Bastiaansen-Jenniskens, Y.M.

A culture model to analyze the acute biomaterial-dependent reaction of human primary macrophages (Article)

2013-03-29T00:00:00Z

Macrophages are important in foreign body reactions. We devised a culture model with human primary macrophages to evaluate the acute response of macrophages to biomaterials. First we selected proteins representative for pro-inflammatory (M1) or anti-inflammatory/repair (M2) response of monocytes isolated from blood of healthy human donors by exposing them to LPS+IFNγ or IL-4. A relative M1/M2 index was calculated using IL-1β, IL-6, tumor necrosis factor (TNF)α, monocyte chemotactic protein (MCP)-3 and macrophage inflammatory protein (MIP)-1α as M1 markers, and IL-1 receptor antagonist (IL-1RA), CCL18, regulated and normal T-cell expressed and secreted (RANTES), and macrophage-derived chemokine (MDC) as M2 markers. Then monocytes were cultured for 3. days on 4 materials selected for known different foreign body reactions: Permacol™, Parietex™ Composite, multifilament polyethylene terephthalate and multifilament polypropylene. Macrophages on polypropylene produced high levels of anti-inflammatory proteins with a low M1/M2 index. Macrophages on Parietex™ Composite produced high levels of inflammatory and anti-inflammatory proteins, with a high M1/M2 index. Macrophages on polyethylene terephthalate also resulted in a high M1/M2 index. Macrophages on Permacol™ produced a low amount of all proteins, with a low M1/M2 index. This model with human primary macrophages and the panel of read-out parameters can be used to evaluate the acute reaction of macrophages to biomaterials in vitro to get more insight in the foreign body reaction.

Effects of new anti-adhesion polyvinyl alcohol gel on healing of colon anastomoses in rats (Article)

2012-12-01T00:00:00Z

Background: Adhesions follow abdominal surgery with an incidence as high as 95%, resulting in invalidating complications such as bowel obstruction, female infertility, and chronic pain. Searches have been performed for a safe and effective adhesion barrier; however, such barriers have impaired anastomotic site healing. The primary aim of this study was to investigate the effect of a new adhesion barrier, polyvinyl alcohol gel, on healing of colonic anastomoses using a rat model. Methods: Thirty-two Wistar rats were divided in two groups. In all animals, an anastomosis was constructed in the ascending colon. The first group received no adhesion barrier, whereas in the second group, 2mL of polyvinyl alcohol gel (A-Part Gel®; Aesculap AG, Tuttlingen, Germany) was applied circularly around the anastomosis. All animals were sacrificed on the seventh post-operative day, and the abdomen was inspected for signs of anastomotic leakage. The anastomotic bursting pressure, the adhesions around the anastomosis, and the collagen content of the excised anastomosis were measured. Results: No significant differences were observed between the two groups in the incidence of anastomotic leakage, the anastomotic bursting pressure (p=0.08), or the collagen concentration (p=0.91). No significant reduction in amount of adhesions was observed in the rats receiving polyvinyl alcohol gel. Conclusions: This experimental study showed no significant differences in anastomotic leakage, anastomotic bursting pressure, or collagen content of the anastomosis when using the adhesion barrier polyvinyl alcohol around colonic anastomoses. The barrier did not prevent adhesion formation.

Cytokine production by infrapatellar fat pad can be stimulated by interleukin 1β and inhibited by peroxisome proliferator activated receptor α agonist (Article)

