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Mike Eshleman, with AC Transit, directs people away from the Salesforce Transit Center following its closure, Tuesday, Sept. 25, 2018, in San Francisco. San Francisco officials shut down the city's celebrated new $2.2 billion transit terminal Tuesday after discovering a crack in a support beam under the center's public roof garden. Coined the "Grand Central of the West," the Salesforce Transit Center opened in August near the heart of downtown after nearly a decade of construction. It was expected to accommodate 100,000 passengers each weekday, and up to 45 million people a year. (AP Photo/Eric Risberg)

Mike Eshleman, with AC Transit, directs people away from the Salesforce Transit Center following its closure, Tuesday, Sept. 25, 2018, in San Francisco. San Francisco officials shut down the city's celebrated new $2.2 billion transit terminal Tuesday after discovering a crack in a support beam under the center's public roof garden. Coined the "Grand Central of the West," the Salesforce Transit Center opened in August near the heart of downtown after nearly a decade of construction. It was expected to accommodate 100,000 passengers each weekday, and up to 45 million people a year. (AP Photo/Eric Risberg)


The lower level of the Salesforce Transit Center remains empty except for police, following its closure Tuesday, Sept. 25, 2018, in San Francisco. San Francisco officials shut down the city's celebrated new $2.2 billion transit terminal Tuesday after discovering a crack in a support beam under the center's public roof garden. Coined the "Grand Central of the West," the Salesforce Transit Center opened in August near the heart of downtown after nearly a decade of construction. It was expected to accommodate 100,000 passengers each weekday, and up to 45 million people a year. (AP Photo/Eric Risberg)


San Francisco Police officers stand watch in the lower level of the Salesforce Transit Center following its closure Tuesday, Sept. 25, 2018, in San Francisco. San Francisco officials shut down the city's celebrated new $2.2 billion transit terminal Tuesday after discovering a crack in a support beam under the center's public roof garden. Coined the "Grand Central of the West," the Salesforce Transit Center opened in August near the heart of downtown after nearly a decade of construction. It was expected to accommodate 100,000 passengers each weekday, and up to 45 million people a year. (AP Photo/Eric Risberg)


San Francisco’s new transit terminal closes over beam crack

By PAUL ELIAS

Associated Press

Wednesday, September 26

SAN FRANCISCO (AP) — The so-called “Grand Central of the West” is closed out of safety concerns after workers discovered a crack in a support beam of the $2 billion transit terminal that opened just last month.

Workers discovered the crack early Tuesday while installing roofing tiles at the Salesforce Transit Center, according to its executive director Mark Zabaneh. Engineers spent the day inspecting the damage and Zabaneh said they decided to shut the station around 5 p.m., just as the afternoon rush hour started.

Zabaneh said the cause and the extent of the damage were unknown and the decision to close the terminal was made out of an “abundance of caution.”

He said structural engineers would be working at the building Tuesday night to assess whether it is safe for people to return.

Zabaneh said the crack was found near a weld on a stress-bearing horizontal beam. Engineers are searching for other cracks in other pipes, but are optimistic the damage is limited to the one pipe.

Buses were rerouted to a temporary transit center about two blocks away that was used during the center’s construction. A downtown street that runs under the beam was also ordered closed indefinitely, causing traffic chaos at the same time some streets were closed for a conference sponsored by Salesforce that was expected to draw 170,000 attendees.

“The beam is cracked,” Zabaneh said. “The behavior of the beam is unpredictable.”

Enveloped in wavy white sheets of metal veil, the five-level center includes a bus deck, a towering sky-lit central entrance hall and a rooftop park with an outdoor amphitheater. Zabaneh said American steel was used in the center’s construction.

The San Francisco Chronicle reported that the complex faced delays in putting out contracts to bid, and the winning bids were ultimately higher than expected. The terminal’s cost rose from $1.6 billion at its 2010 groundbreaking to more than $2 billion in 2016 because of what one analyst called “optimistic assumptions,” according to the Chronicle.

