Understanding Blood Cell Development During Aging and Exploring Rejuvenation Possibilities

What have your Ph.D. studies focused on?

“My thesis work focused on studying the biology of the hematopoietic (blood) system during normal aging. In particular, I examined the function of hematopoietic stem cells (HSCs), the source of mature blood cells, how it changes with age, and I explored whether stem cell transplantation could serve as a potential blood rejuvenating intervention.

Aging exerts profound effects on the blood system and is highly associated with increased incidence of disease-associated conditions, ranging from anemia and compromised immune function to myeloid disorders. Previous research, also from our laboratory, found that many of these age-related conditions result, at least in part, from altered function of aged HSCs. These studies were conducted using state-of-the-art assays to study HSC biology, including stem cell transplantation and molecular profiling. However, over the last years, it became very evident that these methods have several caveats. For instance, the transplantation procedure not only negatively impacts the local microenvironment, but it also enforces cellular responses that are not necessarily present in a more unperturbed (native) setting. On the other hand, molecular profiling typically provides snapshots of cellular states, lacking information on the actual cell behaviors. They also tend to associate with specific technical limitations. Therefore, in my projects we aimed to overcome these challenges to gain a better grasp on the physiology of HSC aging.

To do this, throughout my work, I utilized animal models, high-throughput molecular profiling, non-invasive transplantation assays and in vitro culture systems, which allowed us to gain insights into both cell intrinsic and environmental factors involved in blood aging. In one of our studies, we combined an in vivo lineage tracing mouse system with single cell RNA profiling and found that under physiological conditions, the HSC differentiation gradually declines during aging. Our study also revealed that aging associates with limited production of a specific subset of cells - early lymphoid progenitors, and we speculated that this may likely contribute to reduced lymphoid output in elderly.

Trying to understand molecular basis for reduced function of aged HSCs, many previous studies performed analyses of young and aged HSC transcriptomes. However, while these studies provided important insights into the biology of HSC aging, the reported mechanisms were variable, and often inconsistent. Therefore, in our second project, we set to identify the potential source of variation among these studies. By reanalyzing existing datasets and conducting single cell RNA sequencing, we showed that cell isolation procedures, especially those involving incubation of cells at elevated temperature, can lead to a rapid induction of transcriptional stress response. This signature was uncoupled from aging but had strong implications for interpretation of the mechanisms driving age-related HSC decline. I hope that this study will raise awareness of that signature and all potential limitations that associate with molecular profiling technologies.

In our following projects, I explore cell extrinsic factors that might be implicated in hematopoietic aging. For this, we first established non-invasive transplantation procedure, which allows for successful engraftment of young HSCs into aged recipients. Transplantation usually involves preparatory treatment, referred to as conditioning, which aims to create space in the recipient’s bone marrow for the newly transplanted cells. Standard protocols utilize irradiation and/or chemotherapy for this purpose. However, because of high toxicity and potential complications associated with such approaches, the stem cell transplantation-based therapies are often not recommended for older patients. To overcome this limitation, we applied an alternative strategy using antibody-drug conjugates and small molecule compounds. This method is safer, and hence we envision that it would be more applicable for older individuals. In addition, because the treatment minimally affects non-hematopoietic cells, this enables evaluation of microenvironment in a more physiological context. By examining the function and molecular profiles of young cells exposed to aging environment, our goal is to gain a better understanding of how extrinsic factors regulate the hematopoietic system during aging. Finally, our experimental system also allows to explore transplantation of young HSCs as a potential intervention for rejuvenating blood cell function.

Overall, in my PhD work, I employed various methods to tackle some of the fundamental questions related to HSC and transplantation biology, with the aim of addressing the challenges posed by age-associated hematopoietic deficiencies,” explains Anna.

Can you tell us about the cover of your thesis?

“I have always been fond of art because it provides means for visual communication. In this spirit, I believe that graphical abstracts and science-inspired images can help explain complex biological phenomena and convey research concepts to a broad audience. 

The idea for the cover art emerged during publication of my first first-authored study. The hourglass illustrates the passage of time, and in the context of my thesis work, the process of aging. The liquid at the top represents young bone marrow cells. It takes shape of the vessel that holds it, highlighting the inherent plasticity or potential of young hematopoietic cells to generate mature blood cells. However, as we age, the function of those cells declines, which is symbolized by the stones. In another interpretation, the image refers to different methodologies that I used throughout my studies, including flow cytometry and cell sorting or droplet-based single cell RNA sequencing. 

