Accessible xenografts of human synovium in the subcutaneous tissues of the ears of SCID mice

A novel method to allow noninvasive, longitudinal imaging of the murine immune system in vivo

In vivo imaging has revolutionized understanding of the spatiotemporal complexity that subserves the generation of successful effector and regulatory immune responses. Until now, invasive surgery has been required for microscopic access to lymph nodes (LNs), making repeated imaging of the same animal impractical and potentially affecting lymphocyte behavior. To allow longitudinal in vivo imaging, we conceived the novel approach of transplanting LNs into the mouse ear pinna. Transplanted LNs maintain the structural and cellular organization of conventional secondary lymphoid organs. They participate in lymphocyte recirculation and exhibit the capacity to receive and respond to local antigenic challenge. The same LN could be repeatedly imaged through time without the requirement for surgical exposure, and the dynamic behavior of the cells within the transplanted LN could be characterized. Crucially, the use of blood vessels as fiducial markers also allowed precise re-registration of the same regions for longitudinal imaging. Thus, we provide the first demonstration of a method for repeated, noninvasive, in vivo imaging of lymphocyte behavior.

In vitro and in vivo efficacy of a recombinant immunotoxin against folate receptor beta on the activation and proliferation of rheumatoid arthritis synovial cells

OBJECTIVE

To investigate the effects of the recombinant immunotoxin dsFv anti-FRbeta-PE38, which consists of the disulfide-stabilized Fv fragment (dsFv) of the anti-folate receptor beta (anti-FRbeta) antibody and the 38-kd portion of Pseudomonas exotoxin A (PE38), on the activation and proliferation of cells that function in inflammatory and degradative processes in rheumatoid arthritis (RA) synovial tissue.

METHODS

The Ig VH-PE38 fusion protein and the Ig VL protein were produced in Escherichia coli, and then joined with a disulfide bond by engineering cysteine residues in the framework regions of these proteins. The effects of dsFv anti-FRbeta-PE38 on the activation and proliferation of cells in RA synovial tissue were investigated by immunohistochemistry; the numbers of cells expressing CD68, vascular cell adhesion molecule 1, angiopoietin 1, CD34, proliferating cell nuclear antigen, and interleukin-6 and the numbers of apoptotic cells were counted in RA synovial tissue engrafted into SCID mice treated or not treated with dsFv anti-FRbeta-PE38. The effects of dsFv anti-FRbeta-PE38 on the generation of osteoclasts from RA adherent synovial mononuclear cells in vitro was investigated by counting the number of resorption pits on dentin slices treated or not treated with dsFv anti-FRbeta-PE38.

RESULTS

Administration of dsFv anti-FRbeta-PE38 reduced the numbers of macrophages, activated fibroblast-like cells, endothelial cells, and proliferating cells and increased the numbers of apoptotic cells in RA synovial tissue engrafted into SCID mice. In vitro, the generation of osteoclasts from RA adherent synovial mononuclear cells was largely suppressed by treatment with dsFv anti-FRbeta-PE38.

CONCLUSION

Our findings show that dsFv anti-FRbeta-PE38 immunotoxin would be a promising tool for the treatment of RA synovitis, especially when administered intraarticularly.

Recruitment of mononuclear leucocytes to osteoarthritic human synovial xenografts in the ears of SCID mice

A system has been established to assess the recruitment of 99mTc-hexamethylpropylene amine oxamine (99mTc-HMPAO)-labelled PBMC and [125I]iododeoxyuridine-labelled Con A stimulated lymphoblasts to allogeneic human synovial xenografts in the ears of SCID mice. Successful engraftment of osteoarthritic synovium was achieved in approximately 90% of cases and a connection between the human microvasculature of the xenograft and the circulation of the mouse was shown. Cells were delivered to the xenograft by a system of regional vascular perfusion, thus avoiding the major murine vascular beds. The accumulation of 99mTc-HMPAO-labelled PBMC in mouse ears was monitored in real time. Direct injection of xenograft-bearing ears with recombinant human TNF-alpha, 7 h prior to perfusion, increased the accumulation of both PBMC and lymphoblasts in cytokine-injected ears compared to contralateral control-injected ears. Autoradiography revealed the presence of [125I]iododeoxyuridine-labelled lymphoblasts associated with human microvasculature within the xenograft. However, the increased accumulation of lymphoblasts in cytokine-injected ears occurred in the tissues surrounding the xenograft, where lymphoblasts were associated more often with murine than human vessels. Although the system described offers advantages over similar models, the propensity for mouse endothelium to interact with human leucocytes is likely to be a generic disadvantage for models of human leucocyte recruitment to xenografts in immunodeficient mice.

Transplantation and growth characteristics of human fetal lymph node in immunodeficient mice

OBJECTIVE

The lymph node is an integral component of the immune system and the major site of antigen-dependent lymphocyte proliferation and differentiation. Development of animal models possessing functional primary human lymph nodes will have a significant impact on research in lymphopoiesis and immune response. To date, successful transplantation of primary human lymph nodes in rodents has not yet been reported. This work was undertaken to develop a reliable methodology to engraft primary human fetal lymph nodes in immunodeficient mice.

MATERIALS AND METHODS

Three different sets of parameters, including three different transplantation sites in the mice, two different strains of immunodeficient mice, and two different preconditioning regimens, were evaluated. The growth characteristics of the implanted primary human fetal lymph nodes were examined 3 months after transplantation by histologic, immunocytochemical, and flow cytometric methods.

RESULTS

Transplantation of primary human fetal lymph nodes into subcutaneous pouches in the ears in severe combined immunodeficiency (SCID) mice preconditioned with etoposide reproducibly give rise to >80% engraftment. The engrafted primary human fetal lymph nodes undergo massive growth (>200-fold) and retain the same histology and cellular composition as fresh human fetal lymph nodes from the same donors.

CONCLUSIONS

We report, for the first time, the development of a reliable methodology to successfully engraft human fetal lymph node in SCID mice. The engrafted human lymph nodes are visible and accessible to experimental manipulations. This SCID-hu mouse model with human lymph node should provide a physiologically relevant system to investigate lymphopoiesis, immunologic response, and virus-mediated immunosuppression.