Ex vivo propagation and characterization of lymphocytes from rejecting rat-kidney allografts

Effect of bone morphogenetic protein-2 on tendon-bone integration in an in vitro cell culture

The goal of this study was to evaluate the influence of bone morphogenetic protein-2 (BMP-2) on tendon-bone integration in a bovine in vitro cell culture. Seventy-two bovine tendons were cultivated over 3 months. The effects of BMP-2 were evaluated by generation in 4 subgroups. The groups differed in 2 parameters: the application of BMP-2 and the application of primary bovine osteoblasts. Results were analyzed biochemically by determining alkaline phosphatase activity and histologic tendon calcification, both markers for graft incorporation. Histological analysis demonstrated a positive effect of BMP-2 on the production of extracellular matrix and therefore the induction of osteogenesis. In addition, the results showed a superior cell ingrowth on the tendon in the BMP-2-stimulated groups. Calcium carbonate-like structures and organized ossification zones could only be detected in the BMP-2-stimulated tendons. The histological results matched those of the biochemical alkaline phosphatase analysis. The highest alkaline phosphatase activity was detected using BMP-2 stimulation in the first month (P<.001). High alkaline phosphatase values suggest high osteoblast activity and a high potential for mineralization. Furthermore, a positive effect of BMP-2 on fibroblasts existed with regard to the overall integration process. These results confirm the positive influence and triggering effect of BMP-2 on the mineralization process. Bone morphogenetic protein-2 seems to accelerate and optimize tendon-bone integration in the early process of graft incorporation. Besides the influence of BMP-2 on bovine osteoblasts, an additional positive effect of BMP-2 on bovine fibroblasts was detected; therefore, graft incorporation may be carried out by osteoblasts and fibroblasts.

Lymphocyte propagation from biopsies of kidney allografts

Morphological evaluation of transplant biopsies, usually using the Banff classification, is the most important tool to diagnose rejection after kidney transplantation. However, morphological analysis only scores the amount and localisation of infiltrating cells, and studies show that up to 30% of grafts with a stable function display infiltration of lymphocytes consistent with acute cellular rejection. Methods to study the functional properties of the infiltrating lymphocytes are therefore needed. We applied a tissue culture system on biopsies from transplanted human kidneys, allowing infiltrating cells to propagate out from the tissue. Cells were then counted and subtyped by flow cytometry. The results were correlated to morphology. In total, 92 biopsies from 69 patients were analysed. For 14 patients, serial biopsies were available. In grafts with cellular or combined cellular and vascular rejection, the number of ex vivo propagated mononuclear cells was higher than from non-rejecting grafts. A similar pattern was seen for CD3(+) T cells as well as for T cells expressing CD25 or MHC class II antigens. However, the proportion of CD25(+) or MHC class II(+) T lymphocytes was similar in all groups (no rejection, vascular rejection, borderline changes, cellular rejection, combined cellular and vascular rejection). In all groups the number of CD4(+) cells was higher than the number of CD8(+) cells. The results confirm previous experimental studies showing that graft-infiltrating cells are possible to culture in vitro and that lymphocyte propagation correlates to acute cellular rejection. Tissue culturing is easy to perform and evaluate and can be used to determine and analyse the cellular immune response to allografts and may thus be used as a complement to morphological analyses.

Phenotyping of ex vivo propagated graft-infiltrating cells—A tool to monitor rejection in the early post-operative period

Objective and fast methods to diagnose rejection after organ transplantation are needed. In the present study, the ex vivo propagation technique was evaluated for its ability to detect rejection at two different time-points after experimental heart transplantation. Syngeneic and allogeneic heterotopic heart transplantations were performed using inbred rat strains. After 6 or 15 days, cardiac graft biopsies were put in culture and infiltrating cells isolated by the ex vivo propagation technique. The isolated cells were counted and phenotyped by flow cytometry. In parallel, graft sections were analysed with regard to morphology and the presence of infiltrating cells as determined by immunohistochemical stainings. On day 15 after transplantation, the number of cells possible to isolate through ex vivo propagation reflected the morphological changes of the graft, i.e. considerably more cells were obtained from allogeneic transplants undergoing rejection (1052 +/- 205) than from allogeneic grafts under cyclosporine protection (513 +/- 135; p < 0.05) or from syngeneic grafts (378 +/- 87; p < 0.01). Six days after transplantation the allogeneic grafts were strongly rejected with massive cellular infiltration, still there was no difference between allogeneic and syngeneic grafts as to the number of ex vivo propagated cells. However, the proportion of IL-2-receptor expressing T lymphocytes was increased (15.4 +/- 1.8% vs. 9.5 +/- 1.4%; p < 0.05) and the CD4/CD8 ratio reduced (1.0 +/- 0.1 vs. 2.8 +/- 0.2; p < 0.001) in the allogeneic group as compared with the syngeneic. We conclude that the ex vivo propagation technique can be used to distinguish rejection from non-rejection both early and later after transplantation, provided that not just cell counting but also phenotyping of the graft-infiltrating cells is performed.

