Platelet gel stimulates proliferation of human dermal fibroblasts in vitro.

BACKGROUND: Platelet gel is a source of many soluble proteins that can modulate tissue regeneration. Dermal fibroblasts play an important role in tissue remodeling and wound healing. OBJECTIVE: The study was performed to investigate the influence of platelet gel and its active ingredients on the proliferation of human dermal fibroblasts in vitro. METHODS: A fibroblast culture was established from a normal human skin biopsy. Platelet gel was prepared from platelet-rich plasma (PRP) following the addition of calcified thrombin solution. Cell proliferation was measured by MTT assay. RESULTS: We showed that platelet gel, PRP, and thrombin stimulate the proliferation of dermal fibroblasts, and that stimulation by PRP is dose dependent. CONCLUSION: Platelet gel can be used to treat chronic skin defects.

Immunogenicity of dendritic cells pulsed with cartilage derived soluble alloantigens.

Investigation of allo- and autoreactivity of cartilage components is useful not only for the potential allogeneneic transplantation but also for the treatment of tissue specific degenerative autoimmune diseases. We generated dendritic cells (DCs) to study articular cartilage immunogenicity, by using human peripheral blood mononuclear cells. Dendritic cells are extremely efficient antigen-presenting cells that initiate and modulate T-cell dependant immune responses. After isolation by density centrifugation, GM-CSF and IL-4 were added to adherent mononuclear cells. After 7 days of cultivation the cells in cell culture were: HLA-DR+, CD86+, CD14-, CD80-, CD83, CD19-, CD56-, CD3-. Dendritic cells were then pulsed with a supernatant taken from primary monolayer cell cultures of human allogeneic chondrocytes. The stimulating capacity of antigen-pulsed DCs was measured in a classical proliferation assay using tritium labelled thymidine as a marker of mitosis. Proliferative responses were significantly strong but became much stronger when DCs were concomitantly incubated with soluble antigens and human recombinant TNF-alpha and used subsequently as stimulators. Although TNF-alpha positively influenced the stimulating capacity of pulsed DCs, we were unable to detect major differences in expression of specific DCs' phenotype markers assessed by flow cytometry in the absence or presence of this cytokine.

Protein synthesis of human articular chondrocytes cultured in vitro for autologous transplantation.

Chondrocytes in hyaline cartilage produce typical matrix proteins, the most abundant of them being collagen type II and aggrecan. Chondrocytes in monolayer cell culture dedifferentiate and gain fibroblastic phenotype. The cells gradually start to produce collagen type I while the production of collagen type II and aggrecan decreases. Transplantation of autologous chondrocytes cultured in vitro is used for treatment of aseptic articular cartilage lesions. For this purpose, cartilage biopsy is taken and isolated cells are subsequently proliferated in a monolayer cell culture. When implanted, the cells start to produce specific cartilaginous matrix that fills the defect. Prior to surgical procedure the cells can also be cryopreserved for longer periods of time after reaching appropriate numbers. We tested the influence of cultivation time and number of continuous culture passages as well as the influence of cryopreservation on the matrix protein synthesis of human articular chondrocytes. The ability of dedifferentiated chondrocytes to redifferentiate has been monitored by measuring matrix protein synthesis of the cells, re-seeded in agarose suspension culture. The results obtained show progressive dedifferentiation during monolayer cell culture procedures, facilitated by cryopreservation. Successful redifferentiation of cells re-seeded in suspension cultures was observed regardless of the previous level of chondrocyte dediferentiation.

Determination of optimal transport conditions for biopsies of human articular cartilage as well as for suspensions of cultured chondrocytes used in autologous transplantation.

