Postnatal bone growth involves a dramatic increase in length and girth. Intriguingly, this period of growth is independent of growth hormone and the underlying mechanism is poorly understood. Recently, an mutation was identified in humans with early postnatal growth restriction. Here, we show that IGF2 is essential for longitudinal and appositional murine postnatal bone development, which involves proper timing of chondrocyte maturation and perichondrial cell differentiation and survival. Importantly, the null mouse model does not represent a simple delay of growth but instead uncoordinated growth plate development. Furthermore, biochemical and two-photon imaging analyses identified elevated and imbalanced glucose metabolism in the null mouse. Attenuation of glycolysis rescued the mutant phenotype of premature cartilage maturation, thereby indicating that IGF2 controls bone growth by regulating glucose metabolism in chondrocytes. This work links glucose metabolism with cartilage development and provides insight into the fundamental understanding of human growth abnormalities.

Objectives A major hurdle in osteoarthritis (OA) research is the lack of sensitive detection and monitoring methods. It is hypothesized that proteases, such as matrix metalloproteinases (MMPs), are upregulated at early stages of OA development. The aim of this study was to investigate if a near infrared fluorescence (NIRF) probe activated by MMPs could visualize in vivo OA progression starting from its early stages. Methods Using an MMP activatable NIRF probe (MMPSense680), we assessed the upregulation of MMP activity in vitro by incubating human chondrocytes with the pro-inflammatory cytokine IL-1β. MMP activity was then evaluated in vivo serially in a chronic, injury-induced OA mouse model. For tracking MMP activity over time, mice were imaged 1 – 8 weeks post OA inducing surgery. Imaging results were correlated with histology. Results In vitro studies confirmed that NIRF imaging could identify enhanced MMP activity in IL-1β-treated human chondrocytes. In vivo imaging showed significantly higher fluorescent intensity in OA knees compared to sham knees (control) of the same mice. Additionally, the total emitted fluorescence intensity steadily increased over the entire course of OA progression that was examined. NIRF imaging results correlated with histological analysis, which showed an increase in articular cartilage structural damage over time. Conclusions Imaging of MMP activity in an OA mouse model provided sensitive and consistent visualization of OA progression, beginning from the early stages of OA. In addition to facilitating the preclinical study of OA modulators, this approach has the potential for future human translation.

Summary Heart failure remains a significant cause of morbidity and mortality following myocardial infarction. Cardiac remuscularization with transplantation of human pluripotent stem cell-derived cardiomyocytes is a promising preclinical therapy to restore function. Recent large animal data, however, have revealed a significant risk of engraftment arrhythmia (EA). Although transient, the risk posed by EA presents a barrier to clinical translation. We hypothesized that clinically approved antiarrhythmic drugs can prevent EA-related mortality as well as suppress tachycardia and arrhythmia burden. This study uses a porcine model to provide proof-of-concept evidence that a combination of amiodarone and ivabradine can effectively suppress EA. None of the nine treated subjects experienced the primary endpoint of cardiac death, unstable EA, or heart failure compared with five out of eight (62.5%) in the control cohort (hazard ratio = 0.00; 95% confidence interval: 0–0.297; p = 0.002). Pharmacologic treatment of EA may be a viable strategy to improve safety and allow further clinical development of cardiac remuscularization therapy.

Bronchopulmonary dysplasia is a chronic lung disease of preterm infants characterized by arrested microvascularization and alveolarization. Studies show the importance of proangiogenic factors for alveolarization, but the importance of antiangiogenic factors is unknown. We proposed that hyperoxia increases the potent angiostatin, pigment epithelium-derived factor (PEDF), in neonatal lungs, inhibiting alveolarization and microvascularization. Wild-type (WT) and PEDF(-/-) mice were exposed to room air (RA) or 0.9 fraction of inspired oxygen from Postnatal Day 5 to 13. PEDF protein was increased in hyperoxic lungs compared with RA-exposed lungs (P < 0.05). In situ hybridization and immunofluorescence identified PEDF production primarily in alveolar epithelium. Hyperoxia reduced alveolarization in WT mice (P < 0.05) but not in PEDF(-/-) mice. WT hyperoxic mice had fewer platelet endothelial cell adhesion molecule (PECAM)-positive cells per alveolus (1.4 ± 0.4) than RA-exposed mice (4.3 ± 0.3; P < 0.05); this reduction was absent in hyperoxic PEDF(-/-) mice. The interactive regulation of lung microvascularization by vascular endothelial growth factor and PEDF was studied in vitro using MFLM-91U cells, a fetal mouse lung endothelial cell line. Vascular endothelial growth factor stimulation of proliferation, migration, and capillary tube formation was inhibited by PEDF. MFLM-91U cells exposed to conditioned medium (CM) from E17 fetal mouse lung type II (T2) cells cultured in 0.9 fraction of inspired oxygen formed fewer capillary tubes than CM from T2 cells cultured in RA (hyperoxia CM, 51 ± 10% of RA CM, P < 0.05), an effect abolished by PEDF antibody. We conclude that PEDF mediates reduced vasculogenesis and alveolarization in neonatal hyperoxia. Bronchopulmonary dysplasia likely results from an altered balance between pro- and antiangiogenic factors.