2012-06-01T00:00:00Z

Background: Infrapatellar fat pad (IPFP) might be involved in osteoarthritis (OA) by production of cytokines. It was hypothesised that production of cytokines is sensitive to environmental conditions. Objectives: To evaluate cytokine production by IPFP in response to interleukin (IL)1β and investigate the ability to modulate this response with an agonist for peroxisome proliferator activated receptor α (PPARα), which is also activated by lipid-lowering drugs such as fi brates. Methods: Cytokine secretion of IPFP was analysed in the medium of explant cultures of 29 osteoarthritic patients. IPFP (fi ve donors) and synovium (six donors) were cultured with IL-1β and PPARα agonist Wy14643. Gene expression of IL-1β, monocyte chemoattractant protein (MCP1), (IL-6, tumour necrosis factor (TNF)α, leptin, vascular endothelial growth factor (VEGF), IL-10, prostaglandin-endoperoxide synthase (PTGS)2 and release of TNFα, MCP1 and prostaglandin E2were compared with unstimulated IPFP and synovium explants. Results: IPFP released large amounts of infl ammatory cytokines, adipokines and growth factors. IL-1β increased gene expression of PTGS2, TNFα, IL-1β, IL-6 and VEGF and increased TNFα release in IPFP. MCP1, leptin, IL-10 gene expression and MCP1, leptin and PGE2release did not increase signifi cantly. Synovium responded to IL-1βsimilarly to IPFP, except for VEGF gene expression. Wy14643 decreased gene expression of PTGS2, IL-1β, TNFα, MCP1, VEGF and leptin in IPFP explants and IL-1β, TNFα, IL-6, IL-10 and VEGF in synovium that responded to IL-1β. Conclusion: IPFP is an active tissue within the joint. IPFP cytokine production is increased by IL-1β and decreased by a PPARα agonist. The effects were similar to effects seen in synovium. Fibrates may represent a potential disease-modifying drug for OA by modulating infl ammatory properties of IPFP and synovium.

Statin use is associated with reduced incidence and progression of knee osteoarthritis in the Rotterdam study (Article)

2012-05-01T00:00:00Z

Background: Osteoarthritis is the most frequent chronic joint disease causing pain and disability. Besides biomechanical mechanisms, the pathogenesis of osteoarthritis may involve inflammation, vascular alterations and dysregulation of lipid metabolism. As statins are able to modulate many of these processes, this study examines whether statin use is associated with a decreased incidence and/or progression of osteoarthritis. Methods: Participants in a prospective population-based cohort study aged 55 years and older (n=2921) were included. x-Rays of the knee/hip were obtained at baseline and after on average 6.5 years, and scored using the Kellgren and Lawrence score for osteoarthritis. Any increase in score was defined as overall progression (incidence and progression). Data on covariables were collected at baseline. Information on statin use during follow-up was obtained from computerised pharmacy databases. The overall progression of osteoarthritis was compared between users and non-users of statins. Using a multivariate logistic regression model with generalised estimating equation, OR and 95% CI were calculated after adjusting for confounding variables. Results: Overall progression of knee and hip osteoarthritis occurred in 6.9% and 4.7% of cases, respectively. The adjusted OR for overall progression of knee osteoarthritis in statin users was 0.43 (95% CI 0.25 to 0.77, p=0.01). The use of statins was not associated with overall progression of hip osteoarthritis. Conclusions: Statin use is associated with more than a 50% reduction in overall progression of osteoarthritis of the knee, but not of the hip.

Infrapatellar fat pad of patients with end-stage osteoarthritis inhibits catabolic mediators in cartilage (Article)

2012-02-01T00:00:00Z

Objective: Adipose tissue is known to release inflammatory cytokines and growth factors. In this exploratory study, the authors examined whether the infrapatellar fat pad (IPFP) closely located to cartilage in the knee joint can affect cartilage metabolism. In addition, the authors analysed whether the macrophage types present in IPFP could explain the effect on cartilage. Methods: IPFP explants obtained during total knee replacement of 29 patients with osteoarthritis (OA) were used to make fat-conditioned medium (FCM). Explants of bovine cartilage were cultured with or without FCM. Nitric oxide (NO) and glycosaminoglycan release and gene expression of matrix-degrading enzymes in cartilage were analysed. To stimulate catabolic processes in the cartilage, the authors added interleukin 1β, and the effect of six FCMs was evaluated. The presence of different types of macrophages (CD68+, CD86+ and CD206+) in OA IPFPs was compared with subcutaneous adipose tissue samples and IPFP samples from patients with an anterior cruciate ligament rupture. Results: FCM alone reduced NO and glycosaminoglycan release and matrix metalloproteinase (MMP)1 gene expression by the cartilage. Moreover, when catabolic conditions were enhanced with interleukin 1β, FCM inhibited NO production as well as MMP1 and MMP3 gene expression and increased collagen type II gene expression. Significantly more CD206+ cells were present in OA IPFP samples than in subcutaneous fat or anterior cruciate ligament IPFP samples. Conclusion: In contrast to the authors' expectations, medium conditioned by end-stage OA IPFP inhibited catabolic processes in cartilage. CD206+ cells present in the IPFPs used for making the FCM might have contributed to the inhibition of catabolic processes in the cartilage.

