TLT: What got you interested in biomedical engineering?
Kupratis: I developed an interest in musculoskeletal biology and tissue repair through my experiences as a competitive figure skater. As a teenager, I remember being curious why some injuries seemed to heal readily while others ended athletes’ careers. Initially I thought I might channel this interest into medicine or physical therapy. However, once I discovered cell and tissue engineering, I realized I was much more interested in understanding how the human body performs its functions than treating patients. I thought it was fascinating that engineers have figured out how to build and fix so many things, but short of a joint replacement or organ transplant, the same is not true for the human body.

TLT: Tell us about your research.
Kupratis: I’m interested in articular cartilage tribology in health and disease. From a lubrication perspective, cartilage is perplexing. The dynamic friction coefficient of cartilage-on-cartilage in vivo (approximately 0.002) is unmatched by any manmade material, even Teflon. Paradoxically, though, cartilage violates key design constraints of engineered bearings (for example, it is relatively rough and permeable, and must withstand multiaxial loading that varies orders of magnitude in stress and speed). Furthermore, cartilage lacks blood and nerve supply, which means joint diseases like osteoarthritis are irreversible. I hope that understanding cartilage’s mechanical behavior can help identify new strategies to treat or even prevent osteoarthritis.

Prior studies show that interstitial hydration (high fluid content within the tissue) is essential both to maintain low strain and friction and for cell health.^1-3 Our lab uses a novel testing configuration that permits sliding-driven recovery of interstitial fluid, thereby sustaining physiologically low strain and friction. I use enzymatic digestion to model the protein-level damage that causes mild to severely arthritic cartilage to become softer and more permeable. In my model of “severe” arthritis, I decrease the cartilage stiffness by about 50%, but, interestingly, I’ve found that it still supports fluid recovery. This finding may help explain why osteoarthritis often remains asymptomatic until it is near end-stage. Next, I am using this model to test pre-clinical reinforcement techniques that have been proposed for cartilage repair. I hypothesize that reinforcing cartilage at early stages of osteoarthritis may be able to restore healthy tribological function and, thus, increase tissue longevity. If this is true, perhaps future treatments could delay or eliminate the need for joint replacements!

TLT: What are some of the most technical lubrication-based concepts or topics that you have encountered in your research?
Kupratis: My work primarily uses custom-built testing systems either for stationary contact area tribological testing or for microindentation. Together, I use these systems along with Hertzian contact mechanics to understand how cartilage composition, lubricant selection and sliding conditions (load, contact area, sliding speed) affect dynamic friction coefficients, shear stress, compressive strain and fluid load support during sliding. The enzymatic degradation models I use also allow me to relate concepts like friction coefficients or fluid load support directly to tissue composition using standard biological assays.

TLT: When did you first become involved with STLE?
Kupratis: I was introduced to STLE through Drs. Price and Burris, who encouraged me to engage in the presentation, scholarship and networking opportunities within the society. My first research talk was actually at an STLE Philadelphia Section meeting, and I was fortunate to share my work with such a supportive audience—that experience really helped build my confidence as a public speaker! Through STLE, I have been able to meet different types of engineers with research interests completely outside of biology and medicine, which has strengthened my training as a biomedical engineer.

TLT: What advice would you give to high school or college students who might want to pursue a career in tribology?
Kupratis: At the core, tribology (and engineering fields in general) are about problem solving. I think two values are key to success: curiosity and perseverance. My work is inherently interdisciplinary, so being open to learning both medicine and classical engineering has been key. Research is ripe with opportunity for “failure” since it hinges on discovering new approaches. I would tell students not to let mistakes define you and to seek out mentors to support and guide you along this journey!

REFERENCES
1. Ateshian, G. A. (2009), “The role of interstitial fluid pressurization in articular cartilage lubrication,” J Biomech, 42, pp. 1163-1176.
2. Bonnevie, E. D., Delco, M. L., Bartell, L. R., Jasty, N., Cohen, I., Fortier, L. A. and Bonassar, L. J. (2018), “Microscale frictional strains determine chondrocyte fate in loaded cartilage,” J Biomech, 74, pp. 72-78.
3. Farnham, M. S., Ortved, K. F., Burris, D. L. and Price, C. (2021), “Articular cartilage friction, strain, and viability under physiological to pathological benchtop sliding conditions,” Cell Mol Bioeng, 14 (4), pp. 349-356.

You can reach Meghan Kupratis at kupratis@udel.edu.