Shrinking Bioprinting: A Big Advancement for Tiny Structures
3D bioprinting, one of the fastest growing technologies, is finding vast applications in biomedicine. However, one of the biggest challenges for bioprinting is capturing delicate, miniature structures — such as networks of tiny blood vessels — that are vitally important to the body. Conventional efforts have focused on improving printer hardware or ink properties, but these measures can be prohibitively expensive or time-consuming. Researchers at Brigham and Women’s Hospital, led by Yu Shrike Zhang, PhD, have come up with a new method – shrinking printing – that uses the same hardware and ink to print but can then shrink resulting organs or tissues down to miniature size.
The new approach, which uses a charged solution to expel water molecules out of oppositely charged bioprinted materials, is detailed in a paper published in Nature Communications.
The video below shows the shrinking of bioprinted tubular tissues with hyaluronic acid (top) and with gelatin-based material (bottom), allowing the investigators to generate hollow tubular tissues at a scale (<100 um) not possible or easy before.
Paper cited: Zhang YS et al. “Complexation-induced resolution enhancement of 3D-printed hydrogel constructs” Nature Communications DOI: https://doi.org/10.1038/s41467-020-14997-4
Discovery May Illuminate a Missing Link Between Atherosclerosis and Aging
Novel role for an RNA molecule found in the blood vessel wall may have implications for chronic vascular disease states and aging
Investigators from Brigham and Women’s Hospital have made a potentially exciting discovery by jumping into the abyss of the dark side of the genome. Once dismissed as “junk DNA,” roughly 75 percent of the human genome do not code for proteins. But these dark regions of the genome are far from junk — instead, they may hold tantalizing clues about disease states. A team of Brigham investigators led by Mark Feinberg, MD, of the Division of Cardiovascular Medicine, and an associate professor of Medicine at Harvard Medical School, recently plunged into these regions in search of clues about atherosclerosis — a disease in which the arteries become increasingly hardened and narrow, obstructing blood flow and leading to heart disease. Using a preclinical model of atherosclerosis, Feinberg and colleagues have uncovered a long, noncoding RNA (lncRNA) that may point the way toward new therapies for atherosclerosis and shed light on why the likelihood of the disease increases with age. Results are published in Science Translational Medicine.
“We have identified a new actor in controlling aging in the vessel wall and, surprisingly, it’s not a traditional gene or protein. It’s part of the non-coding genome. That was unexpected,” said Feinberg. “We know a lot about the importance of cholesterol and inflammation in heart disease, but this is a new, additional pathway. We need to think carefully about how it might impact the development of therapeutics for cardiovascular disease.”
Feinberg and colleagues used a mouse model of atherosclerosis in which mice begin to develop atherosclerotic lesions at 12 weeks. The investigators isolated RNA from the inner-most lining of the blood vessel wall and looked across the entire genome at all RNAs, searching for which ones had changes in activity during disease progression or regression. One of the most dynamic was SNHG12, a long stretch of RNA that does not code for a protein but is found across multiple species, including humans, pigs and mice.
To better understand SNHG12’s role, the researchers conducted experiments in which they either knocked down its activity or ramped it up. They found that less SNHG12 led to a profound increase in atherosclerosis but more SNHG12 dramatically reduced disease progression. To understand what SNHG12 was doing, the team looked for who its partners were. One of them turned out to be a molecule involved with DNA damage repair and aging. Without these partners working together, vessel walls became leaky and permeable to bad cholesterol. The team could reverse this phenomenon by adding a small molecule that promotes DNA damage repair, suggesting a potential therapeutic avenue to pursue.
“What’s really exciting is that RNA therapeutics — in which we deliver RNA molecules or small molecules that can help regulate RNA — is a growing area,” said Feinberg. “Our work help lays a foundation for pursuing these kinds of therapies for atherosclerosis.”
Funding for this work was provided by the National Institutes of Health (HL115141, HL117994, HL134849, GM115605, HL134892-01A1 and HL080472), the Arthur K. Watson Charitable Trust, the Dr. Ralph and Marian Falk Medical Research Trust, the RRM Charitable Fund, the École Polytechnique Fédérale de Lausanne, the Swiss National Science Foundation (P2BEP3_162063 and 310030B-160318), the American Heart Association (18POST34030395, 18CSA34080399, and 18SFRN33900144), the National Natural Science Foundation of China (81570334 and 81770358), the Xiangya Eminent Doctor Project (#013), the Heart and Stroke Foundation of Canada (G-16-00013521) and a Canada Research Chair. Feinberg and Brigham and Women’s Hospital filed a patent application for use of atherosclerosis-associated lncRNAs entitled “Targeting lncRNA in cardiovascular disease” (PCT 62/757,832, PCT 62/905,479, PCT/US2019/061006).
