In vivo base editing rescues Hutchinson-Gilford progeria syndrome in mice.

Hutchinson-Gilford progeria syndrome (HGPS or progeria) is typically caused by a dominant-negative C•G-to-T•A mutation (c.1824 C>T; p.G608G) in LMNA, the gene that encodes nuclear lamin A. This mutation causes RNA mis-splicing that produces progerin, a toxic protein that induces rapid ageing and shortens the lifespan of children with progeria to approximately 14 years1-4. Adenine base editors (ABEs) convert targeted A•T base pairs to G•C base pairs with minimal by-products and without requiring double-strand DNA breaks or donor DNA templates5,6. Here we describe the use of an ABE to directly correct the pathogenic HGPS mutation in cultured fibroblasts derived from children with progeria and in a mouse model of HGPS. Lentiviral delivery of the ABE to fibroblasts from children with HGPS resulted in 87-91% correction of the pathogenic allele, mitigation of RNA mis-splicing, reduced levels of progerin and correction of nuclear abnormalities. Unbiased off-target DNA and RNA editing analysis did not detect off-target editing in treated patient-derived fibroblasts. In transgenic mice that are homozygous for the human LMNA c.1824 C>T allele, a single retro-orbital injection of adeno-associated virus 9 (AAV9) encoding the ABE resulted in substantial, durable correction of the pathogenic mutation (around 20-60% across various organs six months after injection), restoration of normal RNA splicing and reduction of progerin protein levels. In vivo base editing rescued the vascular pathology of the mice, preserving vascular smooth muscle cell counts and preventing adventitial fibrosis. A single injection of ABE-expressing AAV9 at postnatal day 14 improved vitality and greatly extended the median lifespan of the mice from 215 to 510 days. These findings demonstrate the potential of in vivo base editing as a possible treatment for HGPS and other genetic diseases by directly correcting their root cause.

Transient induction of telomerase expression mediates senescence and reduces tumorigenesis in primary fibroblasts.

Telomerase is an enzymatic ribonucleoprotein complex that acts as a reverse transcriptase in the elongation of telomeres. Telomerase activity is well documented in embryonic stem cells and the vast majority of tumor cells, but its role in somatic cells remains to be understood. Here, we report an unexpected function of telomerase during cellular senescence and tumorigenesis. We crossed Tert heterozygous knockout mice (mTert+/- ) for 26 generations, during which time there was progressive shortening of telomeres, and obtained primary skin fibroblasts from mTert+/+ and mTert-/- progeny of the 26th cross. As a consequence of insufficient telomerase activities in prior generations, both mTert+/+ and mTert-/- fibroblasts showed comparable and extremely short telomere length. However, mTert-/- cells approached cellular senescence faster and exhibited a significantly higher rate of malignant transformation than mTert+/+ cells. Furthermore, an evident up-regulation of telomerase reverse-transcriptase (TERT) expression was detected in mTert+/+ cells at the presenescence stage. Moreover, removal or down-regulation of TERT expression in mTert+/+ and human primary fibroblast cells via CRISPR/Cas9 or shRNA recapitulated mTert-/- phenotypes of accelerated senescence and transformation, and overexpression of TERT in mTert-/- cells rescued these phenotypes. Taking these data together, this study suggests that TERT has a previously underappreciated, protective role in buffering senescence stresses due to short, dysfunctional telomeres, and preventing malignant transformation.

Impaired LEF1 Activation Accelerates iPSC-Derived Keratinocytes Differentiation in Hutchinson-Gilford Progeria Syndrome.

Hutchinson-Gilford progeria syndrome (HGPS) is a detrimental premature aging disease caused by a point mutation in the human LMNA gene. This mutation results in the abnormal accumulation of a truncated pre-lamin A protein called progerin. Among the drastically accelerated signs of aging in HGPS patients, severe skin phenotypes such as alopecia and sclerotic skins always develop with the disease progression. Here, we studied the HGPS molecular mechanisms focusing on early skin development by differentiating patient-derived induced pluripotent stem cells (iPSCs) to a keratinocyte lineage. Interestingly, HGPS iPSCs showed an accelerated commitment to the keratinocyte lineage than the normal control. To study potential signaling pathways that accelerated skin development in HGPS, we investigated the WNT pathway components during HGPS iPSCs-keratinocytes induction. Surprisingly, despite the unaffected ß-catenin activity, the expression of a critical WNT transcription factor LEF1 was diminished from an early stage in HGPS iPSCs-keratinocytes differentiation. A chromatin immunoprecipitation (ChIP) experiment further revealed strong bindings of LEF1 to the early-stage epithelial developmental markers K8 and K18 and that the LEF1 silencing by siRNA down-regulates the K8/K18 transcription. During the iPSCs-keratinocytes differentiation, correction of HGPS mutation by Adenine base editing (ABE), while in a partial level, rescued the phenotypes for accelerated keratinocyte lineage-commitment. ABE also reduced the cell death in HGPS iPSCs-derived keratinocytes. These findings brought new insight into the molecular basis and therapeutic application for the skin abnormalities in HGPS.

