Presence of donor-derived thymic epithelial cells in [B6-->MRL/lpr] mice after allogeneic intra-bone marrow-bone marrow transplantation (IBM-BMT)

The Influence of Heterochronic Non-Myeloablative Bone Marrow Transplantation on the Immune System, Frailty, General Health, and Longevity of Aged Murine Recipients

The stem cell theory of aging postulates that stem cells become inefficient at maintaining the original functions of the tissues. We, therefore, hypothesized that transplanting young bone marrow (BM) to old recipients would lead to rejuvenating effects on immunity, followed by improved general health, decreased frailty, and possibly life span extension. We developed a murine model of non-myeloablative heterochronic BM transplantation in which old female BALB/c mice at 14, 16, and 18(19) months of age received altogether 125.1 ± 15.6 million nucleated BM cells from young male donors aged 7–13 weeks. At 21 months, donor chimerism was determined, and the immune system’s innate and adaptive arms were analyzed. Mice were then observed for general health and frailty until spontaneous death, when their lifespan, post-mortem examinations, and histopathological changes were recorded. The results showed that the old mice developed on average 18.7 ± 9.6% donor chimerism in the BM and showed certain improvements in their innate and adaptive arms of the immune system, such as favorable counts of neutrophils in the spleen and BM, central memory Th cells, effector/effector memory Th and Tc cells in the spleen, and B1a and B1b cells in the peritoneal cavity. Borderline enhanced lymphocyte proliferation capacity was also seen. The frailty parameters, pathomorphological results, and life spans did not differ significantly in the transplanted vs. control group of mice. In conclusion, although several favorable effects are obtained in our heterochronic non-myeloablative transplantation model, additional optimization is needed for better rejuvenation effects.

Molecular Insights Into the Causes of Human Thymic Hypoplasia With Animal Models

22q11.2 deletion syndrome (DiGeorge), CHARGE syndrome, Nude/SCID and otofaciocervical syndrome type 2 (OTFCS2) are distinct clinical conditions in humans that can result in hypoplasia and occasionally, aplasia of the thymus. Thymic hypoplasia/aplasia is first suggested by absence or significantly reduced numbers of recent thymic emigrants, revealed in standard-of-care newborn screens for T cell receptor excision circles (TRECs). Subsequent clinical assessments will often indicate whether genetic mutations are causal to the low T cell output from the thymus. However, the molecular mechanisms leading to the thymic hypoplasia/aplasia in diverse human syndromes are not fully understood, partly because the problems of the thymus originate during embryogenesis. Rodent and Zebrafish models of these clinical syndromes have been used to better define the underlying basis of the clinical presentations. Results from these animal models are uncovering contributions of different cell types in the specification, differentiation, and expansion of the thymus. Cell populations such as epithelial cells, mesenchymal cells, endothelial cells, and thymocytes are variably affected depending on the human syndrome responsible for the thymic hypoplasia. In the current review, findings from the diverse animal models will be described in relation to the clinical phenotypes. Importantly, these results are suggesting new strategies for regenerating thymic tissue in patients with distinct congenital disorders.

How Could We Slow or Reverse the Human Aging Process and Extend the Healthy Life Span with Heterochronous Autologous Hematopoietic Stem Cell Transplantation

The senescence of the immune system contributes considerably to the age-related diseases that are the main causes of death after the age of 65. In this study, we present an appealing option for the prevention of immune senescence and slowing or reversing the aging process, which can be achieved by heterochronous autologous hematopoietic stem cell transplantation (haHSCT), where healthy autologous bone marrow stem cells are collected from donors while young, cryopreserved and stored for a long period, and reinfused at a later time when indicated. After reinfusion and homing, these young HSCs could participate in normal hemato- and immunopoiesis and improve several immune functions by expanding the immune- as well as hematopoietic cell repertoire. Several animal studies have already confirmed the feasibility of this procedure, which extended the longevity of the treated animals. If translated to human medicine, haHSCT could prevent or mitigate age-related immune defects and extend the healthy life span. In this review, we describe the concept of haHSCT, recent studies that confirm its feasibility, and discuss the further research needed to translate this heterochronous methodology.

