Induction of immune-mediated hearing loss in SCID mice by injection of MRL/lpr mouse spleen cells

Suppression of dsDNA-specific B lymphocytes reduces disease symptoms in SCID model of mouse lupus

Self-specific B cells play a main role in the pathogenesis of lupus. This autoimmune disease is characterized by the generation of autoantibodies against self antigens, and the elimination of B and T cells involved in the pathological immune response is a logical approach for effective therapy. We have previously constructed a chimeric molecule by coupling a DNA-mimotope peptides to an anti-CD32 antibody. Using this protein molecule for the treatment of lupus-prone MRL/lpr mice, we suppressed selectively the autoreactive B-lymphocytes by cross-linking B cell receptors with the inhibitory FcγRIIb receptors. This approach was limited by the development of anti-chimeric antibodies in MRL mice. In order to avoid this problem, we established a murine severe combined immunodeficiency lupus model, allowing a long-term chimera therapy. Elimination of the double-stranded DNA-specific B cells by chimera therapy in MRL-transferred immunodeficient mice resulted in inhibition of T cell proliferation and prevented the appearance of IgG anti-DNA antibodies and of proteinuria.

Transfer of accelerated presbycusis by transplantation of bone marrow cells from senescence-accelerated mice

Until now, there has been no effective therapy for chronic sensorineural hearing impairment. This study investigated the role of bone marrow cells (BMCs) in cochlear dysfunction. BALB/c mice (2 months of age), a non-presbycusis-prone mouse strain, were lethally irradiated and then transplanted with BMCs from SAMP1 mice (2 months of age), a presbycusis-prone mouse strain. Acceleration of age-related hearing loss, early degeneration of spiral ganglion cells (SGCs) and impairment of immune function were observed in the recipient mice as well as in the SAMP1 mice. However, no spiral ganglion cells of donor (SAMP1) origin were detected in the recipient mice. These results indicated that accelerated presbycusis, cochlear pathology, and immune dysfunction of SAMP1 mice can be transferred to BALB/c recipient mice using allogeneic bone marrow transplantation (BMT). However, although the BMCs themselves cannot differentiate into the spiral ganglion cells (SGCs), they indirectly cause the degeneration of the SGCs. Further studies into the relationship between the inner ear cells and BMCs are required.

Bone marrow transplantation as a strategy for the treatment of autoimmune hearing loss in MRL/Mp-lpr/lpr mice

Sensorineural hearing loss (SNHL) has been reported to develop as a main part of or in combination with systemic and organ-specific autoimmune diseases. The aim of the current study is to treat autoimmune SNHL in MRL/Mp-lpr/lpr (MRL/lpr) mice, a murine model of systemic autoimmune disease, using allogeneic bone marrow transplantation (BMT), which replaces recipient bone marrow cells with bone marrow cells from a non-autoimmune-prone donor. The results indicate that BMT can be used to treat SNHL; cochlear pathology, serum autoantibodies and lupus nephritis are ameliorated. Therefore, it is conceivable that the autoimmune SNHL in the MRL/lpr mice results not from defects in the cochlea, including the stria vascularis, but from defects in the bone marrow, and BMT would therefore provide a curative effect on inner ear autoimmune dysfunction associated with systemic autoimmune diseases.

Bone marrow cells as an origin of immune-mediated hearing loss

The MRL/lpr mouse, which is homozygous for the recessive lpr genes and has a mutation in the Fas gene encoding a cell-surface receptor for apoptosis, exhibits severe lymphadenopathy and develops systemic lupus erythematosus (SLE)-like disease. It has recently been reported that this mouse also manifests sensorineural hearing loss (SHL) with cochlear pathology at 20 weeks of age. We examined the effects of reconstituting severe combined immunodeficient (SCID) mice with MRL/lpr bone marrow on the development of SHL. These mice normally develop neither SHL nor cochlear pathology. Immune-mediated SHL and cochlear pathology did, indeed, occur following transfer of MRL/lpr bone marrow into SCID mice. These findings suggest that the development of SHL and cochlear pathology observed in MRL/lpr mice and in SCID mice receiving MRL/lpr bone marrow are the result of bone marrow defects rather than the result of a problem intrinsic to the cochlea.

Correlation between accelerated presbycusis and decreased immune functions

The aim of the current study is to analyze the relationship between presbycusis and the immune system, which is affected by pathogenic environments, and to devise a strategy for the prevention of presbycusis using the SAMP1 mouse, an animal model for accelerated senescence that shows both immunological dysfunction and hearing loss caused by the impairment of spiral ganglion cells in the cochlea. When these mice were bred in different pathogenic environments, we found that the development of age-related diseases such as presbycusis was delayed in the mice bred under clean conditions. Prednisolone administration showed no significant prevention of the development of presbycusis in the mice, suggesting that autoimmune mechanisms are not involved in the acceleration of presbycusis. It is conceivable that pathogen-induced infections impose a severe stress on the host, impairing the host's immune functions. A reduction in the number of pathogens may therefore prevent the acceleration of the aging process. These findings suggest that not only the gene backgrounds but also immune functions affect the development of presbycusis in SAMP1 mice. Further studies into the relationship between systemic immune functions and the neuro-generation system may provide additional information about the treatment for age-related diseases.

Prevention of accelerated presbycusis by bone marrow transplantation in senescence-accelerated mice

A substrain of the senescence-accelerated mouse (SAM), the SAMP1 mouse, is an animal model for accelerated senescence including the age-related acceleration of both immunological dysfunction and hearing loss caused by the impairment of spiral ganglion cells. In the present study, we examine whether the accelerated presbycusis can be prevented by allogeneic BMT. Young SAMP1 (H-2(k)) mice were irradiated with 9 Gy and then reconstituted with bone marrow cells from normal BALB/c (H-2(d)) mice. Allogeneic BMT was found to prevent the development of immunological dysfunction, hearing loss, and apoptosis of spinal ganglion cells in SAMP1 mice. These findings indicate that some types of accelerated presbycusis do not result from defects in the cochlea, but do from defects in the hematopoietic stem cells (HSC) and immunocompetent cells derived from the HSC. If this is the case, either allogeneic BMT, which replaces abnormal HSC with normal HSC and reconstructs a normal immune system in the recipients, or autologous BMT using genetically modified bone marrow cells, could become a new strategy for the treatment of presbycusis.

Prevention of autoimmune hearing loss in MRL/lpr mice by bone marrow transplantation

We examined the effects of bone marrow transplantation (BMT) on immune-mediated inner ear diseases in MRL/Mp-lpr/lpr (MRL/lpr) mice, which manifest not only lupus nephritis but also sensorineural hearing loss (SNHL) at the age of 20 weeks. These mice were treated with cyclophosphamide (CY) and irradiation (5 Gy x 2), followed by the transplantation of bones plus bone marrow cells from allogeneic normal C57BL/6 mice at the age of 12 weeks. Hematolymphoid cells were reconstituted with donor-derived cells 3 months after BMT. Thus-treated MRL/lpr mice showed neither lupus nephritis nor SNHL even 24 weeks after BMT. No pathological findings were observed in either glomeruli or cochleae. These findings suggest that BMT can be used to prevent the development of autoimmune SNHL in MRL/lpr mice.