Cellular therapy and tissue engineering for cartilage repair.

Articular cartilage (AC) has limited capacity for repair. The first attempt to repair cartilage using tissue engineering was reported in 1977. Since then, cell-based interventions have entered clinical practice in orthopaedics, and several tissue engineering approaches to repair cartilage are in the translational pipeline towards clinical application. Classically, these involve a scaffold, substrate or matrix to provide structure, and cells such as chondrocytes or mesenchymal stromal cells to generate the tissue. We discuss the advantages and drawbacks of the use of various cell types, natural and synthetic scaffolds, multiphasic or gradient-based scaffolds, and self-organizing or self-assembling scaffold-free systems, for the engineering of cartilage constructs. Several challenges persist including achieving zonal tissue organization and integration with the surrounding tissue upon implantation. Approaches to improve cartilage thickness, organization and mechanical properties include mechanical stimulation, culture under hypoxic conditions, and stimulation with growth factors or other macromolecules. In addition, advanced technologies such as bioreactors, biosensors and 3D bioprinting are actively being explored. Understanding the underlying mechanisms of action of cell therapy and tissue engineering approaches will help improve and refine therapy development. Finally, we discuss recent studies of the intrinsic cellular and molecular mechanisms of cartilage repair that have identified novel signals and targets and are inspiring the development of molecular therapies to enhance the recruitment and cartilage reparative activity of joint-resident stem and progenitor cells. A one-fits-all solution is unrealistic, and identifying patients who will respond to a specific targeted treatment will be critical.

In vivo phenotypic characterisation of nucleoside label-retaining cells in mouse periosteum.

Periosteum is known to contain cells that, after isolation and culture-expansion, display properties of mesenchymal stromal/stem cells (MSCs). However, the equivalent cells have not been identified in situ mainly due to the lack of specific markers. Postnatally, stem cells are slow-cycling, long-term nucleoside-label-retaining cells. This study aimed to identify and characterise label-retaining cells in mouse periosteum in vivo. Mice received iodo-deoxy-uridine (IdU) via the drinking water for 30 days, followed by a 40-day washout period. IdU+ cells were identified by immunostaining in conjunction with MSC and lineage markers. IdU-labelled cells were detected throughout the periosteum with no apparent focal concentration, and were negative for the endothelial marker von Willebrand factor and the pan-haematopoietic marker CD45. Subsets of IdU+ cells were positive for the mesenchymal/stromal markers vimentin and cadherin-11. IdU+ cells expressed stem cell antigen-1, CD44, CD73, CD105, platelet-derived growth factor receptor-α and p75, thereby displaying an MSC-like phonotype. Co-localisation was not detectable between IdU and the pericyte markers CD146, alpha smooth muscle actin or NG2, nor did IdU co-localise with ß-galactosidase in a transgenic mouse expressing this reporter gene in pericytes and smooth muscle cells. Subsets of IdU+ cells expressed the osteoblast-lineage markers Runx2 and osteocalcin. The IdU+ cells expressing osteocalcin were lining the bone and were negative for the MSC marker p75. In conclusion, mouse periosteum contains nucleoside-label-retaining cells with a phenotype compatible with MSCs that are distinct from pericytes and osteoblasts. Future studies characterising the MSC niche in vivo could reveal novel therapeutic targets for promoting bone regeneration/repair.

Cell-based approaches to joint surface repair: a research perspective.

Repair of lesions of the articular cartilage lining the joints remains a major clinical challenge. Surgical interventions include osteochondral autograft transfer and microfracture. They can provide some relief of symptoms to patients, but generally fail to durably repair the cartilage. Autologous chondrocyte implantation has thus far shown the most promise for the durable repair of cartilage, with long-term follow-up studies indicating improved structural and functional outcomes. However, disadvantages of this technique include the need for additional surgery, availability of sufficient chondrocytes for implantation, and maintenance of their phenotype during culture-expansion. Mesenchymal stem cells offer an attractive alternative cell-source for cartilage repair, due to their ease of isolation and amenability to ex vivo expansion while retaining stem cell properties. Preclinical and clinical studies have demonstrated the potential of mesenchymal stem cells to promote articular cartilage repair, but have also highlighted several key challenges. Most notably, the quality and durability of the repair tissue, its resistance to endochondral ossification, and its effective integration with the surrounding host tissue. In addition, challenges exist related to the heterogeneity of mesenchymal stem cell preparations and their quality-control, as well as optimising the delivery method. Finally, as our knowledge of the cellular and molecular mechanisms underlying articular cartilage repair increases, promising studies are emerging employing bioactive scaffolds or therapeutics that elicit an effective tissue repair response through activation and mobilisation of endogenous stem and progenitor cells.