Regulation of fibroblasts by activated and non-activated immune cells

BACKGROUND

Rejection of transplanted tissue is characterized by cell infiltration and interstitial edema. Graft fibroblasts and fibroblast products are partly involved in the regulation of both these phenomena. Knowledge about the mechanisms behind fibroblast activation may lead to new strategies to prevent rejection. This study investigated whether cells of the immune system have the capacity to regulate fibroblast activation.

METHODS

Fibroblasts isolated from rejecting heart transplants or from normal heart tissue were cultured in the presence of supernatants of stimulated or non-stimulated immune cells. The immune cells were challenged either in vitro (incubation with phytohemagglutinin) or in vivo (organ transplantation). Fibroblast proliferation and hyaluronan production were measured.

RESULTS

Normal, sub-confluent heart fibroblasts showed an increased proliferation rate in the presence of supernatants of activated immunocompetent cells, irrespective of if these cells had been stimulated in vitro or in vivo. As expected, proliferation rate and hyaluronan production were upregulated in fibroblasts isolated from rejecting tissue. However, supernatants of biopsy specimens obtained from non-rejecting organs (syngeneic transplants or normal hearts) had an inhibitory effect on the growth rate of confluent fibroblasts isolated from rejecting tissue.

CONCLUSIONS

We conclude that graft-infiltrating cells and immune cells activated in vitro have the capacity to stimulate fibroblasts, most probably as a result of the production and secretion of fibroblast-stimulating factors.

Quantification of lymphocytes propagating from rat-kidney allografts--a tool to monitor anti-rejection treatment

BACKGROUND

Morphological evaluation of kidney biopsies applying the Banff Classification is closely correlated to clinical parameters of rejection. However, this classification is insufficient for monitoring the effect of instituted anti-rejection therapy. The objective of the present study was to develop a diagnostic tool enabling rapid assessment of the effects of an attempted anti-rejection treatment.

MATERIALS AND METHODS

A kidney allotransplantation model in the rat was applied. All animals were initially maintained on cyclosporine A (CsA). In order to induce an episode of acute cellular rejection, CsA was withdrawn for 5 days. Thereafter, the immunosuppressive treatment was restarted. Core biopsies were taken before, and at various times after, the introduction of anti-rejection therapy. Infiltrating cells were isolated using an in vitro culture system, allowing cells to propagate from the biopsies to culture medium. Propagated cells were counted and analysed for subtype and activation markers using flow cytometry. The results were compared with immunohistochemical and morphological analyses of the grafts.

RESULTS

By applying the in vitro culture system it was possible to demonstrate a reduction in outgrowth of mononuclear cells from core biopsies as early as 2 days after the start of anti-rejection therapy. At this time-point, as well as 2 days later, morphological and immunohistochemical analyses of biopsies showed ongoing acute cellular rejection, with no differences between biopsies taken before and after restart of CsA-therapy. The percentage of propagating T lymphocytes expressing the activation markers CD25 or MHC class II did not differ between grafts with ongoing rejection and grafts obtained from CsA-treated rats, neither did the ratio of CD4/CD8-positive cells.

CONCLUSION

Our findings indicate that the ex vivo propagation method could function as a complement to routine histology, not only in the diagnosis of cellular rejection but also in order to rapidly reveal a failure of an anti-rejection therapy to halt the rejection process.

Isolation of mouse-to-rat cardiac xenograft-infiltrating cells by ex vivo propagation

Ex vivo propagation of graft infiltrating lymphocytes has become a useful method for the examination of the cellular response after allogeneic transplantation. The aim of the present study was to investigate if this method can be used also for isolation of xenograft infiltrating cells, and, if so, to further characterize these cells. The concordant mouse-to-rat heart transplantation model was used for the experiments. Recipient rats were treated either with 15-deoxyspergualin (DSG) or with a combination of DSG and cyclosporine A (CyA) or left untreated. Transplants were removed beating on day 2 (untreated) or day 8 (DSG and CyA + DSG) and biopsies were incubated in culture medium for 48 h, resulting in propagation of cells from the biopsies into culture medium. The propagated cells were counted and phenotyped using flow cytometry. In parallel, the transplants were examined morphologically and immunohistochemically. Infiltrating cells could be isolated from all grafts in all groups. The number of propagated T lymphocytes during cellular rejection (DSG-treatment) was about 3.5 times higher than during 'non-rejection' (CyA + DSG) and six times higher than during acute vascular rejection (untreated). These findings were supported both by the morphological and the immunohistochemical findings. In conclusion, we have shown that graft infiltrating lymphocytes can be isolated from xenogeneic heart transplants by incubation of biopsies for 48 h, resulting in spontaneous propagation of immune cells into culture medium. Propagated cells could be further characterized by flow cytometry. Thus, the technique presented here can be used as a tool for studies of xenogeneic cellular rejection.