Osteoarthritic synovial tissue inhibits proteoglycan production in human osteoarthritic cartilage (Article)

2011-07-01T00:00:00Z

Abstract. OBJECTIVE.: Although both cartilage and synovium are affected in osteoarthritis, no in vitro coculture models of human osteoarthritic tissues have been described. The aim of this study is to develop an in vitro model that includes both synovium and cartilage. METHODS.: Cartilage and synovium explants were cultured alone or in coculture for 21 days. Histology, LDH release, matrix metalloproteinase (MMP) activity, glycosaminoglycan (GAG) content, release and synthesis and cytokine production were used to evaluate synovial tissue functionality and its effect on cartilage metabolism. To assess the possibility of intervention in the model system, the effect of triamcinolone was studied. RESULTS.: Throughout the entire culture period, synovial tissue remained viable and produced cytokines. Monocultures of synovial and cartilage explants produced different cytokine subsets. Cytokine subsets in coculture were most similar to those previously described in osteoarthritis synovial fluid. MMP activity was only detectable in synovial explant monoculture and in coculture. Coculture with synovial tissue reduced final GAG content (P< 0.02) via inhibition of GAG production (P< 0.001) rather than through increase of GAG release. Addition of triamcinolone inhibited cytokine production, MMP activity in coculture and synovial tissue and counteracted the inhibition of GAG production induced by coculture. Triamcinolone in cartilage monoculture, however, reduced GAG production. CONCLUSION.: Synovium affects cartilage metabolism by reduction of GAG production. Triamcinolone relieved this inhibition, while being inhibitory when added to cartilage monoculture. These results clearly indicate the importance of tissue coculture, which may be a promising tool for studying osteoarthritis pathophysiology and evaluation of possible interventions.

Peroxisome proliferator activated receptor alpha activation decreases inflammatory and destructive responses in osteoarthritic cartilage (Article)

2011-07-01T00:00:00Z

Objective: Peroxisome proliferator activated receptor α (PPARα) agonists are used in clinical practice as lipid-lowering drugs and are also known to exert anti-inflammatory effects on various tissues. We hypothesized that PPARα activation leads to anti-inflammatory and anti-destructive effects in human OA cartilage. Methods: Cartilage explants obtained from six OA patients were cultured for 48h with 10ng/ml interleukin (IL)1β as a pro-inflammatory stimulus. 100μM Wy-14643, a potent and selective PPARα agonist, was added to the cultures and gene expression of matrix metalloproteinase (MMP)1, MMP3, MMP13, collagen type II (COL2A1), aggrecan and PPARα in cartilage explants and the release of glycosaminoglycans (GAGs), nitric oxide (NO) and prostaglandin E2(PGE2) in the culture media were analyzed and compared to the control without Wy-14643. Results: Addition of Wy-14643 decreased mRNA expression of MMP1, MMP3 and MMP13 in cartilage explants that responded to IL1β, whereas Wy-14643 did not affect gene expression of COL2A1 and aggrecan. Wy-14643 also decreased secretion of inflammatory marker NO in the culture medium of cartilage explants responding to IL1β. Wy-14643 inhibited the release of GAGs by cartilage explants in culture media. Conclusion: PPARα agonist Wy-14643 inhibited the inflammatory and destructive responses in human OA cartilage explants and did not have an effect on COL2A1 or aggrecan mRNA expression. These effects of PPARα agonists on osteoarthritic cartilage warrant further investigation of these drugs as a potential therapeutic strategy for osteoarthritis (OA).

