The research team, led by Zhe Gao and Xin Zhang, set out to explore a question that has remained surprisingly open: what role, if any, does TRIM28 play in regulating the behavior of macrophages and the keratinocytes they communicate with? TRIM28, short for tripartite motif-containing 28, is a multifunctional protein best known for its involvement in transcriptional regulation and epigenetic modification. It can influence protein stability through ubiquitination and SUMOylation, two post-translational modifications that attach small protein tags to targets and alter their behavior. Despite growing interest in TRIM family proteins across immunology and cancer biology, TRIM28’s role in macrophage polarization had not been clearly defined.

To probe this question, the researchers used a well-established laboratory model. They cultured human THP-1 monocytic cells and differentiated them into macrophage-like cells using a chemical called phorbol 12-myristate 13-acetate. Separately, they maintained HaCaT keratinocytes, an immortalized human skin cell line. Using small interfering RNAs, they silenced TRIM28 expression in the macrophages, and in complementary experiments they boosted TRIM28 levels using an overexpression plasmid. These two approaches, gene knockdown and gene overexpression, allowed the team to observe what happens when TRIM28 is removed or amplified within the same cellular environment.

The results were striking. When TRIM28 was silenced, flow cytometry analysis revealed a marked shift in macrophage phenotype: the proportion of CD68-positive CD206-positive cells, associated with an M2-like or anti-inflammatory profile, increased to 25 percent from lower baseline levels. Conversely, the proportion of CD68-positive CD86-positive cells, associated with an M1-like or pro-inflammatory profile, dropped to just 5 percent. Enzyme-linked immunosorbent assays confirmed the functional consequences: silencing TRIM28 reduced secretion of the pro-inflammatory cytokines IL-6 and TNF-α while increasing the anti-inflammatory cytokine IL-10. Western blotting reinforced these findings, showing decreased expression of the M1-associated marker iNOS and increased expression of the M2-associated marker Arg1. When TRIM28 was overexpressed, every one of these trends reversed, pushing macrophages toward the pro-inflammatory state.

The team then traced the molecular pathway underlying this effect. Prior research had suggested that TRIM28 can stabilize NLRP3, a key component of the inflammasome, a multiprotein complex that triggers inflammatory signaling. NLRP3, in turn, is known to activate its downstream partner SGT1. In the current study, TRIM28 knockdown reduced the expression of both NLRP3 and SGT1, while overexpression raised their levels. Crucially, the researchers also examined functional readouts of inflammasome activation. TRIM28 knockdown decreased levels of cleaved caspase-1 and mature IL-1β, both hallmarks of inflammasome activity, and reduced secretion of IL-1β into the culture medium. Overexpression produced the opposite pattern. Co-immunoprecipitation experiments further revealed that TRIM28 physically interacts with NLRP3 and that TRIM28 overexpression significantly increased the SUMOylation of NLRP3, a modification previously linked to inflammasome stabilization.

With the macrophage-side mechanism established, the investigators turned to the keratinocyte side of the equation. They placed modified macrophages in the upper chamber of a Transwell system, separated by a porous membrane from HaCaT keratinocytes below, allowing soluble factors to pass but preventing direct cell contact. After 24 hours of co-culture, they measured keratinocyte viability and invasive capacity. The differences were dramatic. Co-culture with TRIM28-silenced macrophages reduced HaCaT cell viability to 60 percent of control levels, while co-culture with TRIM28-overexpressing macrophages raised viability to 140 percent. Invasion assays showed a similar pattern: silencing TRIM28 in macrophages reduced keratinocyte invasion to 60 percent of baseline, whereas overexpression increased it to 180 percent. These cellular behaviors, hyperproliferation and invasion, are relevant to inflammatory skin responses, although the authors are careful to note that they do not by themselves demonstrate a role for TRIM28 in psoriasis in living organisms.

To confirm that the NLRP3/SGT1 axis and SUMOylation were genuinely required for these effects rather than incidental, the researchers performed a series of rescue experiments. They knocked down NLRP3 or SGT1 in macrophages overexpressing TRIM28, or treated the cells with 2-D08, a chemical inhibitor of SUMOylation. Each intervention partially reversed the TRIM28-driven shift toward the pro-inflammatory macrophage phenotype, restoring the balance of CD86-positive and CD206-positive populations. The interventions also normalized cytokine secretion patterns, reduced cleaved caspase-1 and mature IL-1β levels, and attenuated the enhanced NLRP3 SUMOylation. Most importantly, these same interventions partially reversed the proliferative and invasive changes observed in co-cultured keratinocytes, confirming that the NLRP3/SGT1 pathway and SUMOylation are functionally required for the macrophage-mediated effects on skin cells.

