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Consider the Stem Cell: A Biology Instructor's Reflection on Calling
When I lecture, I can’t help but feel like I’m a pastor giving a sermon. I stand behind a podium, lecture notes and book at hand, with PowerPoint slides behind me and a congregation of students in front of me. While I don’t have a wireless microphone, I’ve certainly considered getting one for the sake of the students in the back of the classroom when the air vents get too loud or for recording my lectures and posting the audio online. As for the clerical stole and vestments, I wear my share of sweaters and shawls or when necessary, the lab coat.
The sermons I teach are biological rather than hermeneutical in nature, but I find many similarities between the sanctuary and the classroom. However, one difference is that in the classroom I am the instructor, while at church, I become the instructed. Like my students, I find myself sitting, albeit in a pew. I look and listen, but even on my best days, I find that I battle distractions in my own mind. I find myself coming up with an action plan for tackling the remaining work I have to do when I get home or, if I missed breakfast, thinking about the post-service coffee and snacks in the lobby and worrying about what I’ll have for dinner. When I consider this, I realize that I am not far removed from the student experience. Perhaps, none of us really are.
Jesus invited his students (the disciples) to pause when they were anxious, asking them to consider the things around them. Each year with nervous excitement and anticipation, I await the beginning of a new academic year. Amidst finalizing my syllabi and revising my lecture slides, I, like the disciples, pause and listen to the words of Jesus, accepting his invitation to consider the things around me.
The Lesson Inside Cells
“Look at the birds of the air; they do not sow or reap or store away in barns, and yet your heavenly Father feeds them. … See how the flowers of the field grow. They do not labor or spin. Yet I tell you that not even Solomon in all his splendor was dressed like one of these” (Matt. 6:26–29).
I can imagine that Jesus’ invitation to birdwatch and survey a field of lilies excited the nature enthusiasts of his day and still excites the ornithologists and botanists of today. As a cell biologist with an appreciation for the beauty and complexity of the natural world, but with more of an inclination to study things of the great indoors, I can’t help but wonder what Jesus might have said to me. Perhaps he would have challenged me to trade the lab bench for a park bench for an afternoon. While possible, I think it’s more likely that he would have pulled up a chair and sat right beside me at my lab bench asking me to consider the cells that I was studying.
While I’ve since traded the lab bench for the college classroom and the pipette for an editor’s pen, the worries and anxieties I experience, while different, remain. Yet somehow I find that the cells I studied in graduate school and now teach my students about hold more than biological principles inside of them.
When I consider the cell, how it grows and divides, how one gives rise to two, how entire organisms can exist as a single cell, while the existence of others requires cooperation between trillions of them, I am impressed by their ability to persist in natural and unnatural environments, to proliferate and work cooperatively with others. And when I consider how some cells are robust and hearty enough to be grown in dishes for scientific research purposes and live long enough outside the body (under the right conditions) to be transplanted from a donor to a recipient, yet how all cells (at least the non-cancerous ones) are mortal—have a finite lifespan and are susceptible to stresses, in addition to mutation, infection, and disease—I find that there’s something human-like about them, and perhaps something cell-like about being human, besides the fact that humans are made up of cells.
Cells don’t worry, as far as I know, but they can get stressed out just like us. Changes in a cell’s environment such as a drop in temperature, exposure to a toxin or infection by a pathogen can elicit a stress response. Often this results in changes at a molecular level—the cell busies itself making proteins that will promote its survival in the specific stressful condition at hand. The DNA that stores the instructions to make the proteins is unwound like thread on a spool, and opened up like a zipper on a coat, the protein recipe copied and then translated into the specific ingredients necessary to build the protein. We are most familiar with the stress responses that happen on a cellular level when they trigger a response at the level of the organism. For example, shivering when it’s cold and sweating when it’s hot are our body’s collective response to those conditions.
The things I’ve most often found myself stressing about are big questions related to purpose and identity. Having diverse interests in music, science, theology, writing and the arts always seemed to make things challenging, and even now it’s hard to feel like I can really excel at any one thing when devoting more time to one skill, means less time to perfect and build another. It can somehow leave me feeling spread thin and more of a jack of many trades but master of none. My response to stress often involves listening to a preselected playlist of Audrey Assad and Andrew York, lighting my eucalyptus and mint aromatherapy candle and opening the blinds letting a little bit of the outside in.
