The work stands somewhat apart: there is almost nothing right next to it, but conceptually it connects to research on cell competition and aging. Neighboring studies examine how cells of differing fitness interact and how senescent cells accumulate in tissues. This study fills a gap: it shows for the first time that mechanical competition can eliminate specifically progerin-induced senescent cells, and not only cells with oncogenic mutations.
The authors created an MDCK cell line with inducible expression of progerin tagged with mCherry or mNeonGreen. The cells were co-cultured with normal cells at a ratio of 1:50 on an elastic PDMS substrate (stiffness around 15 kPa) coated with fibronectin. After the monolayer formed, doxycycline was added and the fate of senescent cells was tracked by time-lapse imaging. To assess mechanical forces, traction force microscopy was used: fluorescent beads were embedded in the substrate, and the displacement of these beads was used to calculate the forces exerted by neighboring cells. In addition, signaling pathway inhibitors and immunostaining of key proteins were employed.
Progerin-induced senescent cells in co-culture underwent apoptosis: the fraction of apoptotic cells was significantly higher than in the control without doxycycline (for example, for mCherry-Progerin p < 0.0001). Apoptosis required direct contact with normal cells: when cultured alone or when contacts were disrupted (proximity to cells without E-cadherin), death decreased. In senescent cells in co-culture, levels of JNK and phosphorylated p38-MAPK increased, as did p53, while p21 decreased. JNK and p38 inhibitors partially restored p21 levels. Traction force microscopy showed that before apoptosis, neighboring normal cells exerted sustained compressive stress on progerin-expressing cells. In contrast, p16-induced senescent cells did not die under the same conditions and maintained high p21 levels.
This work differs from neighboring studies in that it demonstrates for the first time the mechanical elimination of senescent cells induced by progerin, through activation of JNK/p38-MAPK and a decrease in p21. Neighboring studies focused on cell competition during oncogenic transformation or on the role of p21 in resistance to apoptosis, but did not link mechanical compression specifically to progerin-induced senescence. This broadens our understanding of how tissues can rid themselves of damaged cells without involving the immune system.
The topic could develop toward studying the role of SASP in modulating mechanical interactions. It is possible that differences in the composition of secreted factors between progerin- and p16-induced cells influence how neighbors compress them. It would also be promising to investigate how this mechanism works in vivo in a three-dimensional microenvironment with extracellular matrix and immune cells.
The results could influence gerontology and regenerative medicine by proposing new targets for selectively removing senescent cells in age-related diseases. They are also important for cell biology, since they show that mechanical competition applies not only to oncogenic cells but also to senescent cells.
The next step will be to test mechanical competition in in vivo models, for example in tissues of mice with inducible progerin expression. It is also necessary to study in detail which molecular sensors allow normal cells to recognize and compress specifically progerin-expressing cells.
The work is directly connected to the unresolved problem of aging heterogeneity: why some senescent cells accumulate while others are eliminated. It shows that the fate of a senescent cell depends not only on its internal state but also on its environment, which is important for understanding tissue homeostasis during aging.
Progerin, a mutant form of lamin A, causes progeria, a rare disease in which children age 5–10 times faster than usual. In the experiment, cells with progerin died from compression by neighbors, even though senescent cells are usually resistant to apoptosis.
In the film Blade Runner, replicants are programmed for a short life, and their cells age at an accelerated rate. The mechanism described in the paper resembles a scene where society squeezes out those who are different: normal cells literally press senescent cells out of the tissue.
Not published on arXiv. Here are its page, the PDF and the formalization: you can check it yourself, not only read our account.