B cells in SLE and RA
These studies have focused on defining the role of B cells in systemic autoimmunity and have been instrumental in characterizing the impact of B cell depletion (BCD) on the human immune system and establishing B cell targeted therapies as a major advance in the field of immunologic disease (with broad implications in rheumatoid arthritis, lupus, diabetes, malignancy, immune deficiency. Findings demonstrating a link between clinical response and immunologic reconstitution with transitional B cells was the first delineation of a B regulatory cell population in humans, greatly advancing our understanding of BCD therapy and human B cell development pathways. A prominent publication defining new populations of human transitional B cells provided further fundamental insights into the developmental process followed by human B cells, identifying a new population of human transitional B cells. Recent work has elucidated a previously unrecognized cross-talk between the B cell compartment and neutrophil driven α interferon production in the bone marrow in SLE that alters B cell development and selection. Ongoing work in the lab focuses on: (1) further defining novel phenotypic and functional subsets of human B cells including regulatory cells, (2) defining B cell development and tolerance mechanisms in human autoimmune disease and the etiology and impact of dysregulation in the bone marrow microenvironment, and (3) elucidating the factors that regulate autoreactive plasma cell survival.
Cellular dynamics at the synovium-bone interface and the development of novel treatment targets in rheumatoid arthritis
Our lab has defined key antibody-independent roles for B cells in rheumatoid arthritis, including regulation of bone homeostasis. These functions are mediated at least in part via the secretion of cytokines, with a propensity for pro-inflammatory cytokine secretion that can be fundamentally altered with B cell depletion therapy. We have recently demonstrated that B cells can be a prime secretor of RANKL, thereby promoting osteoclast differentiation and bone erosion. Ongoing work in the lab is investigating the regulatory mechanisms for B cell promotion of osteoclast activation and osteoblast inhibition in RA. Additional goals are to define disease specific pathways within RA synovial tissue using novel technologies including laser capture micro-dissection and RNA sequencing of discrete immune and bone cell populations.
Immunologic and ultrasound biomarker in Primary Sjogren’s Syndrome
These studies seek to elucidate abnormalities in both the peripheral blood and salivary gland target tissue in the B cell and T cell compartment in Sjogren’s syndrome in order to develop biomarkers of disease and treatment. We are also exploring ultrasound of the salivary glands as a diagnostic approach and relating imaging characteristics to B cell activation and other immunologic abnormalities.
Evaluating the impact of novel inhibitors of nuclear pore export in SLE
Given our early observations that there is a disconnect between clinical responses to B cell depletion therapy and changes in autoantibodies, a major focus of the lab has been to define antibody independent roles for B cells including interactions with and regulation of other immune cells. We have developed a mouse model of B cell depletion and demonstrated critical B cell effects on the T cell compartment in SLE. We have also utilized these mouse models as a powerful approach to ask other mechanistic questions, including the immunologic factors that regulate plasma cell survival and the development of novel treatment approaches. One of the goals of the current research program is to define the efficacy and mechanism of a novel treatment approach for lupus via selective inhibition of nuclear pore export. The factors regulating the development and survival of autoreactive plasma cells will be further defined in order to develop novel treatment approaches.
Roles of DC-STAMP in Osteoclast and Osteoblast (OC::OB) Coupling
Bone homeostasis is achieved through a dynamic coordination between bone-degrading osteoclast (OC) and bone-synthesizing osteoblast (OB). Excessive OC activity causes “osteoporosis” with weaker and brittle bones, whereas excessive OB activity generates abnormal dense bones with “osteopetrosis” phenotype. An imbalance between OC & OB activities results in skeletal and joint diseases including osteoporosis, arthritis, and non-union bone repair. These diseases impact the quality of life of patients and there are currently no effective medications. To this end, we have focused our research on the role of Dendritic-Cell-Specific-Transmembrane Protein (DC-STAMP), a master regulator during osteoclastogenesis, in OB::OC coupling. Knocking down of DC-STAMP impairs both OB and OC differentiation. Thus, DC-STAMP knockout (KO) mice provide us a unique experimental paradigm for studying OB::OC coupling. We have previously showed that OB are attracted to DC-STAMP+ OC proximity at bone fracture sites in wild-type mice, a phenomena which was not detected in DC-STAMP KO mice. This piece of data, together with the delayed fracture repair phenotype of DC-STAMP KO mice, suggested that DC-STAMP is involved in OB::OC coupling during bone repair. To address the questions (1) whether OB and OC communicate with each other through clastokine-like cytokines (Charles & Aliprantis, Trends Mol. Med. 2014)and (2) whether cell-cell contact is necessary for OB::OC coupling, we are currently establishing different combinations of co-culture between OB and OC resources, developing biological reagents which can trace OB and OC specifically in vivo by IVIS, studying the effects of bone microenvironments on fracture repair by bone marrow reconstitution, and examining the alternations of local cytokine profiles by nanoparticle-based, DC-STAMP-specific medicine delivery on bone fracture sites. Our long-term goal is to delineate the involvement of DC-STAMP in OB::OC coupling at the molecular level and develop biologics which can facilitate bone healing through modulating DC-STAMP activity.
