The pathology of the involved tendons in patients with familial arthropathy and congenital camptodactyly

Defects in tendon, ligament, and enthesis in response to genetic alterations in key proteoglycans and glycoproteins: a review

This review summarizes the genetic alterations and knockdown approaches published in the literature to assess the role of key proteoglycans and glycoproteins in the structural development, function, and repair of tendon, ligament, and enthesis. The information was collected from (i) genetically altered mice, (ii) in vitro knockdown studies, (iii) genetic variants predisposition to injury, and (iv) human genetic diseases. The genes reviewed are for small leucine-rich proteoglycans (lumican, fibromodulin, biglycan, decorin, and asporin); dermatan sulfate epimerase (Dse) that alters structure of glycosaminoglycan and hence the function of small leucine-rich proteoglycans by converting glucuronic to iduronic acid; matricellular proteins (thrombospondin 2, secreted phosphoprotein 1 (Spp1), secreted protein acidic and rich in cysteine (Sparc), periostin, and tenascin X) including human tenascin C variants; and others, such as tenomodulin, leukocyte cell derived chemotaxin 1 (chondromodulin-I, ChM-I), CD44 antigen (Cd44), lubricin (Prg4), and aggrecan degrading gene, a disintegrin-like and metallopeptidase (reprolysin type) with thrombospondin type 1 motif, 5 (Adamts5). Understanding these genes represents drug targets for disrupting pathological mechanisms that lead to tendinopathy, ligamentopathy, enthesopathy, enthesitis and tendon/ligament injury, that is, osteoarthritis and ankylosing spondylitis.

A novel mutation in PRG4 gene underlying camptodactyly-arthropathy-coxa vara-pericarditis syndrome with the possible expansion of the phenotype to include congenital cataract

BACKGROUND

Camptodactyly-arthropathy-coxa vara-pericarditis syndrome (CACP) is a clinically heterogenous congenital disorder caused by mutations in proteoglycan 4 (PRG4), a chondroitin sulfate proteoglycan that acts as a lubricant for the cartilage surface. Although CACP is a rare genetic disorder, several cases were described in the literature from ethnically different populations including Caucasian, Egyptian, Saudi Arabian, Pakistani, and Korean. We report CACP for the first time in United Arab Emirates.

METHODS

Direct sequencing of all the coding exons and splice sites of the PRG4 gene was performed for all the members of the affected family.

RESULTS

The studied family is consanguineous and has multiple affected members from different branches showing congenital camptodactyly with arthropathy, the hallmarks of CACP. All the affected family members lack pericarditis, but one of them was born with cataract, which has never been documented in any of the previously reported cases of CACP. Molecular analysis revealed a novel homozygous insertion of a cytosine nucleotide (c.1320dupC) in the highly repetitive portion of the coding sequence of the PRG4 gene. The detected mutation caused a frameshift in the cDNA sequence and created a premature termination codon (p.P440fsX197), which is likely to result in a nonfunctional protein.

CONCLUSION

We report a family from the United Arab Emirates with typical features of CACP in whom one of the children had in addition, a bilateral congenital cataract. We also report the identification of a novel null mutation in PRG4 confirming the genetic homogeneity of CACP.

Lubricin surface modification improves tendon gliding after tendon repair in a canine model in vitro

This study investigated the effects of lubricin on the gliding of repaired flexor digitorum profundus (FDP) tendons in vitro. Canine FDP tendons were completely lacerated, repaired with a modified Pennington technique, and treated with one of the following solutions: saline, carbodiimide derivatized gelatin/hyaluronic acid (cd-HA-gelatin), carbodiimide derivatized gelatin to which lubricin was added in a second step (cd-gelatin + lubricin), or carbodiimide derivatized gelatin/HA + lubricin (cd-HA-gelatin + lubricin). After treatment, gliding resistance was measured up to 1,000 cycles of simulated flexion/extension motion. The increase in average and peak gliding resistance in cd-HA-gelatin, cd-gelatin + lubricin, and cd-HA-gelatin + lubricin tendons was less than the control tendons after 1,000 cycles (p < 0.05). The increase in average gliding resistance of cd-HA-gelatin + lubricin treated tendons was also less than that of the cd-HA-gelatin treated tendons (p < 0.05). The surfaces of the repaired tendons and associated pulleys were assessed qualitatively with scanning electron microscopy and appeared smooth after 1,000 cycles of tendon motion for the cd-HA-gelatin, cd-gelatin + lubricin, and cd-HA-gelatin + lubricin treated tendons, while that of the saline control appeared roughened. These results suggest that tendon surface modification can improve tendon gliding ability, with a trend suggesting that lubricin fixed on the repaired tendon may provide additional improvement over that provided by HA and gelatin alone.

