Scientists want the salamander's secret: how they regenerate tissue
All organisms have the capacity to repair or regenerate tissue damage. None can do it better than salamanders or newts, which can regenerate an entire severed limb.
That feat has amazed and delighted man from the dawn of time and led to endless attempts to understand how it happens – and whether we can control it for our own purposes. An exciting new clue toward that understanding has come from a surprising source: research on the decline of cells, called cellular senescence.
Senescence is the last stage in the life of a cell. Whereas some cells simply break up or wither and die off, others transition into a zombie-like state where they can no longer divide. In this liminal phase, the cell still pumps out many different molecules that can affect its neighbors and cause low grade inflammation. Senescence is associated with many of the declining biological functions that characterize aging, such as inflammation and genomic instability.
Oddly enough, newts are one of the few species that do not accumulate senescent cells as they age, according to research over several years by Maximina Yun. A research group leader at the Center for Regenerative Therapies Dresden and the Max Planck Institute of Molecular and Cell Biology and Genetics, in Dresden, Germany, Yun discovered that senescent cells were induced at some stages of regeneration of the salamander limb, “and then, as the regeneration progresses, they disappeared, they were eliminated by the immune system,” she says. “They were present at particular times and then they disappeared.”
Senescent cells added to the edges of the wound helped the healthy muscle cells to “dedifferentiate,” essentially turning back the developmental clock of those cells into more primitive states.
Previous research on senescence in aging had suggested, logically enough, that applying those cells to the stump of a newly severed salamander limb would slow or even stop its regeneration. But Yun stood that idea on its head. She theorized that senescent cells might also play a role in newt limb regeneration, and she tested it by both adding and removing senescent cells from her animals. It turned out she was right, as the newt limbs grew back faster than normal when more senescent cells were included.
Senescent cells added to the edges of the wound helped the healthy muscle cells to “dedifferentiate,” essentially turning back the developmental clock of those cells into more primitive states, which could then be turned into progenitors, a cell type in between stem cells and specialized cells, needed to regrow the muscle tissue of the missing limb. “We think that this ability to dedifferentiate is intrinsically a big part of why salamanders can regenerate all these very complex structures, which other organisms cannot,” she explains.
Yun sees regeneration as a two part problem. First, the cells must be able to sense that their neighbors from the lost limb are not there anymore. Second, they need to be able to produce the intermediary progenitors for regeneration, , to form what is missing. “Molecularly, that must be encoded like a 3D map,” she says, otherwise the new tissue might grow back as a blob, or liver, or fin instead of a limb.
Wound healing
Another recent study, this time at the Mayo Clinic, provides evidence supporting the role of senescent cells in regeneration. Looking closely at molecules that send information between cells in the wound of a mouse, the researchers found that senescent cells appeared near the start of the healing process and then disappeared as healing progressed. In contrast, persistent senescent cells were the hallmark of a chronic wound that did not heal properly. The function and significance of senescence cells depended on both the timing and the context of their environment.
The paper suggests that senescent cells are not all the same. That has become clearer as researchers have been able to identify protein markers on the surface of some senescent cells. The patterns of these proteins differ for some senescent cells compared to others. In biology, such physical differences suggest functional differences, so it is becoming increasingly likely there are subsets of senescent cells with differing functions that have not yet been identified.
There are disagreements within the research community as to whether newts have acquired their regenerative capacity through a unique evolutionary change, or if other animals, including humans, retain this capacity buried somewhere in their genes.
Scientists initially thought that senescent cells couldn’t play a role in regeneration because they could no longer reproduce, says Anthony Atala, a practicing surgeon and bioengineer who leads the Wake Forest Institute for Regenerative Medicine in North Carolina. But Yun’s study points in the other direction. “What this paper shows clearly is that these cells have the potential to be involved in tissue regeneration [in newts]. The question becomes, will these cells be able to do the same in humans.”
As our knowledge of senescent cells increases, Atala thinks we need to embrace a new analogy to help understand them: humans in retirement. They “have acquired a lot of wisdom throughout their whole life and they can help younger people and mentor them to grow to their full potential. We're seeing the same thing with these cells,” he says. They are no longer putting energy into their own reproduction, but the signaling molecules they secrete “can help other cells around them to regenerate.”
There are disagreements within the research community as to whether newts have acquired their regenerative capacity through a unique evolutionary change, or if other animals, including humans, retain this capacity buried somewhere in their genes. If so, it seems that our genes are unable to express this ability, perhaps as part of a tradeoff in acquiring other traits. It is a fertile area of research.
Dedifferentiation is likely to become an important process in the field of regenerative medicine. One extreme example: a lab has been able to turn back the clock and reprogram adult male skin cells into female eggs, a potential milestone in reproductive health. It will be more difficult to control just how far back one wishes to go in the cell's dedifferentiation – part way or all the way back into a stem cell – and then direct it down a different developmental pathway. Yun is optimistic we can learn these tricks from newts.