I can relate to a cell’s experience of stress, but what else can I learn? Are there more than just biological principles inside our cells? I think so. Somehow in the midst of my worry-induced stress, I am surprised to find peace when I consider a certain type of cell: the stem cell.
Considering the Stem Cell
Each minute our bodies slough off tens of thousands of dead skin cells and every two months the entire outermost layer of our skin, the epidermis, is replaced. It escapes our notice for the most part because it happens gradually and the individual cells that make up our skin are too small to see without the aid of a microscope. While it may appear lackluster when compared to a snake molting its skin or a bug shedding its exoskeleton, its importance is underscored by the dramatic consequences that would result if we didn’t have a way to remove and replace the old and damaged cells in our skin, let alone in our entire bodies. I tell my students that without stem cells or cell division, “Our bodies would literally wear away!”. The remarkable ability for organs like our skin to replace old cells after normal wear and tear and even repair tissues after a wound or injury comes from stem cells.
Stem cells are different from other cells in our body for a number of reasons—they can divide and make more of themselves for longer periods of time than other cell types and they are unspecialized yet they can give rise to specialized cells. They are considered unspecialized cells because they lack the discrete specialized functions and structures we generally find in other cells in our bodies. For example, specialized cells inside of our stomach (parietal cells) produce hydrochloric acid that helps our stomach digest and break down the food we eat, specialized cells inside of our pancreas (beta cells) store and release insulin helping our bodies regulate the glucose levels in our blood and specialized cells in our retina (rod cells) produce the light-sensitive protein rhodopsin which helps us see in low-light conditions. While all the cells in our body, with some exceptions, have access to the same information (DNA) that can give rise to all possible combinations of functions and characteristics, each specialized cell type expresses only the relevant parts of that information that give rise to its defining characteristics, which suits the needs of the tissue or organ where it resides. That’s why a cell in the stomach makes acid and a cell in the eye doesn’t—I’m sure glad of this!
But how can an unspecialized cell give rise to cells that are specialized? When a stem cell divides (splits itself in two to make more cells), it produces two daughter cells which have the potential to “remain a stem cell or become another type of cell with a more specialized function.” Stem cells give rise to specialized cells through a process called differentiation, involving internal cues from the cell’s DNA and external cues from its microenvironment (neighboring cells). In the process of differentiation, “the cell usually goes through several stages, (gradually) becoming more specialized at each step.” Stem cells are present in tissues throughout our bodies in special micro-environments called niches. These regions help stem cells maintain their unique stem-cell properties and character.
Our Stem-cell like Character?
I find it encouraging for those of us who feel like unspecialized generalists with an often unclear specialized function or calling to consider the stem cell. Stem cells, while unspecialized, are indispensable—they (if you’ll allow me to anthropomorphize stem cells for a little bit and humor my metaphor) serve the body helping replenish and renew other cells that cannot replenish or renew themselves, and they themselves are replenished, not depleted. In turn, the whole body benefits. Perhaps, we unspecialized-generalist-jack-of-all-trades types can find encouragement when we consider stem-cell inspired questions: What greater purpose can be achieved when we serve or help others in ways that they cannot help themselves? What if there is a multidimensional purpose even in our undifferentiated and unspecialized state that supersedes ourselves? What kind of niche do we occupy? What internal and external signals in and around us help maintain and establish ourselves? How can we intentionally position and surround ourselves in environments (i.e. communities) that will support or if necessary induce us to become what God is calling us to be?
When I consider the classroom and my students, considering the stem cell makes sense. It challenges me to step back and allow them to step forward. It reminds me to serve and help them discover their potential even as I struggle to find my own amidst an undifferentiated mass of interests. Perhaps the stem cell, while typically considered unspecialized, is a specialist after all—it specializes in making specialists.
Ciara Reyes-Ton is a biologist by training and an editor and freelance writer who is passionate about science writing, communication and outreach to diverse audiences. She has a Ph.D. from the University of Michigan and currently teaches biology at a local college in Nashville. She also serves on the editorial staff of God & Nature magazine, an online publication of the American Scientific Affiliation.