The project, a commanding presence in the city’s South of Market neighborhood, is financed by land sales, federal stimulus grants, district fees and taxes, bridge tolls, and federal and state funds.

It sits adjacent to another dubious landmark, the so-called sinking condominium, Millennium Tower, which has settled about 18 inches (45 centimeters) since it opened over a former landfill in 2009. Homeowners have filed multiple lawsuits against the developer and the city, some alleging that construction of the transit center caused the Millennium Tower’s sinking.

Zabaneh said he did not believe that the cracked beam was related to ongoing problems at Millennium Tower.

The online business software company Salesforce, which opened its adjacent 61-story Salesforce Tower three months ago, bought naming rights to the center in 2017 as part of a 25-year, $110 million sponsorship agreement.

The Salesforce Transit Center is operated by the Transbay Joint Powers Authority.

The Conversation

Don’t frack so close to me: Colorado voters will weigh in on drilling distances from homes and schools

September 26, 2018

Authors

Tara Opsal

Associate Professor of Sociology, Colorado State University

Stephanie Malin

Assistant Professor of Sociology, Colorado State University

Disclosure statement

Stephanie Malin has received funding from the National Institute of Environmental Health Sciences, the Rural Sociological Society, and the CSU Water Center.

Tara Opsal does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.

Partners

Colorado State University provides funding as a member of The Conversation US.

Coloradans will vote on a ballot initiative in November that requires new oil and gas projects to be set back at least 2,500 feet from occupied buildings. If approved, the measure – known as both Initiative 97 and Proposition 112 – would mark a major change from their state’s current limits: 500 feet from homes and 1,000 feet from schools.

As sociologists who have researched oil and gas drilling in the communities that host it for the past seven years, we think this measure would provide local governments and Coloradans more say over where drilling occurs and enhance the rights of those who live near these sites.

Fracking boom

Domestic oil and gas production has soared over the past decade, leading the U.S. to become the top global producer of those fossil fuels.

Technological innovations, especially the hydraulic fracturing and horizontal drilling, commonly called fracking, have fueled this growth. So has federal deregulation.

Partly because fracking and related industrial processes often occurs close to homes, schools and other occupied buildings, the debate over Proposition 112 is contentious.

Opponents, especially those funded by industry groups, argue that stricter rules will mean less state tax revenue, job losses and weakened private property rights. Proponents express concerns about air pollution, earthquakes, water well contamination and explosions to explain why they want the public to have more sway.

But many state governments have tried to stymie the attempts of communities to gain this power. For example, Colorado’s Supreme Court ruled in 2016 that local communities have no right to regulate where drilling occurs.

And industry-funded groups and the Colorado Farm Bureau, which represents farmers, ranchers and other agricultural interests, are countering this electoral effort to restrict drilling with their own measure. Known as Amendment 74, it would force any city or county government that limits drilling to compensate property owners if new setback rules were to lower property values or reduce revenue from fracking leases.

Regulations and leasing

Members of the public and local governments have successfully challenged limits on local control over fracking in court before. For example, Pennsylvania’s Supreme Court affirmed the power of communities to regulate the oil and gas industry locally when it ruled in 2016 that parts of a law known as Act 13 were unconstitutional.

In that instance, the court ruled against a provision that barred doctors from sharing information about possible toxic exposure if they were given access to industry information about the chemicals used in fracking. It also blocked the enforcement of a measure that allowed the use of eminent domain to site natural gas storage facilities.

But as far as we can tell, Colorado’s ballot initiative marks the first time voters can potentially control the set-back distances of oil and gas facilities from rivers, homes, schools and other buildings in their communities.

Negotiating terms

Regulating oil and gas leases on private land is hard partly because they are privately negotiated contracts between companies and landowners. To learn more about what happens during these negotiations, we interviewed more than 100 Coloradans and Pennsylvanians about their experiences negotiating these drilling leases.

In our recently published study, we found that these people feel inconvenienced at best. Most told us they felt exploited and mistreated due to the leasing experience despite having made money off of leasing their land or mineral rights.