Lubricin surface modification improves extrasynovial tendon gliding in a canine model in vitro

BACKGROUND

Lubricin is the principal lubricant in synovial fluid. Although lubricin has been identified in tendons, especially on the surface of intrasynovial tendons such as the flexor digitorum profundus tendon, its ability to improve tendon gliding is unknown. The purpose of this study was to investigate the effects of exogenously applied lubricin on the gliding of extrasynovial tendons in a canine model in vitro.

METHODS

Forty peroneus longus tendons, along with the proximal pulley in the ipsilateral hind paw, were harvested from adult mongrel dogs. After the gliding resistance of the normal tendons was measured, the tendons were treated with one of the following solutions: saline solution, lubricin, carbodiimide derivatized gelatin (cd-gelatin), carbodiimide derivatized gelatin with hyaluronic acid (cd-HA-gelatin), or carbodiimide derivatized gelatin to which lubricin had been added in a second step (cd-gelatin plus lubricin). Tendon gliding resistance was measured for 1000 cycles of simulated flexion-extension motion of the tendon. Transverse sections of the tendons were examined qualitatively at 100x magnification to estimate surface smoothness after 1000 cycles.

RESULTS

There was no significant difference in the gliding resistance between the tendons treated with saline solution and those treated with lubricin alone, or between the tendons treated with cd-HA-gelatin and those treated with cd-gelatin plus lubricin; however, the gliding resistance of the tendons treated with cd-gelatin plus lubricin was significantly lower than that of the tendons treated with saline solution, lubricin alone, or cd-gelatin alone (p < 0.05). After 1000 cycles of tendon motion, the gliding resistance of the tendons treated with cd-gelatin plus lubricin decreased 18.7% compared with the resistance before treatment, whereas the gliding resistance of the saline-solution-treated controls increased >400%. The tendon surfaces treated with cd-gelatin plus lubricin or with cd-HA-gelatin appeared smooth even after 1000 cycles of tendon motion, whereas the other surfaces appeared roughened.

CONCLUSIONS

While the addition of lubricin alone did not affect friction in this tendon gliding model, the results indicate that lubricin may preferentially adhere to a tendon surface pretreated with cd-gelatin and, when so fixed in place, lubricin does have an important effect on tendon lubrication.

Expression and mapping of lubricin in canine flexor tendon

Matrix composition and the biomechanical environment are intimately interdependent in most connective tissues. Lubricin has many distinct biological functions, including lubrication, antiadhesion, and cytoprotection in cartilage, tendons, and other tissues. This study investigated the distribution of lubricin in the canine flexor digitorum profundus (FDP) tendon by immunohistochemistry. Lubricin was found both on the tendon surface and at the interface of collagen fiber bundles within the tendon, where the cells are subjected to shear force in addition to tension and compression. The expression of lubricin in regions of the canine flexor tendon that differ in mechanical or nutritional environment was also investigated using RT-PCR. Six N-terminal splicing variants were identified from six distinct anatomical regions of flexor tendon. The variants with larger sizes were noted in regions subjected to significant shear and compressive forces. Lubricin is ubiquitous in the FDP tendon, with variations in distribution and splicing that appear to correspond to discrete anatomic locations that differ by mechanical or nutritional environment.

