Hypertrophic scar formation is associated with an increased number of epidermal Langerhans cells

The exact pathogenesis of hypertrophic scar and keloid formation is still unknown and a good therapy to prevent or treat these scars is lacking. Because immunological processes seem to be important in excessive scar formation, immunological cells and parameters were studied in a standardized breast reduction wound-healing model in the present study. Standardized scar samples were taken from infra-mammary breast reduction scars, 3 and 12 months following surgery. The samples were investigated for their number of mast cells, Langerhans cells, T-lymphocytes, and macrophages, and the presence of interleukin-4 (IL-4) and counter-regulating interferon-gamma (gamma-IFN), in relation to the scar's clinical appearance--normal or hypertrophic. In this study, hypertrophic scar formation was significantly associated with an increased number of epidermal Langerhans cells (p=0.0001) and significantly (p<0.05) increased expression of epidermal IL-4. No relationship was found between mast cell, T-lymphocyte and macrophage numbers or gamma-IFN staining and the formation of normal or hypertrophic scars. These results, combined with previous observation of abnormal keratinocyte behaviour in this context, indicate that the epidermal immune barrier plays an important role in the development of hypertrophic scars.     

Both Fc receptors and lymphocyte-function-associated antigen 1 on human Tγ lymphocytes are required for antibody-dependent cellular cytotoxicity (killer cell activity)

A monoclonal antibody, designated CLB-LFA-1/1, directed to the human lymphocyte-function-associated antigen 1 (LFA-1) was raised by immunization of mice with the peripheral blood lymphocytes of a Tγ lymphocytosis patient. The monoclonal antibody was selected by inhibition of the natural killer cell and the antibody-dependent killer cell activity of the patient's Tγ lymphocytes. In addition, the monoclonal antibody was shown to inhibit the cytotoxic activity of T cell clones specific for either class I or class II HLA molecules. The antigen recognized by CLB-LFA-1/1 consisted of three polypeptide chains with molecular weights of 180000 (α), 155000 and 94000 (β). The antibody reacted with T cells, B cells, monocytes and granulocytes, and stained normal Tγ cells and Tγ cells of patients with Tγ lymphocytosis two- to threefold stronger than normal T cells. It was shown that LFA-1 and the Fc receptor on Tγ cells did not comodulate and it is therefore concluded that Fc receptors and LFA-1 are independent membrane structures, both required for the killer cell activity of Tγ cells.     

Tissue reactions of in situ formed dextran hydrogels crosslinked by stereocomplex formation after subcutaneous implantation in rats

In this study, the in vivo biocompatibility of physically crosslinked dextran hydrogels was investigated. These hydrogels were obtained by mixing aqueous solutions of dextran grafted with L-lactic acid oligomers and dextran grafted with D-lactic acid oligomers. Gelation occurs due to stereocomplex formation of the lactic acid oligomers of opposite chirality. Since gelation takes some time, in situ gel formation is possible with this system. A number of sterilization methods was evaluated for their effect on the chemical and physical properties of the hydrogel. It was shown that of the investigated options (filtration, gamma irradiation, dry-heat and autoclaving) dry-heat sterilization was the preferred method to prepare sterile gels suitable for in vivo evaluations. Two types of stereocomplex gels were prepared and implanted subcutaneously in rats. The tissue reaction was evaluated over a period of 30 days. A mild ongoing foreign body reaction was observed characterized by infiltration of macrophages. Giant cells were only scarcely formed and the low numbers of lymphocytes showed that priming of the immune system is hardly involved. Importantly, the gels fully degraded in vivo within 15 days, which is in good agreement with the in vitro degradation behaviour of these gels. In conclusion, stereocomplexed dextran-oligolactic gels showed good biocompatibility which makes them suitable candidates for the design of controlled release devices for pharmaceutically active proteins.     

The effect of bacillus Calmette-Guérin immunization depends on the genetic predisposition to Th2-type responsiveness

The aim of this study was to investigate whether the effect of bacillus Calmette-Guérin (BCG) immunization on ovalbumin-induced allergic inflammation in a rat model depends on the genetic predisposition to react with a T helper cell (Th) 2-type cytokine response. This study was performed in an inbred Th2-predisposed "asthma prone" rat strain (brown Norway [BN]) and in an outbred nonpredisposed strain (Sprague Dawley [SD]), to differentiate between genetic and environmental factors. BCG decreased numbers of lung eosinophils and macrophages in the SD rat. This effect was not seen in the BN rat. In the BN rat, but not in the SD rat, BCG downregulated levels of total serum IgE. No significant differences were found with respect to frequencies of IFNgamma- or interleukin-4-producing cells in the lung in both rat strains. These results indicate that the degree and pathway of immunomodulatory effect of BCG in two genetically different rat strains is dependent on the genetic predisposition to develop a Th2-type response. Therefore, differences in genotype in relation to environment may result in difference in involvement of contributing pathogenic factors and thus different responsiveness to therapeutic strategies.     