Some scholars who look at how drilling affects local communities argue that this process empowers private property owners because they play a direct role in deciding the terms of these negotiations. And some of these folks can even get rich from fracking lease earnings.

Certainly, landowners – including some of the people we interviewed – have earned income from these contracts, though the amounts can vary from a few dollars to thousands of dollars per acre. But the overwhelming majority of the Pennsylvanians and Coloradans who met with us in their kitchen tables, backyards and farms described feeling disempowered when they signed fracking leases.

“I knew zip about gas production,” explained a man who operates a small-scale dairy farm in northeastern Pennsylvania and we are calling “Anderson” to honor our promise of confidentiality. “We had no time, we either made a decision to do it or not do it.”

During private negotiations, landmen – the company representatives who try to convince people to sell or lease their land and mineral rights – discouraged neighbors from teaming up to get a better deal or even talking with one another about the terms they’re considering, interviewees told us.

In some situations, when residents negotiated for better-than-average lease terms, landmen made them sign nondisclosure agreements that legally forbade sharing information.

Same land, different owners

Occasionally in Pennsylvania and almost always in Colorado, these fracked properties belong to two or more parties. One owns the surface and someone else possesses the rights to whatever minerals lie beneath it.

And, in Colorado, surface landowners are legally required to provide mineral owners access to their resources.

Many people we interviewed owned land but not the rights to the minerals below it. With limited power to stave off drilling in their backyards or on their farms, the surface rights owners we interviewed said they felt like “sitting ducks” and “unprotected.” They told us that they saw attempting to keep an oil and gas company off their land as “futile.”

“John,” a farmer who lives south of Denver, tried to fight the placement of a pipeline that split his farm into two less usable pieces. When he tried to fight the pipeline placement, he told us, he overheard industry representatives speculating that they simply needed to outspend his opposition.

Mineral rights

When the people we interviewed owned the mineral rights tied to their property but did not want to lease them, an energy company could pursue them through a state statute allowing a practice known as “forced pooling” in both Pennsylvania and Colorado.

It makes leasing mineral rights mandatory, leaving landowners with no way to say no when a company wants to frack their property.

We also heard about the personal costs participants experienced after they signed leases. Ranchers explained they lost productive pastureland. Other residents believed they became ill because of air pollution. And many farmers described lasting damage to idyllic homesteads.

Even when these factors violated their leases or laws governing oil and gas practices, nearly all lease signers we interviewed told us they had a hard time getting oil and gas operators with whom they’d signed leases to address any violations of those contracts.

To “Connor,” a homesteader in southern Colorado, the negotiation process felt “like having a second job.” At times,“ he told us, “it was absolutely overwhelming. I think we did absolutely everything we could as private citizens to try and mitigate the impacts and in the end, it was futile.”

The Conversation

How humans fit into Google’s machine future

September 26, 2018

Authors

Ed Finn

Associate Professor of Arts, Media and Engineering; Associate Professor of English; Director, Center for Science and the Imagination, Arizona State University

Andrew Maynard

Director, Risk Innovation Lab, Arizona State University

Disclosure statement

Ed Finn anticipates receiving funding from Google in Fall 2018 to co-sponsor a research project funded by the Hewlett Foundation exploring the relationship between science fiction, artificial intelligence, and technology policy. He owns five shares of Alphabet Inc. Class A stock, not counting some modest and almost inscrutable quantity of partial shares through the managed investments in his Arizona State University retirement account.

Andrew Maynard does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.

Partners

Arizona State University provides funding as a member of The Conversation US.

In 1998, Google began humbly, formally incorporated in a Menlo Park garage, providing search results from a server housed in Lego bricks. It had a straightforward goal: make the poorly indexed World Wide Web accessible to humans. Its success was based on an algorithm that analyzed the linking structure of the internet itself to evaluate what web pages are most reputable and useful. But founders Sergey Brin and Larry Page had a much more ambitious goal: They wanted to organize the world’s information.