Role of Regulatory T Cells in Tumor-Bearing Mice Treated with Allo-Hematopoietic Stem Cell Transplantation Plus Thymus Transplantation

We recently developed a new allogeneic hematopoietic stem cell transplantation method (allo-HSCT) combined with thymus transplantation (TT) from the same donor (allo-HSCT + TT). This method induces elevated T cell function with mild graft-versus-host disease (GVHD) in comparison to conventional HSCT alone and HSCT + donor lymphocyte infusion (DLI). This new method is effective against several intractable diseases, including malignant tumors, for which conventional treatments are ineffective. Regulatory T (T_reg) cells play an important role in the enhanced graft-versus-tumor (GVT) effect and reduction of GVHD, thus leading to longer survival. Replacement and reduction of elevated T_reg cells by donor-derived allo-T_reg cells from the transplanted thymus may play one of crucial roles in the effect. This review discusses the role of T_reg cells in a tumor-bearing mouse model treated with allo-HSCT + TT.

The potential of non-myeloablative heterochronous autologous hematopoietic stem cell transplantation for extending a healthy life span

Aging is a complex multifactorial process, a prominent component being the senescence of the immune system. Consequently, immune-related diseases develop, including atherosclerosis, cancer, and life-threatening infections, which impact on health and longevity. Rejuvenating the aged immune system could mitigate these diseases, thereby contributing to longevity and health. Currently, an appealing option for rejuvenating the immune system is heterochronous autologous hematopoietic stem cell transplantation (haHSCT), where healthy autologous bone marrow/peripheral blood stem cells are collected during the youth of an individual, cryopreserved, and re-infused when he or she has reached an older age. After infusion, young hematopoietic stem cells can reconstitute the compromised immune system and improve immune function. Several studies using animal models have achieved substantial extension of the life span of animals treated with haHSCT. Therefore, haHSCT could be regarded as a potential procedure for preventing age-related immune defects and extending healthy longevity. In this review, the pros, cons, and future feasibility of this approach are discussed.

Role of Bone Marrow Maturity, Insulin-Like Growth Factor 1 Receptor, and Forkhead Box Protein N1 in Thymic Involution and Rejuvenation

Thymic involution is associated with age-related changes of the immune system. Utilizing our innovative technique of transplantation of a thymus as an isolated vascularized graft in MHC-inbred miniature swine, we have previously demonstrated that aged thymi are rejuvenated after transplantation into juvenile swine. Here we have studied the role of insulin-like growth factor (IGF) and forkhead-box protein-N1 (FOXN1) as well as bone marrow (BM) in thymic rejuvenation and involution. We examined thymic rejuvenation and involution by means of histology and flow cytometry. Thymic function was assessed by the ability to induce tolerance of allogeneic kidneys. Aged thymi were rejuvenated in a juvenile environment, and successfully induced organ tolerance, while juvenile thymi in aged recipients involuted and had a limited ability to induce tolerance. However, juvenile BM inhibited the involution process of juvenile thymi in aged recipients. An elevated expression of both FOXN1 and IGF1 receptors (IGF-1R) was observed in juvenile thymi and rejuvenated thymi. Juvenile BM plays a role in promoting the local thymic milieu as indicated by its ability to inhibit thymic involution in aged animals. The expression of FOXN1 and IGF-1R was noted to increase under conditions that stimulated rejuvenation, suggesting that these factors are involved in thymic recovery.

Stem cell treatment for Alzheimer's disease

Alzheimer’s disease (AD) is a progressive and neurodegenerative disorder that induces dementia in older people. It was first reported in 1907 by Alois Alzheimer, who characterized the disease as causing memory loss and cognitive impairment. Pathologic characteristics of AD are β-amyloid plaques, neurofibrillary tangles and neurodegeneration. Current therapies only target the relief of symptoms using various drugs, and do not cure the disease. Recently, stem cell therapy has been shown to be a potential approach to various diseases, including neurodegenerative disorders, and in this review, we focus on stem cell therapies for AD.

Stem cell transplantation improves aging-related diseases

Aging is a complex process of damage accumulation, and has been viewed as experimentally and medically intractable. The number of patients with age-associated diseases such as type 2 diabetes mellitus (T2DM), osteoporosis, Alzheimer's disease (AD), Parkinson's disease, atherosclerosis, and cancer has increased recently. Aging-related diseases are related to a deficiency of the immune system, which results from an aged thymus and bone marrow cells. Intra bone marrow-bone marrow transplantation (IBM-BMT) is a useful method to treat intractable diseases. This review summarizes findings that IBM-BMT can improve and treat aging-related diseases, including T2DM, osteoporosis and AD, in animal models.

