Assessment of anti-inflammatory activity by sponge implantation techniques

The Sponge Implant Model of Angiogenesis

The host response observed after the application of an appropriate stimulus, such as mechanical injury or injection of neoplastic or normal tissue implants, has allowed the cataloging of a number of molecules and cells involved in the vascularization of normal repair or neoplastic tissue. Implantation of sponge matrices has been adopted as a model for the accurate quantification of angiogenic and fibrogenic responses, as they may occur during wound healing, in vivo. Such implants are particularly useful because they offer scope for modulating the environment within which angiogenesis occurs. Sponge implantation model has been optimized and adapted to characterize essential components and their roles in blood vessels formation in a variety of physiological and pathological conditions. As a direct consequence of advances in genetic manipulation, mouse models (i.e., knockouts, SCID, nude) have provided resources to delineate the mechanisms regulating the healing associated with implants. Here we outline the usefulness of the sponge implant model of angiogenesis and detailed description of the methodology.

The sponge implant model of angiogenesis

The host response observed after the application of an appropriate stimulus, such as mechanical injury or injection of neoplastic or normal tissue implants, has allowed the cataloguing of a number of molecules and cells involved in the vascularization of normal repair or neoplastic tissue. Implantation of sponge matrices has been adopted as a model for the accurate quantification of angiogenic and fibrogenic responses as they may occur during wound healing in vivo. Such implants are particularly useful because they offer scope for modulating the environment within which angiogenesis occurs. A sponge implantation model has been optimised and adapted to characterise essential components and their roles in blood vessel formation in a variety of physiological and pathological conditions. As a direct consequence of advances in genetic manipulation, mouse models (i.e., knockouts, severe combined immunodeficient [SCID], nude) have provided resources to delineate the mechanisms regulating the healing associated with implants. Here, we outline the usefulness of the cannulated sponge implant model of angiogenesis and provide a detailed description of the methodology.

V antigen of Yersinia pestis inhibits neutrophil chemotaxis

V antigen (V), a secreted protein encoded by the 70 kb low-calcium response plasmid of Yersinia pestis, is an essential virulence factor. In animal models, it inhibits the early host inflammatory response to infection which is associated with decreased blood and tissue levels of proinflammatory cytokine synthesis. To elucidate further the pathogenetic mechanism(s) of V, in vitrosystems are needed to measure and analyse relevant functional activities of V. We studied the effect of V on the migration of neutrophils to a chemoattractant both in vivo and in vitro. Peripheral injection of V was associated with a reduction in the number of PMN migrating into s.c. sponges and i.p. exudates. Similarly, pre-incubating human peripheral blood neutrophils with >/=ng/ml V significantly inhibited the in vitro chemotactic response to the peptide chemoattractant FMLP. The inhibitory activity of V was inactivated by heat and was neutralized by rabbit polyclonal anti-V IgG as well as by sera from mice surviving infection with Y. pestis. Recombinant polyhistidine-tagged V fusion proteins retained biological activity compared to V proteins lacking the tag. Inhibition of chemotaxis appears to be the first demonstration of an in vitro biological effect of V and may be a useful model to elucidate its molecular mechanism of action.

Late-stage mediators of the inflammatory response: identification of interleukin-1 and a casein-degrading enzyme in equine acute inflammatory exudates

Interleukin-1 and a casein-degrading enzyme have been identified in an experimental system for studying acute inflammation in the horse. The levels of both the cytokine and the proteinase increased over the first 24 hours following initiation of the inflammatory response, and remained at high levels through to the last sample collected at 48 hours. This is in marked contrast to prostaglandin E2 concentrations which were low initially, peaked at four to eight hours and had returned to low levels by 12 to 24 hours. It is likely that interleukin-1 and various proteinases are involved in the later stages of the inflammatory response, such as the tissue remodelling associated with wound repair, and control of this cytokine may be important in the progression from acute to chronic inflammation.