Twenty years later, they have built a company going far beyond even that lofty goal, providing individuals and businesses alike with email, file sharing, web hosting, home automation, smartphones and countless other services. The playful startup that began as a surveyor of the web has become an architect of reality, creating and defining what its billions of users find, see, know or are even aware of.

Google controls more than 90 percent of the global search market, driving users and companies alike to design websites that appeal to the company’s algorithms. If Google can’t find a piece of information, that knowledge simply doesn’t exist for Google users. If it’s not on Google, does it really exist at all?

The intimacy machine

Despite its billions of answered search queries, Google is not just an answer machine. Google monitors what responses people click on, assuming those are more relevant and of higher value, and returning them more prominently in future searches on that topic. The company also monitors user activities on its email, business applications, music and mobile operating systems, using that data as part of a feedback loop to give users more of what they like.

All the data it collects is the real source of Google’s dominance, making the company’s services ever better at providing users what they want. Through autocomplete and the personalized filtering of search results, Google tries to anticipate your needs, sometimes before you even have them. As Google’s former executive chairman Eric Schmidt once put it, “I actually think most people don’t want Google to answer their questions. They want Google to tell them what they should be doing next.”

Twenty years from now, with two more decades of progress, Google will be even more accomplished, perhaps approaching a vision Brin expressed years ago: “The perfect search engine would be like the mind of God.” People are coming to rely on these tools, with their advanced artificial intelligence-based algorithms, not just to know things but to help them think.

The search bar has already become a place people ask personal questions, a kind of confessional or stream of consciousness that is deeply revealing about who users are, what they believe and what they want. In the future, Google will know you even more intimately, combining search results, browsing history and location tracking with biophysical health data from wearables and other sources that could offer powerful insights into your state of mind.

A new kind of vulnerability

It is not far-fetched to imagine that, in the future, Google might know if an individual is depressed, or has cancer, before that user realizes it for herself. But even beyond that, Google may have the crucial role in an ever-tightening alignment between what you think your needs are, and what Google tells you they are.

Beyond its effects on individual people, Google is amassing power to influence society – perhaps invisibly. Fiction has a warning about what that might look like: In the movie “Ex Machina,” an entrepreneurial genius reveals how he assembled the raw material of billions of search queries into an artificial mind that is highly effective at manipulating humans based on what it learns about people’s behaviors and biases.

But this situation isn’t really fiction. As long ago as 2014, researchers at Facebook infamously demonstrated how easy it is to manipulate users with positive or negative posts in their news feeds. As people hand algorithms more power over their daily lives, will they notice how the machines are steering them?

Surviving the glorious future

Whether Google ultimately exercises this power depends on its human leaders – and on the digital society Google is so central to building. The company is investing heavily in machine intelligence, committing itself to a highly automated future where the mechanics and, perhaps, the true insights of the quest for knowledge become difficult or impossible for humans to understand.

Google is gradually becoming an extension of individual and collective thought. It will get harder to recognize where people end and Google begins. People will become both empowered by and dependent on the technology – which will be easy for anyone to access but hard for people to control.

Humans will need to find ways to collaborate with – and direct the activities of – increasingly sophisticated machine intelligence, rather than merely becoming users who blindly follow the leads of black boxes they no longer understand or control.

Based on our studies of the complex relationships between people and technologies, a critical key to this new understanding of algorithms will be storytelling. The human brain is bad at understanding and processing data – which is, of course, a machine’s core strength. To work together, a new human-machine relationship will have to depend on a uniquely human strength – storytelling. People will work best with systems that can work through stories and explain their actions in ways humans can understand and modify.

The more that people entrust computer-based systems with organizing culture and society, the more they should demand those systems function according to rules humans can comprehend. The day we stop being the primary authors of the story of humankind is the day it stops being a story about us.

Deported man is suspect in deadly California beatings

By CHRISTOPHER WEBER

Associated Press

Wednesday, September 26

LOS ANGELES (AP) — A man who was deported from the United States six times was expected in court Wednesday to face charges after police say he killed three people and injured four in attacks targeting sleeping homeless men in California.

