POS0404 VOLUNTARY WHEEL RUNNING MODEL IN MICE TO MECHANICALLY STIMULATE THE ENTHESIS OF THE ACHILLES TENDON

Background:

Excessive bone formation in the entheses is one of the features of peripheral spondyloarthritis. Biomechanical stress is proposed to occupy a central place in spondyloarthritis pathophysiology, but the precise molecular and cellular mechanisms underlying the pathological response of the enthesis are still largely unknown [1]. Besides, physical therapy and exercise are recommended as non-pharmacologic therapies for patients. We focused on the effect of exercising on enthesis ossification.

Objectives:

We aimed to develop and characterize an in vivo model in mice to study the impact of mechanical stimulation on the enthesis of the Achilles tendon.

Methods:

DBA/1 mice were subjected to voluntary running exercise by the use of activity wheels for two weeks, and compared to mice housed in standard conditions (n=17 per group). The running performances were recorded. mRNAs were extracted from the long bones (flushed tibia and femur) and the ankles’ entheses for real-time PCR analysis. µCT was performed on the femurs. Alkaline phosphatase activity was detected by histology on the anchorage of the Achilles tendon to the calcaneum, and by enzymatic assay in serum samples. Luminex analysis was also conducted on serum samples for Il-6 and Il-8/Kc detection.

Results:

Free access to the activity wheel resulted in a running exercise of 5.5±0.8 km/day (approximately 80 km in total) at 14.5±0.5 m/min. No effect was detected on the femur architecture by µCT. Sclerostin (Sost) gene expression was monitored as a mechanosensitive marker. Its expression was expectedly reduced by half in entheseal tissues, but no modulation was observed in long bones (Figure 1). Similarly, exercise-induced regulation of Osterix and Runx2 expressions was observed only in enthesis samples. This tissue-specific pattern was also verified for key genes of the sphingosine-1 phosphate metabolic pathway, which we recently implicated in spondyloarthritis pathophysiology [2]. The in situ staining of alkaline phosphatase activity suggested the presence of more positive cells in the anchorage of Achilles tendon of running mice, compared to control ones. However, alkaline phosphatase activity in serum samples and its gene expression in rough tissue extracts were unchanged. No inflammatory response was detected as Il-8/Kc serum levels were similar in the control and the exercising group (59±14 vs 57±14 pg/mL). In addition, Il-6 was not detected in the serum and its expression was very faint and constant in the tissue extracts.

Conclusion:

This work is still in progress for a more complete characterization of the model. We believe that this experimental design will be useful to study the role of mechanical stimulation specifically in the enthesis and that it can help to better understand the spondyloarthritis pathophysiology.

References:

[1]Cambré, et al. Nat Commun, 2018; [2] El Jamal, et al. J Bone Miner Res, 2019

Figure 1.

Expression level of the mechanosensitive gene Sclerostin (Sost). It dropped in response to exercise in entheseal tissues, but not in long bones, revealing a tissue-specific response to mechanical stimulation.

Acknowledgements:

Société Arthritis R&D (2020)

Disclosure of Interests:

None declared

Tissue-nonspecific alkaline phosphatase is an anti-inflammatory nucleotidase

Tissue-nonspecific alkaline phosphatase (TNAP) is necessary for skeletal mineralization by its ability to hydrolyze the mineralization inhibitor inorganic pyrophosphate (PP_i), which is mainly generated from extracellular ATP by ectonucleotide pyrophosphatase phosphodiesterase 1 (NPP1). Since children with TNAP deficiency develop bone metaphyseal auto-inflammations in addition to rickets, we hypothesized that TNAP also exerts anti-inflammatory effects relying on the hydrolysis of pro-inflammatory adenosine nucleotides into the anti-inflammatory adenosine. We explored this hypothesis in bone metaphyses of 7-day-old Alpl^+/- mice (encoding TNAP), in mineralizing hypertrophic chondrocytes and osteoblasts, and non-mineralizing mesenchymal stem cells (MSCs) and neutrophils, which express TNAP and are present, or can be recruited in the metaphysis. Bone metaphyses of 7-day-old Alpl^+/- mice had significantly increased levels of Il-1β and Il-6 and decreased levels of the anti-inflammatory Il-10 cytokine as compared with Alpl^+/+ mice. In bone metaphyses, murine hypertrophic chondrocytes and osteoblasts, Alpl mRNA levels were much higher than those of the adenosine nucleotidases Npp1, Cd39 and Cd73. In hypertrophic chondrocytes, inhibition of TNAP with 25 μM of MLS-0038949 decreased the hydrolysis of AMP and ATP. However, TNAP inhibition did not significantly modulate ATP- and adenosine-associated effects in these cells. We observed that part of TNAP proteins in hypertrophic chondrocytes was sent from the cell membrane to matrix vesicles, which may explain why TNAP participated in the hydrolysis of ATP but did not significantly modulate its autocrine pro-inflammatory effects. In MSCs, TNAP did not participate in ATP hydrolysis nor in secretion of inflammatory mediators. In contrast, in neutrophils, TNAP inhibition with MLS-0038949 significantly exacerbated ATP-associated activation and secretion of IL-1β, and extended cell survival. Collectively, these results demonstrate that TNAP is a nucleotidase in both hypertrophic chondrocytes and neutrophils, and that this nucleotidase function is associated with autocrine effects on inflammation only in neutrophils.

Imported malaria in pregnant women: report from a French University Centre

OBJECTIVE

To describe malaria during pregnancy outside endemic areas.

MATERIALS AND METHODS

We retrospectively reviewed all cases of imported malaria during pregnancy, diagnosed over a 11-year period in a French hospital.

RESULTS AND CONCLUSION

We recovered 18 cases, all from sub-Saharan countries. The infection could appear distantly from arrival in France (up to 36 months), was asymptomatic in 3 cases, with anemia being the most common marker of infection (n = 14). The adverse consequences for the fetus (n = 3) or the newborn (n = 4) were frequent. Physicians should be aware of these atypical presentations in order to anticipate the diagnosis and improve the maternal and fetal prognosis.

