Human iPSC-based modeling of late-onset disease via progerin-induced aging

Reprogramming somatic cells to induced pluripotent stem cells (iPSCs) resets their identity back to an embryonic age and, thus, presents a significant hurdle for modeling late-onset disorders. In this study, we describe a strategy for inducing aging-related features in human iPSC-derived lineages and apply it to the modeling of Parkinson's disease (PD). Our approach involves expression of progerin, a truncated form of lamin A associated with premature aging. We found that expression of progerin in iPSC-derived fibroblasts and neurons induces multiple aging-related markers and characteristics, including dopamine-specific phenotypes such as neuromelanin accumulation. Induced aging in PD iPSC-derived dopamine neurons revealed disease phenotypes that require both aging and genetic susceptibility, such as pronounced dendrite degeneration, progressive loss of tyrosine hydroxylase (TH) expression, and enlarged mitochondria or Lewy-body-precursor inclusions. Thus, our study suggests that progerin-induced aging can be used to reveal late-onset age-related disease features in hiPSC-based disease models.

ZFX controls the self-renewal of human embryonic stem cells

Embryonic stem cells (ESCs) and induced pluripotent stem cells (iPSCs) offer great promise in regenerative medicine and disease modeling due to their unlimited self-renewal and broad differentiation capacity. There is evidence that the growth properties and critical signaling pathways differ between murine and human ESCs; therefore, it is essential to perform functional studies to test the putatively conserved mechanisms of pluripotent stem cell self-renewal between species. Previously, we identified the transcription factor Zfx as a key regulator of self-renewal in murine ESCs. Here we extend those findings to human ESCs. ZFX knockdown in hESCs hindered clonal growth and decreased colony size after serial replating. ZFX overexpression enhanced clone formation in the presence of Y-27632, increased colony size at low density and decreased expression of differentiation-related genes in human ESCs. ZFX-overexpressing hESCs resisted spontaneous differentiation but could be directed to differentiate into endodermal and neural cell fates when provided with the appropriate cues. Thus, ZFX acts as a molecular rheostat regulating the balance between self-renewal and differentiation in hESCs, revealing the close evolutionary conservation of the self-renewal mechanisms in murine and human ESCs.

Identification of embryonic stem cell-derived midbrain dopaminergic neurons for engraftment

Embryonic stem cells (ESCs) represent a promising source of midbrain dopaminergic (DA) neurons for applications in Parkinson disease. However, ESC-based transplantation paradigms carry a risk of introducing inappropriate or tumorigenic cells. Cell purification before transplantation may alleviate these concerns and enable identification of the specific DA neuron stage most suitable for cell therapy. Here, we used 3 transgenic mouse ESC reporter lines to mark DA neurons at 3 stages of differentiation (early, middle, and late) following induction of differentiation using Hes5::GFP, Nurr1::GFP, and Pitx3::YFP transgenes, respectively. Transplantation of FACS-purified cells from each line resulted in DA neuron engraftment, with the mid-stage and late-stage neuron grafts being composed almost exclusively of midbrain DA neurons. Mid-stage neuron cell grafts had the greatest amount of DA neuron survival and robustly induced recovery of motor deficits in hemiparkinsonian mice. Our data suggest that the Nurr1+ stage (middle stage) of neuronal differentiation is particularly suitable for grafting ESC-derived DA neurons. Moreover, global transcriptome analysis of progeny from each of the ESC reporter lines revealed expression of known midbrain DA neuron genes and also uncovered previously uncharacterized midbrain genes. These data demonstrate remarkable fate specificity of ESC-derived DA neurons and outline a sequential stage-specific ESC reporter line paradigm for in vivo gene discovery.