Investigators believe Ramon Escobar, 47, began attacking the men at random on Sept. 8, shortly after he arrived in California from Houston, where he’s considered a person of interest in the disappearance of his uncle and aunt.

Escobar, who was believed homeless himself, likely targeted victims to rob them, Los Angeles police Capt. William Hayes told reporters Tuesday.

Detectives have seized a wooden baseball bat and bolt cutters that they believe were used to bludgeon men as they lay sleeping on the beach or on the street in Los Angeles and suburban Santa Monica, police said. All but one of the men was homeless.

Escobar was arrested Monday and was expected to be charged with murder and attempted murder as early as Wednesday, followed by his arraignment.

It wasn’t immediately known whether Escobar had an attorney who could speak for him.

Escobar was being held without bail but U.S. Immigrations and Customs Enforcement officials have filed a detainer seeking to take him into custody if he is released, the agency said.

Escobar was first ordered removed from the country in 1988 and was deported to his native El Salvador six times between 1997 and 2011, ICE said in a statement Tuesday night.

He was released from ICE custody last year after successfully appealing his latest immigration case, ICE said. The agency didn’t indicate his current legal status.

However, Escobar has six felony convictions for burglary and illegal reentry, ICE said.

Escobar spent five years in prison for robbery starting in the mid-1990s, Hayes said. Records in Texas show Escobar has had arrests for vehicle burglary, trespassing, failure to stop, public intoxication and two assaults, most recently in November 2017. That case was described as a misdemeanor.

Texas authorities also want to talk to Escobar about the disappearances late last month of 60-year-old Dina Escobar and her brother, 65-year-old Rogelio Escobar, Houston police said in a statement.

Dina Escobar’s burned van was found in Galveston, Texas, a few days after she went looking for her brother. She was last seen Aug. 28, two days after her brother vanished, the statement said.

Dina Escobar’s daughter, Ligia Salamanca, told KTRK-TV in Houston earlier Tuesday that her cousin, Ramon Escobar, had never come across as violent and wasn’t a source of trouble for the family.

“She loved him as she would a son,” Salamanca said of her mother’s devotion to Ramon Escobar.

Salamanca said he had been looking for work and needed a place to stay, so he was taken in by his uncle, who went missing days later.

Investigators believe Escobar was the man who used a baseball bat to bash the heads of three homeless men sleeping on downtown Los Angeles streets before dawn on Sept. 16, police said in a statement. Two died.

Escobar is believed to be the man captured on surveillance video ransacking the pockets and belongings of some downtown Los Angeles victims.

Two homeless men sleeping on the beach were bludgeoned in the head early on Sept. 8 and Sept. 10, leaving one in critical condition, officials said.

Another man who apparently was sleeping on the beach was found dead under the Santa Monica Pier on Sept. 20. Steven Ray Cruze Jr., 39, of San Gabriel, had been beaten to death.

Authorities at first described him as homeless, but family and friends said the father of two, who loved to fish at the pier, worked boats in neighboring Marina del Rey and sometimes camped out under the pier to avoid the long commute home.

Follow Weber at https://twitter.com/WeberCM.

Associated Press journalists Robert Jablon and John Antczak in Los Angeles, David Warren in Dallas and researcher Jennifer Farrar in New York contributed to this report.

The Conversation

You can trust the polls in 2018, if you read them carefully

September 26, 2018

Authors

Josh Pasek

Assistant Professor of Communication Studies, University of Michigan

Michael Traugott

Research Professor at the Center for Political Studies, University of Michigan

Disclosure statement

Michael Traugott receives funding from National Science Foundation, University of Michigan.

Josh Pasek does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.

Partners

University of Michigan provides funding as a founding partner of The Conversation US.

On the morning of Nov. 8, 2016, many Americans went to bed confident that Hillary Clinton would be elected the nation’s first female president.

Their confidence was driven, in no small part, by a pervasive message that Clinton was ahead in the polls and forecasts leading up to the election. Polling aggregation sites, such as Huffington Post’s Pollster and The New York Times Upshot blog, reported that Clinton was virtually certain to win. It soon became clear that these models were off the mark.