Autologous transplantation of chondrocytes is currently being promoted as a novel approach for the treatment of deep cartilage lesions. Briefly, the method involves enzyme-mediated release of chondrocytes from cartilage biopsies, the expansion of cells by in vitro cultivation and their re-implantation into the defect. The success of this technique depends on many factors including transport conditions for both, cartilage biopsies from the operating hall to the laboratory and the return transport of final suspension of cultured chondrocytes. To determine the extent of cellular damage in biopsies, chondrocytes were enzymatically isolated following a few days of tissue preservation in different tissue culture media. The proportion of dead cells was assessed by Trypan blue staining and counting. The viability was not dependant of the type of the medium used and remained approximately 50% in all samples, even after 72 h. To develop optimal conditions for transport of final chondrocyte suspension, isolated cells were firstly grown in monolayer cultures. Cell suspensions in media with different additives were injected into special glass containers used for the transport and left at 4 degrees C or 25 degrees C for up to 3 days. During this period every 24 h the samples were taken and viability as well as apoptosis levels were assessed. Viability of cells in suspensions at 25 degrees C decreased significantly and became inadequate already after 48 h. In contrast to that, the proportion of viable cells at 4 degrees C remained above 80% even after 48 h. In the majority of the samples, culture medium containing serum and vitamin C provided the best conditions for long-term preservation of chondrocytes.

Vitamin C induced apoptosis in human articular chondrocytes.

Chondrocytes present in articular cartilage survive as a resident cell population throughout the lifespan of the individual organism. However, articular chondrocytes as other cells also undergo apoptosis and there is an ever increasing list of diverse stimuli that can induce this phenomenon in vitro. Our main interest was to investigate potential cytotoxic effects of vitamin C (L-ascorbic acid) on human articular chondrocytes. The present study suggests that vitamin C can induce apoptosis in a cell culture of chondrocytes after 18 h of cultivation. Apoptosis-inducing activity of L-ascorbic acid is dose dependent and significantly affected by the presence of serum. The increased number of vitamin C induced apoptotic cells was associated with DNA fragmentation and morphological changes of the cells.

In vitro functional tests for evaluation of stimulating capacity of cultured human dendritic cells.

Basic functional test for evaluation of in vitro cultured human dendritic cells (DC) is primary allogeneic one-way mixed lymphocyte reaction (MLR). In this way, one can evaluate stimulating capacity, which is a basic characteristic of DC. The proliferation of cells is measured through incorporation of 3H-thymidine. Normally proliferation is measured at days 5-7. We studied kinetics of proliferative responses initiated with different stimulating cell suspensions to evaluate differences and possibly reduce time needed to perform this test. Gradual increase in response from days 1 to 7 and a significant difference from controls (peripheral blood mononuclear cells) seen from day 4 was noted if macrophages were used as stimulators. A consistently higher proliferation, compared to controls, was always found already on day 2 when mature DC were used as stimulators. The reaction peaked 2 to 3 days earlier and was also more than two times more intense. This maximal and significantly higher response, consistently seen already after 48 hours, allows us to confirm the presence of mature DC in stimulating suspensions much earlier than previously.

The contribution of HLA-Class II antigens in humoral non-response and delayed response to HBsAG vaccination.

The variability in the immune response modulated by HLA alleles may be an important factor for the induction of the protective effect of HBsAg vaccines. We present here the analysis of HLA-DRB1, DQB1 and DQA1 alleles and their combinations in the group of 36 individuals with poor humoral immmune response to HBsAg vaccination. Comparison with the control group, consisted of 60 randomly choosen healthy subjects, revealed that the DRB1*1601, DQB1*0502, DQA1*0102 haplotype is overrepresented in the group of hyporesponders and may therefore be regarded as a factor influencing poor antibody responsiveness. We observed that after revaccination two of three individuals who failed to develop anti-HBs antibodies carry the same phenotype DRB1*0101,DRB1*0301;DQB1*0501,DQB1*0201;DQA1+ ++*0101,DQA1*0501, which supports the conjecture that immunogenicity of the HBsAg vaccine depends on specific combination of HLA DR and DQ molecules on antigen presenting cells.

Possible influence of genes located on chromosome 6 within or near to the major histocompatibility complex on development of essential hypertension.

Studies both in spontaneously hypertensive rats and in humans have suggested that genes within or near to the HLA complex on chromosome 6p may be associated and linked to the regulation of blood pressure. The aim of this study was to determine whether HLA alleles and their combinations contribute to increased blood pressure, as well as to identify chromosome region that may contain genes involved in the pathogenesis of essential hypertension. Our results suggest that presence of HLA-DRB1*0101/2 DQB1*0501/2 DQA1*0102 allelic combination represents risk factor for development of essential hypertension in Slovenians, while the risk is decreased in individuals possessing HLA-DRB1*1601/2 DQB1*0502 DQA1*0102 or DRB3*. The linkage study indicates a possibility that at least one of the genes responsible for increased blood pressure is located near or within the HLA complex. A possible candidate is human endotelin-1 gene encoding a highly potent vasoactive peptide.