Bone fractures induce the aggregation of DC-STAMP+ osteoclasts to osteoblast proximity.
Develop Nanoparticle/Exosome-based Strategies for Treating Psoriatic & Autoimmune Diseases
Targeted delivery of therapeutic agents to inflammatory sites remains a major challenge for treating autoimmune diseases. Among several drug delivery platforms, nanoparticles (NPs) are currently considered to be one of the novel tools that are able to encapsulate therapeutics for targeted delivery. The advantages of NP-based drug delivery platforms include their flexibility of conjugating different biological reagents (siRNA, antibodies, cell-subset-specific targeting peptides); their ability to encapsulate various quantities and formats of medication; and their endocytosis natures that can deliver siRNA intracellularlly for specific gene knockout. Dr. Benoit’s laboratory (Biomedical Engineering at UR) has previously demonstrated the success of targeted delivery of OC-specific, IR780-encapsulated NPs to bone fractures in mouse cranial crest and femur fracture models. Given that the outcome of psoriatic diseases and arthritis progression can be determined through modulating local cytokine profiles in the inflammatory sites (Schukur et al., 2015, Sci. Transl. Med. 7(318)) or switching the activity of immunoreceptor tyrosine-based activation motif (ITAM) (Ben Mkaddem., et al., 2014, JCI 124(9)), Dr. Chiu is currently collaborating with Dr. Benoit’s group to develop new NPs which can not only trace osteoclasts but also knock down DC-STAMP, a master regulator of osteoclast differentiation, in vivo for targeted drug delivery in a stage- and time-specific manner. In addition, Dr. Chiu is working together with Dr. Sheu to develop organ specific exosome-based therapeutics for treating bone and autoimmune diseases. The exosome-based therapeutic platform has the advantage over other traditional delivery systems by preventing the induction of non-specific immune responses & avoiding MHC-incompatibility (Lu et al., 2014, PNAS; Hoshino et al., 2015, Nature).
Osteoclast-specific nanoparticles (NPs) could be recruited to bone fracture sites.
TBP-loaded NPs are injected into mice on day-3 post-fracture and the trafficking of NPs
in vivo was monitored by the IVIS system. (A) Visualization of fracture repair by x-ray;
(B) Structure of the TBP-loaded NPs. They aggregate and concentrate on bone
fractures in vivo during bone repair. (pictures: courtesy of the Benoit laboratory).
Inhibition of G protein beta gamma signaling in SLE
A classic feature in lupus is the production of autoantibodies that eventually deposit in multiple organs. In the lupus kidney, Ig G deposition is key in the attraction and local accumulation of inflammatory cells. These inflammatory cells produce molecules that exacerbate local inflammation, create a niche for auto reactive plasma cells and cause tissue damage. In a pilot project supported by the Clinical and Translational Science Institute (CTSI) at the University of Rochester, we found that inhibition of G protein beta gamma signaling abrogated lupus nephritis by modulating the germinal center response and preventing the accumulation of auto reactive plasma cells in the kidney. These results suggest the potential therapeutic value of inhibitors of G protein beta gamma signaling in SLE.
Disease mechanisms and rheumatoid arthritis (RA)
The remarkable heterogeneity in the composition of inflammatory cell infiltrates in the synovium of RA patients suggests that disease progression and severity should be driven by different molecular and cellular mechanisms in each RA patient. In a project supported by the National Institute of Arthritis and Musculoskeletal and Skin Diseases, we are seeking to define the molecular signatures of immune cells in the inflamed RA synovium by using single cell sorting and laser capture micro dissection, coupled to RNA sequencing. The main goal of this study is to identify potential markers of disease progression and novel therapeutic targets, which may have an impact on the quality of life of RA patients.