Mesenchymal differentiation propensity of a human embryonic stem cell line.

OBJECTIVES: To characterize basal differentiation tendencies of a human embryonic stem (hES) cell line, KCL-002. MATERIALS AND METHODS: In vitro specification and differentiation of hES cells were carried out using embryoid body (EB) cultures and tests of pluripotency and in vivo differentiation were performed by teratoma assays in SCID mice. Real-time PCR, immunohistochemistry, flow cytometry and histological analyses were used to identify expression of genes and proteins associated with the ectodermal, endodermal and mesodermal germ layers. RESULTS: Undifferentiated KCL-002 cells expressed characteristic markers of pluripotent stem cells such as Nanog, Sox-2, Oct-4 and TRA 1-60. When differentiated in vitro as EB cultures, expression of pluripotency, endodermal and ectodermal markers decreased rapidly. In contrast, mesodermal and mesenchymal markers such as VEGFR-2, α-actin and vimentin increased during EB differentiation as shown by qPCR, immunostaining and flow cytometric analyses. Teratoma formation in SCID mice demonstrated the potential to form all germ layers in vivo with a greater proportion of the tumours containing mesenchymal derivatives. CONCLUSIONS: The data presented suggest that the KCL-002 hES cell line is pluripotent and harbours a bias in basal differentiation tendencies towards mesodermal and mesenchymal lineage cells. Characterizing innate differentiation propensities of hES cell lines is important for understanding heterogeneity between different cell lines and for further studies aimed at deriving specific lineages from hES cells.

A novel in vivo murine model of cartilage regeneration. Age and strain-dependent outcome after joint surface injury.

OBJECTIVES: To generate and validate a murine model of joint surface repair following acute mechanical injury. METHODS: Full thickness defects were generated in the patellar groove of C57BL/6 and DBA/1 mice by microsurgery. Control knees were either sham-operated or non-operated. Outcome was evaluated by histological scoring systems. Apoptosis and proliferation were studied using TUNEL and Phospho-Histone H3 staining, respectively. Type II collagen neo-deposition and degradation were evaluated by immunostaining using antibodies to the CPII telopeptide and C1,2C (Col2-3/4Cshort), respectively. Aggrecanases and matrix metalloproteinases (MMPs) activity were assessed by immunostaining for TEGE(373) and VDIPEN neo-epitopes. RESULTS: Young 8-week-old DBA/1 mice displayed consistent and superior healing of the articular cartilage defect. Age-matched C57BL/6 mice repaired poorly and developed features of osteoarthritis (OA). Compared to C57BL/6, DBA/1 mice displayed a progressive decline of chondrocyte apoptosis, cell proliferation within the repair tissue, persistent type II collagen neo-deposition, less type II collagen degradation, less aggrecanases and more MMP-induced aggrecan degradation. Eight-month-old DBA/1 mice failed to repair, but, in contrast to age-matched C57BL/6 mice, developed no signs of OA. CONCLUSION: We have generated and validated a murine model of cartilage regeneration in which the outcome of joint surface injury is strain and age dependent. This model will allow, for the first time, the dissection of different pathways involved in joint surface regeneration in adult mammals using the powerful technology of mouse genetics.

Stem cells for tooth engineering.

Tooth development results from sequential and reciprocal interactions between the oral epithelium and the underlying neural crest-derived mesenchyme. The generation of dental structures and/or entire teeth in the laboratory depends upon the manipulation of stem cells and requires a synergy of all cellular and molecular events that finally lead to the formation of tooth-specific hard tissues, dentin and enamel. Although mesenchymal stem cells from different origins have been extensively studied in their capacity to form dentin in vitro, information is not yet available concerning the use of epithelial stem cells. The odontogenic potential resides in the oral epithelium and thus epithelial stem cells are necessary for both the initiation of tooth formation and enamel matrix production. This review focuses on the different sources of stem cells that have been used for making teeth in vitro and their relative efficiency. Embryonic, post-natal or even adult stem cells were assessed and proved to possess an enormous regenerative potential, but their application in dental practice is still problematic and limited due to various parameters that are not yet under control such as the high risk of rejection, cell behaviour, long tooth eruption period, appropriate crown morphology and suitable colour. Nevertheless, the development of biological approaches for dental reconstruction using stem cells is promising and remains one of the greatest challenges in the dental field for the years to come.