The study places TRIM28 within a growing family of TRIM proteins implicated in inflammatory skin biology. Previous work has shown that TRIM14 promotes psoriasis-like inflammation by activating NF-κB signaling, and that TRIM27 amplifies IL-6/STAT3 signaling in keratinocytes. The current research extends this picture by suggesting that TRIM28 operates through a distinct mechanism, one involving post-translational modification of the NLRP3 inflammasome rather than transcriptional regulation alone. This positions TRIM28 as a potential bridging molecule between the epigenetic machinery of the cell and the innate immune response, a role that has parallels in other inflammatory conditions. The researchers draw comparisons to the HSP90β-SGT1 complex, which stabilizes NLRP3 in autoinflammatory syndromes, and to studies in fatty liver disease where HSP90 inhibition suppresses NLRP3 activation.

Nevertheless, the authors are emphatic about the limitations of their work. All experiments were performed in simplified in vitro systems using immortalized cell lines, which cannot fully replicate the cellular diversity, tissue architecture, and immune microenvironment of human psoriatic skin. The team did not examine TRIM28 expression in actual psoriatic lesions, did not analyze patient-derived samples, and did not correlate TRIM28 levels with disease severity. Macrophage polarization was assessed using a limited marker panel, and the authors acknowledge that the M1/M2 framework is a simplified operational model rather than a definitive classification of macrophage states. More comprehensive approaches, including single-cell RNA sequencing and multiplex flow cytometry, would be needed to fully characterize the macrophage phenotypes regulated by TRIM28. Additionally, the specific enzyme responsible for NLRP3 SUMOylation in this context remains unknown, as TRIM28 itself lacks SUMO ligase activity, suggesting intermediary proteins may be involved.

Looking forward, the researchers outline several priorities for future investigation. They propose examining TRIM28 expression and localization in human psoriatic tissue alongside clinical markers, validating the TRIM28–NLRP3/SGT1 axis in patient-derived cells and three-dimensional organotypic skin cultures, and testing whether modulating TRIM28 alters inflammation in animal models of psoriasis-like dermatitis. They also call for a more precise mapping of the molecular interactions between TRIM28, NLRP3, and SGT1, including identification of the relevant SUMO E3 ligase and assessment of downstream inflammasome assembly events. Until such work is completed, the current study stands as a rigorous piece of mechanistic cell biology, defining a TRIM28-dependent inflammatory pathway in a controlled laboratory setting. Its contribution is foundational rather than translational: it illuminates how a single regulatory protein can reshape the inflammatory conversation between two cell types central to skin immunity, while leaving open the critical question of whether that conversation drives human disease.

Subject of Research: TRIM28 regulation of macrophage polarization and keratinocyte behavior via the NLRP3/SGT1 axis in vitro

Article Title: TRIM28 Promotes Keratinocyte Proliferation and Invasion by Activating NLRP3/SGT1 Axis‐Mediated Macrophage Pro‐Inflammatory Polarization in an In Vitro Macrophage–Keratinocyte Co‐Culture Model

Article References: Gao, Z., Zhang, X., Wang, J., & Yang, N. (2026). TRIM28 Promotes Keratinocyte Proliferation and Invasion by Activating NLRP3/SGT1 Axis‐Mediated Macrophage Pro‐Inflammatory Polarization in an In Vitro Macrophage–Keratinocyte Co‐Culture Model. Immunity, Inflammation and Disease, 14(9), Article e70522. https://doi.org/10.1002/iid3.70522

Image Credits: AI Generated

DOI: 10.1002/iid3.70522

Keywords: TRIM28, macrophage polarization, NLRP3 inflammasome, SGT1, SUMOylation, keratinocytes, psoriasis, inflammation, IL-1β, co-culture, innate immunity, skin biology

The research, led by a team working at the interface of mechanobiology and skin biology, addresses a long-standing puzzle in tissue physiology. Skin must maintain structural integrity while simultaneously accommodating growth, wound repair, and chronic mechanical stress such as repeated friction or tension. How a tissue senses these forces and translates them into molecular remodeling programs has been studied extensively at the level of individual mechanosensitive channels and cytoskeletal adapters. Far less is understood about which specialized cell subpopulations act as the conductors of this whole-tissue response.