New allogeneic hematopoietic stem cell transplantation method: hematopoietic stem cell transplantation plus thymus transplantation for intractable diseases

Although allogeneic hematopoietic stem cell transplantation (allo-HSCT) has become a valuable strategy for some intractable diseases, a number of problems remain to be resolved. We have developed a new HSCT method, HSCT + thymus transplantation (TT) from the same donor, which induces elevated T cell function with mild graft-versus-host disease (GVHD) in comparison to conventional HSCT alone and HSCT + donor lymphocyte infusion (HSCT + DLI). This new method is effective in the treatment of several intractable diseases and conditions, such as autoimmune diseases in aging, advanced malignant tumors, exposure to supralethal irradiation, multiple organ transplantation from different donors, and type 2 diabetes mellitus, for which conventional methods are ineffective. Our findings suggest that allo-HSCT + TT is preferable to conventional allo-HSCT alone or allo-HSCT + DLI. This method may become a valuable next-generation HSCT technique.

Upregulation of RCAN1 causes Down syndrome-like immune dysfunction

BACKGROUND

People with Down syndrome (DS) are more susceptible to infections and autoimmune disease, but the molecular genetic basis for these immune defects remains undetermined. In this study, we tested whether increased expression of the chromosome 21 gene RCAN1 contributes to immune dysregulation.

METHODS

We investigated the immune phenotype of a mouse model that overexpresses RCAN1. RCAN1 transgenic (TG) mice exhibit T cell abnormalities that bear a striking similarity to the abnormalities described in individuals with DS.

RESULTS

RCAN1-TG mice display T cell developmental defects in the thymus and peripheral immune tissues. Thymic cellularity is reduced by substantial losses of mature CD4 and CD8 thymocytes and medullary epithelium. In peripheral immune organs T lymphocytes are reduced in number and exhibit reduced proliferative capacity and aberrant cytokine production. These T cell defects are stem cell intrinsic in that transfer of wild type bone marrow into RCAN1-TG recipients restored medullary thymic epithelium and T cell numbers in the thymus, spleen and lymph nodes. However, bone marrow transplantation failed to improve T cell function, suggesting an additional role for RCAN1 in the non-haemopoietic compartment.

CONCLUSIONS

RCAN1 therefore facilitates T cell development and function, and when overexpressed, may contribute to immune dysfunction in DS.

Improved expression of Sirt1 on thymic epithelial cells of SAMP10 after Intrabone marrow-bone marrow transplantation

Aging is accompanied by various forms of immune dysfunction, leading to an increase in frequency of infections and the development of malignant tumors in mice and humans. Sirt1 has been implicated in processes as varied as metabolism, differentiation, cancer, and the stress response and aging. Senescence-accelerated mice prone 10 (SAMP10) show not only spontaneously occurring brain atrophy, with deficits in learning and memory, but also emotional disorders. We attempted in this study to clarify the deficits and found that the percentage of CD4/TNF-α T-cells in the spleen of 24-week-old (but not 6-week-old) SAMP10 to be significantly reduced. The thymus was significantly lighter, and the percentage of CD4⁺CD8⁺ cells was significantly lower in the 24-week-old SAMP10 than 6-week-old SAMP10. Microarray analyses indicated that genes related to transcription coactivator activity, growth factor activity, hormone activity, cytokine activity, receptor activity, and regulation of the immune system were downregulated in the thymus of 24-week-old SAMP10. Real-time PCR analysis showed that the expression of KGF, Aire, and Sirt1 was decreased on the thymic epithelial cells (TECs) of 24-week-old SAMP10. However, these parameters improved after the mice were treated with intrabone marrow-bone marrow transplantation. This is the first report of age-related changes in immune system dysfunction in 24-week-old SAMP10 and the first to show that dysfunction on the TECs of 24-week-old SAMP10 was modulated by allogeneic bone marrow cells.