What understanding tendon cell differentiation can teach us about pathological tendon ossification

Tendons are the structures that attach muscles to bones and transmit mechanical forces. Tendon cells are composed of mature tenocytes and a rare population of tendon stem cells. Both cell types ensure homeostasis and repair of tendon extracellular matrix to guarantee its specific mechanical properties. Moreover, tendon cells seem to present a marked potential for trans-differentiation, predominantly into the chondrocyte and osteoblast lineages. In this review article, we first present chronic tendon pathologies associated with abnormal ossification, such as spondyloarthritis and calcifying tendinopathy, and discuss how tendon cell differentiation and trans-differentiation may participate in these diseases. We moreover present the factors known to influence tendon cell differentiation and trans-differentiation, with a particular emphasis on extracellular environment, mechanical stimulation and several soluble factors that can tip the balance toward one or another lineage. A better understanding of the neglected tendon cell biology may be extremely useful to understand the pathological mechanisms of spondyloarthritis and calcifying tendinopathy.

Inflammation: a culprit for vascular calcification in atherosclerosis and diabetes

It is today acknowledged that aging is associated with a low-grade chronic inflammatory status, and that inflammation exacerbates age-related diseases such as osteoporosis, Alzheimer's disease, atherosclerosis and type 2 diabetes mellitus (T2DM). Vascular calcification is a complication that also occurs during aging, in particular in association with atherosclerosis and T2DM. Recent studies provided compelling evidence that vascular calcification is associated with inflammatory status and is enhanced by inflammatory cytokines. In the present review, we propose on one hand to highlight the most important and recent findings on the cellular and molecular mechanisms of vascular inflammation in atherosclerosis and T2DM. On the other hand, we will present the effects of inflammatory mediators on the trans-differentiation of vascular smooth muscle cell and on the deposition of crystals. Since vascular calcification significantly impacts morbidity and mortality in affected individuals, a better understanding of its induction and development will pave the way to develop new therapeutic strategies.

Autocrine stimulation of osteoblast activity by Wnt5a in response to TNF-α in human mesenchymal stem cells

Although anti-tumor necrosis factor (TNF)-α treatments efficiently block inflammation in ankylosing spondylitis (AS), they are inefficient to prevent excessive bone formation. In AS, ossification seems more prone to develop in sites where inflammation has resolved following anti-TNF therapy, suggesting that TNF-α indirectly stimulates ossification. In this context, our objectives were to determine and compare the involvement of Wnt proteins, which are potent growth factors of bone formation, in the effects of TNF-α on osteoblast function. In human mesenchymal stem cells (MSCs), TNF-α significantly increased the levels of Wnt10b and Wnt5a. Associated with this effect, TNF-α stimulated tissue-non specific alkaline phosphatase (TNAP) and mineralization. This effect was mimicked by activation of the canonical β-catenin pathway with either anti-Dkk1 antibodies, lithium chloride (LiCl) or SB216763. TNF-α reduced, and activation of β-catenin had little effect on expression of osteocalcin, a late marker of osteoblast differentiation. Surprisingly, TNF-α failed to stabilize β-catenin and Dkk1 did not inhibit TNF-α effects. In fact, Dkk1 expression was also enhanced in response to TNF-α, perhaps explaining why canonical signaling by Wnt10b was not activated by TNF-α. However, we found that Wnt5a also stimulated TNAP in MSCs cultured in osteogenic conditions, and increased the levels of inflammatory markers such as COX-2. Interestingly, treatment with anti-Wnt5a antibodies reduced endogenous TNAP expression and activity. Collectively, these data suggest that increased levels of Dkk1 may blunt the autocrine effects of Wnt10b, but not that of Wnt5a, acting through non-canonical signaling. Thus, Wnt5a may be potentially involved in the effects of inflammation on bone formation.

[Malaria among immigrants, experience of a Parisian hospital (2006-2010)]

In recent days immigrants represent the main risk group for imported malaria in northern countries. Most of them are migrants returning to their country of origin to visit friends and relatives (VFR). We retrospectively examined the main clinical, biological, and therapeutic data of all malaria cases in immigrants from 2006 to 2010 in Tenon hospital, Paris. The hospital is situated in a Paris district with an important African community. During the study period 239 imported malaria cases were observed in adults of which 199 were immigrants, 186 VFR, and 13 recently arrived. Most cases were from sub-Saharan Africa and Comoro islands. Chimioprophylaxis was not taken in 81.2% of VFR. It was inadequate in 43.7% and not taken correctly in 84.4%. Plasmodium falciparum was the most frequent species identified: 190/199 (95.5%). Severe P. falciparum malaria was observed in 25 cases (13.2%); two of them were recently arrived. One patient, African VFR, died. In this series two high-risk groups were represented: HIV-infected patients and pregnant women. Six of the HIV patients had severe malaria and all pregnant women had anemia. Our results are similar to those observed recently in other European countries. Mean age of VFR is increasing and the risk for severe P. falciparum malaria became identical to the one observed in non-immune travelers. Protection measures remain still insufficient in this population of travelers.

TNF-α stimulates alkaline phosphatase and mineralization through PPARγ inhibition in human osteoblasts

The aims of the present study were to determine whether prostaglandins (PGs) and PPARγ are involved in the stimulation of tissue-non-specific alkaline phosphatase (TNAP) activity and mineralization by TNF-α in human osteoblasts. We used osteoblasts differentiated from MSCs from three different donors and MG-63 osteoblast-like cells. Inhibition of prostaglandin synthesis with the cyclooxygenase (COX) inhibitor indomethacin or the specific COX-2 blocker NS-398 abolished mineralization in the absence and presence of 1 ng/ml of TNF-α, suggesting that PGs were involved. The TNAP inhibitor levamisole abolished TNF-α effects on mineralization, suggesting that PGs were involved in TNAP expression and mineralization. TNF-α stimulated expression of COX-2 and PG E synthase before that of TNAP, but expression of PG D synthase later suggesting that PGE₂ and PGF₂α but not 15d-PGJ₂ were involved in TNF-α effects. However, both PGE₂ and PGF₂α dose-dependently inhibited mineralization indicating that endogenous PG are required for mineralization but that TNF-α does not increase mineralization by increasing PG synthesis. Interestingly, TNF-α inhibited PPARγ expression and binding activity to PPRE consensus sequences independently of 15d-PGJ₂. Inhibition of PPARγ activity with GW-9662 mimicked TNF-α effects in MG-63 cells, indicating that TNF-α stimulates mineralization by inhibiting PPARγ in osteoblasts. In MSC-derived osteoblast cultures, inhibition of PPARγ dropped TNAP expression and mineralization. Treatment of MG-63 cells with conditioned media from MSC-derived osteoblasts or MSC-derived adipocytes treated or not with GW-9662 revealed that TNF-α inhibition of PPARγ in undifferentiated MSCs and/or adipocytes was responsible for the decreased expression of TNAP in osteoblasts. In conclusion, TNF-α increases TNAP expression and stimulates mineralization by inhibiting PPARγ in osteoblasts, but PPARγ in adipocytes or undifferentiated MSCs controls the secretion of a factor leading to TNAP stimulation in osteoblasts.