The infrapatellar fat pad of patients with osteoarthritis has an inflammatory phenotype (Article)

2011-05-01T00:00:00Z

Objectives: Obesity is a risk factor for the development of osteoarthritis (OA) in hands and knees. Adipose tissue can secrete different adipokines with powerful immunomodulatory effects. The infrapatellar fat pad (IFP) is an intra-articular organ in the vicinity of the synovium and cartilage. It is hypothesised that IFP-derived soluble factors could contribute to pathological processes in the knee joint. A study was therefore undertaken to compare the release of inflammatory mediators in the IFP and subcutaneous adipose tissue (ScAT) and to characterise the adipocytes and immune cell infiltrate in these tissues. Methods: Paired IFP and ScAT samples were obtained from 27 patients with primary OA. The stromal vascular cell fraction (SVF) was isolated and characterised by fluorescence activated cell sorting. Cytokine and adipokine release in fat- and adipocyte-conditioned media was measured by luminex. Results: IFP secreted higher levels of inflammatory mediators such as interleukin 6 (IL-6), adipsin, adiponectin and visfatin than ScAT. This could be due to differences in the phenotype of adipocytes and/or in the composition and phenotype of the SVF cells. IFP adipocyte-conditioned media showed a trend towards more IL-6 and adipsin than ScAT. Moreover, the SVF fraction of IFP contained more cells/g tissue, a lower percentage of T cells and a higher percentage of mast cells than ScAT. In addition, T cells had a predominantly pro-inflammatory phenotype while macrophages had a mixed pro- and antiinflammatory phenotype in the IFP. Conclusion: There are profound differences in secreted inflammatory factors and immune cell composition between the IFP and ScAT. These data indicate that IFP-derived soluble mediators could contribute to pathophysiological processes in the OA knee joint.

The infrapatellar fat pad should be considered as an active osteoarthritic joint tissue: A narrative review (Article)

2010-07-01T00:00:00Z

Introduction: Osteoarthritis (OA) of the knee joint is caused by genetic and hormonal factors and by inflammation, in combination with biomechanical alterations. It is characterized by loss of articular cartilage, synovial inflammation and subchondral bone sclerosis. Considerable evidence indicates that the menisci, ligaments, periarticular muscles and the joint capsule are also involved in the OA process. This paper will outline the theoretical framework for investigating the infrapatellar fat pad (IPFP) as an additional joint tissue involved in the development and progression of knee-OA. Methods: A literature search was performed in Pubmed from 1948 until October 2009 with keywords InFrapatellar fat pad, Hoffa fat pad, intraarticular adipose tissue, knee, cartilage, bone, cytokine, adipokine, inflammation, growth factor, arthritis, and OA. Results: The IPFP is situated intracapsularly and extrasynovially in the knee joint. Besides adipocytes, the IPFP from patients with knee-OA contains macrophages, lymphocytes and granulocytes, which are able to contribute to the disease process of knee-OA. Furthermore, the IPFP contains nociceptive nerve fibers that could in part be responsible for anterior pain in knee-OA. These nerve fibers secrete substance P, which is able to induce inflammatory responses and cause vasodilation, which may lead to IPFP edema and extravasation of the immune cells.The IPFP secretes cytokines, interleukins, growth factors and adipokines that influence cartilage by upregulating the production of matrix metalloproteinases (MMPs), stimulating the expression of pro-inflammatory cytokines and inhibiting the production of cartilage matrix proteins. They may also stimulate the production of pro-inflammatory mediators, growth factors and MMPs in synovium. Conclusion: These data are consistent with the hypothesis that the IPFP is an osteoarthritic joint tissue capable of modulating inflammatory and destructive responses in knee-OA.

Elevated levels of cartilage oligomeric matrix protein during in vitro cartilage matrix generation decrease collagen fibril diameter (Article)

2010-07-01T00:00:00Z

Cartilage oligomeric matrix protein (COMP) is a protein present in the cartilage matrix and is expressed more abundantly in osteoarthritis cartilage than in healthy cartilage. The present study was designed to investigate the effect of transforming growth factor β (TGFβ) on COMP deposition and the influence of COMP on collagen biochemistry in a long-term 3-dimensional culture. Bovine chondrocytes in alginate beads were cultured with or without 25 ng/mL TGFβ2 for 21 or 35 days. COMP was overexpressed in bovine chondrocytes using lentiviral transfection. COMP gene expression, COMP protein production, collagen and proteoglycan deposition, and collagen fibril thickness were determined. Addition of TGFβ2 resulted in more COMP mRNA and protein than the control condition without growth factors. Lentiviral transduction with COMP resulted in elevated gene expression of COMP and increased COMP levels in the alginate bead and culture medium compared to untransfected cells. Overexpression of COMP did not affect the deposition of collagen, collagen cross-linking, proteoglycan deposition, or the mechanical properties. Stimulating COMP production by either TGFβ2 or lentivirus resulted in collagen fibrils with a smaller diameter. Taken together, COMP deposition can be modulated in cartilage matrix production by the addition of growth factors or by overexpression of COMP. Inducing COMP protein expression resulted in collagen fibrils with a smaller diameter. Because it has been demonstrated that the collagen fibril diameter is associated with mechanical functioning of the matrix, modulating COMP levels should be taken into account in cartilage regeneration strategies.

