Interactions between lymphocytes and dermal fibroblasts: an in vitro model of cutaneous lymphocyte trafficking

ICAM-1-mediated osteoblast-T lymphocyte direct interaction increases mineralization through TGF-β1 suppression

Modulation of osteoblast functions by T lymphocytes is important in inflammation-associated mineralized tissue diseases. The study aimed to determine whether direct interaction between these two cell types affects osteoblast functions and mineralization. The results showed that direct contact between the two cell types was evident by scanning electron microscopy and transmission electron microscopy. Under osteogenic induction, higher hydroxyapatite precipitation was observed in cocultures with direct contact with T lymphocytes compared with that by osteoblasts cultured alone. Cocultures without direct cell contact caused a decrease in mineralization. Direct cell contact also upregulated intercellular adhesion molecule (ICAM)-1 and simultaneously downregulated transforming growth factor (TGF)-β1 in osteoblasts. However, the downregulation of TGF-β1 was reversed by ICAM-1 blocking. Exogenously added TGF-β1 in cocultures with direct cell contact suppressed mineralization. In conclusion, studies are consistent with ICAM-1-mediated direct contact between osteoblasts and T lymphocytes increasing mineralization via downregulation of TGF-β1 in osteoblasts in vitro. This suggests a possible unexpected, but crucial, role of T lymphocytes in enhancing matrix mineralization during the repair process in vivo. The study identifies ICAM-1/TGF-β1 as possible novel therapeutic targets for the treatment and prevention of inflammation-associated mineralized tissue diseases.

Fibrosis in scleroderma

The pathogenesis of fibrosis in scleroderma involves a complex set of interactions between the fibroblast and its surroundings. Multiple fibrotic pathways are activated for reasons that are not completely clear, but involve immune activation, microvascular damage, and fibroblast transformation into the myofibroblast. Differential proliferation and apoptosis preserve the myofibroblast phenotype rather that leading to a selective depletion of activated fibroblasts after an acute injury has healed. Disproportionate fibroblast activity could result from a combination of possible cellular and matrix defects that include fibrillin protein abnormalities, autoantibody formation, type II immune response, excessive endothelial reaction to injury, and excessive fibroblast response to TGF-beta. Development of therapies that are targeted to correcting these abnormalities will eventually lead to effective treatment for the fibrotic complications of scleroderma.

Enhanced cyclooxygenase-2 mRNA expression in human gingival fibroblasts induced by cell contact with human lymphocytes

Prostaglandins, especially prostaglandin E2 (PGE2), play a crucial role in the pathogenesis of periodontal disease. We have previously reported that inflammatory mediators interleukin-1 (IL-1) and tumor necrosis factor alpha (TNFalpha) increase the production of PGE2 in human gingival fibroblasts. In this study, we investigated the effect of cell-to-cell interactions between gingival fibroblasts and lymphocytes on PGE2 production by using co-culture technique. Cell-to-cell contact between gingival fibroblasts and lymphocytes synergistically enhanced the production of PGE2 in co-cultures. In contrast to lymphocytes, the cyclooxygenase-2 (COX-2) mRNA expression in gingival fibroblasts was strongly enhanced following cell contact between gingival fibroblasts and lymphocytes. The level of COX-1 mRNA expression, however, was not affected either in gingival fibroblasts or in lymphocytes by the interactions between fibroblasts and lymphocytes. The study demonstrates that cell contact between gingival fibroblasts and lymphocytes strongly stimulates PGE2 production partly due to enhanced COX-2 mRNA expression in gingival fibroblasts. The cell-to-cell contact between gingival fibroblasts and lymphocytes should be considered as an important regulatory aspect for the enhancement of PGE2 in periodontal disease.

Expression and shedding of intercellular adhesion molecule 1 and lymphocyte function-associated antigen 3 by normal and scleroderma fibroblasts. Effects of interferon-gamma, tumor necrosis factor alpha, and estrogen

OBJECTIVE

To examine intercellular adhesion molecule 1 (ICAM-1) and lymphocyte function-associated antigen 3 (LFA-3) in cultures of normal and systemic sclerosis (SSc) dermal fibroblasts.

METHODS

The surface and soluble forms of ICAM-1 and LFA-3 were measured by flow cytometry and capture enzyme-linked immunosorbent assay, respectively.

RESULTS

Surface ICAM-1 was significantly higher on SSc fibroblasts compared with normal controls. Beta-estradiol did not directly enhance ICAM-1 or LFA-3 expression in either normal or SSc cells, but significantly augmented the cytokine-induced increase in ICAM-1. Soluble ICAM-1 (sICAM-1) and sLFA-3 were detected in fibroblast cultures. While no difference was found in the level of sLFA-3, the shedding of sICAM-1 was significantly increased (P < 0.001) in cells from SSc patients.

CONCLUSION

SSc fibroblasts express intrinsically elevated levels of surface ICAM-1 and release higher levels of sICAM-1 in vitro. Increased expression of ICAM-1 by interferon-gamma and tumor necrosis factor alpha alone, and the further induction in combination with beta-estradiol may underlie an aspect of fibroblast dysfunction in SSc and the female predisposition to the disease.

Lysosomal storage diseases: mechanisms of enzyme replacement therapy

Lysosomal diseases result from deficiency of one of the many enzymes involved in the normal, step-wise breakdown of macromolecules. Studies in vitro have shown that cells from enzyme-deficient patients can be corrected by an exogenous supply of the missing enzyme. This occurs by receptor-mediated endocytosis of normal enzyme added to tissue culture medium and also by direct transfer from normal leukocytes during cell-to-cell contact. Immunohistochemical analysis has revealed that these processes have similar pathways of intracellular transport of the acquired enzymes, which ultimately reach mature lysosomes in the recipient cells. Moreover, recent studies suggest that both mechanisms are important in the therapy of lysosomal storage diseases by bone marrow transplantation. Advances in gene technology are likely to improve the successful treatment of these disorders, by facilitating the large scale production of clinically effective proteins and also by enabling the stable and safe introduction of normal lysosomal genes into cells of affected patients.

Expression and function of surface antigens on scleroderma fibroblasts

Dermal fibroblasts from patients with systemic sclerosis (SSc) bound a much greater number of T lymphocytes than did normal dermal fibroblasts. Monoclonal antibodies (MAb) against classes I and II antigens of the major histocompatibility complex (MHC) and their receptors, CD8 and CD4, had no effect on T cell interaction with SSc and normal cells, while MAb against lymphocyte function-associated antigen type 3 (LFA-3) and CD2 both strongly inhibited lymphocyte attachment. MAb against intercellular adhesion molecule type 1 (ICAM-1) and LFA-1 also prevented binding of T lymphocytes, but had a more marked effect on adhesion to SSc fibroblasts than to normal fibroblasts; they also completely abolished the increased binding to fibroblasts treated with interleukin-1 alpha, tumor necrosis factor alpha, and interferon-gamma. No difference was found in the proportion of normal and SSc fibroblasts that expressed MHC classes I and II and LFA-3, but more SSc cells expressed ICAM-1, and at a higher level, than did normal fibroblasts. These results show that cultured SSc cells have elevated binding to T lymphocytes, which possibly results from expansion of a subset of fibroblasts that produces high levels of ICAM-1.