Paper cited: Haemmig, S et al. “Long noncoding RNA SNHG12 integrates a DNA-PK–mediated DNA damage response and vascular senescence” Science Translational Medicine DOI: 10.1126/scitranslmed.eaaw1868
Ceramides Predict Vascular Brain Injury and Dementia
Higher ratios of very-long-chain to long-chain ceramides were associated with a reduced risk of dementia and Alzheimer’s disease
Novel blood-based biomarkers for dementia could identify disease at an early preclinical stage, serve as surrogate outcomes for clinical trials of investigational therapies and even identify future potential therapeutic targets. Unlike cerebrospinal fluid biomarkers that require a spinal tap, plasma biomarkers can be extracted from the blood, making their collection much less invasive and much more appealing for patients. In a study published in Annals of Clinical and Translational Neurology, a team led by investigators from Brigham and Women’s Hospital describes the role of plasma ceramides in dementia and Alzheimer’s disease (AD) and their potential as a blood-based biomarker.
“Our findings indicate that circulating ceramide ratios may be useful predictors of future dementia risk and may have a role in predicting dementia at an early, preclinical stage, when the greatest opportunity for disease modification exists,” said Emer McGrath, MD, PhD, associate neurologist in the Department of Neurology at the Brigham. “However, these results will require replication in other cohorts.”
Altered lipid metabolism is believed to play an important role in the development of dementia and Alzheimer’s disease. Ceramides are a type of lipid belonging to the sphingolipid family and are thought to play an important role in lipid aggregation, inflammation, endothelial dysfunction and neuronal cell death. Recently, attention has focused on the possibility that the adverse effects of ceramides may be related to the relative proportions of circulating very-long-chain to long-chain fatty acyl chains, rather than simply due to elevated total ceramide levels. Very-long-chain fatty acyl ceramides are important for myelin function and may have a protective effect against dementia, while long-chain ceramide species are linked with deleterious pro-inflammatory and apoptotic effects.
In their study, McGrath and colleagues compared levels of very-long chain and long-chain ceramides in blood samples from approximately 1,900 participants in the Framingham Heart Study Offspring cohort. They analyzed the risk of dementia, MRI structural measures of vascular brain injury and β-amyloid burden on brain PET, AD’s gold-standard imaging marker. The team found that an elevated ratio of very-long-chain to long-chain ceramides was associated with a 27 percent reduction in the risk of dementia and AD dementia as well as a lower burden of white matter injury on MRI of the brain.
In an exploratory analysis of 48 individuals with available amyloid-PET data, an elevated ratio of ceramide 24:0 (very-long chain ceramide) to ceramide 16:0 (long-chain ceramide) was associated with a reduced burden of ß-amyloid. Ceramides have previously been shown to stimulate ß-amyloid formation and inhibition of ceramide synthesis results in reduced production of ß-amyloid. It is possible that pharmacological inhibition of long-chain ceramide synthesis could slow down or even prevent the progression of AD dementia through prevention of ß-amyloid accumulation. Modification of ceramides could represent an attractive therapeutic option for prevention of vascular contributions to dementia, although this remains to be tested.
Funding for this work was provided by an Alzheimer’s Association Clinician Scientist Fellowship (AACSF-18- 566570), the National Heart, Lung, and Blood Institute (R01 HL60040 and R01 HL70100), the National Institute on Aging (R01 AG054076, R01AG049607, R01 AG033193, U01 AG049505, U01 AG052409), and National Institute of Neurological Disorders and Stroke (NS017950 and UH2 NS100605).
Paper cited: McGrath ER, Himali JJ, Xanthakis V, Duncan MS, Schaffer JE, Ory DS, Peterson LR, DeCarli C, Pase MP, Satizabal CL, Vasan RS, Beiser AS, Seshadri S. Circulating ceramide ratios and risk of vascular brain aging and dementia. Ann Clin Transl Neurol. 2020 Jan 16. PMID: 31950603.