Increased Bcl-2/p53 ratio in human osteoarthritic cartilage: a possible role in regulation of chondrocyte metabolism.

OBJECTIVE: To determine whether Bcl-2, p53, and Fas/CD95 help to control cartilage metabolism. METHODS: Six normal and 14 osteoarthritic (OA) cartilage samples were examined, and two zones from each sample showing the least (Min) and most (Max) anatomical damage were selected. Chondrocytes were isolated by sequential enzymatic digestion and freshly processed. Bcl-2, p53, and Fas/CD95 expression was evaluated by immunofluorescence and FACS analysis; the cell cycle was analysed using propidium iodide, and chondrocyte proliferation assessed by [(3)H]thymidine incorporation. RESULTS: Intracellular levels of Bcl-2 were significantly higher in Max (27.5%) than in Min (21%, p<0.01) OA or normal chondrocytes (18.5%, p<0.01). Intracellular p53 expression was significantly decreased in Max (25.5%) compared with Min (37%, p<0.01) OA or normal cartilage (41.5%, p<0.05). Fas/CD95 receptor expression on surface chondrocytes did not significantly differ between OA and normal cartilage. Cell cycle analysis showed that the proportion of activated chondrocytes in the S phase was significantly higher in Max (69%) than in Min (49%) OA or normal cartilage (43%). The prevalence of proliferating chondrocytes progressively increased according to the degree of OA damage (mean (SEM) Min 1247 (260), Max 2423 (460), p<0.05). Chondrocyte [(3)H]thymidine uptake correlated positively with Bcl-2 (r(s) = 0.62, p = 0.009) and correlated inversely with p53 levels (r(s) = -0.55, p = 0.02). CONCLUSIONS: Bcl-2 and p53 play a part in apoptosis, but also help to regulate chondrocyte growth and differentiation. Whereas Bcl-2 promotes cell survival, p53 can arrest cell cycle. The data confirm that chondrocyte activity is enhanced in OA and suggest that the increased Bcl-2/p53 ratio sustains the metabolic boost of chondrocytes.

Morphological and immunocytochemical characterization of cultured fibroblast-like cells derived from adult human synovial membrane.

The synovial membrane (SM) is a source of multipotent mesenchymal stem cells (MSCs), which appeared microscopically to be a relatively homogeneous population of fibroblast-like cells (FCs) in culture (De Bari et al., 2001). The aim of this study was to investigate phenotypic characteristics of the SM-derived FCs (SD-FCs) that could elucidate their origin inside the synovial tissue. Morphological characterization of SD-FCs was assessed by electron microscopy and by expression of surfactant protein A (SPA). This study, yielded substantial evidence that SD-FCs show ultrastructural and immunocytochemical features of type B synoviocytes; they contained characteristic lamellar bodies (LBs) that are secreted by exocytosis. LB secretion ability was maintained upon passaging (P3-P10). Immunocytochemistry showed that SD-FCs express surfactant protein A (SP-A). Taken together, these results indicate that multipotent SD-MSCs may originate from the synovial lining, having a phenotype highly similar to that of type B synoviocytes. We believe our data highlight the potent ability of type B synoviocytes to have a multilineage differentiation potential.

In vitro growth rate of fibroblast-like synovial cells is reduced by methotrexate treatment.

BACKGROUND: Fibroblast-like synovial cells (FLS) can be cultured and expanded in vitro in monolayer. Little is known about the growth characteristics of FLS derived from different patients. OBJECTIVE: To study FLS cultures, with particular attention to differences in growth rate of FLS from patients with rheumatoid arthritis (RA) and from other arthritic patients. Additionally, to analyse the influence of methotrexate (MTX) treatment, patient age, and disease duration on FLS growth characteristics. MATERIALS AND METHODS: FLS were isolated from needle arthroscopy biopsy specimens. Twenty four patients (11 RA, 8 spondyloarthropathy, 1 osteoarthritis, and 4 undifferentiated arthritis) were studied. FLS population doubling time was determined between passage 2 and passage 5. Differences in population doubling time between RA and non-RA FLS and between FLS from patients receiving MTX and those not receiving this drug were analysed. In addition, possible correlations between FLS population doubling time and patient age or disease duration were examined. RESULTS: In vitro monolayer FLS cultures from needle arthroscopy biopsy specimens showed linear growth characteristics. Cell growth rate was not correlated with type of disease. Cells from patients undergoing treatment with MTX showed a longer population doubling time than FLS from patients not receiving this drug (Mann-Whitney test, p<0.05). No correlation was found with patient age or disease duration. CONCLUSION: The results suggest that FLS growth in monolayer is not dependent on the disease affecting the joint. MTX treatment, however, was more relevant in determining FLS growth rate.