Mapping lubricin in canine musculoskeletal tissues

Lubricin, also known as superficial zone protein or PRG4, has many distinct biological functions, including lubrication, antiadhesion, and as a regulator of cell growth. This study investigated lubricin in canine musculoskeletal tissues using RT-PCR and immunohistochemistry. One or more variants were noted in canine flexor digitorum profundus (FDP) tendon, Achilles tendon, patellar tendon, A2 pulley, anterior cruciate ligament (ACL), knee lateral collateral ligament (LCL), articular cartilage, meniscus, muscle, and skin. We found 6 N-terminal lubricin splicing variants. The variants with larger sizes were identified in FDP tendon, ACL, LCL, A2 pulley, and cartilage. Lubricin was distributed both on the tissue surfaces and at the interface of fiber bundles within tissues, but this distribution varied by tissue type. We conclude that lubricin is present in many tissues; variations in splicing and physical distribution suggest that the variants of lubricin may play different roles in different locations.

Synovial pathology in camptodactyly-arthropathy-coxa vara-pericarditis syndrome

At least 25 families with camptodactyly-arthropathy-coxa vara-pericarditis (CACP syndrome) have been reported, with descriptions of a distinctive synovial pathology based largely on light microscopy. Although described as "proliferative," with numerous multinucleated giant cells, the natures of proliferating cells and giant cells have not been determined. To clarify the pathogenesis of this disorder, we studied 3 patients who had CACP syndrome and underwent synovial biopsy. Cells in the biopsies were studied by immunohistochemistry and electron microscopy. Giant cells were identified as macrophage in origin based on CD68 expression and electron microscopic features of macrophages. Most cells in the synovium were CD68 positive, in keeping with macrophages. The degree of proliferation in synovial biopsies was estimated by MIB1 immunostaining, which showed that up to 30% of cells were cycling compared with fewer than 10% in control synovial biopsies. None of the giant cells was cycling. By double immunostaining, proliferating cells were determined to be fibroblastic synoviocytes rather than macrophages. Thus the proliferative synovitis in this CACP syndrome can be more accurately thought of as hypercellularity by infiltrating macrophages with a contribution by proliferating fibroblastic synoviocytes. The synoviocyte proliferation is likely a response to the underlying genetic mutations involving the proteoglycan-4 (or CACP) gene. The encoded protein normally acts as a lubricant and possibly controls cell proliferation. Loss of one or another of these functions may be a possible mechanism that leads to synoviocyte proliferation in this disease, but the exact pathophysiology leading to this change requires further study.

Camptodactyly, arthropathy, coxa vara, pericarditis (CACP)syndrome: a case report

The camptodactyly-arthropathy-coxa vara-pericarditis syndrome (CACP) is characterized by congenital or early-onset camptodactyly, childhood-onset noninflammatory arthropathy associated with synovial hyperplasia. Some patients have progressive coxa vara deformity and/or noninflammatory pericardial effusion. CACP is inherited as an autosomal recessive mode and the disease gene is assigned to a 1.9-cM interval on human chromosome 1q25-31. We describe a 10-yr-old boy who has typical features of CACP without familial association.

Biology of Fibrocartilage Cells

Fibrocartilage is an avascular tissue that is best documented in menisci, intervertebral discs, tendons, ligaments, and the temporomandibular joint. Several of these sites are of particular interest to those in the emerging field of tissue engineering. Fibrocartilage cells frequently resemble chondrocytes in having prominent rough endoplasmic reticulum, many glycogen granules, and lipid droplets, and intermediate filaments together with and actin stress fibers that help to determine cell organization in the intervertebral disc. Fibrocartilage cells can synthesize a variety of matrix molecules including collagens, proteoglycans, and noncollagenous proteins. All the fibrillar collagens (types I, II, III, V, and XI) have been reported, together with FACIT (types IX and XII) and network-forming collagens (types VI and X). The proteoglycans include large, aggregating types (aggrecan and versican) and small, leucine-rich types (decorin, biglycan, lumican, and fibromodulin). Less attention has been paid to noncollagenous proteins, although tenascin-C expression may be modulated by mechanical strain. As in hyaline cartilage, matrix metalloproteinases are important in matrix turnover and fibrocartilage cells are capable of apoptosis.