The thesis also includes a complementary second image. In this illustration, petri dishes are used to depict different stages of aging: from youth portrayed as a vibrant and green landscape to advanced aging, represented by dry, arid land. The hand with the dropper symbolizes us, the scientists, creating new research avenues and tools to enhance healthy hematopoiesis during aging.

Both images were created in collaboration with a French-Canadian illustrator. I found her style and technique particularly effective in conveying the abstract scenes on both illustrations. I enjoyed this collaboration also because it provided another perspective and alternative interpretations of the (art)work,” reflects Anna.

How did you end up doing a Ph.D. at Lund Stem Cell Center?

“I am originally from Poland, and I have been in Sweden for over six years now. During my undergraduate studies, I worked on projects related to hematopoietic system function in disease settings. It was a great experience, where I gained solid understanding of basic biology and mastered important skills for experimental research. Seeking further insights into the blood cell development and training in stem cell biology, I joined David Bryder’s team at Lund Stem Cell Center for the summer internship project. It worked out really well and therefore I decided to stay for the remainder of the master’s program. Once I completed this, and a half year complementary program in human biology for pre-doctoral students, I enrolled to the PhD program in January 2019. Choosing to pursue a PhD in Lund was also partly influenced by the fact that my husband was undergoing postdoctoral training at BMC at that time. Reflecting on my journey, I feel this was one of the best decisions that I have made and if given a chance to redo my PhD, I would choose the same path,” notes Anna.

What have you found the most enjoyable during your Ph.D. studies? 

“Overall, I really enjoy the learning process. I like to explore new research avenues, challenge my current understanding of the subject, and engage with alternative viewpoints. As an experimental biologist, I particularly enjoy the hands-on laboratory work, because it provides a means for assessing research hypotheses and ideas. 

Throughout my studies, I also found it exciting to work with undergraduate students on their internship projects, at different courses or during initiatives like “Taking science to school” or UniStem Day. These were great for reaching out to a broader audience and gaining another perspective on our work. It was also very rewarding to see other people’s growth and education,” highlights Anna.

What has been the most challenging aspect?

“This is a difficult question, as my overall experience during PhD studies was quite fulfilling and I am happy with how everything worked out. As I said, I would do it all again. Of course, some aspects of PhD work were more challenging than others. For example, I found it difficult to learn and apply more advanced statistical methods or bioinformatic analysis, because of my limited background in computational work. Nonetheless, I always try to consider such challenges as learning opportunities rather than obstacles. 

Perhaps one of the bigger challenges during my training was to face things that can be considered as failures, such as rejections of manuscripts or grant applications. I used to take it personally, often feeling disappointed with my performance. But I am grateful to the research community in our division for offering support, guidance and for teaching the students how to embrace these challenges as opportunities to grow, rather than outright defeats,” says Anna.

What are your plans following your Ph.D. defense?

“Since undergraduate studies, I felt that academic research is the right choice for me. It offers the opportunity to pursue one own’s research interests while also engaging in the education of students and younger scientists. 

Currently, I will continue working in David’s lab to finalize our ongoing project. From spring, I plan to start postdoctoral training to further explore mechanisms governing stem cell identity and function. 

My long-term goal is to remain within academia. I hope that by combining the knowledge and expertise acquired during PhD studies and subsequent postdoctoral training, I will be able to establish independent lines of research,” notes Anna.

Any tips or advice for future Ph.D. students? 

“What has helped me, especially in the beginning of PhD studies, was to engage in many different projects. By doing so, I developed basic understanding of the field, explored different research concepts, and acquired diverse technical skills, which turned useful in the later stages of my education.

While pursuing a PhD often entails an independent work (ultimately, one has to learn things oneself) the research itself is frequently collaborative. I feel that it is very fulfilling to interact with others, being open to obtain and provide help and seeking input from peers on our respective work.

My last piece of advice relates to good and clear communication. I think this is really the key for professional development and personal growth. When we openly communicate our goals, challenges or doubts to mentors or peers, it not only helps advance the project, but also minimizes potential disappointments. Overall, taking initiative and being proactive will really help in the long run during the PhD process,” summarizes Anna.