Pneumocystosis: a network survey in the Paris area 2003-2008

The aims of this network group were to collect epidemiological data of PcP cases in 14 hospitals in the Paris area and to determine the Di-Hydro Pteroate Synthase (DHPS) genotypes, genetic markers for possible sulfamide resistance. From January 1, 2003 to December 31, 2008, 993 (mean 166/year) PcP cases have been reported. Sixty-five percent of patients were HIV-positive. The median count of CD4 lymphocytes was 32/mm(3) (30 in HIV-positive patients, 152 in HIV-negative patients). In HIV-positive patients, PcP revealed the HIV infection in 39%. Among 304 PcP occurring in HIV known infected patients, no prophylaxis was prescribed for 64%; cotrimoxazole prophylaxis had been prescribed to 47 patients but only one of them had the right compliance. In HIV-negative patients (264), corticosteroids were prescribed in 59% and cytotoxic chemotherapies in 34%; 78% did not receive prophylaxis. One hundred sixty nine tumoral pathologies and 116 transplantations were notified. The mortality rate was 16% at day 14 (13% in HIV-positive patients, 26% in HIV-negative patients). Mutations in DHPS genes were detected in 18.5% of samples; 12.5% of patients were infected with several strains. The total annual number of cases has been stable for five years but the proportion of HIV-negative patients increased from 25% to 43%.

IL-33 is expressed in human osteoblasts, but has no direct effect on bone remodeling

The aim of the present study was to investigate the potential role of the recently discovered IL-1 family member IL-33 in bone remodeling. Our results indicate that IL-33 mRNA is expressed in osteocytes in non-inflammatory human bone. Moreover, IL-33 levels are increased by TNF-α and IL-1β in human bone marrow stromal cells, osteoblasts and adipocytes obtained from three healthy donors. Experiments with the inhibitor GW-9662 suggested that expression of IL-33, in contrast to that of IL-1β, is not repressed by PPARγ likely explaining why IL-33, but not IL-1β, is expressed in adipocytes. The IL-33 receptor ST2L is not constitutively expressed in human bone marrow stromal cells, osteoblasts or CD14-positive monocytes, and IL-33 has no effect on these cells. In addition, although ST2L mRNA is induced by TNF-α and IL-1β in bone marrow stromal cells, IL-33 has the same effects as TNF-α and IL-1β, and, therefore, the biological activity of IL-33 may be redundant in this system. In agreement with this hypothesis, MC3T3-E1 osteoblast-like cells constitutively express ST2L mRNA, and IL-33 and TNF-α/IL-1β similarly decrease osteocalcin RNA levels in these cells. In conclusion, our results suggest that IL-33 has no direct effects on normal bone remodeling.

Do cytokines induce vascular calcification by the mere stimulation of TNAP activity?

Vascular calcification occurs during aging in the general population and is increased in the intima by atherosclerosis and in the media by diabetes type 2. In both intima and media, calcification may lead to the formation of a tissue very similar if not identical to bone, with bone cells and bone marrow. Since vascular calcification is associated with cardiovascular complications, a better understanding of the inducing mechanisms could lead to the development of new therapeutic strategies. Many studies have provided evidence for a role of inflammation and inflammatory cytokines such as tumour necrosis factor (TNF)-α and interleukin (IL)-1β in the vascular calcification process. TNF-α and IL-1β have indeed been shown to stimulate in vitro the expression by vascular smooth muscle cells (VSMCs) of tissue-non specific alkaline phosphatase (TNAP), a key enzyme in the mineralization process, and to trigger the trans-differentiation of VSMCs into osteoblast-like cells, expressing the master transcription factor RUNX2. These data are however somewhat contradictory with the known inhibitory effects of inflammatory cytokines on bone formation. TNF-α for instance dramatically decreases RUNX2 RNA expression, protein stability and activity, and as a consequence, is a potent inhibitor of osteoblast differentiation and bone formation. In the present article, we propose a new hypothesis to explain this calcification paradox. We propose that cytokines block bone formation by decreasing RUNX2-mediated type I collagen production in osteoblasts, whereas they induce vascular ossification by the mere stimulation of TNAP by VSMCs, independently of RUNX2. We propose that this stimulation of TNAP in VSMCs in vitro and in vivo may be sufficient to induce the calcification of collagen fibrils, and that the absence of crystal clearance, in turn, induces the differentiation of VSMCs and/or mesenchymal stem cells into bone-forming cells, eventually leading to formation of a bone-like tissue. In case future experimental studies support this hypothesis, the early stimulatory and late inhibitory effects of inflammation on vascular calcification will have to be taken into consideration in the development of new therapeutic strategies.

TNF-alpha and IL-1beta inhibit RUNX2 and collagen expression but increase alkaline phosphatase activity and mineralization in human mesenchymal stem cells

AIMS

Joint inflammation leads to bone erosion in rheumatoid arthritis (RA), whereas it induces new bone formation in spondyloarthropathies (SpAs). Our aims were to clarify the effects of tumour necrosis factor alpha (TNF-alpha) and interleukin 1beta (IL-1beta) on osteoblast differentiation and mineralization in human mesenchymal stem cells (MSCs).