Combined role of type IX collagen and cartilage oligomeric matrix protein in cartilage matrix assembly: Cartilage oligomeric matrix protein counteracts type IX collagen-induced limitation of cartilage collagen fibril growth in mouse chondrocyte cultures (Article)

2009-12-01T00:00:00Z

Objective. Defects in the assembly and composition of cartilage extracellular matrix are likely to result in impaired matrix integrity and increased susceptibility to cartilage degeneration. The aim of this study was to determine the functional interaction of the collagen fibril-associated proteins type IX collagen and cartilage oligomeric matrix protein (COMP) during cartilage matrix formation. Methods. Primary chondrocytes from mice deficient in type IX collagen and COMP (double-deficient) were cultured in monolayer or alginate beads. Anchorage of matrix proteins, proteoglycan and collagen content, collagen crosslinks, matrix metalloproteinase activity, and mechanical properties of the matrix were measured. Electron microscopy was used to study the formation of fibrillar structures. Results. In cartilage lacking both type IX collagen and COMP, matrilin 3 showed decreased matrix anchorage. Less matrilin 3 was deposited in the matrix of double-deficient chondrocytes, while larger amounts were secreted into the medium. Proteoglycans were less well retained in the matrix formed in alginate cultures, while collagen deposition was not significantly affected. Electron microscopy revealed similar cartilage collagen fibril diameters in the cultures of double-deficient and wild-type chondrocytes. In contrast, a larger fibril diameter was observed in the matrix of chondrocytes deficient in only type IX collagen. Conclusion. Our results show that type IX collagen and COMP are involved in matrix assembly by mediating the anchorage and regulating the distribution of other matrix macromolecules such as proteoglycans and matrilins and have counteracting effects on collagen fibril growth. Loss of type IX collagen and COMP leads to matrix aberrations that may make cartilage more susceptible to degeneration.

A Novel Approach to Stimulate Cartilage Repair: Targeting Collagen Turnover (Doctoral Thesis)

2009-06-04T00:00:00Z

OA is a complex disease of which the ethiopathology is not completely known and therapies to repair cartilage are still under investigation. The increase of collagen type II expression in osteoarthritic cartilage suggests an activated repair mechanism that is however ineffective in repairing or maintaining the ECM homeostasis. We therefore investigated the ability to modulate the formation of a functional collagen type II network that can ultimately contribute to innovation of cartilage repair in OA. To do so we used different approaches: addition of growth factors, inhibition of collagen cross-links, inhibition of proteoglycan formation, overexpression of cartilage oligomeric matrix protein (COMP) and knock-down of COMP and collagen IX, Of the growth factors used in this thesis, IGF1 had positive effects on the parameters in our chondrocyte alginate cultures. It stimulated chondrocytes to deposit more collagen and proteoglycans without affecting collagen cross-linking, it increased mechanical functioning and decreased MMP-1 gene expression. FGF2 on the other hand had no positive effects in our culture system: It lowered the collagen deposition and did not affect the proteoglycan deposition. The effect TGFb had on chondrocytes in culture was more complex. Addition of TGFb to chondrocytes in alginate had no large effect on proteoglycan and collagen deposition but did lower the number of cross-links per collagen molecule and reduced the fibril thickness. The effect of TGF-beta appeared to depend on the physical environment of the cell as concluded from our comparison between chondrocytes cultured in monolayer on plastic or in alginate beads. We inhibited crosslink formation by addition of beta-aminopropionitrile (BAPN), which inhibits one of the key enzymes for crosslink formation, lysyloxidase, via covalent binding. As a result, the chondrocyte produced more collagen (as shown by increased collagen type II gene expression) and also more collagen was deposited. Furthermore we were also interested in the effect of other extracellular matrix components on collagen network formation. Addition of FGF2 decreased and addition of TGF-beta increased COMP deposition. We overexpressed COMP in chondrocytes and found no effect on matrix deposition. However, COMP overexpression also resulted in collagen fibrils with a smaller diameter, like we saw after addition of TGFb. By inhibiting the formation of a proteoglycan network using para-nitrophenyl-beta-D-xyloside (PNPX) and therefore proteoglycan deposition, collagen deposition was decreased. The absence of an intact proteoglycan network lowered the collagen retention in our culture system. Cultures of collagen type IX deficient chondrocytes also had altered collagen retention. Since collagen type IX forms a network together with collagen type II and other matrix molecules, the absence of this network probably also reduced collagen retention in the alginate bead. However, GAG distribution was also altered when collagen type IX was absent in the newly formed matrix. Which in turn could also have contributed to altered collagen retention. Interestingly, the absence of COMP in addition to collagen type IX deficiency did not alter matrix production and distribution. This leads to the conclusion that collagen type IX is more important in the matrix interaction than COMP. Taken together, it seems that for the production of collagen in cartilage, focussing on the formation of an intact cartilage network is as important as stimulating collagen type II production. This network formation is important to retain the collagen type II in the newly formed matrix. Growth factors can influence collagen network formation, either directly or via their effect on other extracellular matrix components.

