RANK signaling is not required for TNFalpha-mediated increase in CD11(hi) osteoclast precursors but is essential for mature osteoclast formation in TNFalpha-mediated inflammatory arthritis.

To address the controversy of whether TNFalpha can compensate for RANKL in osteoclastogenesis in vivo, we used a TNFalpha-induced animal model of inflammatory arthritis and blocked RANKL/RANK signaling. TNFalpha increased osteoclast precursors available for RANK-dependent osteoclastogenesis. RANK signaling is not required for the TNFalpha-stimulated increase in CD11b(hi) osteoclast precursors but is essential for mature osteoclast formation. INTRODUCTION: Although critical roles of TNFalpha in inflammatory arthritis and RANKL in bone resorption have been firmly established, a central controversy remains about the extent to which TNFalpha can compensate for RANKL during osteoclastogenesis and the stage at which RANK signaling is required for osteoclastogenesis. Here, we used the human TNFalpha transgenic mouse model (TNF-Tg) of erosive arthritis to determine if there are both RANK-dependent and -independent stages of osteoclastogenesis in TNFalpha-induced erosive arthritis. MATERIALS AND METHODS: Osteoclastogenesis and osteoclast precursor (OCP) frequency were analyzed using histology, fluorescence-activated cell sorting (FACS), and cell culture from (1) TNF-Tg mice treated with the RANKL antagonist, RANK:Fc, or (2) TNF-Tg X RANK -/- mice generated by crossing TNF-Tg mice with RANK-/- mice. RESULTS: Treatment of TNF-Tg mice, which have increased OCPs in their spleens, with RANK:Fc dramatically reduced osteoclast numbers on the surface of their arthritic joints and within their bones, but did not decrease CD11b(hi) OCP numbers in their spleens. Long-term RANK:Fc administration alleviated joint erosion. Furthermore, TNF-Tg x RANK -/- mice had severe osteopetrosis, no osteoclasts, and no joint erosion, but increased CD11b(hi) precursor numbers that failed to form mature osteoclasts in vitro. CONCLUSION: RANK signaling is essential for mature osteoclast formation in TNFalpha-mediated inflammatory arthritis but not for the TNFalpha-induced increase in CD11b(hi) OCP that subsequently can differentiate into osteoclasts in inflamed joints.     

Parainfluenza Virus Infection in Adult Lung Transplant Recipients: An Emergent Clinical Syndrome with Implications on Allograft Function

Parainfluenza virus is a common cause of seasonal upper respiratory tract infections in children and adults. Studies indicate that parainfluenza virus may play an important role in the etiology of respiratory tract infections in lung transplant recipients with an estimated incidence of 5.3 per 100 patients. Parainfluenza virus type 3 is the most frequent serotype in lung transplant patients. The rate of lower respiratory tract infections with parainfluenza virus among lung transplant recipients is between 10 and 66% of cases. In addition, trans-bronchial biopsy at the time of parainfluenza infection shows signs of acute allograft rejection. Subsequently, 32% of patients have been found to have active bronchiolitis obliterans at a median time of 6 months (range 1-14) postviral infection. These findings indicate that parainfluenza virus infections may have long-term implications for lung transplant recipients. Further studies are required to identify the mechanisms of immunomodulation of parainfluenza virus among these patients. In addition, controlled studies are needed to evaluate the efficacy of aerosolized ribavarin in the treatment of parainfluenza virus infection and to determine whether vaccines may be effective in these high-risk patients.     

A cellular model for myeloma cell growth and maturation based on an intraclonal CD45 hierarchy

Summary: Multiple myeloma (MM) is a plasma cell malignancy mainly characterized by the accumulation of malignant plasma cells within the bone marrow. This review shows that the biology of CD45 illuminates that of MM and, more specifically, provides a better delineation of a tumor cell ‘hierarchy’ of clinical interest. We show that in MM, as in normal plasma cell differentiation, there is an intraclonal CD45 hierarchy that is a gradient of CD45 expression on myeloma cells directly related to their proliferation rate and differentiation status. This CD45 hierarchy allows for the design of a cellular model for MM‐cell growth and maturation in which CD45 bright myeloma cells represent the proliferating compartment and CD45 low myeloma cells the quiescent compartment. This model includes an aberrant phenotype that is annihilation rather than decline of CD45, annihilation reflecting the terminal phase of the disease and/or an aggressive presentation of MM. Data from the literature suggest that CD45 bright myeloma cells are targeted by interleukin (IL)‐6, whereas CD45 negative myeloma cells with a high clonogenic capacity are targeted by insulin/insulin‐like growth factor 1 (IGF‐1). This model will be useful for both a better understanding of the basic biology of MM and a better stratification of and therapeutic approach to the patients. Finally, this model presents MM as a self‐renewing plasma cell disease, although the first oncogenic events such as 14q32 translocations clearly occur earlier in a B cell.     

Expression studies of two novel in CIS-mutations identified in an intermediate case of Hunter syndrome

Hunter syndrome (Mucopolysaccharidosis type II) is a rare X-linked recessive lysosomal storage disorder caused by the deficiency of the enzyme iduronate-2-sulfatase (IDS). To date, more than 200 different mutations have been reported in the IDS gene, located on Xq27.3-q28. Here, we report two new mutations (M488I and G489A) identified in hemizygosity in an Italian Hunter patient. Their "in vitro" expression by COS 7 cells was carried out in order to evaluate their functional consequence on enzyme activity as well as their possible cumulative effect on the malfunctioning of the protein. The results obtained enabled us to confirm the G489A mutation as causative. The M488I mutation, however, could not be unequivocally considered as causing disease because of its residual activity. Although a cumulative effect of the two mutations can be excluded "in vitro," we are cautious about drawing a conclusion with regard to the possible role that the two mutations could have played "in vivo" in modulating the phenotype of the patient. Finally, the knowledge of the molecular defect of the patient has enabled us to identify the carriers, providing reliable genetic counselling to the females of the family.     

Effects of endothelin-1 on epithelial ion transport in human airways

Endothelin-1 (ET-1) exerts many biological effects in airways, including bronchoconstriction, airway mucus secretion, cell proliferation, and inflammation. We investigated the effect of ET-1 on Na absorption and Cl secretion in human bronchial epithelial cells. Addition of 10(-7) M ET-1 had no effect on the inhibition of the short circuit current (Isc) induced by amiloride, a Na channel blocker. Addition of 10(-7) M ET-1 to the apical bath in the presence of amiloride increased Isc in cultured human bronchial epithelial cells studied in Ussing chambers. No effect was observed when ET-1 was added to basolateral bath, indicating that the involved ET-1 receptors are likely present only in the apical membrane of the cells. Use of Cl-free solutions and bumetanide reduced the ET-1-induced increases in Isc, indicating that ET-1 stimulates Cl secretion. The ET-1-induced increase in Isc was prevented by exposure to the ETB receptor antagonist BQ-788 but not to the ETA receptor antagonist BQ-123. ET-1 did not raise intracellular Ca levels, but increased the intracellular concentration of cAMP. These findings indicate that ET-1 is a Cl secretagogue in human airways and acts presumably through apically located ETB receptors and activation of the cAMP pathway.