Cartilage-free areas in the elbow joint of young golden retrievers

The present study describes cartilage-free areas on the ulnar trochlear notch and the humeral condyle of eight very young golden retrievers with otherwise healthy elbow joints. Remarkably, the youngest dog with full-thickness cartilage-free areas was only 8 weeks old. The younger dogs showed no macroscopic abnormalities on the locations that were affected in the older dogs. Two kinds of cartilage modifications were found. Cartilage-free areas at the edges of the articular cartilage layer were present on the humeral capitulum and on two locations of the ulna, (the medial and lateral at the base of the anconeal process, and the trochlear notch near the lateral coronoid process, which was fractured in two cases). Histological examination showed that these cartilage-free areas were filled with dense supportive tissue. Synovial cells covered this tissue as well as the surrounding hyaline cartilage. The synovial membrane covering the areas was macroscopically enlarged, but histological examination revealed no signs of inflammation. The second type of modification consisted of discoloration of the articular surface at the humeral trochlea. Histological examination revealed that in this area the articular surface was composed of fibrocartilage instead of hyaline cartilage. Apparently, there are locations within the elbow joint in which articular cartilage is not necessary for normal joint functioning. The presence of fibrocartilage on the articular surface of the humeral condyle is a surprising finding, for which no explanation has yet been found.     

Brachytelephalangic chondrodysplasia punctata in an extremely premature infant

We report on 3 sibs (2 males and one female) with sensorineural deafness. The presence of ovarian dysgenesis in the girl suggested a diagnosis of Perrault syndrome. In addition our patients have a sensory polyneuropathy and amelogenesis imperfecta. Two of the patients have mild mental retardation, fine choreatic movements, and dyspraxia. It is discussed whether these findings are part of a separate clinical entity or should be included within the spectrum of the Perrault syndrome. © 1994 Wiley-Liss, Inc.     

A novel regulation mechanism of DNA repair by damage-induced and RAD23-dependent stabilization of xeroderma pigmentosum group C protein

Primary DNA damage sensing in mammalian global genome nucleotide excision repair (GG-NER) is performed by the xeroderma pigmentosum group C (XPC)/HR23B protein complex. HR23B and HR23A are human homologs of the yeast ubiquitin-domain repair factor RAD23, the function of which is unknown. Knockout mice revealed that mHR23A and mHR23B have a fully redundant role in NER, and a partially redundant function in embryonic development. Inactivation of both genes causes embryonic lethality, but appeared still compatible with cellular viability. Analysis of mHR23A/B double-mutant cells showed that HR23 proteins function in NER by governing XPC stability via partial protection against proteasomal degradation. Interestingly, NER-type DNA damage further stabilizes XPC and thereby enhances repair. These findings resolve the primary function of RAD23 in repair and reveal a novel DNA-damage-dependent regulation mechanism of DNA repair in eukaryotes, which may be part of a more global damage-response circuitry.     

The disintegrin/metalloprotease ADAM 10 is essential for Notch signalling but not for alpha-secretase activity in fibroblasts

The metalloprotease ADAM 10 is an important APP alpha-secretase candidate, but in vivo proof of this is lacking. Furthermore, invertebrate models point towards a key role of the ADAM 10 orthologues Kuzbanian and sup-17 in Notch signalling. In the mouse, this function is, however, currently attributed to ADAM 17/TACE, while the role of ADAM 10 remains unknown. We have created ADAM 10-deficient mice. They die at day 9.5 of embryogenesis with multiple defects of the developing central nervous system, somites, and cardiovascular system. In situ hybridization revealed a reduced expression of the Notch target gene hes-5 in the neural tube and an increased expression of the Notch ligand dll-1, supporting an important role for ADAM 10 in Notch signalling in the vertebrates as well. Since the early lethality precluded the establishment of primary neuronal cultures, APPs alpha generation was analyzed in embryonic fibroblasts and found to be preserved in 15 out of 17 independently generated ADAM 10-deficient fibroblast cell lines, albeit at a quantitatively more variable level than in controls, whereas a severe reduction was found in only two cases. The variability was not due to differences in genetic background or to variable expression of the alternative alpha-secretase candidates ADAM 9 and ADAM 17. These results indicate, therefore, either a regulation between ADAMs on the post-translational level or that other, not yet known, proteases are able to compensate for ADAM 10 deficiency. Thus, the observed variability, together with recent reports on tissue-specific expression patterns of ADAMs 9, 10 and 17, points to the existence of tissue-specific 'teams' of different proteases exerting alpha-secretase activity.     

Differential expression of FIZZ1 and Ym1 in alternatively versus classically activated macrophages

Alternatively activated macrophages (aaMphi) display molecular and biological characteristics that differ from those of classically activated macrophages (caMphi). Recently, we described an experimental model of murine trypanosomosis in which the early stage of infection of mice with a Trypanosoma brucei brucei variant is characterized by the development of caMphi, whereas in the late and chronic stages of infection, aaMphi develop. In the present study, we used suppression subtractive hybridization (SSH) to identify genes that are expressed differentially in aaMphi versus caMphi elicited during infection with this T. b. brucei variant. We show that FIZZ1 and Ym1 are induced strongly in in vivo- and in vitro-elicited aaMphi as compared with caMphi. Furthermore, we demonstrate that the in vivo induction of FIZZ1 and Ym1 in macrophages depends on IL-4 and that in vitro, IFN-gamma antagonizes the effect of IL-4 on the expression of FIZZ1 and Ym1. Collectively, these results open perspectives for new insights into the functional properties of aaMphi and establish FIZZ1 and Ym1 as markers for aaMphi.