Cartilage repair: past and future – lessons for regenerative medicine (Article)

2009-05-01T00:00:00Z

Since the first cell therapeutic study to repair articular cartilage defects in the knee in 1994, several clinical studies have been reported. An overview of the results of clinical studies did not conclusively show improvement over conventional methods, mainly because few studies reach level I of evidence for effects on middle or long term. However, these explorative trials have provided valuable information about study design, mechanisms of repair and clinical outcome and have revealed that much is still unknown and further improvements are required. Furthermore, cellular and molecular studies using new technologies such as cell tracking, gene arrays and proteomics have provided more insight in the cell biology and mechanisms of joint surface regeneration. Besides articular cartilage, cartilage of other anatomical locations as well as progenitor cells are now considered as alternative cell sources. Growth Factor research has revealed some information on optimal conditions to support cartilage repair. Thus, there is hope for improvement. In order to obtain more robust and reproducible results, more detailed information is needed on many aspects including the fate of the cells, choice of cell type and culture parameters. As for the clinical aspects, it becomes clear that careful selection of patient groups is an important input parameter that should be optimized for each application. In addition, the study outcome parameters should be improved. Although reduced pain and improved function are, from the patient’s perspective, the most important outcomes, there is a need for more structure/tissuerelated outcome measures. Ideally, criteria and/or markers to identify patients at risk and responders to treatment are the ultimate goal for these more sophisticated regenerative approaches in joint surface repair in particular, and regenerative medicine in general.

Inhibition of glycosaminoglycan incorporation influences collagen network formation during cartilage matrix production (Article)

2009-02-06T00:00:00Z

To understand cartilage degenerative diseases and improve repair procedures, we investigate the influence of glycosaminoglycans (GAGs) on cartilage matrix biochemistry and functionality. Bovine articular chondrocytes were cultured in alginate beads with(out) para-nitrophenyl-beta-d-xyloside (PNPX) to inhibit GAG incorporation into newly formed proteoglycans. As expected, GAG deposition in alginate beads decreased with increasing PNPX concentration. Next to GAGs, collagen deposition and cross-linking also decreased. In the presence of PNPX, GAGs and collagen were deposited further away from the chondrocyte than in the control and increased amounts were found in the culture medium. These changes resulted in decreased functional properties of the construct. We conclude that in our culture system, intact proteoglycans play a role in deposition of collagen and thus the formation of a functional matrix. The effect of less proteoglycans on the collagen network could explain why cartilage repair is ineffective in osteoarthritis and help us with development of new therapies.