Background: Engraftment arrhythmias (EAs) are observed in large animal studies of intramyocardial transplantation of human pluripotent stem cell-derived cardiomyocytes (hPSC-CMs) for myocardial infarction. Although transient, the risk posed by EA presents a barrier to clinical translation. Objectives We hypothesized that clinically approved antiarrhythmic drugs can prevent EA-related mortality as well as suppress tachycardia and arrhythmia burden. Methods: hPSC-CM were transplanted into the infarcted porcine heart by surgical or percutaneous delivery to induce EA. Following a screen of antiarrhythmic agents, a prospective study was conducted to determine the effectiveness of amiodarone plus ivabradine in preventing cardiac death and suppressing EA. Results: EA was observed in all subjects, and amiodarone-ivabradine treatment was well-tolerated. None of the treated subjects experienced the primary endpoint of cardiac death, unstable EA or heart failure compared to 5/8 (62.5%) in the control cohort (hazard ratio 0.00; 95% confidence interval, 0-0.297; p = 0.002). Overall survival including two deaths in the treated cohort from immunosuppression-related infection showed borderline improvement with treatment (hazard ratio 0.21; 95% confidence interval, 0.03-1.01; p = 0.05). Without treatment, peak heart rate averaged 305 +/- 29 beats per min (bpm), whereas in treated subjects peak daily heart rate was significantly restricted to 185+/-9 bpm (p = 0.006). Similarly, treatment reduced peak daily EA burden from 96.8 +/- 2.9% to 76.5 +/- 7.9% (p = 0.003). Antiarrhythmic treatment was safely discontinued after approximately one-month of treatment without recrudescence of arrhythmia. Conclusions: The risk of engraftment arrhythmia following hPSC-CM transplantation can be reduced significantly by combined amiodarone and ivabradine drug therapy.

BackgroundInflammation is a major cause of cartilage destruction and leads to the imbalance of metabolic activities in the arthritic joint. Pigment epithelium-derived factor (PEDF) has been reported to have both pro- and anti-inflammatory activities in various cell types and to be upregulated in the arthritic joint, but its role in joint destruction is unclear. Our aim was to investigate the role of PEDF in cartilage degeneration under inflammatory conditions.MethodsPEDF was ectopically expressed in primary human articular chondrocytes, and catabolic gene expression and protein secretion in response to the pro-inflammatory cytokine interleukin 1 beta (IL-1β) were evaluated. Metatarsal bones from PEDF-deficient and wild type mice were cultured in the presence or absence of IL-1β. Cartilage matrix integrity and matrix metalloproteinases MMP-1, MMP-3, and MMP-13 were evaluated. PEDF-deficient and wild type mice were evaluated in the monosodium iodoacetate (MIA) inflammatory joint destruction animal model to determine the role of PEDF in inflammatory arthritis in vivo. Student’s t-tests and Mann–Whitney tests were employed where appropriate, for parametric and non-parametric data, respectively.ResultsWe showed that PEDF protein levels were higher in human osteoarthritis samples compared to normal samples. We demonstrated that ectopic PEDF expression in primary human articular chondrocytes exacerbated catabolic gene expression in the presence of IL-1β. In whole bone organ cultures, IL-1β induced MMP-1, MMP-3 and MMP-13 protein production, and caused significant cartilage matrix loss. Interestingly, Toluidine Blue staining showed that PEDF-deficient bones from 29 week old animals, but not 10 week old animals, had reduced matrix loss in response to IL-1β compared to their wild type counterparts. In addition, PEDF-deficiency in 29 week old animals preserved matrix integrity and protected against cell loss in the MIA joint destruction model in vivo.ConclusionWe conclude that PEDF exacerbates cartilage degeneration in an age-dependent manner under an inflammatory setting. This is the first study identifying a specific role for PEDF in joint inflammation and highlights the multi-faceted activities of PEDF.Electronic supplementary materialThe online version of this article (doi:10.1186/s12891-017-1410-y) contains supplementary material, which is available to authorized users.

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