Limiting dilution analysis of human IL-2 producing T-cell precursors. Determination of hierarchical alloantigenic potential of human leukocyte antigens and evaluation of alloimune responses to single HLA-DP molecules.

Twenty nine healthy unrelated individuals were carefully selected and divided into three groups according to their HLA (Human Leukocyte Antigens) phenotypes. A sensitive and reproducible limiting dilution analysis (LDA) based bioassay using CTLL-20 cells for detection of human IL-2 was set up and used to assess the hierarchical impact of highly polymorphic HLA molecules on individual's alloreactivity. Our main interest was to evaluate the role of HLA-DP molecules in this process. By calculating frequencies of IL-2 producing helper T cell precursors (HTLp) and amounts of IL-2 produced in each experiment, we were able to confirm that HLA-DR molecules are the most potent alloantigens. In 29 different combinations where a single HLA-DP mismatch between stimulating and responding cells was evaluated, some were reasonably tolerant, while the other ones evoked moderate to relatively strong alloimmune responses. Finally, two groups with statistically significant difference in alloimmune responses to stimulating HLA-DP molecules carrying D,E,A,V or G,G,P,M amino acid sequences at positions 84,85,86 and 87 in the sixth variable region F of the molecule could be formed, according to HTLp frequencies and amounts of IL-2 detected. Data presented are of great importance for the selection of unrelated as well as related bone marrow donors for haematological patients.

Possible influence of genes located on chromosome 6 within or near to the major histocompatibility complex on development of essential hypertension.

Studies both in spontaneously hypertensive rats and in humans have suggested that genes within or near to the HLA complex on chromosome 6p may be associated and linked to the regulation of blood pressure. The aim of this study was to determine whether HLA alleles and their combinations contribute to increased blood pressure, as well as to identify chromosome region that may contain genes involved in the pathogenesis of essential hypertension. Our results suggest that presence of HLA-DRB1*0101/2 DQB1*0501/2 DQA1*0102 allelic combination represents risk factor for development of essential hypertension in Slovenians, while the risk is decreased in individuals possessing HLA-DRB1*1601/2 DQB1*0502 DQA1*0102 or DRB3*. The linkage study indicates a possibility that at least one of the genes responsible for increased blood pressure is located near or within the HLA complex. A possible candidate is human endotelin-1 gene encoding a highly potent vasoactive peptide.

Limiting dilution analysis of human IL-2 producing T-cell precursors. Determination of hierarchical alloantigenic potential of human leukocyte antigens and evaluation of alloimune responses to single HLA-DP molecules.

Twenty nine healthy unrelated individuals were carefully selected and divided into three groups according to their HLA (Human Leukocyte Antigens) phenotypes. A sensitive and reproducible limiting dilution analysis (LDA) based bioassay using CTLL-20 cells for detection of human IL-2 was set up and used to assess the hierarchical impact of highly polymorphic HLA molecules on individual's alloreactivity. Our main interest was to evaluate the role of HLA-DP molecules in this process. By calculating frequencies of IL-2 producing helper T cell precursors (HTLp) and amounts of IL-2 produced in each experiment, we were able to confirm that HLA-DR molecules are the most potent alloantigens. In 29 different combinations where a single HLA-DP mismatch between stimulating and responding cells was evaluated, some were reasonably tolerant, while the other ones evoked moderate to relatively strong alloimune responses. Finally, two groups with statistically significant difference in alloimune responses to stimulating HLA-DP molecules carrying D,E,A,V or G,G,P,M amino acid sequences at positions 84,85,86 and 87 in the sixth variable region F of the molecule could be formed, according to HTLp frequencies and amounts of IL-2 detected. Data presented are of great importance for the selection of unrelated as well as related bone marrow donors for haematological patients.