Proteoglycan production is required in initial stages of new cartilage matrix formation but inhibits integrative cartilage repair (Article)

2009-02-01T00:00:00Z

The optimal stimulus to repair or regenerate cartilage is not known. We therefore modulated collagen deposition, collagen crosslinking and GAG deposition simultaneously during cartilage matrix production and integrative repair, creating more insight into their role in cartilage repair processes. Insulin-like growth factor 1 (IGF-1; increases proteoglycan and collagen synthesis), beta-aminopropionitrile (BAPN; a reversible inhibitor of collagen crosslinking) and para-nitrophenyl-beta-D-xyloside (PNPX; interferes with proteoglycan production) were used. Bovine articular chondrocytes were cultured in alginate beads for 3 weeks with or without IGF-1, BAPN or PNPX alone and in all possible combinations, followed by 3 weeks in control medium. DNA content, GAG and collagen deposition and collagen crosslinks were determined. Cartilage constructs were cultured under the same conditions and histologically analysed for integration of two opposing cartilage matrices. In alginate cultures, inhibition of collagen crosslinking with BAPN, in combination with promotion of matrix synthesis using IGF1, was most beneficial for matrix deposition. Addition of PNPX was always detrimental for matrix deposition. For integration of opposing cartilage constructs, the combination of BAPN, IGF1 and temporary prevention of proteoglycan formation with PNPX was most beneficial. When a new matrix is produced, proteoglycans are important to retain collagen in the matrix. When two already formed cartilage matrices have to integrate, a temporary absence of proteoglycans and temporary inhibition of collagen crosslinking might be more beneficial in combination with stimulation of collagen production, e.g. by IGF1. Therefore, the choice of soluble factors to promote cartilage regeneration depends on the type of therapy that will be used.

TGFbeta affects collagen cross-linking independent of chondrocyte phenotype but strongly depending on physical environment (Article)

2008-06-01T00:00:00Z

Transforming growth factor beta (TGFbeta) is often used in cartilage tissue engineering to increase matrix formation by cells with various phenotypes. However, adverse effects of TGFbeta, such as extensive crosslinking in cultured fibroblasts, have also been reported. Our goal was to study effects of TGFbeta on collagen cross-linking and evaluating the role of cellular phenotype and physical environment. We therefore used four different cell populations in two very different physical environments: primary and expanded chondrocytes and fibroblasts embedded in alginate gel and attached to tissue culture plastic. Matrix production, collagen cross-linking, and alpha-smooth muscle actin (alphaSMA) were analyzed during 4 weeks with or without 2.5 ng/ mL TGFbeta2. TGFbeta2 did not affect collagen deposition by primary cells. In expanded cells, TGFbeta2 increased collagen deposition. Chondrocytes and fibroblasts in monolayer produced more collagen cross-links with TGFbeta2. In alginate, primary and expanded cells displayed an unexpected decrease in collagen cross-linking with TGFbeta2. alphaSMA was not present in alginate cultures and barely upregulated by TGFbeta2. Organized alphaSMA fibers were present in all monolayer cultures and became more pronounced with TGFbeta2. This study demonstrates that the physical environment determined by the substrate used co-determines the response of cells to TGFbeta. The presence of mechanical stress, determined with alphaSMA-staining, is probably responsible for the increase in collagen cross-linking upon addition of TGFbeta.

Contribution of collagen network features to functional properties of engineered cartilage (Article)

2008-03-01T00:00:00Z

BACKGROUND: Damage to articular cartilage is one of the features of osteoarthritis (OA). Cartilage damage is characterised by a net loss of collagen and proteoglycans. The collagen network is considered highly important for cartilage function but little is known about processes that control composition and function of the cartilage collagen network in cartilage tissue engineering. Therefore, our aim was to study the contribution of collagen amount and number of crosslinks on the functionality of newly formed matrix during cartilage repair. METHODS: Bovine articular chondrocytes were cultured in alginate beads. Collagen network formation was modulated using the crosslink inhibitor beta-aminopropionitrile (BAPN; 0.25mM). Constructs were cultured for 10 weeks with/without BAPN or for 5 weeks with BAPN followed by 5 weeks without. Collagen deposition, number of crosslinks and susceptibility to degradation by matrix metalloproteinase-1 (MMP-1) were examined. Mechanical properties of the constructs were determined by unconfined compression. RESULTS: BAPN for 5 weeks increased collagen deposition accompanied by increased construct stiffness, despite the absence of crosslinks. BAPN for 10 weeks further increased collagen amounts. Absence of collagen crosslinks did not affect stiffness but ability to hold water was lower and susceptibility to MMP-mediated degradation was increased. Removal of BAPN after 5 weeks increased collagen amounts, allowed crosslink formation and increased stiffness. DISCUSSION: This study demonstrates that both collagen amounts and its proper crosslinking are important for a functional cartilage matrix. Even in conditions with elevated collagen deposition, crosslinks are needed to provide matrix stiffness. Crosslinks also contribute to the ability to hold water and to the resistance against degradation by MMP-1