Bone marrow mesenchymal cells for haemophilia A gene therapy using retroviral vectors with modified long-terminal repeats.

Bone marrow (BM) cells are attractive target cells for ex vivo gene therapy of genetic diseases, including haemophilia A. However, BM-derived haematopoietic stem/progenitor cells (HSCs) transduced with factor VIII (FVIII) retroviral vectors, failed to express FVIII in vivo. To overcome the limitations of HSCs for haemophilia gene therapy, BM-derived mesenchymal cells were explored as alternative target cells. The BM mesenchymal cell population contains self-renewing mesenchymal stem/progenitor cells that give rise to different mesenchymal lineages and have been used safely in phase I gene-marking trials. Human BM mesenchymal cells were transduced in vitro with an improved retroviral vector encoding a human B-domain deleted FVIII (hFVIIIdeltaB) cDNA (MND-MFG-hFVIIIdeltaB). This vector contains multiple modifications in the cis-acting elements within the MoMLV long-terminal repeats (LTR) that prevent the binding of repressive transcription factors. These modifications were previously shown to increase and prolong gene expression in embryonic stem (ES) cells and HSCs. Transduction of BM mesenchymal cells with the MND-MFG-hFVIIIdeltaB retroviral vector resulted in high levels of functional human FVIII in vitro, ranging between 300 +/- 50 SD and 700 +/- 100 SD mU per 106 cells per 24 h. Following xenografting of the transduced human BM cells into immunodeficient NOD-SCID mice, therapeutic hFVIII levels of 12 +/- 10 ng mL-1 were detected in the plasma. Polymerase chain reaction analysis demonstrated long-term engraftment (>3 months) of the human BM mesenchymal cells. The long-term persistence of BM mesenchymal cells in the absence of myelo-ablative conditioning and the therapeutic FVIII levels in vivo underscore the potential usefulness of BM-derived mesenchymal cells for haemophilia gene therapy, as opposed to BM-derived HSCs. Despite the modifications of the MoMLV LTR, FVIII expression declined, which coincided with a decrease in FVIII mRNA transcription levels, indicating that the salutary effect of the LTR modification on transgene expression is not universally applicable to all cell types.

Increased expression of nerve growth factor (NGF) and high affinity NGF receptor (p140 TrkA) in human osteoarthritic chondrocytes.

OBJECTIVE: We aimed to investigate the expression of nerve growth factor (NGF) and high affinity NGF receptor (p140 TrkA) on chondrocytes from human healthy and osteoarthritic cartilage. METHODS: We recruited 12 patients with osteoarthritis (OA) undergoing surgical knee replacement. Articular cartilage was split into two zones showing macroscopically and histologically the lowest (MIN) and highest (MAX) degree of osteoarthritic damage. Additional specimens of cartilage were obtained from three healthy donors. Chondrocytes were isolated by enzymatic digestion and freshly processed for NGF protein, Trk A detection and mRNA extraction. NGF-beta mRNA was determined by a reverse transcriptase-polymerase chain reaction (RT-PCR). NGF-beta and TrkA expression was evaluated by immunofluorescence and flow cytometry analysis. RESULTS: NGF-beta-specific mRNA was detected in normal and osteoarthritic chondrocytes. NGF-beta protein levels were low in normal chondrocytes, increased in MIN osteoarthritic cartilage and further enhanced in MAX osteoarthritic cartilage. Likewise, TrkA was scarcely expressed on normal chondrocytes and progressively increased on osteoarthritic chondrocytes based on the extent of anatomic damage. CONCLUSIONS: This is the first study showing that human chondrocytes synthesize NFG-beta and express on their surface the high affinity NGFR (p140 TrkA). Of note, NGF-beta and TrkA were upregulated in osteoarthritic chondrocytes suggesting a role of NGF in the pathophysiology of OA. We can speculate that NGF, like other growth factors, stimulates chondrocyte metabolism in the osteoarthritic process.