MAIN METHODS

In MSCs, expression of osteoblast markers was assessed by real-time PCR and ELISA. Activity of tissue-nonspecific alkaline phosphatase (TNAP) and mineralization were determined by the method of Lowry and alizarin red staining respectively. Involvement of RUNX2 in cytokine effects was investigated in osteoblast-like cells transfected with a dominant negative construct.

KEY FINDINGS

TNF-alpha (from 0.1 to 10 ng/ml) and IL-1beta (from 0.1 to 1 ng/ml) stimulated TNAP activity and mineralization in MSCs. Addition of 50 ng/ml of IL-1 receptor antagonist in TNF-alpha-treated cultures did not reverse TNF-alpha effects, indicating that IL-1 was not involved in TNF-alpha-stimulated TNAP activity. Both TNF-alpha and IL-1beta decreased RUNX2 expression and osteocalcin secretion, suggesting that RUNX2 was not involved in mineralization. This hypothesis was confirmed in osteoblast-like cells expressing a dominant negative RUNX2, in which TNAP expression and activity were not reduced. Finally, since mineralization may merely rely on increased TNAP activity in a collagen-rich tissue, we investigated cytokine effects on collagen expression, and observed that cytokines decreased collagen expression in osteoblasts from MSC cultures.

SIGNIFICANCE

The different effects of cytokines on TNAP activity and collagen expression may therefore help explain why inflammation decreases bone formation in RA whereas it induces ectopic ossification from collagen-rich entheses during SpAs.

Engineering cartilage with human nasal chondrocytes and a silanized hydroxypropyl methylcellulose hydrogel

Tissue engineering strategies, based on developing three-dimensional scaffolds capable of transferring autologous chondrogenic cells, holds promise for the restoration of damaged cartilage. In this study, the authors aimed at determining whether a recently developed silanized hydroxypropyl methylcellulose (Si-HPMC) hydrogel can be a suitable scaffold for human nasal chondrocytes (HNC)-based cartilage engineering. Methyltetrazolium salt assay and cell counting experiments first revealed that Si-HPMC enabled the proliferation of HNC. Cell tracker green staining further demonstrated that HNC were able to form nodular structures in this three-dimensional scaffold. HNC phenotype was then assessed by RT-PCR analysis of type II collagen and aggrecan expression as well as alcian blue staining of extracellular matrix. Our data indicated that Si-HPMC allowed the maintenance and the recovery of a chondrocytic phenotype. The ability of constructs HNC/Si-HPMC to form a cartilaginous tissue in vivo was finally investigated after 3 weeks of implantation in subcutaneous pockets of nude mice. Histological examination of the engineered constructs revealed the formation of a cartilage-like tissue with an extracellular matrix containing glycosaminoglycans and type II collagen. The whole of these results demonstrate that Si-HPMC hydrogel associated to HNC is a convenient approach for cartilage tissue engineering.

The active metabolite of leflunomide, A77 1726, increases proliferation of human synovial fibroblasts in presence of IL-1β and TNF-α

OBJECTIVE AND DESIGN

Excessive synovial fibroblast (SF) proliferation is detrimental in rheumatoid arthritis. We therefore sought to determine the effects of A77 1726, the active metabolite of leflunomide, on SF proliferation.

METHODS

Human SFs were used. Cell proliferation was investigated using MTS assay, by (3)H-thymidine incorporation and cell counts.

RESULTS

Whereas A77 1726 alone had no effects, it significantly increased the mitogenic effects of interleukin-1beta (IL-1beta) and tumor necrosis factor-alpha (TNF-alpha). Cyclooxygenase inhibition might be at least partly involved, since indomethacin displayed similar effects, and since prostaglandin E2 inhibited SF proliferation. In contrast, the effect of A77 1726 did not appear to be mediated through depletion of the pyrimidine pool or inhibition of tyrosine kinases.

CONCLUSION

A77 1726 displays proliferative effects in presence of IL-1beta and TNF-alpha. Further elucidation of involved mechanisms may prove useful for the utilization of leflunomide, the development of related compounds or elaboration of new therapeutic strategies.

Culture medium modulates the behaviour of human dental pulp-derived cells: technical note

In vitro approaches have extensively been developed to study reparative dentinogenesis. While dental pulp is a source of unidentified progenitors able to differentiate into odontoblast-like cells, we investigated the effect of two media; MEM (1.8 mM Ca and 1 mM Pi) and RPMI 1640 (0.8 mM Ca and 5 mM Pi) on the behaviour of human dental pulp cells. Our data indicate that MEM significantly increased cell proliferation and markedly enhanced the proportion of alpha-smooth muscle actin positive cells, which represent a putative source of progenitors able to give rise to odontoblast-like cells. In addition, MEM strongly stimulated alkaline phosphatase activity and was found to induce expression of transcripts encoding dentin sialophosphoprotein, an odontoblastic marker, without affecting that of parathyroid hormone/parathyroid hormone related protein-receptor and osteonectin. In conclusion, these observations demonstrate that not only proliferation but also differentiation into odontoblast-like cells was induced by rich calcium and poor phosphate medium (MEM) as compared to RPMI 1640. This study provides important data for the determination of the optimal culture conditions allowing odontoblast-like differentiation in human pulp cell culture.

A silanized hydroxypropyl methylcellulose hydrogel for the three-dimensional culture of chondrocytes

Articular cartilage has limited intrinsic repair capacity. In order to promote cartilage repair, the amplification and transfer of autologous chondrocytes using three-dimensional scaffolds have been proposed. We have developed an injectable and self-setting hydrogel consisting of hydroxypropyl methylcellulose grafted with silanol groups (Si-HPMC). The aim of the present work is to assess both the in vitro cytocompatibility of this hydrogel and its ability to maintain a chondrocyte-specific phenotype. Primary chondrocytes isolated from rabbit articular cartilage (RAC) and two human chondrocytic cell lines (SW1353 and C28/I2) were cultured into the hydrogel. Methyl tetrazolium salt (MTS) assay and cell counting indicated that Si-HPMC hydrogel did not affect respectively chondrocyte viability and proliferation. Fluorescent microscopic observations of RAC and C28/I2 chondrocytes double-labeled with cell tracker green and ethidium homodimer-1 revealed that chondrocytes proliferated within Si-HPMC. Phenotypic analysis (RT-PCR and Alcian blue staining) indicates that chondrocytes, when three-dimensionnally cultured within Si-HPMC, expressed transcripts encoding type II collagen and aggrecan and produced sulfated glycosaminoglycans. These results show that Si-HPMC allows the growth of differentiated chondrocytes. Si-HPMC therefore appears as a potential scaffold for three-dimensional amplification and transfer of chondrocytes in cartilage tissue engineering.