FGFR2 mutations in bent bone dysplasia syndrome activate nucleolar stress and perturb cell fate determination.

Fibroblast Growth Factor (FGF) signaling promotes self-renewal in progenitor cells by encouraging proliferation and inhibiting cellular senescence. Yet, these beneficial effects can be hijacked by disease-causing mutations in FGF receptor (FGFR) during embryogenesis. By studying dominant FGFR2 mutations that are germline in bent bone dysplasia syndrome (BBDS), we reveal a mechanistic connection between FGFR2, ribosome biogenesis, and cellular stress that links cell fate determination to disease pathology. We previously showed that FGFR2 mutations in BBDS, which amplify nucleolar targeting of FGFR2, activate ribosomal DNA (rDNA) transcription and delay differentiation in osteoprogenitor cells and patient-derived bone. Here we find that the BBDS mutations augment the ability of FGFR2 to recruit histone-remodeling factors that epigenetically activate transcriptionally silent rDNA. Nucleolar morphology is controlled by chromatin structure, and the high levels of euchromatic rDNA induced by the BBDS mutations direct nucleolar disorganization, alter ribosome biogenesis, and activate the Rpl11-Mdm2-p53 nucleolar stress response pathway. Inhibition of p53 in cells expressing the FGFR2 mutations in BBDS rescues delayed osteoblast differentiation, suggesting that p53 activation is an essential pathogenic factor in, and potential therapeutic target for, BBDS. This work establishes rDNA as developmentally regulated loci that receive direct input from FGF signaling to balance self-renewal and cell fate determination.

Ultraviolet radiation protection potentials of Methylene Blue for human skin and coral reef health.

Methylene blue (MB) is a century-old medicine, a laboratory dye, and recently shown as a premier antioxidant that combats ROS-induced cellular aging in human skins. Given MB's molecular structure and light absorption properties, we hypothesize that MB has the potential to be considered as a sunscreen active for UV radiation protection. In this study, we tested the effects of MB on UVB ray-induced DNA double-strand breaks in primary human keratinocytes. We found that MB treatment reduced DNA damages caused by UVB irradiation and subsequent cell death. Next, we compared MB with Oxybenzone, which is the most commonly used chemical active ingredient in sunscreens but recently proven to be hazardous to aquatic ecosystems, in particular to coral reefs. At the same concentrations, MB showed more effective UVB absorption ability than Oxybenzone and significantly outperformed Oxybenzone in the prevention of UVB-induced DNA damage and the clearance of UVA-induced cellular ROS. Furthermore, unlike Oxybenzone, MB-containing seawater did not affect the growth of the coral species Xenia umbellata. Altogether, our study suggests that MB has the potential to be a coral reef-friendly sunscreen active ingredient that can provide broad-spectrum protection against UVA and UVB.

Mechanisms of angiogenic incompetence in Hutchinson-Gilford progeria via downregulation of endothelial NOS.

Hutchinson-Gilford progeria syndrome (HGPS) is a rare genetic disorder with features of accelerated aging. The majority of HGPS cases are caused by a de novo point mutation in the LMNA gene (c.1824C>T; p.G608G) resulting in progerin, a toxic lamin A protein variant. Children with HGPS typically die from coronary artery diseases or strokes at an average age of 14.6 years. Endothelial dysfunction is a known driver of cardiovascular pathogenesis; however, it is currently unknown how progerin antagonizes normal angiogenic function in HGPS. Here, we use human iPSC-derived endothelial cell (iPSC-EC) models to study angiogenesis in HGPS. We cultured normal and HGPS iPSC-ECs under both static and fluidic culture conditions. HGPS iPSC-ECs show reduced endothelial nitric oxide synthase (eNOS) expression and activity compared with normal controls and concomitant decreases in intracellular nitric oxide (NO) level, which result in deficits in capillary-like microvascular network formation. Furthermore, the expression of matrix metalloproteinase 9 (MMP-9) was reduced in HGPS iPSC-ECs, while the expression of tissue inhibitor metalloproteinases 1 and 2 (TIMP1 and TIMP2) was upregulated relative to healthy controls. Finally, we used an adenine base editor (ABE7.10max-VRQR) to correct the pathogenic c.1824C>T allele in HGPS iPSC-ECs. Remarkably, ABE7.10max-VRQR correction of the HGPS mutation significantly reduced progerin expression to a basal level, rescued nuclear blebbing, increased intracellular NO level, normalized the misregulated TIMPs, and restored angiogenic competence in HGPS iPSC-ECs. Together, these results provide molecular insights of endothelial dysfunction in HGPS and suggest that ABE could be a promising therapeutic approach for correcting HGPS-related cardiovascular phenotypes.