Effects of intrabone marrow-bone marrow transplantation plus adult thymus transplantation on survival of mice bearing leukemia

We recently found that allogeneic intrabone marrow-bone marrow transplantation (IBM-BMT) plus adult thymus transplantation (ATT) from the same donor is effective in mice bearing solid tumors. In the current study, we examined the effects of this strategy on the survival of mice with leukemia. One week after intravenous injection of 1×10(6) leukemic cells (EL-4, H-2(b)) into 8-week-old B6 (H-2(b)) mice, the mice were 8 Gy irradiated and transplanted with 1×10(7) bone marrow cells (BMCs) from 8-week-old BALB/c mice (H-2(d)) by IBM-BMT with or without donor lymphocyte infusion (DLI) or ATT. All the mice without treatment died within 70 days after injection of EL-4. About 40% of those treated with IBM-BMT alone died within 100 days due to tumor relapse. In contrast, those treated with IBM-BMT+DLI or ATT showed the longest survival rate without relapse of leukemia. In addition, the former showed less graft versus host disease (GVHD) than the latter. The mice treated with IBM-BMT+ATT also showed an intermediate percentage of effector memory (EM) and central memory (CM) cells between those treated with BMT alone and those treated with IBM-BMT+DLI. The numbers and functions of T cells increased in those treated with IBM-BMT+ATT with interleukin-2 and interferon-γ production. These results suggest that IBM-BMT+ATT is effective in the treatment of leukemia with strong graft versus leukemia without increased risk of GVHD.

First use of thymus transplantation therapy for FOXN1 deficiency (nude/SCID): a report of 2 cases

FOXN1 deficiency is a primary immunodeficiency characterized by athymia, alopecia totalis, and nail dystrophy. Two infants with FOXN1 deficiency were transplanted with cultured postnatal thymus tissue. Subject 1 presented with disseminated Bacillus Calmette-Guérin infection and oligoclonal T cells with no naive markers. Subject 2 had respiratory failure, human herpes virus 6 infection, cytopenias, and no circulating T cells. The subjects were given thymus transplants at 14 and 9 months of life, respectively. Subject 1 received immunosuppression before and for 10 months after transplantation. With follow up of 4.9 and 2.9 years, subjects 1 and 2 are well without infectious complications. The pretransplantation mycobacterial disease in subject 1 and cytopenias in subject 2 resolved. Subject 2 developed autoimmune thyroid disease 1.6 years after transplantation. Both subjects developed functional immunity. Subjects 1 and 2 have 1053/mm(3) and 1232/mm(3) CD3(+) cells, 647/mm(3) and 868/mm(3) CD4(+) T cells, 213/mm(3) and 425/mm(3) naive CD4(+) T cells, and 10 200 and 5700 T-cell receptor rearrangement excision circles per 100 000 CD3(+) cells, respectively. They have normal CD4 T-cell receptor β variable repertoires. Both subjects developed antigen-specific proliferative responses and have discontinued immunoglobulin replacement. In summary, thymus transplantation led to T-cell reconstitution and function in these FOXN1 deficient infants.

Effects of allogeneic hematopoietic stem cell transplantation plus thymus transplantation on malignant tumors: comparison between fetal, newborn, and adult mice

We have recently shown that allogeneic intrabone marrow-bone marrow transplantation + adult thymus transplantation (TT) is effective for hosts with malignant tumors. However, since thymic and hematopoietic cell functions differ with age, the most effective age for such intervention needed to be determined. We performed hematopoietic stem cell transplantation (HSCT) using the intrabone marrow method with or without TT from fetal, newborn, and adult B6 mice (H-2(b)) into BALB/c mice (H-2(d)) bearing Meth-A sarcoma (H-2(d)). The mice treated with all types of HSCT + TT showed more pronounced regression and longer survival than those treated with HSCT alone in all age groups. Those treated with HSCT + TT showed increased numbers of CD4(+) and CD8(+) T cells but decreased numbers of Gr-1/Mac-1 myeloid suppressor cells and decreased percentages of FoxP3 cells in CD4(+) T cells, compared with those treated with HSCT alone. In all mice, those treated with fetal liver cell (as fetal HSCs) transplantation + fetal TT or with newborn liver cell (as newborn HSCs) transplantation (NLT) + newborn TT (NTT) showed the most regression, and the latter showed the longest survival. The number of Gr-1/Mac-1 cells was the lowest, whereas the percentage of CD62L(-)CD44(+) effector memory T cells and the production of interferon γ (IFN-γ) were highest in the mice treated with NLT + NTT. These findings indicate that, at any age, HSCT + TT is more effective against cancer than HSCT alone and that NLT + NTT is most effective.