Cartilage formation in growth plate and arteries: from physiology to pathology

Vascular calcifications are the consequence of several pathological conditions such as atherosclerosis, diabetes, hypercholesterolemia and chronic renal insufficiency. They are associated with risks of amputation, ischemic heart disease, stroke and increased mortality. A growing body of evidence indicates that vascular smooth muscle cells (VSMCs) undergo chondrogenic commitment eventually leading to vascular calcification, by mechanisms similar to those governing ossification in the cartilage growth plate. Our knowledge of the formation of cartilage growth plate can therefore help us to understand why and how arteries calcify and, consequently, develop new therapeutic strategies. Reciprocally, thorough consideration of the events leading to ectopic chondrocyte differentiation appears crucial to further increase our understanding of growth plate formation. In this context, we will review the effects of known or suspected factors that promote chondrogenic differentiation in growth plate and arteries.

Synchrotron X-ray microtomography (on a micron scale) provides three-dimensional imaging representation of bone ingrowth in calcium phosphate biomaterials

This study used synchrotron X-ray microtomography on a micron scale to compare three-dimensional (3D) bone ingrowth after implantation of various calcium phosphate bone substitutes in a rabbit model. The advantage of using this new method for the study of biomaterials was then compared with histomorphometry for analysis of interconnection and bone ingrowth. The study focused on the newly formed bone-biomaterial interface. Macroporous Biphasic Calcium Phosphate (MBCP) ceramic blocks and two different injectable calcium phosphate biomaterials [an injectable bone substitute (IBS) consisting of a biphasic calcium phosphate granule suspension in hydrosoluble polymer and a calcium phosphate cement material (CPC)] were studied after in vivo implantation. Absorption or phase-contrast microtomography was performed with the dedicated set-up at beamline ID22. Experimental spatial resolution was between 1 and 1.4 microm, depending on experimental radiation. All calcium phosphates tested showed osteoconduction. IBS observations after 3D reconstruction showed interconnected bioactive biomaterial with total open macroporosity and complete bone ingrowth as early as 3 weeks after implantation. This experimentation was consistent with two-dimensional histomorphometric analysis, which confirmed its suitability for biomaterials. This 3D study relates the different types of bone substitution to biomaterial architecture. As porosity and interconnection increase, bone ingrowth becomes greater at the expense of the bone substitute: IBS>MBCP>CPC.

Noninvasive bone replacement with a new injectable calcium phosphate biomaterial

The use of injectable calcium phosphate (CaP) biomaterials in noninvasive surgery should provide efficient bone colonization and implantation. Two different kinds of injectable biomaterials are presently under development: ionic hydraulic bone cements that harden in vivo after injection, and an association of biphasic calcium phosphate (BCP) ceramic granules and a water-soluble polymer vehicle (a technique particularly investigated by our group), providing an injectable CaP bone substitute (IBS). In our study, we compared these two approaches, using physicochemical characterizations and in vivo evaluations in light microscopy, scanning electron microscopy, and three-dimensional microtomography with synchrotron technology. Three weeks after implantation in rabbit bone, both biomaterials showed perfect biocompatibility and bioactivity, but new bone formation and degradation of the biomaterial were significantly greater for BCP granules than for ionic cement. Newly formed bone developed, binding the BCP granules together, whereas new bone grew only on the surface of the cement, which remained dense, with no obvious degradation 3 weeks after implantation. This study confirms that BCP granules carried by a cellulosic polymer conserve bioactivity and are conducive to earlier and more extensive bone substitution than a carbonated-hydroxyapatite bone cement. The presence of intergranular spaces in the BCP preparation, as shown on microtomography imaging, seems particularly favorable, allowing body fluids to reach each BCP granule immediately after implantation. Thus, the IBS functions as a completely interconnected ceramic with total open macroporosity. This new bone replacement approach should facilitate microinvasive bone surgery and local delivery of bone therapy agents.

Fourier transform infrared microspectroscopic investigation of the organic and mineral constituents of peritubular dentin: a horse study

Peritubular dentin (PTD) is a relatively dense mineralized tissue surrounding tooth dentin tubules, whose composition and mode of formation are still unclear. Fourier transform infrared microspectroscopic studies of the organic and mineral components of the highly developed horse PTD indicate that the peritubular matrix is less abundant than the intertubular matrix but is also mainly composed of collagen, which is more hydrated. These data suggest that most of the crystals are located outside the collagen fibrils and probably not associated with protein components. The crystals in PTD have nearly the same crystallinity as those in intertubular spaces, showing comparable amounts of carbonate ions, although some PO4 groups have different nonapatitic environments. Horse PTD composition is very similar to that of ITD, with collagen as the main protein component and carbonated apatite as the mineral fraction but the different proportions of these constituents and the greater water content in PTD suggest a different organization.

In vitro characterization and in vivo properties of a carbonated apatite bone cement

This study evaluated the in vivo behavior of an injectable calcium phosphate bone cement implanted in bone defects at the distal end of rabbit femora. After 3 weeks, samples were harvested and processed for undecalcified sectioning. Scanning electron microscopy, transmission electron microscopy, and Fourier transform infrared microspectroscopy showed direct contact of bone and cement without soft tissue interposition, biocompatibility, and bioactivity with osteoconductive properties.