Peroxisomal abnormalities and catalase deficiency in Hutchinson-Gilford Progeria Syndrome.

Peroxisomes are small, membrane-enclosed eukaryotic organelles that house various enzymes with metabolic functions. One important feature in both Hutchinson-Gilford Progeria Syndrome (HGPS) and normal aging is the elevated levels of Reactive Oxygen Species (ROS), which are generated from metabolic pathways with the capacity to cause oxidative damage to macromolecules within the cells. Although peroxisomal bioreactions can generate free radicals as their byproducts, many metabolic enzymes within the peroxisomes play critical roles as ROS scavengers, in particular, catalase. Here, we observed impaired peroxisomes-targeting protein trafficking, which suggested that the poorly assembled peroxisomes might cause high oxidative stress, contributing to the premature senescent phenotype in HGPS. We then investigated the ROS clearance efficiency by peroxisomal enzymes and found a significantly decreased expression of catalase in HGPS. Furthermore, we evaluated the effects of two promising HGPS-treatment drugs Methylene Blue and RAD001 (Everolimus, a rapamycin analog) on catalase in HGPS fibroblasts. We found that both drugs effectively reduced cellular ROS levels. MB, as a well-known antioxidant, did not affect catalase expression or activity. Interestingly, RAD001 treatment significantly upregulated catalase activity in HGPS cells. Our study presents the first characterization of peroxisomal function in HGPS and provides new insights into the cellular aspects of HGPS and the ongoing clinical trial.

Hierarchically porous poly(ethylenimine) modified poly(styrene-co-divinylbenzene) microspheres for the adsorption of gold nanoparticles and simultaneously being transformed as the nanoparticles immobilized catalyst.

With the extensive applications of gold nanoparticles (AuNPs) and the confirmation of their toxicity on human health and environment, it was urgent to remove AuNPs from environment. The hierarchically porous poly(ethylenimine) modified poly(styrene-co-divinylbenzene) microsphere (PEI-PS-DVB) was prepared and characterized by scanning electron microscopy, X-ray diffraction, transform infrared spectrometry, energy dispersive X-ray spectrometry, elemental analysis, contact angle, zeta potential analysis, N2 adsorption-desorption and mercury intrusion porosimetry. PEI-PS-DVB possessed abundant flow-through pores (70-120 nm) and meso/micropores (<50 nm); the former pores enabled full availability of the adsorbent to relatively large adsorbate, i.e. AuNPs, with fast mass transfer, while the latter ones ensured large surface area for high adsorption capacity. Thanks to its plentiful nitrogen and special hierarchical pores, PEI-PS-DVB was suitable for the adsorption of AuNPs by electrostatic interaction and special affinity between nitrogen and Au. The adsorption obeyed the pseudo-first-order kinetic and Langmuir isotherm models. The maximum adsorption capacity based on Langmuir model was 806.5 mg/g. Moreover, PEI-PS-DVB adsorbing AuNPs could be the efficient catalyst for the reduction of 4-nitrophenol with satisfactory reusability. The developed hierarchically porous PEI-PS-DVB was a promising adsorbent for AuNPs with high adsorption capacity, and recycling usage of waste AuNPs conformed to the green and sustainable concept.

Flow-through silica: A potential matrix for fast chromatographic enantioseparation with high enantioselectivity.

The demand for fast chromatographic enantioseparation aroused the hot research in stationary phase matrix. In the present study, the flow-through silica, which is characterized by hierarchical pores of through pores in several hundred nanometer range and mesopores about 20nm, was attempted for fast enantioseparation. Thanks to the large surface area and full openness of the through pores, the flow-through silica had comparable cellulose derivative loading amount as the commercial wide-pore silica, which was impracticable for most of the core-shell particles and sub-2-µm fully porous silica. In addition, the backpressure was about two times lower in the case of the flow-through silica of the same particle size to the commercial wide-pore silica, due to the highly porous structure of the former. Another appreciated merit of the flow-through silica in small size (~2µm) was the less dependence of column efficiency on the flow rate. All of the above features rendered the flow-through silica a tremendous potential for fast enantioseparation with desired enantioselectivity, especially suitable for the polysaccharide chiral selector.

