Clinical Characteristics and Predictors of the Recurrence of Organizing Pneumonia Associated With Rheumatoid Arthritis.

OBJECTIVE: To clarify the clinical characteristics of organizing pneumonia (OP) in rheumatoid arthritis (RA; RA-OP) and the association of OP development with RA exacerbation, and to identify OP recurrence predictors. METHODS: Data from 33 patients with RA-OP admitted to our hospital were retrospectively analyzed (2006-2016). RESULTS: RA onset preceded OP onset in 82% of patients, whereas OP onset preceded (OP-preceding) or co-occurred with RA in 9% of patients each. Median age at first OP onset was 64.0 years, and the period from RA onset to first OP onset was 5.5 years. At OP onset, 42% of events exhibited unilateral involvement and 76% had normal Krebs von den Lungen-6. RA disease control remained optimal in 52% of events and was exacerbated in 18% of events. Ten patients (30%) experienced OP recurrence with an interval of 13.0 months between events, and the first OP recurrence rate was 127/1000 person-years. Compared with nonrecurrent cases (n = 14), recurrent cases (n = 10) showed lower age at first OP onset (59.5 vs 67.1 yrs; P = 0.04) and a shorter period from RA onset to first OP onset (6.4 vs 14.2 yrs; P = 0.047); moreover, these cases included a higher number of OP-preceding patients (30% vs 0%; P = 0.03) and ever smokers (80% vs 36%; P = 0.03). OP-preceding patients showed shorter median recurrence-free survival time (15 vs 136 months; P = 0.01) and higher recurrence risk (hazard ratio 5.45; P = 0.02). CONCLUSION: RA-OP showed a high recurrence rate and was not associated with RA exacerbation. Four RA-OP recurrence predictors were identified.

In vivo imaging of the phagocytic dynamics underlying efficient clearance of adult-born hippocampal granule cells by ramified microglia.

The phagocytosis of dead cells by microglia is essential in brain development and homeostasis. However, the mechanism underlying the efficient removal of cell corpses by ramified microglia remains poorly understood. Here, we investigated the phagocytosis of dead cells by ramified microglia in the hippocampal dentate gyrus, where adult neurogenesis and homeostatic cell clearance occur. Two-color imaging of microglia and apoptotic newborn neurons revealed two important characteristics. Firstly, frequent environmental surveillance and rapid engulfment reduced the time required for dead cell clearance. The motile microglial processes frequently contacted and enwrapped apoptotic neurons at the protrusion tips and completely digested them within 3-6 h of the initial contact. Secondly, while a single microglial process engaged in phagocytosis, the remaining processes continued environmental surveillance and initiated the removal of other dead cells. The simultaneous removal of multiple dead cells increases the clearance capacity of a single microglial cell. These two characteristics of ramified microglia contributed to their phagocytic speed and capacity, respectively. Consistently, the cell clearance rate was estimated to be 8-20 dead cells/microglia/day, supporting the efficiency of removing apoptotic newborn neurons. We concluded that ramified microglia specialize in utilizing individual motile processes to detect stochastic cell death events and execute parallel phagocytoses.

Simultaneous Imaging of Microglial Dynamics and Neuronal Activity in Awake Mice.

Since brain functions are under the continuous influence of the signals derived from peripheral tissues, it is critical to elucidate how glial cells in the brain sense various biological conditions in the periphery and transmit the signals to neurons. Microglia, immune cells in the brain, are involved in synaptic development and plasticity. Therefore, the contribution of microglia to neural circuit construction in response to the internal state of the body should be tested critically by intravital imaging of the relationship between microglial dynamics and neuronal activity. Here, we describe a technique for the simultaneous imaging of microglial dynamics and neuronal activity in awake mice. Adeno-associated virus encoding R-CaMP, a gene-encoded calcium indicator of red fluorescence protein, was injected into layer 2/3 of the primary visual cortex in CX3CR1-EGFP transgenic mice expressing EGFP in microglia. After viral injection, a cranial window was installed onto the brain surface of the injected region. In vivo two-photon imaging in awake mice 4 weeks after the surgery demonstrated that neural activity and microglial dynamics could be recorded simultaneously at the sub-second temporal resolution. This technique can uncover the coordination between microglial dynamics and neuronal activity, with the former responding to peripheral immunological states and the latter encoding the internal brain states.