Fourier transform infrared microspectroscopic investigation of the maturation of nonstoichiometric apatites in mineralized tissues: a horse dentin study

Fourier transform infrared microspectroscopy (FTIRM) was used to study carbonated apatite/collagen interactions and maturation in horse secondary dentin. Unlike human dentin, this model contains no peritubular material around the odontoblastic processes and is thus quite similar to bone in composition, but not subject to tissue turnover. Crystals close to the mineralization front were very immature, showing high HPO(4) and very low CO(3) levels. Carbonate ions were located essentially in very labile, reactive environments, probably on the crystal surface. Removal of some of the HPO(4) ions from crystals during maturation was linked to an increase in total carbonate content. The CO(3) ions in labile environments decreased, probably after incorporation into more organized regions of the lattice. However, this increase of total carbonate content was associated with greater mineral crystallinity, confirming findings in other studies of synthetic apatite maturation in vitro. The good correlation between these results and those of in vitro experiments suggests that crystal maturation is essentially due to physicochemical processes and that the organic matrix controls only crystal size, multiplication, and/or organization.

Impairment of amino-acid absorption in suckling rats infected with Cryptosporidium parvum

In the present study. we explored the nutritional consequences of cryptosporidiosis. In order to ascertain the direct responsibility of C. parvum for impairment of staturoponderal development observed during the infection in neonatal animals, we investigated the absorption of two major components of the total amino acids in dam's milk (leucine and glutamate) across the ileal mucosa. The infection resulted in significant (47% and 34%, respectively) reductions in leucine and glutamate fluxes (P<0.01). Moreover, the leucine aminopeptidase and alkaline phosphatase activities were reduced in the infected ileal mucosa. Interestingly, the reduction in weight gain, which began at day 6 post-infection (PI), persisted until day 20 PI, although no cryptosporidia were detected in the ileal mucosa after day 12 PI. We thus provide evidence that the malabsorption of amino acids during cryptosporidiosis contributes to impairing the development of neonatal animals, with consequences that persist beyond eradication of the parasite.

[Cryptosporidium parvum: functional study of the intestinal malabsorption syndrome]

Cryptosporidiosis is an important cause of diarrhea associated with growth retardation in children and severe malnutrition in immunocompromised patients. The pathophysiology is poorly understood. In the suckling rat model, we show that C. parvum infection impairs net electrogenic transport across the ileal mucosa without involvement of prostaglandins, as well as trans- and paracellular permeability and leucine and glutamate absorption. These results provide evidence for the development of an intestinal malabsorptive syndrome during cryptosporidiosis. Unspecific process such as villous atrophy and inflammatory cytokines secretion should be regarded as possible mediators of this syndrome. However, specific mechanisms have to be considered since C. parvum induces a rearrangement of the host enterocyte cytoskeleton which might impaired intracellular trafficking thus reducing the membrane expression of nutrient transporters. Infection and malnutrition are known to be tightly associated, making each other worse. As no specific efficient therapy exists, cryptosporidiosis-induced malnutrition must be taken into account when establishing therapeutic scheme.

Study of the maturation of the organic (type I collagen) and mineral (nonstoichiometric apatite) constituents of a calcified tissue (dentin) as a function of location: a Fourier transform infrared microspectroscopic investigation

Fourier transform infrared microspectroscopy (FTIRM) was used to investigate the organic and mineral phases of a calcified tissue (dentin) as a function of its location from predentin toward enamel. Thin dentin slices (decalcified or not) were fixed in formaldehyde and embedded in glycolmethylmethacrylate (GMA). Fixation did not denature collagen, and GMA did not interact with organic or mineral constituents of dentin. The v1v3 PO4 domain was studied in particular in order to estimate mineral maturity and amide I, II, A, and B to obtain data on protein conformation. The results showed that dentin apatite became increasingly mature (stoichiometric) from the mineralization front toward the enamel, especially through loss of HPO4(2-) groups and vacancies. Moreover, collagen fibrils became less and less hydrated, suggesting that intrafibrillar mineralization partially dehydrated the collagen. Combined study of the organic and mineral fractions of calcified tissues may help clarify their relationships in physiological and pathological tissues.

Cryptosporidium parvum infection in suckling rats: impairment of mucosal permeability and Na(+)-glucose cotransport

Na(+)-glucose transport and transepithelial permeability were investigated during symptomatic acute cryptosporidiosis in newborn rats. The infection resulted in a significant (P < 0.01) decrease in the ileal short-circuit current and a nonsignificant fall in the transepithelial potential difference and conductance. In glucose-stimulated conditions, the rise in ileal short-circuit current and transepithelial permeability were significantly lower in Cryptosporidium parvum-infected rats than in controls (delta Isc = 3.24 +/- 1.21 microA.cm-2 vs delta Isc = 5.09 +/- 2.23 microA.cm-2 in infected and control animals, respectively; P < 0.001; delta PD = -0.35 +/- 0.13 mV vs delta PD = -0.44 +/- 0.14 mV for infected and control animals, respectively; P < 0.01). Electrical parameters were not affected by addition of the cyclooxygenase inhibitor indomethacin in either Cryptosporidium-infected newborn rats or controls. Horseradish peroxidase and mannitol flux studies demonstrated a significant decrease (P < 0.05) in transepithelial molecular permeability in infected enterocyte rats, HRP flux = 380, range 68-5570 ng.cm-2, and mannitol flux = 1.06, range, 0.34-1.44%.cm-2.min-1, compared with controls rats, HRP flux = 4446 range, 1121-124,363 ng.cm-2, and mannitol flux = 1.99, range, 0.57-5.09%.cm-2.min-1; P < 0.05. These effects could originate from C. parvum-induced alteration of intracellular trafficking of pinocytosis vesicles and therefore account for the decrease in permeability to solute and macromolecules, together with impaired transcellular nutrient transport, in suckling rats.