Senolytics
A growing field of research is using drugs called senolytics to remove senescent cells and slow or even reverse disease of aging.
“Senolytics are great, but senolytics target different types of senescence,” Yun says. “If senescent cells have positive effects in the context of regeneration, of wound healing, then maybe at the beginning of the regeneration process, you may not want to take them out for a little while.”
“If you look at pretty much all biological systems, too little or too much of something can be bad, you have to be in that central zone” and at the proper time, says Atala. “That's true for proteins, sugars, and the drugs that you take. I think the same thing is true for these cells. Why would they be different?”
Our growing understanding that senescence is not a single thing but a variety of things likely means that effective senolytic drugs will not resemble a single sledge hammer but more a carefully manipulated scalpel where some types of senescent cells are removed while others are added. Combinations and timing could be crucial, meaning the difference between regenerating healthy tissue, a scar, or worse.
The Friday Five: Artificial DNA Could Give Cancer the Hook
The Friday Five covers five stories in research that you may have missed this week. There are plenty of controversies and troubling ethical issues in science – and we get into many of them in our online magazine – but this news roundup focuses on scientific creativity and progress to give you a therapeutic dose of inspiration headed into the weekend.
Listen on Apple | Listen on Spotify | Listen on Stitcher | Listen on Amazon | Listen on Google
Here are the promising studies covered in this week's Friday Five:
- Artificial DNA gives cancer the hook
- This daily practice could improve relationships
- Can social media handle the truth?
- Injecting a gel could speed up recovery
- A blood pressure medicine for a long healthy life
9 Tips for Online Mental Health Therapy
Telehealth offers a vast improvement in access and convenience to all sorts of medical services, and online therapy for mental health is one of the most promising case studies for telehealth. With many online therapy options available, you can choose whatever works best for you. Yet many people are hesitant about using online therapy. Even if they do give it a try, they often don’t know how to make the most effective use of this treatment modality.
Why do so many feel uncertain about online therapy? A major reason stems from its novelty. Humans are creatures of habit, prone to falling for what behavioral scientists like myself call the status quo bias, a predisposition to stick to traditional practices and behaviors. Many people reject innovative solutions even when they would be helpful. Thus, while teletherapy was available long before the pandemic, and might have fit the needs of many potential clients, relatively few took advantage of this option.
Even when we do try new methodologies, we often don’t do so effectively, because we cling to the same approaches that worked in previous situations. Scientists call this behavior functional fixedness. It’s kind of like the saying about the hammer-nail syndrome: “when you have a hammer, everything looks like a nail.”
These two mental blindspots, the status quo bias and functional fixedness, impact decision making in many areas of life. Fortunately, recent research has shown effective and pragmatic strategies to defeat these dangerous errors in judgment. The nine tips below will help you make the best decisions to get effective online therapy, based on the latest research.
Trust the science of online therapy
Extensive research shows that, for most patients, online therapy offers the same benefits as in-person therapy.
For instance, a 2014 study in the Journal of Affective Disorders reported that online treatment proved just as effective as face-to-face treatment for depression. A 2018 study, published in Journal of Psychological Disorders, found that online cognitive behavioral therapy, or CBT, was just as effective as face-to-face treatment for major depression, panic disorder, social anxiety disorder, and generalized anxiety disorder. And a 2014 study in Behaviour Research and Therapy discovered that online CBT proved effective in treating anxiety disorders, and helped lower costs of treatment.
During the forced teletherapy of COVID, therapists worried that those with serious mental health conditions would be less likely to convert to teletherapy. Yet research published in Counselling Psychology Quarterly has helped to alleviate that concern. It found that those with schizophrenia, bipolar disorder, severe depression, PTSD, and even suicidality converted to teletherapy at about the same rate as those with less severe mental health challenges.
Yet teletherapy may not be for everyone. For example, adolescents had the most varied response to teletherapy, according to a 2020 study in Family Process. Some adapted quickly and easily, while others found it awkward and anxiety-inducing. On the whole, children with trauma respond worse to online therapy, per a 2020 study in Child Abuse & Neglect. The treatment of mental health issues can sometimes require in-person interactions, such as the use of eye movement desensitization and reprocessing to treat post-traumatic stress disorder. And according to a 2020 study from the Journal of Humanistic Psychology, online therapy may not be as effective for those suffering from loneliness.
Leverage the strengths of online therapy
Online therapy is much more accessible than in-person therapy for those with a decent internet connection, webcam, mic, and digital skills. You don’t have to commute to your therapist’s office, wasting money and time. You can take much less medical leave from work, saving you money and hassle with your boss. If you live in a sparsely populated area, online therapy could allow you to access many specialized kinds of therapy that isn’t accessible locally.