Since then, forecasters and media prognosticators have dissected what went wrong. The finger-pointing almost inevitably landed on public opinion polling, especially at the state level. The polls, critics argued, led modelers and the public to vastly overestimate the likelihood of a Clinton win.

With the 2018 elections coming up, many in the public have expressed their skepticism that public opinion polls can be trusted this time around. Indeed, in an era where a majority of American adults no longer even have landline telephones, where many people answer only when calls originate from a known number, and where pollsters’ calls are sometimes flagged as likely spam, there are lots of reasons to worry.

But polling firms seem to be going about their business as usual, and those of us who do research on the quality of public opinion research are not particularly alarmed about what’s going on.

Looking back

One might be tempted to think that those of us in the polling community are simply out to lunch. But the data from 2016 tell a distinctly different story.

The national polls were fairly accurate both in their national estimate of the popular vote in 2016 and in historical perspective. In the average preelection national poll, Clinton was ahead of Donald Trump by 3.3 percentage points. She proceeded to win the popular vote by 2.1 percentage points. Pollsters missed the mark by a mere 1.2 percentage points on average.

The polls in the Upper Midwest states missed by larger margins. These polls were conducted in ways that pollsters widely know to be suboptimal. They relied heavily on robocalls; on surveys of people who volunteer to take surveys on the internet; and on samples of respondents from voter files with incomplete information.

What went wrong

So why was the 2016 election so shocking? The big reason wasn’t the polls, it was our expectations.

In the last few years, members of the public have come to expect that a series of highly confident models can tell us exactly what is going to happen in the future. But in the runup to the 2016 election, these models made a few big, problematic assumptions.

For one, they largely assumed that the different errors that different polls had were independent of one another. But the challenges that face contemporary polling, such as the difficulty of reaching potential respondents, can induce small but consistent errors across almost all polls.

When modelers treat errors as independent of one another, they make conclusions that are far more precise than they should be. The average poll is indeed the best guess at the outcome of an election, but national polling averages are often off by around 2 percentage points. State polls can be off by even more at times.

In addition, polling aggregators and public polling information have been flooded by a deluge of lower-quality surveys based on suboptimal methods. These methods can sometimes produce accurate estimates, but the processes by which they do so is not well-understood on theoretical grounds. There are lots of reasons to think that these methods may not produce consistently accurate results in the future. Unfortunately, there will likely continue to be lots of low-quality polls, because they are so much less expensive to conduct.

Research out of our lab suggests yet another reason that the polls were shocking to so many: When ordinary people look at the evidence from polling, just as with other sources of information, they tend to see the results they desire.

During the 2016 election campaign, we asked Americans to compare two preelection polls – one where Clinton was leading and one where Trump was ahead. Across the board, Clinton supporters told us that the Clinton-leading poll was more accurate than the Trump-leading poll. Trump supporters reported exactly the opposite perceptions. In other studies, we saw the same phenomenon when people were exposed to poll results showing majorities in favor of or opposed to their own views on policy issues such as gun control or abortion.

What polls really say

So, what does this all mean for someone reading the polls in 2018?

You don’t have to ignore the results – just recognize that all polling has some error. While even the experts may not know quite which way that error is going to point, we do have a sense of the size of that error. Error is likely to be smaller when considering a polling average instead of an individual poll.

It’s also a good bet that the actual result will be within 3 percentage points for an averaging of high-quality national polls. For similarly high-quality state polls, it will likely be within more like 5 percentage points, because these polls usually have smaller sample sizes.

What makes a high-quality poll? It will either use live interviewers with both landlines and cellphones or recruit respondents using offline methods to take surveys online. Look for polls conducted around the same time to see whether they got the same result. If not, see whether they sampled the same kind of people, used the same interviewing technique or used a similar question wording. This is often the explanation for reported differences.