Biotransformation of NSAIDs by pig liver microsomes in vitro: Kinetics, metabolites identification and toxicity prediction.

Non-steroidal anti-inflammatory drugs (NSAIDs) are one of the most frequently used pharmaceuticals in animals. In the current study, the biotransformation of five NSAIDs by pig liver microsomes (PLMs) was studied. The pseudo-first-order kinetics mode was obtained for the metabolization of the studied NSAIDs by PLMs in vitro. The metabolites were identified by high performance liquid chromatography with a high-resolution LTQ-Orbitrap mass spectrometry. The hydroxylation of benzene was confirmed to be the dominating metabolic pathway. Finally, the toxicity of the metabolites was predicted by the Estimation Programs Interface Suite software based on quantitative structure-activity relationships. Decreased toxicity was expected for the most metabolites of the studied NSAIDs except flurbiprofen, whose main metabolite exhibited slightly more toxicity. The present study provided a preliminary foundation to understand the metabolites of some NSAIDs and their toxicity, which was of great significance in animal food safety.

Ribosome biogenesis is dynamically regulated during osteoblast differentiation.

Changes in ribosome biogenesis are tightly linked to cell growth, proliferation, and differentiation. The rate of ribosome biogenesis is established by RNA Pol I-mediated transcription of ribosomal RNA (rRNA). Thus, rRNA gene transcription is a key determinant of cell behavior. Here, we show that ribosome biogenesis is dynamically regulated during osteoblast differentiation. Upon osteoinduction, osteoprogenitor cells transiently silence a subset of rRNA genes through a reversible mechanism that is initiated through biphasic nucleolar depletion of UBF1 and then RNA Pol I. Nucleolar depletion of UBF1 is coincident with an increase in the number of silent but transcriptionally permissible rRNA genes. This increase in the number of silent rRNA genes reduces levels of ribosome biogenesis and subsequently, protein synthesis. Together these findings demonstrate that fluctuations in rRNA gene transcription are determined by nucleolar occupancy of UBF1 and closely coordinated with the early events necessary for acquisition of the osteoblast cell fate.

Preformed gelatin microcryogels as injectable cell carriers for enhanced skin wound healing.

Wound dressings of cell-laden bulk hydrogel or scaffold were mainly applied for enhanced cell engraftment in contrast to free cell injection. However, dressing of cells laden in biomaterials on wound surface might not effectively and timely exert functions on deep or chronic wounds where insufficient blood supply exists. Previously, we developed injectable gelatin microcryogels (GMs) which could load cells for enhanced cell delivery and cell therapy. In this study, biological changes of human adipose-derived stem cells (hASCs) laden in GMs were compared in varied aspects with traditional two dimensional (2D) cell culture, such as cell phenotype markers, stemness genes, differentiation, secretion of growth factors, cell apoptosis and cell memory by FACS, QRT-PCR and ELISA, that demonstrated the priming effects of GMs on upregulation of stemness genes and improved secretion of growth factors of hASCs for potential augmented wound healing. In a full-thickness skin wound model in nude mice, multisite injection and dressing of hASCs-laden GMs could significantly accelerate the healing compared to free cell injection. Bioluminescence imaging and protein analysis indicated improved cell retention and secretion of multiple growth factors. Our study suggests that GMs as primed injectable 3D micro-niches represent a new cell delivery methodology for skin wound healing which could not only benefit on the recovery of wound bed but also play direct effects on wound basal layer for healing enhancement. Injectable GMs as facile multisite cell delivery approach potentially provide new minimally-invasive therapeutic strategy for refractory wounds such as diabetic ulcer or radiative skin wound. STATEMENT OF SIGNIFICANCE: This work applied a type of elastic micro-scaffold (GMs) to load and prime hMSCs for skin wound healing. Due to the injectability of GMs, the 3D cellular micro-niches could simply realize minimally-invasive and multisite cell delivery approach for accelerating the wound healing process superior to free cell injection. The biological features of MSCs has been thoroughly characterized during 3D culture in GMs (i.e. cell proliferation, characterization of cell surface markers, stemness of MSCs in GMs, differentiation of MSCs in GMs, secretion of MSCs in GMs, induced apoptosis of MSCs in GMs). Multiple methods such as bioluminescent imaging, immunohistochemistry, immunofluorescence, qRT-PCR, ELSA and western blot were used to assess the in vivo results between groups.