Fecal tumor necrosis factor alpha, eosinophil cationic protein and IgE levels in infants with cow's milk allergy and gastrointestinal manifestations

Infants with atopic eczema exhibit a specific fecal protein pattern after oral challenge with cow's milk, characterized by an increase in both eosinophil cationic protein (ECP) and tumor necrosis factor (TNF)alpha. The aim of our study was to determine the pattern of these proteins in allergic infants with intestinal manifestations. TNFalpha, ECP and immunoglobulin E (IgE) were measured in stools from 13 infants with intestinal symptoms and 10 healthy infants. The allergic infants underwent two stool collections, one before a cow's milk challenge and the other after the challenge, either at the onset of clinical manifestations (n=6) or 15 days after the challenge if no clinical manifestations occurred (n=7). Baseline TNFalpha, ECP and IgE levels were low in all infants. The concentration of TNFalpha increased after the challenge in infants positive to challenge (p<0.05) but not in those negative to challenge. ECP and IgE levels remained low after the challenge in all the allergic infants. These data confirm that fecal TNFalpha and ECP levels indicate various reaction types of food allergy and that different immunologic disturbances lead to atopic eczema or intestinal symptoms during food allergy. Fecal protein pattern can thus be a useful tool in diagnosing food allergy in infants with intestinal manifestations.

Cryptosporidiosis-induced impairment of ion transport and Na+-glucose absorption in adult immunocompromised mice

Electrolyte transport was investigated during chronic cryptosporidiosis in adult anti-interferon-gamma-treated SCID mice by means of Ussing chamber techniques. In basal conditions, infection of immunocompromised mice with Cryptosporidium parvum resulted in a 30% reduction (P < .05) in the ileal short-circuit (Isc) current related to a 28% reduction (P < .05) in tissue conductance compared with controls. The rises in Isc and transepithelial potential difference induced by glucose (10 mM) were significantly reduced by Cryptosporidium infection (P < .01) compared with controls. In contrast, responses to mucosal glutamine were marginally affected. Electrical parameters of the ileum were not affected by the addition of indomethacin or furosemide, in either control or Cryptosporidium-infected mice. Thus, long-term cryptosporidiosis in immunocompromised animals leads to a reduction in net ion exchanges, decreased paracellular shunting, and impaired Na+-glucose cotransport in the ileum, without prostanoid- or enterotoxin-mediated electrogenic Cl- secretion.

Kinetics of mucosal ileal gamma-interferon response during cryptosporidiosis in immunocompetent neonatal mice

The kinetics of serum and ileal interferon-gamma (IFN-gamma) content were determined during recovery from cryptosporidiosis in NMRI suckling mice. A total of 60 mice aged 4 days were inoculated by intragastric gavage with 10(4) cryptosporidia (n = 30) or phosphate-buffered saline (n = 30). Six animals per group were killed on days 0, 3, 6, 9 and 13 postinoculation. Blood samples and ileum were collected. Experimental infection was followed by a rise in parasite load in the ileum starting on day 3 postinfection, which peaked at day 6 postinoculation. Ileal IFN-gamma levels increased rapidly in parasitized mice from day 3 to day 6, then fell rapidly. These levels were significantly higher than the control values (day 3 P < 0.05, days 6 and 9 P < 0.001). IFN-gamma secretion began before parasite excretion, but the curves of these two parameters correlated positively. Recovery from cryptosporidiosis in immunocompetent neonatal mice is thus associated with an early and marked increase in ileal IFN-gamma content.

Inefficacy of intestinal secretory immune response to Cryptosporidium in acquired immunodeficiency syndrome

BACKGROUND/AIMS

An alteration of the secretory immune response has been forwarded to explain frequent and chronic mucosal infections in patients with acquired immunodeficiency syndrome (AIDS). The aim of this study was to explore the intestinal immunoglobulin (Ig) secretions in patients with AIDS and their relationships to cryptosporidiosis.

METHODS

Patients with AIDS and enteric cryptosporidiosis (n = 12), other enteric infections (n = 10), and no identifiable enteric pathogen (n = 10) and human immunodeficiency virus-seronegative controls (n = 18) were studied. The number of intestinal IgA and IgM plasma cells of the duodenal lamina propria mucosa and total and anti-Cryptosporidium IgA, IgM, and IgG were measured in serum and feces.

RESULTS

Although not significantly increased, the number of IgA and IgM plasma cells was greater in patients with AIDS (n = 20) than in controls (n = 5). In feces, total IgA outputs and specific anti-Cryptosporidium IgA levels were significantly higher in patients with AIDS and cryptosporidiosis than in the two other groups of patients with AIDS (P < 0.05 and P < 0.01, respectively) and controls (P < 0.001 and P < 0.01, respectively). Total fecal IgM output and specific anti-Cryptosporidium IgM coproantibodies were increased only in the Cryptosporidium-infected patients relative to the controls (P < 0.05).

CONCLUSIONS

Despite the development of pathogen-specific mucosal antibody responses, patients with AIDS and cryptosporidiosis fail to clear the parasite.

Intestinal lipid metabolism in suckling rats infected with Giardia duodenalis

We carried out a quantitative and qualitative analysis of intestinal digestion of neutral lipids in suckling rats infected with Giardia duodenalis. Total lipids were measured after extraction from the contents of the stomach, proximal and distal small bowel, caecum and colon. Amounts gradually fell from the stomach to the colon and were identical in infected animals and controls, although high values were occasionally found in the caecum of infected rats. Relative glyceride quantities were determined by means of high-performance thin-layer chromatography. Triglycerides were absent from the distal small bowel, and only free fatty acids and cholesterol were present in the caecum, reflecting normal digestion of neutral lipids in infected suckling rats. Our results suggest that G. duodenalis does not impair intestinal fat digestion in suckling rats.

Determination of anti-Cryptosporidium coproantibodies by time-resolved immunofluorometric assay

The role of the mucosal immune response against Cryptosporidium has been suggested by studies on the therapeutic effects of hyperimmune colostrum. In order to study the intestinal response to this infection, we have developed a sandwich-type time-resolved immunofluorometric assay for the determination of anti-Cryptosporidium coproantibodies. This assay has the inherent sensitivity of an immunoassay without the problems due to background responses from other biological compounds, and is thus suitable for faecal samples. The intra-assay coefficients of variation (5.1%, 4.6%, and 5.8% for immunoglobulins (Ig) A, M and G respectively), inter-assay coefficients of variation (9.4%; 10.5% and 12.2% for IgA, IgM and IgG, respectively) and specificity (100% for all 3 isotypes) were all satisfactory. Using this assay to study 12 patients with the acquired immune deficiency syndrome (AIDS) who were infected with cryptosporidiosis, we found a marked elevation of anti-Cryptosporidium IgA and IgM coproantibody titres relative to 18 healthy control values, but no correlation with the gravity of the infection in terms of oocyst shedding. These results suggest that a non-protective mucosal immune response develops to Cryptosporidium in AIDS patients.