The good news is that news consumers can easily find out about a poll’s quality. This information is regularly included in news stories and is shown by many poll aggregators. What’s more, pollsters are increasingly transparent about the methods they use.

Polls that don’t use these methods should be taken with a big grain of salt. We simply don’t know enough about when they will succeed and when they will fail.

The Conversation

Why older skin heals with less scarring

September 25, 2018

Author

Thomas Leung

Assistant Professor of Dermatology, University of Pennsylvania

Disclosure statement

Thomas Leung receives funding from National Institutes of Health, U.S. Department of Veterans Affairs, and the Moseley Foundation.

When it comes to your skin, getting older isn’t all bad news. Older people heal skin wounds with thinner scars.

As a practicing dermatologist, my physician colleagues and I make this somewhat counter-intuitive observation routinely. But how this occurs is not well understood. Mailyn Nishiguchi, a graduate student, Casey Spencer, a research technician, and I worked together to discover how aging normally modulates how our skin heals and the thickness of our scars.

My laboratory at the University of Pennsylvania studies how to heal human tissues without a scar. Organisms heal skin wounds using two different processes: scar formation and tissue regeneration. Tissue regeneration results in the return of the original tissue architecture and absence of scars. Scar formation results in fibrous tissue deposition that obliterates the tissue architecture, and generates a thick line of raised red skin. Mammals generally repair injured tissue with scar formation.

In experiments we observed that when young mice were injured, they healed with a scar. However, when elderly mice were injured, their skin wounds regenerated and repaired without a scar. These results reflected what we have observed in our clinic patients. We concluded that aging improves tissue regeneration in both mice and humans, and we set out to understand how this works.

First, we wanted to see if this change was due to a circulating factor in the blood. We exchanged blood between young and old mice through a technique called parabiosis. When elderly mice were exposed to young blood, their skin no longer regenerated as well. Thus, young blood contained a circulating chemical that promotes scar formation and prevents tissue regeneration from occurring.

To identify this factor, we compared gene activity between injured young and elderly human skin. We focused only on the genes of proteins circulating in the blood and found 13 different proteins in old versus young skin. One of them, SDF1, had previously been shown to regulate tissue regeneration in the skin, lung and liver.

To prove that SDF1 may be the mysterious factor responsible for scarring in the young animals, we engineered a mouse that lacked the SDF1 protein in the skin. When SDF1 was eliminated, young mice regenerated their skin with no scarring, just as in elderly mice. Therefore, we concluded that SDF1 promotes scar formation in young mice.

How does getting older shut off SDF1 production? We discovered that a different protein, called EZH2, turns off the SDF1 gene, and as mice aged, the amount of EZH2 rose. To take this one step further, we used a drug to block EZH2 function in elderly mice. In the absence of EZH2, elderly mice reactivated SDF1 and lost their ability to regenerate their skin.

We wanted to see if these findings also held true in human skin. Similar to mice, skin injury in young people triggered SDF1 production, and this induction was diminished in elderly human skin. We also showed that EZH2 is the reason behind this change. In this case, mouse and human skin behaved in the same way.

Why do mice and humans form more scars when they are young? We speculate that this is a trade-off between speed and quality. Tissue regeneration is a slow process – it takes a month for our skin injuries to regenerate. Meanwhile, a scar can form in little as three to five days. As a young animal, one would want an injury to heal as quickly as possible to live to fight another day. You will tolerate imperfect healing for a faster response. Whereas, older animals that have passed their reproductive prime may not need to heal as fast.

Taken together, we identified a rare example where aging improves tissue function, specifically the tissue repair process. We are planning a clinical trial with the drug, plerixafor, an existing FDA-approved SDF1 inhibitor which is currently used to mobilize stem cells for bone marrow transplant patients, to test its efficacy in preventing scar formation in humans.

Currently, there are no effective treatments on the market to prevent scar formation. In addition to scars from acne and incidental trauma, we hope this approach may be beneficial for many types of human tissue injuries, including the genetic disease epidermolysis bullosa, an extremely debilitating blistering skin disease, in burn patients, or patients with keloid scars.