Prolonged survival in mice with advanced tumors treated with syngeneic or allogeneic intra-bone marrow-bone marrow transplantation plus fetal thymus transplantation

Thymic function decreases in line with tumor progression in patients with cancer, resulting in immunodeficiency and a poor prognosis. In the present study, we attempted to restore thymic function by BALB/c (H-2(d)) syngeneic (Syn), or B6 (H-2(b)) allogeneic (Allo) bone marrow transplantation (BMT) using intra-bone marrow-bone marrow transplantation (IBM-BMT) plus Syn-, Allo- or C3H (H-2(k)) 3rd-party fetal thymus transplantation (TT). Although the BALB/c mice with advanced tumors (Meth-A sarcoma; H-2(d), >4 cm(2)) treated with either Syn- or Allo-BMT alone showed a slight improvement in survival compared with non-treated controls, the mice treated with BMT + TT showed a longer survival. The mice treated with Allo-BMT + Allo-TT or 3rd-party TT showed the longest survival. Interestingly, although there was no difference in main tumor size among the BMT groups, lung metastasis was significantly inhibited by Allo-BMT + Allo-TT or 3rd-party TT. Numbers of CD4(+) and CD8(+) T cells, Con A response, and IFN-gamma production increased significantly, whereas number of Gr-1(+)/CD11b(+) myeloid suppressor cells and the percentage of FoxP3(+) cells in CD4(+) T cells significantly decreased in these mice. Furthermore, there was a positive correlation between survival days and the number of T cells or T cell function, while there was a negative correlation between survival days and lung metastasis, the number of Gr-1(+)/CD11b(+) cells, or the percentage of FoxP3(+) cells. These results suggest that BMT + TT, particularly Allo-BMT + Allo-TT or 3rd-party TT, is most effective in prolonging survival as a result of the restoration of T cell function in hosts with advanced tumors.

The worldwide gradient of autoimmune conditions

Among the numerous consequences of globalization, the dissemination of scientific research allows real-time comparisons of clinical and basic experimental data between different geographical areas. As a result, the field of geoepidemiology is now vigorously supported by multiple lines of evidence. This special issue of Autoimmunity Reviews is dedicated to the 2010 International Congress on Autoimmunity and aims to provide a state-of-the-art representation of what is currently known in the field of geoepidemiology for autoimmune diseases. The obvious implications of these observations is a role for environmental factors. We will herein review selected publications from prominent scientific journals to provide the bases to understand some of the lines of evidence proposed in the subsequent papers of this comprehensive volume. The ultimate goal is thus to define whether geoepidemiology should be considered a new challenge for autoimmunologists.

Consideration of strategies for hematopoietic cell transplantation

Bone marrow transplantation has been adoptively transferred from oncology to the treatment of autoimmune disorders. Along with extension of prevalent transplant-related concepts, the assumed mechanism that arrests autoimmunity involves elimination of pathogenic cells and resetting of immune homeostasis. Similar to graft versus tumor (GVT) reactivity, allogeneic transplants are considered to provide a better platform of immunomodulation to induce a graft versus autoimmunity reaction (GVA). It is yet unclear whether recurrence of autoimmunity in both autologous and allogeneic settings reflects relapse of the disease, transplant-associated immune dysfunction or insufficient immune modulation. Possible causes of disease recurrence include reactivation of residual host pathogenic cells and persistence of memory cells, genetic predisposition to autoimmunity and pro-inflammatory characteristics of the target tissues. Most important, there is little evidence that autoimmune disorders are indeed abrogated by current transplant procedures, despite reinstitution of both peripheral and thymic immune homeostasis. It is postulated that non-specific immunosuppressive therapy that precedes and accompanies current bone marrow transplant strategies is detrimental to the active immune process that restores self-tolerance. This proposition refocuses the need to develop strategies of immunomodulation without immunosuppression.