Multipotent mesenchymal stem cells from adult human synovial membrane.

OBJECTIVE: To characterize mesenchymal stem cells (MSCs) from human synovial membrane (SM). METHODS: Cell populations were enzymatically released from the SM obtained from knee joints of adult human donors and were expanded in monolayer with serial passages at confluence. Cell clones were obtained by limiting dilution. At different passages, SM-derived cells were subjected to in vitro assays to investigate their multilineage potential. Upon treatments, phenotypes of cell cultures were analyzed by histo- and immunohistochemistry and by semiquantitative reverse transcription-polymerase chain reaction for the expression of lineage-retated marker genes. RESULTS: SM-derived cells could be expanded extensively in monolayer, with limited senescence. Under appropriate culture conditions, SM-derived cells were induced to differentiate to the chondrocyte, osteocyte, and adipocyte lineages. Sporadic myogenesis was also observed. Five independent cell clones displayed multilineage potential. Interestingly, only 1 clone was myogenic. Donor age, cell passaging, and cryopreservation did not affect the multilineage potential of SM-derived cells. In contrast, normal dermal fibroblasts under the same culture conditions did not display this potential. CONCLUSION: Our study demonstrates that human multipotent MSCs can be isolated from the SM of knee joints. These cells have the ability to proliferate extensively in culture, and they maintain their multilineage differentiation potential in vitro, establishing their progenitor cell nature. SM-derived MSCs may play a role in the regenerative response during arthritic diseases and are promising candidates for developing novel cell-based therapeutic approaches for postnatal skeletal tissue repair.

Molecular markers predictive of the capacity of expanded human articular chondrocytes to form stable cartilage in vivo.

OBJECTIVE: To establish a model and associated molecular markers for monitoring the capacity of in vitro-expanded chondrocytes to generate stable cartilage in vivo. METHODS: Adult human articular chondrocytes (AHAC) were prepared by collagenase digestion of samples obtained postmortem and were expanded in monolayer. Upon passaging, aliquots of chondrocyte suspensions were either injected intramuscularly into nude mice, cultured in agarose, or used for gene expression analysis. Cartilage formation in vivo was documented by histology, histochemistry, immunofluorescence for type II collagen, and proteoglycan analysis by 35S-sulfate incorporation and molecular sieve chromatography of the radiolabeled macromolecules. In situ hybridization for species-specific genomic repeats was used to discriminate human-derived from mouse-derived cells. Gene expression dynamics were analyzed by semiquantitative reverse transcription-polymerase chain reaction. RESULTS: Intramuscular injection of freshly isolated AHAC into nude mice resulted in stable cartilage implants that were resistant to mineralization, vascular invasion, and replacement by bone. In vitro expansion of AHAC resulted in the loss of in vivo cartilage formation. This capacity was positively associated with the expression of fibroblast growth factor receptor 3, bone morphogenetic protein 2, and alpha1(II) collagen (COL2A1), and its loss was marked by the up-regulation of activin receptor-like kinase 1 messenger RNA. Anchorage-independent growth and the reexpression of COL2A1 in agarose culture were insufficient to predict cartilage formation in vivo. CONCLUSION: AHAC have a finite capacity to form stable cartilage in vivo; this capacity is lost throughout passaging and can be monitored using a nude mouse model and associated molecular markers. This cartilage-forming ability in vivo may be pivotal for successful cell-based joint surface defect repair protocols.

Interleukin-10 and interleukin-10 receptor in human osteoarthritic and healthy chondrocytes.