Online options are much quicker compared to the long waiting lines for in-person therapy. You also have much more convenient scheduling options. And you won’t have to worry about running into someone you know in the waiting room. Online therapy is easier to conceal from others and reduces stigma. Many patients may feel more comfortable and open to sharing in the privacy and comfort of their own home.
You can use a variety of communication tools suited to your needs at any given time. Video can be used to start a relationship with a therapist and have more intense and nuanced discussions, but can be draining, especially for those with social anxiety. Voice-only may work well for less intense discussions. Email offers a useful option for long-form, well-thought-out messages. Texting is useful for quick, real-time questions, answers, and reinforcement.
Plus, online therapy is often cheaper than in-person therapy. In the midst of COVID, many insurance providers have decided to cover online therapy.
Address the weaknesses
One weakness is the requirement for appropriate technology and skills to engage in online therapy. Another is the difficulty of forming a close therapeutic relationship with your therapist. You won’t be able to communicate non-verbals as fully and the therapist will not be able to read you as well, requiring you to be more deliberate in how you express yourself.
Another important issue is that online therapy is subject to less government oversight compared to the in-person approach, which is regulated in each state, providing a baseline of quality control. As a result, you have to do more research on the providers that offer online therapy to make sure they’re reputable, use only licensed therapists, and have a clear and transparent pay structure.
Be intentional about advocating for yourself
Figure out what kind of goals you want to achieve. Consider how, within the context of your goals, you can leverage the benefits of online therapy while addressing the weaknesses. Write down and commit to achieving your goals. Remember, you need to be your own advocate, especially in the less regulated space of online therapy, so focus on being proactive in achieving your goals.
Develop your Hero’s Journey
Because online therapy can occur at various times of day through videos calls, emails and text, it might feel more open-ended and less organized, which can have advantages and disadvantages. One way you can give it more structure is to ground these interactions in the story of your self-improvement. Our minds perceive the world through narratives. Create a story of how you’ll get from where you are to where you want to go, meaning your goals.
A good template to use is the Hero’s Journey. Start the narrative with where you are, and what caused you to seek therapy. Write about the obstacles you will need to overcome, and the kind of help from a therapist that you’ll need in the process. Then, describe the final end state: how will you be better off after this journey, including what you will have learned.
Especially in online therapy, you need to be on top of things. Too many people let the therapist manage the treatment plan. As you pursue your hero’s journey, another way to organize for success is to take notes on your progress, and reevaluate how you’re doing every month with your therapist.
Identify your ideal mentor
Since it’s more difficult to be confident about the quality of service providers in an online setting, you should identify in advance the traits of your desired therapist. Every Hero’s Journey involves a mentor figure who guides the protagonist through this journey. So who’s your ideal mentor? Write out their top 10 characteristics, from most to least important.
For example, you might want someone who is:
- Empathetic
- Caring
- Good listener
- Logical
- Direct
- Questioning
- Non-judgmental
- Organized
- Curious
- Flexible
That’s my list. Depending on what challenge you’re facing and your personality and preferences, you should make your own. Then, when you are matched with a therapist, evaluate how well they fit your ideal list.
Fail fast
When you first match with a therapist, try to fail fast. That means, instead of focusing on getting treatment, focus on figuring out if the therapist is a good match based on the traits you identified above. That will enable you to move on quickly if they’re not, and it’s very much worth it to figure that out early.
Tell them your goals, your story, and your vision of your ideal mentor. Ask them whether they think they are a match, and what kind of a treatment plan they would suggest based on the information you provided. And observe them yourself in your initial interactions, focusing on whether they’re a good match. Often, you’ll find that your initial vision of your ideal mentor is incomplete, and you’ll learn through doing therapy what kind of a therapist is the best fit for you.
Choose a small but meaningful subgoal to work on first
This small subgoal should be sufficient to be meaningful and impactful for improving your mental health, but not a big stretch for you to achieve. This subgoal should be a tool for you to use to evaluate whether the therapist is indeed a good fit for you. It will also help you evaluate whether the treatment plan makes sense, or whether it needs to be revised.
Know when to wrap things up
As you approach the end of your planned work and you see you’re reaching your goals, talk to the therapist about how to wrap up rather than letting things drag on for too long. You don’t want to become dependent on therapy: it’s meant to be a temporary intervention. Some less scrupulous therapists will insist that therapy should never end and we should all stay in therapy forever, and you want to avoid falling for this line. When you reach your goals, end your therapy, unless you discover a serious new reason to continue it. Still, it may be wise to set up occasional check-ins once every three to six months to make sure you’re staying on the right track.