Growth and metastasis of human tumors in nude mice following tumor-cell inoculation into a vascularized polyurethane sponge matrix

Growth and metastasis of human tumor cells in immunodeficient nude mice were improved when tumor cells were inoculated within a vascularized artificial polyurethane sponge matrix. The sponges had been implanted 7-10 days earlier and were vascularized at the time of cell injection. All cell lines tested, including colon carcinoma-derived lines from primary tumors (HT29, PT3 and PT4) or from liver metastasis (LM3), and a metastatic variant from a melanoma (MeWo-Met) grew in a high percentage (78-94%) of the inoculated sponge grafts. When growth in sponge grafts is compared with growth at a subcutaneous site, the sponge matrix appears to increase tumorigenicity, at least for some cell lines. Regular formation of metastases was observed when cells had been injected into sponges. Most metastases were found in a second sponge graft implanted at a contralateral site, but some were also found at other s.c. sites. In vivo depletion of NK cells by pre-treatment with cyclophosphamide could not further enhance the formation of metastasis. Tumor cells from fresh surgical specimens could be propagated in sponge matrix grafts and subsequently established as cell lines in tissue culture.

The cored sponge model of in vivo leucocyte chemotaxis

A method has been developed for the in vivo measurement of leucocyte chemotaxis in response to the bacterial chemotactic peptide F-met-leu-phe (FMLP). Polyurethane sponges were pre-treated with FMLP and implanted subcutaneously in rats and after a suitable interval removed for determination of leucocyte influx. In vivo concentration gradients of chemotactic factors within intact sponges were shallow and leucocyte accumulation unsatisfactory. Accordingly a cored sponge model was developed in which the cylindrical core only was treated with chemotactic factor and the sponge reassembled prior to subcutaneous implantation. Steep concentration gradients were established within the outer sponge matrix with marked effects on leucocyte accumulation, permitting studies of the time course of in vivo chemotaxis. With cored sponges test to control cell number ratios were maximal at 4 hours using both free and albumin-bound FMLP. This model of in vivo chemotaxis may prove useful in several areas of inflammation research.

Leukotriene involvement in pathologic processes

Leukotrienes (LTs) have potent biologic properties, suggesting a role in human disease. LTB4 release has been detected in inflammatory exudates in the rat. LTC4 release has been detected after antigen challenge of lung tissue in vitro and in tear fluid in man in vivo. There is some evidence to suggest that LTB4 is a mediator of ulcerative colitis in man and considerable evidence to suggest that LTB4, LTC4, and LTD4 may be involved in the pathogenesis of psoriasis.

The mechanism of the anti-inflammatory effect of turpentine in the rat

The influence of counter irritation by turpentine on carrageenan-oedema, leucocyte count, plasma kininogen stores and composition of sponge-induced exudates has been investigated in the rat. Counter irritation reduced the carrageenan-oedema in normal as well as in adrenalectomized rats. It induced leucopenia with lymphopenia but did not modify the plasma kininogen stores. In turpentine-pretreated rats, the exudates induced by sponge implantation 18 h previously had a lower content in leucocytes. Their levels in beta-glucuronidase and beta-galactosidase were slightly reduced, their content in PGE2 was not modified and their level in malonaldehyde was increased. The exudates induced by sponge implantation 4 h previously had a lower content in leucocytes and PGE2 while their level in kinins was not modified. The mechanism of the anti-inflammatory effect of counter irritation by turpentine is discussed. We suggest that the main factor involved is a decrease in leucocyte accumulation into the exudates.

