Larsen, Brandon T.

Abstract The value of induced pluripotent stem cells (iPSCs) within regenerative medicine is contingent on predictable and consistent iPSC differentiation. However, residual influence of the somatic origin or reprogramming technique may variegate differentiation propensity and confound comparative genotype/phenotype analyses. The objective of this study was to define quality control measures to select iPSC clones that minimize the influence of somatic origin on differentiation propensity independent of the reprogramming strategy. More than 60 murine iPSC lines were derived from different fibroblast origins (embryonic, cardiac, and tail tip) via lentiviral integration and doxycycline-induced transgene expression. Despite apparent equivalency according to established iPSC histologic and cytomorphologic criteria, clustering of clonal variability in pluripotency-related gene expression identified transcriptional outliers that highlighted cell lines with unpredictable cardiogenic propensity. Following selection according to a standardized gene expression profile calibrated by embryonic stem cells, the influence of somatic origin on iPSC methylation and transcriptional patterns was negated. Furthermore, doxycycline-induced iPSCs consistently demonstrated earlier differentiation than lentiviral-reprogrammed lines using contractile cardiac tissue as a measure of functional differentiation. Moreover, delayed cardiac differentiation was predominately associated with upregulation in pluripotency-related gene expression upon differentiation. Starting from a standardized pool of iPSCs, relative expression levels of two pluripotency genes, Oct4 and Zfp42, statistically correlated with enhanced cardiogenicity independent of somatic origin or reprogramming strategy (R2 = 0.85). These studies demonstrate that predictable iPSC differentiation is independent of somatic origin with standardized gene expression selection criteria, while the residual impact of reprogramming strategy greatly influences predictable output of tissue-specification required for comparative genotype/phenotype analyses. Stem Cells 2014;32:2350–2359

Giant-cell tumor of the bone (GCTB) is a rare neoplasm that affects young adults. The tumor is generally benign but sometimes can be locally aggressive. There are no standardized approaches to the treatment of GCTB. Recently, the RANKL inhibitor denosumab has shown activity in this tumor type. We present the case of a young female who presented with locally advanced disease and was successfully managed with the neoadjuvant use of denosumab allowing for surgical resection of the tumor that was previously deemed unresectable. Following surgery, the patient is being managed with continued use of denosumab as ‘maintenance,’ and she continues to be free of disease. Our case highlights a novel approach for the management of locally advanced and aggressive giant cell tumor of the bone.

Nitrofurantoin-induced lung toxicity is relatively common, but rare histologic patterns sometimes occur that may make diagnosis difficult. We present the case of a 69-year-old woman taking prophylactic nitrofurantoin for urinary tract infections, who developed granulomatous interstitial pneumonia. She improved with cessation of nitrofurantoin, without other therapy. To our knowledge, this is the fourth reported case of granulomatous interstitial pneumonia associated with nitrofurantoin, and the first to show complete resolution with cessation of the drug alone, without steroids. It is important to recognize that idiosyncratic reactions to nitrofurantoin can produce a wide spectrum of histologic patterns. Of these patterns, granulomatous interstitial pneumonia is a rarely evidenced manifestation (possibly because few cases undergo a confirmatory lung biopsy). Recognition of granulomatous interstitial pneumonia as a manifestation of nitrofurantoin toxicity can aid in early identification of the reaction and prompt withdrawal of the drug, both of which are essential to prevent long-term complications.

Background— Giant cell myocarditis (GCM) typically causes fulminant heart failure, arrhythmias, or heart block, necessitating aggressive immunosuppression, ventricular assist device insertion, or cardiac transplantation. We describe a novel variant of GCM, primarily involving the atria, that displays distinctive clinical features and follows a more benign course than ventricular GCM. Methods and Results— We identified 6 patients (median age 67.5 years, 4 male) with atrial GCM in our pathology consultation practices from 2010 to 2012. Clinical history, imaging, and pathology materials were reviewed. Clinically, 4 patients had atrial fibrillation, 1 had acute heart failure, and 1 had incidental disease at autopsy. Among the 5 living patients, echocardiography revealed severe atrial dilatation (5 cases), mitral/tricuspid regurgitation (5), atrial mural thrombus (3), atrial wall thickening (2), and atrial hypokinesis (2). Ventricular function was preserved in all 5. Histological review of surgically resected atria showed giant cell and lymphocytic infiltrates, lymphocytic myocarditis-like foci, cardiomyocyte necrosis, and cardiomyocyte hypertrophy in all cases. Other features included interstitial fibrosis (5), poorly-formed granulomas (4), eosinophils (4), neutrophils (1), and vasculitis (1). Treatment consisted of steroids and cyclosporine (1), pacemaker placement for sick sinus syndrome (1), and supportive care (3). All 5 living patients returned to baseline exercise tolerance after 6 to 16 weeks of follow-up. Conclusions— Atrial GCM represents a distinct clinicopathologic entity with a more favorable prognosis than classic ventricular GCM. This disorder should be included in the differential diagnosis of atrial dilatation, particularly when associated with atrial wall thickening. The utility of immunomodulatory therapy for this condition remains unknown.

Context.—Idiopathic interstitial pneumonias are a subset of diffuse pulmonary interstitial diseases classified by international consensus in 2002 as idiopathic pulmonary fibrosis, nonspecific interstitial pneumonia, cryptogenic organizing pneumonia, acute interstitial pneumonia, respiratory bronchiolitis interstitial lung disease, desquamative interstitial pneumonia, and lymphoid interstitial pneumonia. Each is associated with a characteristic histopathologic pattern. In 2011, updated consensus guidelines were released for diagnosis and management of idiopathic pulmonary fibrosis. The entire group of idiopathic interstitial pneumonias is currently undergoing refinement, with updates expected in a forthcoming consensus classification. Many of these recent and anticipated changes are relevant to pathologists. Objectives.—To review international consensus guidelines for diagnosis of idiopathic pulmonary fibrosis and other idiopathic interstitial pneumonias and to discuss recent and expected future classification updates. Data Sources.—Published peer-reviewed literature and personal experience of the authors. Conclusions.—Diagnosis of idiopathic interstitial pneumonias by multidisciplinary discussion among clinicians, radiologists, and pathologists is now strongly encouraged. Diagnosis of idiopathic pulmonary fibrosis no longer requires surgical lung biopsy; high-resolution computed tomography is an acceptable surrogate. In the context of clinical trials, pathologists are being asked to assign levels of confidence for histologic diagnosis of usual interstitial pneumonia in patients with idiopathic pulmonary fibrosis. Acute exacerbation of idiopathic pulmonary fibrosis is now accepted and should be considered when acute lung injury is superimposed on a background of usual interstitial pneumonia. The updated classification of idiopathic interstitial pneumonias will include a separate category for rare entities, including lymphoid interstitial pneumonia and idiopathic pleuroparenchymal fibroelastosis.