Fibroblasts, the connective tissue workhorses of the dermis, have long been treated as a relatively uniform population of cells that deposit collagen and other extracellular matrix components. Over the past decade, single-cell technologies have shattered that view, revealing that fibroblasts exist in a spectrum of functionally distinct states, each occupying specific anatomical niches and performing specialized duties. Among the markers that have drawn intense interest is LGR5, a receptor best characterized as a Wnt target gene and a hallmark of adult stem cells in the intestine, hair follicle, and several other organs. Its appearance on a subset of dermal fibroblasts hinted that these cells might occupy a privileged regulatory position within skin.

The new findings place those LGR5-positive fibroblasts at the center of what the authors describe as skin mechanoadaptation, the process by which the tissue adjusts its architecture and mechanical properties in response to physical forces. According to the study, when skin is subjected to mechanical loading, these cells do not merely respond passively. Instead, they act as orchestrators, integrating mechanical cues and broadcasting instructions to surrounding cells through inflammatory and remodeling pathways, with JAK1 serving as a critical signaling node in that communication.

JAK1, or Janus kinase 1, is a cytoplasmic tyrosine kinase that relays signals from a family of cytokine receptors into the cell interior, most famously activating the STAT transcription factors that drive genes involved in immunity, cell growth, and tissue repair. Drugs targeting the JAK family have transformed the treatment of inflammatory diseases and certain cancers, making JAK1 one of the most pharmacologically scrutinized kinases in modern medicine. The revelation that JAK1 functions as a mechanotransductive regulator within a specialized fibroblast subset adds an entirely new dimension to its biological portfolio, and suggests that mechanical stress and inflammatory signaling in skin are more deeply intertwined than previously appreciated.

The implications extend well beyond basic cell biology. Excessive or aberrant mechanical stress is implicated in a range of cutaneous pathologies, from hypertrophic scarring and fibrosis to pressure ulcers and the progressive stiffening of aged skin. Conversely, insufficient mechanoadaptation can compromise wound closure and tissue resilience. If LGR5-positive fibroblasts genuinely coordinate the tissue-wide response to force through JAK1 signaling, then therapeutic strategies aimed at this specific cellular niche could, in principle, recalibrate how skin responds to stress, promoting healthy remodeling while dampening pathological fibrosis.

To reach these conclusions, the research team combined state-of-the-art lineage tracing with mechanical perturbation of skin tissue. Genetic fate-mapping approaches, in which cells expressing LGR5 and their descendants are permanently labeled, allowed the investigators to follow the behavior of this fibroblast subset under basal conditions and in response to mechanical challenge. Complementing the lineage studies, transcriptomic profiling revealed the molecular identity of the mechanoadaptive program, pinpointing JAK1-dependent signaling as a central feature of how these cells translate physical input into changes in gene expression and, ultimately, tissue architecture.

When the investigators disrupted JAK1 function in the context of mechanical loading, the coordinated adaptive response faltered, supporting the model that LGR5-positive fibroblasts require this kinase to fulfill their regulatory role. The finding reframes mechanotransduction not as a cell-autonomous affair confined to force-sensing proteins at the membrane, but as an intercellular program in which a small population of specialized stromal cells interprets mechanical context and modulates the behavior of the tissue as a collective. In this view, fibroblasts act less like passive scaffolding cells and more like mechanical stethoscopes and loudspeakers rolled into one, listening to the physical state of the skin and broadcasting chemical instructions accordingly.

For the broader field of mechanobiology, the study contributes to a growing recognition that stromal cells are active participants in how organs sense and respond to their physical environment. Similar sentinel populations have been described in other tissues, where specialized fibroblasts guide immune responses, organize repair zones after injury, and maintain niche architecture. The identification of an LGR5-marked, JAK1-modulating subset in skin strengthens the argument that tissue-level mechanoadaptation depends on a division of labor among fibroblast states, and that understanding this division of labor is essential for regenerative medicine.

Translational questions now loom large. Because JAK inhibitors are already in widespread clinical use, the findings raise the possibility that existing drugs, or more selective derivatives, could be repurposed to modulate skin mechanoadaptation in contexts ranging from scar prevention to anti-fibrotic therapy. At the same time, the study serves as a caution: wholesale blockade of JAK signaling in skin could interfere with beneficial adaptive remodeling, and the challenge ahead lies in achieving the right specificity, both at the level of the kinase and at the level of the cell type. As researchers work toward that precision, the humble dermal fibroblast, once dismissed as connective tissue filler, has firmly claimed its place as a master regulator of how skin meets the mechanical world.

