritis. Arthritis Rheum 27:388-397,
21. Mankin HJ, Dorfman H, Lippiello L, Zarins A Biochemical and
metabolic abnormalities in articular cartilage from osteo-arthritic
human hips. J Bone Joint Surg Am 53-A523-537, 1971
22. Altman R, Alarc6n G, Appelrouth D, Bloch D, Borenstein D,
Brandt K, Brown C, Cooke TD, Daniel W, Feldman D, Greenwald
R, Hochberg M, Howell D, Ike R, Kapila P, Kaplan D, Koopman
W, Marino C, McDonald E, McShane DJ, Medsger T, Michel B,
Murphy WA, Osial T, Ramsey-Goldrnan R, Rothschild B, Wolfe
F: The American College of Rheumatology criteria for the classification and reporting of osteoarthritis of <he hip. Arthritis Rheum
34505-514, 1991
23. Altman R, Asch E, Bloch D, Bole G, Borenstein D, Brandt K,
Christy W, Cooke TD, Greenwald R, Hochberg M, Howell D,
Kaplan D, Koopman W, Longley S 111, Mankin H, McShane DJ,
Medsger T Jr, Meenan R, Mikkelsen W, Moskowitz R, Murphy W,
Rothschild B, Segal M, Sokoloff L, Wolfe F: Development of
criteria for the classification and reporting of osteoarthritis: classification of osteoarthritis of the knee. Arthritis Rheum 29:10391049, 1986
24. Rosenberg LC: Chemical basis for the histological use of safranin
0 in the study of articular cartilage. J Bone Joint Surg Am
53:69-82, 1971
25. Kiviranta I, Tymmi M, Jurvelin J, Saamanen A-M, Helminen HJ:
Fixation, decalcification, and tissue processing effects on articular
cartilage proteoglycans. Histochemistry 8020569-573, 1984
26. Aigner T, Bertling W, StoR H, Weseloh G, von der Mark K.
Independent expression of fibril-forming collagens I, 11, and 111 in
chondrocytes in human osteoarthritic cartilage. J Clin Invest
915329-837, 1993
27. Dudhia J, Davidson CM, Wells T, Vynos D, Hardingham TE,
Bayliss MT: Age-related studies in the content of the carboxylterminal region of aggrecan in human cartilage. Biochem J 313:
933-940, 1996
28. Dudhia J, Hardingham TE: The primary structure of human
cartilage link protein. Nucleic Acids Res 18:1292, 1990 (Published
erratum in 18:2214, 1990)
29. Grushko G, Schneiderman R, Maroudas A Some biochemical and
biophysical parameters for the study of the pathogenesis of
osteoarthritis: a comparison between the processes of aging and
degeneration in human hip cartilage. Connect Tissue Res 19:149176, 1989
30. Nguyen Q, Liu J, Roughley PJ, Mort JS: Link protein as a monitor
in situ of endogenous proteolysis in adult human articular cartilage. Biochem J 278:143-147, 1991
31. Dodge GR, Poole AR: Immunohistochemical detection and immunohistochemical analysis of type I1 collagen degradation in
human normal, rheumatoid, and osteoarthritic articular cartilages
and in explants of bovine articular cartilage cultured with interleukin 1. J Clin Invest 83:647-661, 1989
32. Sweet BME, Thonar EJA, Immelman AR, Solomon L Biochem-
ical changes in progressive osteoarthrosis. Ann Rheum Dis 36:
387-398, 1977
Rizkalla G, Reiner A, Bogoch E, Poole AR: Studies of the
articular cartilage proteoglycan aggrecan in health and osteoarthritis. J Clin Invest 90:2268-2277, 1992
Matyas JR, Adams ME, Huang D, Sandell LJ: Discoordinate gene
expression of aggrecan and type I1 collagen in experimental
osteoarthritis. Arthritis Rheum 38:420-425, 1995
Mundlos S, Meyer R, Yamada Y, Zabel B: Distribution of
cartilage proteoglycan (aggrecan) core protein and link protein
gene expression during human skeletal development. Matrix 11:
339-346, 1991
Vornehm SI, Dudhia J, von der Mark K, Aigner T: Expression of
collagen types IX and XI as well as other major cartilage matrix
components by human fetal chondrocytes in vivo. Matrix Biol
15:91-98, 1996
Aigner T, Dietz U, StoB H, von der Mark K Differential expression of collagen types I, 11, 111, and X in human osteophytes. Lab
Invest 73:236-243, 1995
Teshima R, Treadwell BV, Trahan CA, Mankin HJ: Comparative
rates of proteoglycan synthesis and size of proteoglycans in normal
and osteoarthritic chondrocytes. Arthritis Rheum 26:1225-1230,
39. Mankin HJ, Lippiello L: Biochemical and metabolic abnormalities
in articular cartilage from osteoarthritic human hips. J Bone Joint
Surg Am 52:424-434, 1970
40. Thompson RC, Oegema TR: Metabolic activity of articular cartilage in osteoarthritis. J Bone Joint Surg Am 59:407-416, 1979
41. Maroudas A: Balance between swelling pressure and collagen
tension in normal and degenerate cartilage. Nature 260:808-809,
42. Lafeber FPJG, van der Kraan PM, van Roy JLAM, van den Berg
WB, Bijlsma JWJ: Local changes in proteoglycan synthesis during
culture are different for normal and osteoarthritic cartilage. Am J
Pathol 140:1421-1429, 1992
43. Bonaventure J, Khadom N, Cohen-Solal L, Ng KH, Bourguignon
J, Lasselin C, Freisinger P: Re-expression of cartilage-specific
genes by dedifferentiated human articular chondrocytes cultured
in alginate beads. Exp Cell Res 212:97-104, 1994
44. Benya PD, Shaffer JD: Dedifferentiated chondrocytes reexpress
the differentiated collagen phenotype when cultured in agarose
gels. Cell 30:215-224, 1982
45. Rayan V, Hardingham TE: The recovery of articular cartilage in
explant culture from interleukin-la: effects on proteoglycan synthesis and degradation. Matrix Biol 14:263-271, 1994
In the letter to the editor by Simon M. Helfgott and Raphael I. Kieval (reply to letters by Caplan and by Olsson
et al) published in the January 1997 issue of Arthritis & Rheumatism (pp 192-1 93), the list of references was
inadvertently omitted. The references are printed below. We regret the error.
1. Hamilton CR Jr, Shelley WM, Tumulty P A Giant cell arteritis: including
temporal arteritis and polymyalgia rheumatica. Medicine (Baltimore) 50:l-27,
2. Hunder GG, Disney TF, Ward LE: Polymyalgia rheumatica. Mayo Clin Proc
44:849-875, 1969
3. Chuang TY, Hunder GG, Ilstrup DM, Kurland L T Polymyalgia rheumatica: a
10-year epidemiologic and clinical study. Ann Intern Med 97:672-680, 1982
4. Weyand CM, Hicok KC, Hunder GG, Goronzy J J Tissue cytokine patterns in
patients with polymyalgia rheumatica and giant cell arteritis. Ann Intern Med
121:484-491, 1994
5. Elling H, Elling P, Olsson A CD8+ lymphocyte subset in polymylagia rheumatica and arteritis temporalis: inverse relationship between the acute hepatic
phase reactants and the CD8+ T-cell subset. Clin Exp Rheumatol 7:627-639,
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expressions, matrix, suppression, upper, osteoarthritis, genes, zone, cartilage, chondrocyte
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