Biochemical and functional modulation of the cartilage collagen network by IGF1, TGFbeta2 and FGF2 (Article)

2006-11-01T00:00:00Z

OBJECTIVE: Examine effects of insulin-like growth factor 1 (IGF1), transforming growth factor beta2 (TGFbeta2) and fibroblast growth factor 2 (FGF2) on proteoglycan and collagen network and biomechanical properties of the newly formed cartilage matrix. METHODS: Bovine articular chondrocytes were cultured in alginate beads for 3 weeks with or without FGF2, TGFbeta2 or IGF1 in the presence of 10% FCS. Proteoglycan content, collagen content, hydroxylysylpyridinoline cross-links and overall matrix metalloproteinase (MMP) activity in the culture medium were measured. Alginate disks cultured for 5 weeks were used to evaluate the effect of growth factors on mechanical properties of the construct by determining the equilibrium aggregate modulus and secant modulus. RESULTS: IGF1 increased collagen and proteoglycan deposition. FGF2 mainly decreased collagen deposition and TGFbeta2 proteoglycan deposition. A decrease in cross-links was observed in matrix produced by chondrocytes cultured in the presence of TGFbeta2. IGF1 and FGF2 had no influence on the number of cross-links per collagen molecule. Overall MMP activity was significantly higher in culture medium of cells cultured with FGF2. TGFbeta2 and IGF1 had no effect on MMP activity. After 35 days of culture, the matrix produced under influence of IGF1 had a lower permeability and a trend to increase stiffness. FGF2 showed a trend to lower both properties. TGFbeta2 had no effect on these parameters. CONCLUSION: IGF1, TGFbeta2 and FGF2 had differential effects on collagen network formation. Of the three growth factors tested, IGF1 seems to be best in promoting the formation of a functional collagen network since it increased proteoglycan and collagen deposition and improved the mechanical properties.

Glucosamine decreases expression of anabolic and catabolic genes in human osteoarthritic cartilage explants (Article)

2006-03-01T00:00:00Z

OBJECTIVE: To investigate the effect of glucosamine (GlcN) in a human osteoarthritic explant model on expression of genes involved in anabolic and catabolic activities of chondrocytes. METHODS: Human osteoarthritic explants, obtained during knee arthroplasty surgery, were pre-cultured (3 days) and treated with glucosamine-hydrochloride (GlcN-HCl) or glucosamine-3-sulphate (GlcN-S) at 0.5mM and 5mM (4 days). RNA was isolated from the explants and real time RT-PCR was performed. Additionally, total matrix metalloproteinase (MMP) activity was measured in culture medium. RESULTS: Addition of 5mM GlcN led to significant down-regulation of aggrecan (2.65-7.73-fold) and collagen type II (7.75-22.17-fold) gene expression, indicating inhibited anabolic activity. Considering catabolic activities, 5mM GlcN significantly down-regulated aggrecanase-1 and MMP3 and 5mM GlcN-S additionally down-regulated aggrecanase-2 and tissue inhibitor of MMP gene expression significantly. Gene expression was not significantly altered by 0.5mM GlcN. Total MMP activity in culture medium was only significantly reduced after addition of 5mM GlcN-HCl. CONCLUSION: The effects of GlcN on gene expression in a human osteoarthritic explant model suggest that enzymatic breakdown of the extra-cellular matrix might be reduced by the addition of 5mM GlcN. Additionally, restoration of already damaged cartilage is not to be expected, because gene expression of anabolic genes is also down-regulated. We suggest that chondroprotective properties of GlcN in vivo may be based on inhibiting further degradation due to catabolic activities, rather than on the ability to rebuild cartilage.