OBJECTIVE: To evaluate the expression of interleukin-10 (IL-10) and interleukin-10 receptor (IL-10R) on chondrocytes from healthy, osteoarthritic, and foetal cartilage from human subjects. METHODS: Articular cartilage was obtained from 12 patients with osteoarthritis (OA) undergoing surgical knee replacement. Chondrocytes were isolated from the two zones of cartilage showing macroscopically and histologically the lowest (MIN) and highest (MAX) extent of osteoarthritic damage. Additional specimens of cartilage were obtained from 3 healthy donors and 3 human foetuses. IL-10 mRNA expression was determined by a reverse transcriptase-polymerase chain reaction (RT-PCR). For detection of intracellular IL-10 protein, chondrocytes were permeabilized and then incubated with R-phycoerythrin (PE) conjugated rat anti-human IL-10 mAb. Cell surface IL-10R was detected by incubation with biotinylated recombinant human IL-10; after washing, bound IL-10 was revealed by fluorescein (FITC) conjugated streptavidin. Positive chondrocytes were analysed by flowcytometry. RESULTS: IL-10 mRNA expression was higher in osteoarthritic than in normal chondrocytes. IL-10 protein intracellular levels were significantly higher in MAX than in MIN osteoarthritic cartilage or in healthy cartilage. Cell surface IL-10R was expressed on osteoarthritic chondrocytes with no difference in the degree of cartilage damage. The highest levels of IL-10 protein and IL-10R were found in foetal cartilage. CONCLUSION: Human chondrocytes synthesise IL-10 and express on their surface IL-10R. Since IL-10 inhibits IL-1 and TNF-alpha expression, its upregulation in osteoarthritic chondrocytes may counteract the detrimental effects of these catabolic cytokines. However, the functions of IL-10 in cartilage may go beyond those activities established in the immunological setting. The high levels of IL-10 and IL-10R in foetal cartilage, an active growing tissue, suggest that IL-10 may play a role in controlling chondrocyte metabolism under physiological conditions.

Human periosteum-derived cells maintain phenotypic stability and chondrogenic potential throughout expansion regardless of donor age.

OBJECTIVE: To assess the in vitro chondrogenic potential of adult human periosteum-derived cells (PDCs) with regard to the number of cell passages and the age of the donor. METHODS: Cells were enzymatically released from the periosteum of the proximal tibia obtained from adult human donors and expanded in monolayer. PDCs were harvested at multiple passages for total RNA extraction and semiquantitative reverse transcription-polymerase chain reaction (RT-PCR) gene expression analysis. For the chondrogenesis assay, cells were plated in micromass and treated with transforming growth factor beta1 (TGFbeta1) in a chemically defined medium. At different time points, micromasses were either harvested for RT-PCR analysis for cartilage and bone markers or fixed, paraffin-embedded, and stained for cartilage matrix, and immunostained for type II collagen. RESULTS: At the first 2 passages, human PDCs from young donors formed chondrogenic nodules. This spontaneous chondrogenic activity was lost upon passaging, and it was not observed in donors older than 30 years. Using a panel of marker genes, PDCs were shown to be phenotypically stable during cell expansion. Regardless of donor age or cell passage, chondrogenesis could be induced consistently by combining micromass culture and TGFbeta1 treatment. Histochemical and immunohistochemical analyses demonstrated the hyaline-like cartilage phenotype of the tissue generated in vitro. Other TGFbeta superfamily members, such as growth differentiation factor 5/cartilage-derived morphogenetic protein 1, and bone morphogenetic proteins 2, 4, and 7, were poorly chondrogenic under the same culture conditions. CONCLUSION: Adult human PDCs have the potential to differentiate toward the chondrocytic lineage in vitro, retaining this property even after extensive subculture. Human PDCs are easily accessible, expandable, and maintain their chondrogenic potential, and are therefore promising progenitor cells for use in the repair of joint surface defects.

Skeletal tissue engineering: opportunities and challenges.

Tissue engineering is a field of biomedicine that is growing rapidly and is critically driven by scientific advances in the areas of developmental and cell biology and biomaterial sciences. Regeneration of skeletal tissues is among the most promising areas of biological tissue repair and is providing a broad spectrum of potential clinical applications, including joint resurfacing. The availability of novel tools such as pluripotent stem cells, morphogens, smart biomaterials and gene transfer technologies, makes us dream of many exciting novel therapeutic approaches. Despite these opportunities in regenerative medicine, good clinical practice requires the clinician to question the consistency, reproducibility, validation and appropriate regulation of these new biological treatments.

Coexisting psoriatic arthritis, gout, and chondrocalcinosis.

The authors describe the case of a 63-year-old Caucasian man with a history of psoriatic arthritis who subsequently developed gout and chondrocalcinosis. This is the first report documenting the simultaneous occurrence of psoriatic arthritis, gout, and chondrocalcinosis in a single patient. The relations of these rheumatic diseases are discussed.