The choice of LGR5 as a marker reflects a broader shift in how biologists identify functionally important cell types. Because LGR5 marks actively cycling stem cells in rapidly renewing epithelia, its expression in the dermis initially suggested that these fibroblasts might retain an unusual developmental plasticity. Fate-mapping studies in other organs have shown that LGR5-positive populations can generate diverse progeny, and the present work extends that logic to the stromal compartment, where a marked subset appears to exert influence less through self-renewal than through signaling authority over its neighbors.

The dermal microenvironment in which these cells reside is itself worth considering. The dermis is organized into papillary and reticular layers with distinct collagen densities, vascular supplies, and resident cell compositions, and fibroblasts occupying these layers differ in gene expression and in the mechanical properties of the matrix they produce. Mechanical forces impinging on the skin surface are transmitted through this layered architecture in complex ways, so a subset positioned at a particular depth or niche may be uniquely situated to sense deformation and relay that information to immune cells, endothelial cells, and epithelial stem cells above.

The connection between mechanical loading and cytokine signaling illuminated here also fits with accumulating evidence that physical forces can modulate inflammatory pathways independently of infection or tissue damage. Stretch, compression, and fluid shear have all been shown to alter cytokine production in cultured cells, and the JAK-STAT pathway is a common downstream convergence point for such signals. Placing JAK1 within a mechanotransductive circuit in intact skin provides an in vivo anchor for observations that had largely been made in simplified culture systems, where the multicellular architecture of real tissue is absent.

From a clinical standpoint, the findings intersect with a persistent therapeutic dilemma in dermatology. Antifibrotic interventions aim to reduce excessive collagen deposition, yet collagen synthesis is also essential for normal wound healing, and blunt suppression of matrix production can impair closure and strength of repaired skin. A regulatory node that acts specifically during mechanical adaptation offers a potential middle path: modulating it might allow clinicians to distinguish pathological responses to chronic aberrant loading from the beneficial remodeling that follows injury or surgical repair.

The study also speaks to the biology of skin aging, in which the dermis loses elasticity and becomes progressively stiffer, in part through changes in fibroblast number, phenotype, and extracellular matrix turnover. Whether the LGR5-positive mechanoadaptive population declines, shifts state, or becomes functionally silenced with age is an obvious next question, and one that could connect mechanoadaptation to the well-documented observation that aged skin heals more slowly and scars differently than young skin.

Methodologically, the work illustrates the value of combining lineage tracing with controlled mechanical perturbation, an approach that is becoming more common as researchers recognize that static snapshots of gene expression cannot capture how cells respond dynamically to force. Transcriptomic profiling under defined loading conditions, paired with genetic disruption of candidate signaling mediators, provides a framework that other groups studying lung, gut, or cardiovascular mechanobiology may adapt, since stromal sentinel populations are increasingly suspected in those organs as well.

Important caveats remain before the model can be considered complete. Mouse studies with genetic fate mapping do not automatically translate to human skin, whose dermal architecture and fibroblast heterogeneity differ in notable ways, and the precise identity of the upstream mechanical sensor in these cells has yet to be defined. Whether JAK1 modulation acts directly on mechanosensitive transcription or indirectly through cytokines released by neighboring cells will require careful dissection. Nonetheless, the demonstration that a defined fibroblast subset can govern tissue-wide mechanical adaptation marks a substantive step toward a cell-type-resolved understanding of how skin endures the physical demands of daily life.

Subject of Research: The role of LGR5-positive fibroblasts in coordinating skin mechanoadaptation via JAK1 signaling

Article Title: LGR5-positive fibroblasts orchestrate skin mechanoadaptation through JAK1 modulation

Article References: Fu, Q., Cheng, X., Chen, N., Sun, Y., Xu, L., Cheng, Y., Wang, C., Li, Y., Yu, T., Yan, Y., Zhang, W., Bu, Y., Lei, L., Chen, Y., Li, Z., Zhu, P., Wang, C., Zhang, L., Liu, C., & Li, Q. (2026). LGR5-positive fibroblasts orchestrate skin mechanoadaptation through JAK1 modulation. Nature Communications. https://doi.org/10.1038/s41467-026-77113-y

Image Credits: AI Generated

DOI: 10.1038/s41467-026-77113-y

Keywords: LGR5, fibroblasts, skin, mechanoadaptation, JAK1, mechanotransduction, Nature Communications, dermis, tissue remodeling, JAK inhibitors, single-cell analysis, skin biology