Microsporidia and Acanthamoeba: the role of emerging corneal pathogens

Parasitic organisms are increasingly recognized as human corneal pathogens. A notable increase in both well-defined Acanthamoeba keratitis and a more dramatic increase in reported cases of Microsporidia keratitis have suggested significant outbreaks of parasitic keratitis around the world. Historical and contemporary baselines as well as a familiar associated clinical presentation reinforce the significant outbreak of Acanthamoeba keratitis in the United States. The remarkable rise in cases of Microsporidia keratitis, however, lacks these established baselines and, further, describes a disease that is inconsistent with previous definitions of disease. While a well-defined, abrupt increase strongly suggests temporally related risk factors, most likely environmental, involved in the Acanthamoeba outbreak, the rise in Microsporidia keratitis suggests that increased awareness and improved diagnostic acumen are a significant factor in case ascertainment. Regardless, recent evidence indicates that both parasitic diseases are likely underreported in various forms of infectious keratitis, which may have unrecognized but significant implications in the pathogenesis of both primary protozoal and polymicrobial keratitis. Further understanding of the incidence and interaction of these organisms with current therapeutic regimens and more commonly recognized pathogens should significantly improve diagnosis and alter clinical outcomes.

Estimating the total exposure to air pollutants for different population age groups in Hong Kong

Given that Hong Kong is one of the most densely populated cities in the world, the exposure of the Hong Kong people is one of the interesting research areas. In this study, an indirect approach was used to estimate the exposure to nitrogen dioxide (NO2), respiratory dust (PM10) and carbon monoxide (CO) pollutants experienced by different age groups of people in Hong Kong. The average concentrations of the 20 major microenvironments obtained from our measurement survey data, together with the people activity pattern data obtained from 7-day recall questionnaires, were used to predict frequency distributions to exposure assessment. Our results showed that Hong Kong people spent more than 86% of their time indoors. Homes were shown to be the one of the major exposure sites to NO2, CO and PM10 for all age groups. Our results also indicate that the 24-h NO2 exposure for individuals, irrespective of age, spending more than 2 h in commuting daily, was observed to be exceeding the 24-h NO2 exposure standards. This study was one of the pioneering studies with valuable contribution for modeling the estimates of exposures to NO2, PM10 and CO of different age groups in Hong Kong.

Corneal First Surface Optical Aberrations and Visual Performance

PURPOSE

Wavefront analysis has demonstrated that refractive surgery-induced corneal first surface aberrations are large, are dominated by symmetric aberrations (spherical-like aberrations), and are correlated to measures of visual performance. It is not clear whether the correlation between corneal first surface aberrations and visual performance can be generalized to other corneal conditions where large asymmetric aberrations (coma-like aberrations) may dominate the aberration structure. The purpose of the research reported here was to determine the general utility of corneal first surface wavefront analysis in predicting visual performance.

METHODS

Patients were 13 normals and 78 patients with a variety of corneal conditions including surgically removed pterygia, penetrating keratoplasty, keratoconus, radial keratotomy, laser in situ keratomileusis, and others. Videokeratographs were taken for all patients and used to calculate corneal first surface wavefront variance for 3 and 7 mm pupils. Similarly, visual performance was quantified by measurements of contrast sensitivity and high and low contrast acuities through both 3 and 7 mm pupils.

RESULTS

Statistically significant correlations existed between all three measures of visual performance and the corneal wavefront variance. All relationships were stronger for the 7 mm diameter-pupil condition than the 3 mm pupil.

CONCLUSION

Regardless of the cause, corneas with increased wavefront variance showed a quantifiable decrease in visual performance that was pupil size dependent.

Therapy of nonnecrotizing anterior scleritis with subconjunctival corticosteroid injection

OBJECTIVE

To determine the safety and efficacy of subconjunctival triamcinolone (Kenalog) in treating nonnecrotizing anterior scleritis.

DESIGN

The authors conducted a retrospective review of all patients treated with depot subconjunctival corticosteroid injection for scleritis from January 1988 to May 1993. Response to therapy was determined by subjective improvement in pain and a decrease in clinical signs of ocular inflammation. All patients received subconjunctival injections of triamcinolone by the same technique, and the minimum observation period for complications was 6 weeks.

RESULTS

Eighteen patients (90%) had relief of their symptoms with clinically observable improvement in inflammation, whereas two patients (10%) responded poorly. Nine patients (45%) required no further therapy. Average symptom-free interval was 18 weeks in patients with recurrent scleritis. No complications of scleral thinning, perforation, or glaucoma occurred in any patients.

CONCLUSION

Subconjunctival triamcinolone injection is highly efficacious in treating nonnecrotizing anterior scleritis without unreasonable risk of thinning and/or perforation and should be considered as adjunctive therapy in localized disease.