Recruitment of mononuclear cells by endothelial cell binding into wounded skin is a selective, time-dependent process with defined molecular interactions

Biocompatibility and immunostimulatory properties of fish collagen and shrimp chitosan towards peripheral blood mononuclear cells (PBMCs)

Several naturally occurring biopolymers are commercially produced from livestock and farmed animals processing wastes, including aquatic organisms. These wastes are considered valuable coproducts of fishery processing industry, from which biopolymers may be recovered and exploited for their bioactive potential. The aim of this work was to prepare polymeric films from collagen and chitosan solutions, extracted from fishery discards, and investigate the cytotoxicity and immunomodulatory activity towards human peripheral blood mononuclear cells (PBMCs). PBMCs were isolated from healthy donors and treated with Chitosan, Collagen, Chitosan+Collagen solutions and Chitosan+Collagen film in order to measure the changes in cell viability, cytosolic calcium concentration ([Ca²⁺]cyt), mitochondrial membrane potential (ΔΨm), reactive oxygen species (ROS) levels, differentiation and activation of T CD8⁺ and CD4⁺ lymphocytes, and cytokine production. Results showed that collagen and chitosan preparations did not show cytotoxic effect, while cellular IL-6, IL-10, and TNF-α release was observed. Chitosan and collagen were able to promote non-cytotoxic PBMCs activation through cytosolic and mitochondrial ROS production. There was a noteworthy phenotyping of lymphocytes T CD8⁺ and CD4⁺ counting and an increase of [Ca²⁺] cyt and ΔΨm levels. These results suggest that chitosan/collagen-based biomaterials produce immunostimulatory effects on PBMC with potential to biomedical approaches.

The potential role of the lymphocyte in fetal wound healing

Wound healing is a complex process involving a number of different cell populations. Since fetal wounds contain only a small number of mononuclear cells and no fibrosis immunohistochemical techniques using monoclonal antibodies specific to T and B lymphocytes, as well as macrophages, were used to identify the mononuclear cells in fetal wounds and to compare the lymphocyte response with the adult wound healing response. Polyvinyl alcohol sponges were placed subcutaneously in fetal rabbits on day 24 of gestation (then 31 days). Adult rabbits underwent similar implantation. Implants (8 to 14 per group) were harvested 5 days later and examined by H&E and trichrome staining as well as immunohistochemical staining with monoclonal antibody (Mab) specific for rabbit T and B lymphocytes. The sponges in one group of fetal rabbits were impregnated with the polypeptide growth factor, transforming growth factor-beta (TGF-beta), a known regulator of adult tissue repair. Adult wounds showed an intense inflammatory response with extensive collagen deposition; 80% of the infiltrating cellular elements were T lymphocytes. Fetal wounds were less cellular with minimal collagen deposition; 40% of the cells were T lymphocytes. The fetal wounds treated with TGF-beta were intensely cellular and fibrotic with 71% of the cellular infiltrate comprised of T lymphocytes. The increased cellularity of the TGF-beta wounds appears to be primarily the result of increased numbers of T lymphocytes. These findings demonstrate that the fetus mounts an attenuated T lymphocyte response compared to the adult. The increased response of T lymphocytes with TGF-beta suggests that the specific growth factor milieu may account for the fetal response to wounding.(ABSTRACT TRUNCATED AT 250 WORDS)

Growth factors and wound healing

BACKGROUND

Over the last decade, there has been an exponential increase in our knowledge of the biology of growth factors. The hope has been and remains that these potent biologic agents will effect a fundamental improvement in the way we treat wounds.

OBJECTIVE

We will discuss the biology of growth factors and the dramatic effects these proteins have on cell proliferation, cell chemotaxis, and on the formation of extracellular matrix molecules.

RESULTS

Growth factors are extremely potent biologic agents that show promise in accelerating wound repair in both animal and human studies. They improve granulation tissue, enhance tensile strength, and promote reepithelialization. Cosmetic effects are also to be expected by antagonizing and blocking the action of these peptides.

CONCLUSION

Growth factors are likely to become an important therapeutic tool for the dermatologic surgeon.