Immunolocalisation and expression of proteoglycan 4 (cartilage superficial zone proteoglycan) in tendon

Cartilage superficial zone protein/proteoglycan (SZP) or proteoglycan 4 (PRG4), has been demonstrated to have the potential for several distinct biological functions including cytoprotection, lubrication and matrix binding. In the present study, we have examined both the immunolocalisation and the mRNA expression pattern of PRG4 in tissue harvested from the compressed and tensional regions of young and mature bovine tendons. Immunohistochemical analyses, utilizing monoclonal antibody 3-A-4 which recognizes a conformational-dependent epitope on native PRG4, demonstrated that PRG4 is present predominantly at the surface of fibrocartilaginous regions of tendon, with the intensity of immunoreactivity in this region increasing with age. RT-PCR analyses revealed that the expression of PRG4 mRNA can be modulated by exposure to cytokines and growth factors. In addition, analyses of human pathological tendon revealed that PRG4 may also be expressed as an alternatively spliced form lacking exons which encode part of the N-terminal matrix-binding and cell-proliferative domain; however, it remains to be determined whether such splice variants are a feature of human tendon, regardless of disease state. Taken together, these data indicate that PRG4 may play an important cytoprotective role by preventing cellular adhesion to the tendon surface as well as providing lubrication during normal tendon function, in a manner complimentary to cartilage PRG4. Structural modifications to SZP, together with a reduction in synthesis during tendon inflammation with injury and disease may account for the formation of tendon adhesions and contribute to the overall dysfunction of the tissue.

Clinical variability and genetic homogeneity of the camptodactyly-arthropathy-coxa vara-pericarditis syndrome

The camptodactyly-arthropathy-coxa vara-pericarditis syndrome (CACP) is an autosomal recessive condition characterized by the association of congenital or early onset camptodactyly and noninflammatory arthropathy with synovial hyperplasia. Progressive coxa vara deformity and/or noninflammatory pericardial or pleural effusions have been observed in some patients. Recently, the disease gene has been assigned to human chromosome region 1q25-q31, and truncating mutations have been identified in the megakaryocyte stimulating factor gene. Studying 12 patients from 8 unrelated families, we emphasized hip and spine involvement, particularly in the course of the disease as shown in a 58-year-old patient. Despite clinical variability, linkage studies support genetic homogeneity of the disease.

A 6-Mb high-resolution physical and transcription map encompassing the hereditary prostate cancer 1 (HPC1) region

Several hereditary disease loci have been genetically mapped to the chromosome 1q24-q31 interval, including the hereditary prostate cancer 1 (HPC1) locus. Here, we report the construction of a 20-Mb yeast artificial chromosome contig and a high-resolution 6-Mb sequence-ready bacterial artificial chromosome (BAC)/P1-derived artificial chromosome (PAC) contig of 1q25 by sequence and computational analysis, STS content mapping, and chromosome walking. One hundred thirty-six new STSs, including 10 novel simple sequence repeat polymorphisms that are being used for genetic refinement of multiple disease loci, have been generated from this contig and are shown to map to the 1q25 interval. The integrity of the 6-Mb BAC/PAC contig has been confirmed by restriction fingerprinting, and this contig is being used as a template for human chromosome 1 genome sequencing. A transcription mapping effort has resulted in the precise localization of 18 known genes and 31 ESTs by database searching, exon trapping, direct cDNA hybridization, and sample sequencing of BACs from the 1q25 contig. An additional 11 known genes and ESTs have been placed within the larger 1q24-q31 interval. These transcription units represent candidate genes for multiple hereditary diseases, including HPC1.