In vivo Chronic Two-Photon Imaging of Microglia in the Mouse Hippocampus.

Microglia, the only immune cells resident in the brain, actively participate in neural circuit maintenance by modifying synapses and neuronal excitability. Recent studies have revealed the differential gene expression and functional heterogeneity of microglia in different brain regions. The unique functions of the hippocampal neural network in learning and memory may be associated with the active roles of microglia in synapse remodeling. However, inflammatory responses induced by surgical procedures have been problematic in the two-photon microscopic analysis of hippocampal microglia. Here, a method is presented that enables the chronic observation of microglia in all layers of the hippocampal CA1 through an imaging window. This method allows the analysis of morphological changes in microglial processes for more than 1 month. Long-term and high-resolution imaging of the resting microglia requires minimally invasive surgical procedures, appropriate objective lens selection, and optimized imaging techniques. The transient inflammatory response of hippocampal microglia may prevent imaging immediately after surgery, but the microglia restore their quiescent morphology within a few weeks. Furthermore, imaging neurons simultaneously with microglia allows us to analyze the interactions of multiple cell types in the hippocampus. This technique may provide essential information about microglial function in the hippocampus.

Classifications of scleroderma renal crisis and reconsideration of its pathophysiology.

Categorization of scleroderma renal crisis (SRC) as hypertensive or normotensive can potentially overlook the underlying pathophysiology that might be unique in each patient, as they often exhibit a mixture of distinct pathological characteristics of narrowly defined SRC (nd-SRC) and systemic sclerosis associated thrombocytic micro-angiopathy (SSc-TMA). In this review, we provide evidence suggesting that better categorization of patients presenting with certain clinical features of both nd-SRC and TMA will improve treatment approaches. Based on our clinical experience and literature review, distinguishing between nd-SRC and SSc-TMA is important because the association of SSc-TMA with prior steroid administration and poor prognosis was stronger than that of nd-SRC. Although the two pathological entities cannot be easily distinguished based on blood pressure, we suggest that the detailed clinical course is helpful. Typically, nd-SRC exhibits prominently elevated blood pressure and worsening of renal function initially, followed by mild thrombocytopenia. Conversely, SSc-TMA presents first with severe thrombocytopenia, followed by elevated blood pressure and renal function deterioration. The degree of involvement in each pathological condition should be considered for determination of appropriate therapeutic interventions and prognostic prediction.

Regulation of endothelial Fas expression as a mechanism of promotion of vascular integrity by mural cells in tumors.

Angiogenesis is a multi-step process that culminates in vascular maturation whereby nascent vessels stabilize to become functional, and mural cells play an essential role in this process. Recent studies have shown that mural cells in tumors also promote and maintain vascular integrity, with wide-reaching clinical implications including the regulation of tumor growth, metastases, and drug delivery. Various regulatory signaling pathways have been hitherto implicated, but whether regulation of Fas-dependent apoptotic mechanisms is involved has not yet been fully investigated. We first compared endothelial FAS staining in human pancreatic ductal adenocarcinomas and colon carcinomas and show that the latter, characterized by lower mural cell coverage of tumor vasculature, demonstrated higher expression of FAS than the former. Next, in an in vitro coculture system of MS-1 and 10T1/2 cells as endothelial and mural cells respectively, we show that mural cells decreased endothelial Fas expression. Then, in an in vivo model in which C26 colon carcinoma cells were inoculated together with MS-1 cells alone or with the further addition of 10T1/2 cells, we demonstrate that mural cells prevented hemorrhage. Finally, knockdown of endothelial Fas sufficiently recapitulated the protection against hemorrhage seen with the addition of mural cells. These results together suggest that regulation of endothelial Fas signaling is involved in the promotion of vascular integrity by mural cells in tumors.