Factors influencing the reaction of alpha 1-fetoprotein with concanavalin A and Lens culinaris agglutinin in crossed affinoimmunoelectrophoresis

Concanavalin A (Con A) and lentil lectin (LCA) analysis of alpha-fetoprotein (AFP) glycosylation heterogeneity is used in a variety of clinical situations. We studied the influence of analytical conditions on the separation of AFP glycoforms by using lectin-crossed affinoimmunoelectrophoresis, regardless of the AFP concentration, which can vary over a wide range in biological fluids. We defined the optimal concentration of Con A (2 g/L) and LCA (0.35 g/L) in the first-dimension gel, together with the optimum antigen (AFP)/antibody ratio in the second-dimension gel. The presence of protein in the diluent used for AFP samples was found to change the shape of crossed affinoimmunoelectrophoresis patterns without changing the percentage composition of AFP fractions. The within-run CV was less than 4% for both lectins, and the between-run CV was less than 6.3%. The minimal quantity of AFP that provided a visible pattern with both lectins was 4 ng, corresponding to 50 microL of an 80 micrograms/L AFP sample. These technical conditions allow the cellular origin of AFP to be determined, regardless of the concentration in the sample. Typical AFP lectin patterns of secreting tumors are compared with fetal and cord serum AFP.

Factors Influencing the Reaction of α1-Fetoprotein with Concanavalin A and Lens Culinaris Agglutinin in Crossed Affinoimmunoelectrophoresis

Concanavalin A (Con A) and lentil lectin (LCA) analysis of alpha-fetoprotein (AFP) glycosylation heterogeneity is used in a variety of clinical situations. We studied the influence of analytical conditions on the separation of AFP glycoforms by using lectin-crossed affinoimmunoelectrophoresis, regardless of the AFP concentration, which can vary over a wide range in biological fluids. We defined the optimal concentration of Con A (2 g/L) and LCA (0.35 g/L) in the first-dimension gel, together with the optimum antigen (AFP)/antibody ratio in the second-dimension gel. The presence of protein in the diluent used for AFP samples was found to change the shape of crossed affinoimmunoelectrophoresis patterns without changing the percentage composition of AFP fractions. The within-run CV was less than 4% for both lectins, and the between-run CV was less than 6.3%. The minimal quantity of AFP that provided a visible pattern with both lectins was 4 ng, corresponding to 50 microL of an 80 micrograms/L AFP sample. These technical conditions allow the cellular origin of AFP to be determined, regardless of the concentration in the sample. Typical AFP lectin patterns of secreting tumors are compared with fetal and cord serum AFP.

Evaluation of intestinal clearance and faecal excretion of alpha 1-antiproteinase and immunoglobulins during Crohn's disease and ulcerative colitis

The intestinal clearance of alpha 1-antiproteinase, monomeric IgA and IgG, and the daily fecal output of polymeric IgA and IgM were investigated in patients with inflammatory bowel diseases (inactive and active Crohn's disease, ulcerative colitis) and in a control group. The intestinal clearance of alpha 1-antiproteinase was significantly increased in all patients with inflammatory bowel diseases (p less than 0.01), irrespective of the grade of the disease. In contrast, increases in intestinal clearances of monomeric IgA and IgG were more closely related to the severity of the intestinal lesions. The associate determination of these three quantities should therefore be of interest for monitoring the degree of intestinal bowel inflammation. Faecal output of polymeric IgA was significantly increased in active intestinal disease (p less than 0.01), whereas faecal IgM levels were not. The determination of the faecal output of polymeric IgA should contribute to the assessment of the activity of inflammatory bowel diseases, and may provide insight into the activation of the mucosal immune system.

Role of cytoskeleton and surface lectins in Giardia duodenalis attachment to Caco2 cells

An in vitro model of Giardia duodenalis and the Caco2 cell line enable the study of parameters that could play a part in trophozoite attachment. We explored the role of membranous lectins of G. duodenalis in attachment-inhibition studies using carbohydrates in solution. Attachment rates were reduced by 14% and 23% in the presence of 100 mmol/l mannose-6-phosphate and glucose, respectively, as compared with control values. No significant modification was observed after trophozoite trypsinization at room temperature or at 37 degrees C. The inhibitory effects of colchicine (35%) and nocodazole (70%) suggest a primordial role of the cytoskeleton; microtubules appear to be the principal effectors of trophozoite fixation. Scanning electron microscopy revealed circular imprints on the Caco2 brush border after trophozoite detachment. The mechanisms of attachment of G. duodenalis to intestinal enterocyte-like cells in culture are thus essentially of the mechanical or hydrodynamic type; surface lectins would appear to intervene in the specificity for duodenal cells.

Adherence and multiplication of Giardia intestinalis on human enterocyte-like differentiated cells in vitro

This report describes a technique for studying the adherence and growth of Giardia intestinalis trophozoites (strains PARIS/86/LCF/1, PARIS/86/LCF/2 and PARIS/88/LCF/8) using the human colon carcinoma cell line Caco2. Giardia trophozoites were cultured with Caco2 cells in a modified HSP3 culture medium. The biochemical differentiation of Caco2 cells was established by an increase in sucrase isomaltase activities to values of 4.51 +/- 0.90 and 10.39 +/- 3.00 milliunits/mg protein for 8- and 12-day-old cultures, respectively. Giardia, adherence to 8- and 12-day-old Caco2 cells reached a value of greater than 75% after 60 and 30 min, respectively. Adherence diminished significantly at 24 degrees C and was almost undetectable at 4 degrees C. Depletion of divalent cations reduced the proportion of adherent trophozoites by up to 46%. Adherence was pH-independent between pH 6.0 and 7.6. Parasite growth increased when Caco2 cell monolayers were used instead of axenic cultures. This in vitro human cell model may contribute to the study of the mechanisms and factors involved in the host-parasite interaction.