Biomedical subjects

D Grcević

Publications and source records attributed to D Grcević.

6 recordsLinked to original sources

PubMed2006

Activated T lymphocytes suppress osteoclastogenesis by diverting early monocyte/macrophage progenitor lineage commitment towards dendritic cell differentiation through down-regulation of receptor activator of nuclear factor-kappaB and c-Fos.

Activated T lymphocytes either stimulate or inhibit osteoclastogenesis from haematopoietic progenitors in different experimental models. To address this controversy, we used several modes of T lymphocyte activation in osteoclast differentiation--mitogen-pulse, anti-CD3/CD28 stimulation and in vivo and in vitro alloactivation. Osteoclast-like cells were generated from non-adherent immature haematopoietic monocyte/macrophage progenitors in murine bone-marrow in the presence of receptor activator of nuclear factor (NF)-kappaB ligand (RANKL) and monocyte-macrophage colony-stimulating factor (M-CSF). All modes of in vivo and in vitro T lymphocyte activation and both CD4(+) and CD8(+) subpopulations produced similar inhibitory effects on osteoclastogenesis paralleled by enhanced dendritic cell (DC) differentiation. Osteoclast-inhibitory effect was associated with T lymphocyte activation and not proliferation, and could be replaced by their culture supernatants. The stage of osteoclast differentiation was crucial for the inhibitory action of activated T lymphocytes on osteoclastogenesis, because the suppressive effect was visible only on early osteoclast progenitors but not on committed osteoclasts. Inhibition was associated specifically with increased granulocyte-macrophage colony-stimulating factor (GM-CSF) expression by the mechanism of progenitor commitment toward lineages other than osteoclast because activated T lymphocytes down-regulated RANK, CD115, c-Fos and calcitonin receptor expression, and increased differentiation towards CD11c-positive DC. An activated T lymphocyte inhibitory role in osteoclastogenesis, confirmed in vitro and in vivo, mediated through GM-CSF release, may be used to counteract activated bone resorption mediated by T lymphocyte-derived cytokines in inflammatory and immune disorders. We also demonstrated the importance of alloactivation in osteoclast differentiation and the ability of cyclosporin A to abrogate T lymphocyte inhibition of osteoclastogenesis, thereby confirming the functional link between alloreaction and bone metabolism.

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PubMed2005

Alteration of newly induced endochondral bone formation in adult mice without tumour necrosis factor receptor 1.

Tumour necrosis factor (TNF)-alpha, a major proinflammatory cytokine, exerts its role on bone cells through two receptors (TNFR1 and TNFR2). TNFR1, but not TNFR2, is expressed by osteoblasts and its function in bone formation in vivo is not fully understood. We compared in vivo new bone formation in TNFR1-deficient (TNFR1(-/-)) mice and wild-type mice, using two models of bone formation: intramembranous ossification following tibial marrow ablation and endochondral ossification induced by bone morphogenetic protein (BMP)-2. Intramembranous osteogenesis in TNFR1(-/-) mice did not differ from the wild-type mice either in histomorphometric parameters or mRNA expression of bone-related markers and inflammatory cytokines. During endochondral osteogenesis, TNFR1(-/-) mice formed more cartilage (at post-implantation day 9), followed by more bone and bone marrow (at day 12). mRNAs for BMP-2, -4 and -7 were increased during the endochondral differentiation sequence in TNFR1(-/-) mice. The expression of receptor activator of NF-kappa B ligand (RANKL) and receptor activator of NF-kappa B (RANK), as assessed by quantitative reverse transcription polymerase chain reaction (RT-PCR), was also increased significantly during endochondral ossification in TNFR1(-/-) mice. In conclusion, signalling through the TNFR1 seems to be a negative regulator of new tissue formation during endochondral but not intramembranous osteogenesis in an adult organism. BMPs and RANKL and its receptor RANK may be involved in the change of local environment in the absence of TNFR1 signalling.

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PubMed2001

Cellular and molecular interactions between immune system and bone.

Functional interdependence between immune and bone systems is reflected in a number of regulatory molecules acting on the cells of both systems and common precursors for bone and immune cells. Therefore, the disturbances of the immune system may affect bone metabolism, and vice versa. This review addresses the roles of two major immune cell populations, T and B lymphocytes, in the regulation of bone metabolism. Experimental models and human diseases demonstrated that T lymphocytes may produce many bone cell regulatory cytokines, including two essential stimulators of osteoclastogenesis: receptor for activation of nuclear factor kappa b (NF-kappa B) (RANK) ligand (RANKL) and macrophage colony-stimulating factor. The effect of T lymphocytes on osteoclastogenesis may be both stimulatory and inhibitory, and depends on the activation stage and pattern of cytokine production. We showed that acute removal of T lymphocytes stimulated osteoclast differentiation in vitro and enhanced new cartilage and bone formation at non-osseous sites in vivo. B lymphocytes may be even more closely related to bone cells, as B lymphopoiesis requires an intimate contact with osteoblastic/stromal cells, and estrogens, powerful regulators of bone mass, are also involved in the differentiation of the B lymphocyte lineage. Also, B lymphocyte progenitors may give rise to functional osteoclasts. Both B and T lymphocytes may act through the RANKL/RANK/osteoprotegerin cytokine system, which has been independently discovered within immune and bone systems. These cytokines have crucial roles in the development and function of osteoclasts, dendritic cells, and T and B lymphocytes, as well as in the thymus and lymph node organogenesis. The cytokines produced by immune cells may affect bone cell function and vice versa, but the full complexity of these interactions awaits further investigation.