CACP, encoding a secreted proteoglycan, is mutated in camptodactyly-arthropathy-coxa vara-pericarditis syndrome

Altered growth and function of synoviocytes, the intimal cells which line joint cavities and tendon sheaths, occur in a number of skeletal diseases. Hyperplasia of synoviocytes is found in both rheumatoid arthritis and osteoarthritis, despite differences in the underlying aetiologies of the two disorders. We have studied the autosomal recessive disorder camptodactyly-arthropathy-coxa vara-pericarditis syndrome (CACP; MIM 208250) to identify biological pathways that lead to synoviocyte hyperplasia, the principal pathological feature of this syndrome. Using a positional-candidate approach, we identified mutations in a gene (CACP) encoding a secreted proteoglycan as the cause of CACP. The CACP protein, which has previously been identified as both 'megakaryocyte stimulating factor precursor' and 'superficial zone protein', contains domains that have homology to somatomedin B, heparin-binding proteins, mucins and haemopexins. In addition to expression in joint synovium and cartilage, CACP is expressed in non-skeletal tissues including liver and pericardium. The similarity of CACP sequence to that of other protein families and the expression of CACP in non-skeletal tissues suggest it may have diverse biological activities.

The camptodactyly-arthropathy-coxa vara-pericarditis syndrome: clinical features and genetic mapping to human chromosome 1

OBJECTIVE

To delineate the clinical features in patients with the autosomal recessive camptodactyly-arthropathy-coxa vara-pericarditis syndrome (CACP) and to determine the location of the involved gene.

METHODS

Eight affected individuals (ages 2-15 years) with CACP from 4 consanguineous kindreds were clinically evaluated. Four patients are newly described and 4 have been reported previously. Findings were compared with those in 21 other previously reported cases. DNA obtained from the 8 affected patients and their available siblings and parents was used in a genome-wide search for linkage.

RESULTS

Congenital camptodactyly and childhood-onset noninflammatory arthropathy were present in all affected patients. Seven patients developed bilateral coxa vara deformity, and 1 developed coxa magna with cystic erosions. Two of the patients also had symptoms or signs of pericarditis. A genome-wide search for linkage identified homozygosity for a series of genetic markers on human chromosome 1q in all affected patients. The marker D1S191 yielded a maximum logarithm of the odds ratio (LOD score) of 3.3 at theta = 0. The CACP gene lies within a 1.9-cM candidate interval defined by the markers D1S2107 and D1S222.

CONCLUSION

The principal features of the CACP syndrome are congenital or early-onset camptodactyly and childhood-onset noninflammatory arthropathy. Coxa vara deformity or other dysplasia associated with progressive hip disease may develop over time. Clinical pericarditis may also occur. A locus responsible for causing CACP syndrome is assigned to a 1.9-cM interval on human chromosome 1q25-31 by homozygosity mapping. This now facilitates the identification of the responsible gene and permits testing for locus homogeneity in other CACP kindreds.

Syndrome of camptodactyly, arthropathy and coxa vara (CAC syndrome)

Three Saudi children (two female, one male) are described who presented with familial arthropathy associated with congenital camptodactyly. This rare but recognized clinical entity has a variable clinical presentation and may be associated with pericarditis and coxa vara. Camptodactyly was observed in the neonatal period in all patients, while joint swelling was observed between the third and 11th month. Pericarditis was suspected in the referral hospital in one patient but was not subsequently confirmed at our institution, raising the possibility that pericarditis may be reversible. Radiological examination of the hips showed coxa vara with short femoral neck in all patients. Synovial biopsy in the three patients revealed proliferating synovial epithelium with moderate fibrocollagenous densities and multinucleated giant cells, occasional lymphocytes or neutrophils but no plasma cells were identified. This is the first series of this familial arthropathy with a triad of camptodactyly, arthropathy and coxa vara (CAC syndrome) in Saudi Arabia which is to be considered in patients where more than one family member has juvenile arthritis.

Congenital contractural deformities of the fingers and arthropathy

Four patients are described who presented with congenital finger contractures and arthropathy. There was synovial cell hyperplasia and giant cells but no inflammatory process. Radiographs showed flattening of the metacarpal and metatarsal heads and the proximal femoral ossification centres. In the oldest patient the process had subsided leaving slight contractures but severe impairment of hip mobility. In another the arthropathy was still prominent in the early teens. In a third, finger contractures had failed to respond to conservative or surgical measures.