The effects of occlusive dressings on the recruitment of mononuclear cells by endothelial binding into acute wounds

Mononuclear cell infiltration is a characteristic feature of wounds and may play an important role in the healing process. We have previously shown that the recruitment of peripheral blood mononuclear cells into wounded skin is an active, dynamic, and regulated process mediated at least in part by specific interactions between mononuclear leukocytes and specialized dermal microvascular endothelial cells in the wounded skin. The purpose of this study was to investigate the capacity of dermal microvascular endothelial cells in wounds exposed to air or covered with occlusive dressings to promote the adhesion of monocytes and lymphocytes. The results showed that dermal microvascular endothelial cells in both air-exposed and occluded wounds were capable of supporting peripheral blood mononuclear cell and monocyte adherence. However, in comparison with air exposed wounds, the level of peripheral blood mononuclear cell binding was significantly higher in occluded biopsies obtained at 0 to 9, 12, 15, and 21 days after wounding. In addition, monocyte and peripheral blood mononuclear cells binding to occluded wounds peaked earlier than peripheral blood mononuclear cell binding to air exposed wounds. These studies provide evidence that differences in the kinetics and magnitude of mononuclear cell adherence may account at least in part for the beneficial effects of occlusive dressing on wound healing.

Transforming growth factor-beta differentially regulates the adhesiveness of normal and psoriatic dermal microvascular endothelial cells for peripheral blood mononuclear cells

Lymphocytes adhere to dermal microvascular endothelial cells (DMEC) as the first step in their migration from the bloodstream into diseased skin. Psoriasis is characterized by an intense T-lymphocytic infiltrate in the dermis, which may be a consequence of the abnormal regulation of endothelial adhesiveness by cytokines released locally. In the present study, we investigated the effects of tumor necrosis factor-alpha (TNF), interleukin-1 (IL-1), IL-4, and transforming growth factor-beta 1 (TGF-beta) on the adhesiveness of DMEC isolated from psoriatic plaques or normal skin for human peripheral blood mononuclear cells (PBMC). The results showed that DMEC from both normal and psoriatic skin retain the capacity to adhere to 51Cr-labeled PBMC. Pretreatment of DMEC from normal skin with human recombinant IL-1 or TNF alone or in combination for 8 h significantly (p less than 0.01) enhanced their capacity to adhere to human PBMC. Similarly, treatment of normal DMEC with IL-4 also increased endothelial adhesiveness, although this cytokine required an incubation period of 24 h. In parallel studies, DMEC from psoriatic plaques were found to respond to the stimulatory effects of TNF, IL-1, and IL-4 in similar dose- and time-dependent manner. In contrast, although pretreatment of normal DMEC with TGF-beta (0.1 to 0.25 ng/ml) for 6 to 12 h significantly reduced (p less than 0.01) both the unstimulated and IL-1- and TNF-stimulated endothelial adhesiveness for normal PBMC, TGF-beta had no effect on the binding of unstimulated or cytokine-stimulated psoriatic DMEC to PBMC, even at concentrations as high as 2 ng/ml and incubation period of 36 h. These results suggest that cytokines stimulate the adhesiveness of DMEC through distinct pathways and provide evidence that TGF-beta may play an important regulatory role in the control of lymphocyte extravasation into normal skin. The altered responsiveness of psoriatic DMEC to TGF-beta may contribute to the intense dermal lymphocytic infiltrates in psoriasis.

Transforming growth factor-beta regulates the adhesive interactions between mononuclear cells and microvascular endothelium

Adhesion of leukocytes to the vascular endothelium is essential for the movements of cells from the bloodstream into inflammatory sites. In the present study, dermal microvascular endothelial cells (DMEC) isolated from normal porcine skin retained the capacity to adhere 51Cr-labeled porcine peripheral blood mononuclear cells (PBMC), nylon-wool-purified T cells, and isolated monocytes. Transforming growth factor-beta 1 (TGF-beta) decreased the capacities of DMEC to support the adhesion of these cells in a dose-dependent manner. Maximal inhibition was observed with a TGF-beta dose of 0.25 ng/ml and an incubation time of 6-12 h. TGF-beta did not affect the morphology of DMEC and had no adverse effect on the viability of the treated cells. The blocking effects of TGF-beta on PBMC adhesion to DMEC was neutralized by a polyclonal turkey anti-TGF-beta antiserum but not by control turkey serum. Although pretreatment of PBMC with TGF-beta decreased the capacity of these cells to adhere to normal DMEC monolayers, kinetic studies demonstrated that these effects required between 4 and 8 h incubation time. In addition, preincubation of DMEC with TGF-beta completely blocked their response to the stimulating effects of TNF-alpha, IL-1-beta, or both cytokines. Furthermore, TGF-beta also abrogated the enhanced adhesiveness of DMEC pretreated with TNF-alpha and IL-1-beta. These findings suggest that TGF-beta may play an important role in the down-regulation of inflammatory responses by decreasing vascular endothelial adhesiveness for mononuclear cells and monocytes.