Leukotriene B4, polymorphonuclear leukocytes and inflammatory exudates in the rat

Leukocyte numbers and Leukotriene B4- (LTB4-) and LTC4-immunoreactivity were measured in inflammatory exudates obtained from sponges impregnated with several irritants implanted subcutaneously in the rat. Sponges containing 1% uric acid, carrageenan or zymosan were implanted for 5h and compared to saline sponges. Increases in leukocyte numbers and LTB4-immunoreactivity were found in the presence of irritants, the highest concentrations being observed in the presence of zymosan. The presence of LTB4 was confirmed by liquid chromatographic (HPLC) analysis. A time course study was carried out with zymosan-impregnated sponges and the maximal rate of leukocyte infiltration was found to coincide with the maximal levels of LTB4-immunoreactivity. The LTC4-immunoreactivity was low and following analysis by HPLC was concluded to be unrelated to leukotrienes. The levels of LTB4-immunoreactivity, but not the numbers of leukocytes, were elevated compared to corresponding controls in sponges containing 0.01% ionophore A23187 (untreated rats) or in sponges containing zymosan (rats pretreated with indomethacin; 3 and 10 mg/kg p.o.). Impregnation of sponges with 3 X 10(-6)M LTB4 but not 3 X 10(-5) and 3 X 10(-7)M LTB4 induced a significant leukocyte migration. It was concluded that LTB4 can induce leukocyte migration into sponge exudates in the rat but that measurements of LTB4 in such exudates can not be correlated with the degree of leukocyte infiltration.

The effect of anti-inflammatory and anti-rheumatic drugs on cell accumulation onto nitrocellulose discs implanted subcutaneously into mice

Nitrocellulose discs were implanted subcutaneously into mice and cell accumulation measured 96 hours later. Cell accumulation was inhibited by the anti-inflammatory steroids hydrocortisone, dexamethasone and triamcinolone acetonide, but higher doses of the latter two compounds were required than are normally used in rat models of inflammation. Cell accumulation was not inhibited by the cyclo-oxygenase inhibitors naproxen, indomethacin, tolmetin or aspirin, nor by the dual cyclo-oxygenase and lipoxygenase inhibitors BW 755C and benoxaprofen. Anti-rheumatic drugs such as D-penicillamine, dapsone and colchicine and the metal chelator 1,10 phenanthroline were all inactive on cell accumulation in this model.

The effect of a novel, non-steroidal anti-inflammatory compound, nabumetone (BRL 14777), on cellular infiltration into 24-hour polyvinyl sponge implants in the rat, compared with some steroidal and non-steroidal anti-inflammatory drugs

The time-course of cell migration into saline-soaked sponge implants over 5 days showed peak polymorphonuclear leucocyte (PMNL) infiltration at 24 h. In common with the corticosteroids dexamethasone and hydrocortisone, and the non-steroidal anti-inflammatory drugs indomethacin, (+)-naproxen, BW 755C and benoxaprofen, nabumetone decreased cell migration into the sponges. PMNLs and mononuclear cells were reduced at 24 h, and there was a parallel decrease in exudate levels of the lysosomal acid hydrolase beta-N-acetyl glucosaminidase [NAG ECB, 3, 2, 1, 30]. Impregnation of sponges with lambda-carrageenan (1%) caused a 2-3 fold increase in cell numbers, with a relatively greater proportion of PMNLs; drug effects were more marked in these implants.

A study of the effects of nabumetone (BRL 14777), a novel anti-inflammatory drug, on cell infiltration into sterile cotton pellets implanted in rats

Nabumetone a new non-steroidal anti-inflammatory drug is active in reducing the DNA content of implanted cotton pellets in rats on various dosing regimens. The effect of nabumetone can be seen during the early and late phases of the cellular reaction to the implant implicating effects upon polymorphonuclear leucocytes and monocytes. The levels of two lysosomal enzymes are reduced in the exudate by the drug treatment.

Migration of peritoneal polymorphonuclear leucocytes in the rat

The migration of PMNs into inflammatory sites in the rat has been studied using elicited peritoneal cells. These cells exhibit normal random migration and phagocytosis in vitro but their chemotactic response towards activated serum is significantly reduced when compared to cells isolated from peripheral blood. When injected intravenously, peritoneal cells not only show a greatly diminished ability to accumulate in inflammatory exudates but also block the migration of peripheral PMNs. Thus while PMNs obtained from the peritoneum may be suitable for some studies, they are not representative of peripheral cells with respect to their ability to accumulate in inflammatory exudates due to implanted inert sponges.