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PubMed2000

Depletion of CD4 and CD8 T lymphocytes in mice in vivo enhances 1,25-dihydroxyvitamin D3-stimulated osteoclast-like cell formation in vitro by a mechanism that is dependent on prostaglandin synthesis.

To investigate the role of T lymphocytes in osteoclastogenesis, we performed in vivo depletion of CD4 and/or CD8 T lymphocyte subsets and evaluated in vitro osteoclast-like cell (OCL) formation. T lymphocyte depletion (TLD) with mAbs was confirmed 24 h later by flow cytometry. OCL formation was stimulated with 1, 25-dihydroxyvitamin D(3) (1,25-(OH)(2)D(3)) in bone marrow and with recombinant mouse (rm) receptor activator of NF-kappaB ligand (RANK-L) and rmM-CSF in bone marrow and spleen cell cultures. OCL formation was up to 2-fold greater in 1,25-(OH)(2)D(3)-stimulated bone marrow cultures from TLD mice than in those from intact mice. In contrast, TLD did not alter OCL formation in bone marrow or spleen cell cultures that were stimulated with rmRANK-L and rmM-CSF. The effects of TLD seemed to be mediated by enhanced PG synthesis, because the PGE(2) concentration in the medium of 1, 25-(OH)(2)D(3)-stimulated bone marrow cultures from TLD mice was 5-fold higher than that in cultures from intact mice, and indomethacin treatment abolished the stimulatory effect of TLD on OCL formation. There was a 2-fold increase in RANK-L expression and an almost complete suppression of osteoprotegerin expression in 1, 25-(OH)(2)D(3)-stimulated bone marrow cultures from TLD mice compared with those from intact mice. Although there was a small (20%) increase in IL-1alpha expression in 1, 25-(OH)(2)D(3)-stimulated bone marrow cultures from TLD mice, TLD in mice lacking type I IL-1R and wild-type mice produced similar effects on OCL formation. Our data demonstrate that TLD up-regulates OCL formation in vitro by increasing PG production, which, in turn, produces reciprocal changes in RANK-L and osteoprotegerin expression. These results suggest that T lymphocytes influence osteoclastogenesis by altering bone marrow stromal cell function.

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PubMed1999

Genetic variability of new bone induction in mice.

We studied differences in ectopic osteoinduction in eight mouse inbred strains and an outbred strain. Antigen-extracted autolyzed rat bone gelatin was implanted under hind limb muscle fascia of 12-week-old males, and new bone formation was morphologically assessed on serial sections. Four weeks after implantation, less than half of the implants from CBA/J, A/J, BALB/cJ, and C3Hf/Bu mice showed induction of only cartilage. New cartilage was observed in all, and bone and bone marrow in 80% of the implants from AKR/J, C57BL/6J, DBA/2J, and RFM/Rij mice. Volume of the newly formed tissue ranged from 1.3% of the old matrix in A/J strain to 74.6% in DBA/2J strain. Outbred CD1 mice showed only weak cartilage induction. The "good" responders differed among themselves in the volume and type of newly induced tissue: DBA/2J, RFM/Rij, and AKR/J mice had a similar ratio of new bone and cartilage and abundant bone marrow, whereas the predominant newly induced tissue in C57Bl/6J mice was cartilage. The pattern of the expression of BMP-2, -4, and -7, alkaline phosphatase, osteocalcin, interferon-gamma, and granulocyte-macrophage colony-stimulating factor, measured by reverse transcriptase polymerase chain reaction, did not correlate with the type and the quantity of the newly induced tissue. Our results show that adult mice of inbred strains differ not only in the peak bone mass and morphology, but also ability to form new bone after an osteoinductive stimulus. Ectopic osteoinduction may be a useful in vivo model to investigate genetic determinants of endochondral osteogenesis, especially its immunological component.

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PubMed1999

Pre-treatment of transplant bone marrow cells with hydrocortisone and cyclosporin A alleviates graft-versus-host reaction in a murine allogeneic host-donor combination.

The aim of the study was to alleviate graft-versus-host reaction (GVHR) by pre-treatment of the bone marrow (BM) transplant with hydrocortisone (HC) and cyclosporin A (CsA) in C57BL/6J (donor) --> CBA/J (recipient) mouse combination. BM cells were exposed to HC and CsA for 1 h at 37 degrees C and then injected into lethally irradiated (9.5 Gy) mice at a dose of 2 x 10(6) BM cells/mouse. Haematopoietic recovery was assessed on day 12, and survival was followed for 100 days. Combinations of 1000 microg/ml HC and 100 microg/ml CsA, and 100 microg/ml HC and 10 microg/ml CsA significantly reduced MLR and additively mitigated GVHR in vivo, achieving 40% and 26% survival rates, respectively. However, HC and CsA altered neither the peripheral blood cell counts nor in vitro and in vivo BM cell clonogenic potential. Additional studies have shown that HC and CsA blocked con A-driven differentiation of CD8+ and CD4+ CD8+ lymph node cells (LNC) and progression of LNC to S + G2/M cell cycle phases, and inhibited IL-1, IL-2 and TGF-beta while enhancing GM-CSF gene expression in BM cells. Taken together, these data indicate that the pre-treatment of the BM transplant with HC and CsA results in inactivation of GVHR effector cells and mitigation of GVHR while sparing BM repopulating capacity.

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