1 Comment

Jojo Smith

Interesting! I’ve also wondered why cuts on hands generally don’t scar like cuts on other body parts do (I am an older person). I’ve cut my hands many times over the years but have no real scars. Even the pinky finger tip that I almost completely sliced off as a 16 y.o. has only a very minimal scar.

Mike Eshleman, with AC Transit, directs people away from the Salesforce Transit Center following its closure, Tuesday, Sept. 25, 2018, in San Francisco. San Francisco officials shut down the city’s celebrated new $2.2 billion transit terminal Tuesday after discovering a crack in a support beam under the center’s public roof garden. Coined the "Grand Central of the West," the Salesforce Transit Center opened in August near the heart of downtown after nearly a decade of construction. It was expected to accommodate 100,000 passengers each weekday, and up to 45 million people a year. (AP Photo/Eric Risberg)
https://www.sunburynews.com/wp-content/uploads/sites/48/2018/09/web1_121440707-43bec2abf3fa4d279dfb63171949cf29.jpgMike Eshleman, with AC Transit, directs people away from the Salesforce Transit Center following its closure, Tuesday, Sept. 25, 2018, in San Francisco. San Francisco officials shut down the city’s celebrated new $2.2 billion transit terminal Tuesday after discovering a crack in a support beam under the center’s public roof garden. Coined the "Grand Central of the West," the Salesforce Transit Center opened in August near the heart of downtown after nearly a decade of construction. It was expected to accommodate 100,000 passengers each weekday, and up to 45 million people a year. (AP Photo/Eric Risberg)

The lower level of the Salesforce Transit Center remains empty except for police, following its closure Tuesday, Sept. 25, 2018, in San Francisco. San Francisco officials shut down the city’s celebrated new $2.2 billion transit terminal Tuesday after discovering a crack in a support beam under the center’s public roof garden. Coined the "Grand Central of the West," the Salesforce Transit Center opened in August near the heart of downtown after nearly a decade of construction. It was expected to accommodate 100,000 passengers each weekday, and up to 45 million people a year. (AP Photo/Eric Risberg)
https://www.sunburynews.com/wp-content/uploads/sites/48/2018/09/web1_121440707-47633ff024bd46c6bc3e1047759fd960.jpgThe lower level of the Salesforce Transit Center remains empty except for police, following its closure Tuesday, Sept. 25, 2018, in San Francisco. San Francisco officials shut down the city’s celebrated new $2.2 billion transit terminal Tuesday after discovering a crack in a support beam under the center’s public roof garden. Coined the "Grand Central of the West," the Salesforce Transit Center opened in August near the heart of downtown after nearly a decade of construction. It was expected to accommodate 100,000 passengers each weekday, and up to 45 million people a year. (AP Photo/Eric Risberg)

San Francisco Police officers stand watch in the lower level of the Salesforce Transit Center following its closure Tuesday, Sept. 25, 2018, in San Francisco. San Francisco officials shut down the city’s celebrated new $2.2 billion transit terminal Tuesday after discovering a crack in a support beam under the center’s public roof garden. Coined the "Grand Central of the West," the Salesforce Transit Center opened in August near the heart of downtown after nearly a decade of construction. It was expected to accommodate 100,000 passengers each weekday, and up to 45 million people a year. (AP Photo/Eric Risberg)
https://www.sunburynews.com/wp-content/uploads/sites/48/2018/09/web1_121440707-bae65ef64b7340558f65bac62f92dc9d.jpgSan Francisco Police officers stand watch in the lower level of the Salesforce Transit Center following its closure Tuesday, Sept. 25, 2018, in San Francisco. San Francisco officials shut down the city’s celebrated new $2.2 billion transit terminal Tuesday after discovering a crack in a support beam under the center’s public roof garden. Coined the "Grand Central of the West," the Salesforce Transit Center opened in August near the heart of downtown after nearly a decade of construction. It was expected to accommodate 100,000 passengers each weekday, and up to 45 million people a year. (AP Photo/Eric Risberg)
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