The research team, led by Andrés Caicedo of Universidad San Francisco de Quito in Ecuador together with a broad international consortium, set out to answer a deceptively simple question: do skin cells share mitochondria with one another under normal conditions, and does that sharing change when the skin is under assault from sunlight? Horizontal mitochondrial transfer, or HMT, is an emerging form of intercellular communication that has been documented in other tissues, where stressed or damaged cells can receive functioning mitochondria from healthier neighbors, restoring their energy supply and improving their survival. But whether the cells of the epidermis and dermis engage in this exchange, and how it might relate to regenerative strategies built around mitochondria, remained poorly understood.

To find out, the investigators used a coculture system in which donor cells were labeled with MitoTracker Red, a fluorescent dye that stains active mitochondria, while recipient cells carried a green tag. When red-labeled organelles appeared inside green recipient cells, transfer had occurred, and fluorescence microscopy allowed the team to quantify how often it happened. The experiments were run in two configurations: direct two-dimensional coculture, in which donor and recipient cells physically touch, and transwell systems, in which a porous membrane separates the two populations while still allowing soluble factors to diffuse through. This design allowed the researchers to distinguish contact-dependent transfer from contact-independent mechanisms.

The results were unambiguous. Under basal conditions, transfer from melanocytes to keratinocytes was already the dominant route of exchange, and when the cells were exposed to ultraviolet radiation the transfer rate climbed dramatically, reaching approximately 39 percent of recipient keratinocytes in direct coculture. In transwell assays, where cells could not touch, the same donor–recipient pair transferred at less than 9 percent, indicating that the exchange relies overwhelmingly on direct cell-to-cell contact rather than on mitochondria or mitochondrial fragments drifting through the culture medium. Every other donor–recipient combination among the three skin cell types remained below 4 percent, and some pairs—melanocyte to melanocyte, keratinocyte to keratinocyte, melanocyte to fibroblast, and keratinocyte to melanocyte—showed no detectable transfer at all. Fibroblasts, notably, took up very few mitochondria from any source, whether from their own kind or from other skin cells, even after ultraviolet exposure.

That last observation may carry the most physiological weight. Keratinocytes, which form the outermost barrier of the skin and absorb much of the ultraviolet dose, appear to receive mitochondrial help precisely when they need it most, drawing functional organelles from melanocytes, the pigment-producing cells that sit alongside them in the basal epidermis. Fibroblasts, by contrast, live deeper in the dermis where ultraviolet penetration is weaker, but their apparent inability to import mitochondria suggests they may lack a stress-adaptation pathway available to their epidermal neighbors. The authors propose that this contact-dependent, cell-type-specific exchange represents a built-in resilience mechanism for the skin’s protective barrier, one that has gone unnoticed because it only operates at meaningful levels between particular cell pairs and under particular kinds of stress.

Having established that skin cells naturally share mitochondria, the team turned to the therapeutic question: can this process be exploited deliberately? The answer came in two stages. The first was artificial mitochondrial transfer, or AMT, performed in the laboratory. The researchers isolated mitochondria from three sources—human dermal fibroblasts, human Wharton’s jelly mesenchymal stem/stromal cells (WJ-MSCs) derived from umbilical cord tissue, and mouse bone marrow mesenchymal stem cells (BM-MSCs)—and delivered them to recipient fibroblasts. Before use, the isolated organelles were rigorously quality-controlled: scanning electron microscopy confirmed their structural integrity, tetramethylrhodamine methyl ester staining demonstrated that they retained an active membrane potential, and oxygraph measurements confirmed that they consumed oxygen and respired on substrates such as glutamate, pyruvate, and malate. These were not cellular debris but functioning bioenergetic machines.

When these stem-cell-derived mitochondria were delivered to fibroblasts, two clinically relevant effects emerged. First, WJ-MSC-derived mitochondria reduced the burst of reactive oxygen species, or ROS, that ultraviolet radiation normally triggers in skin cells, pointing to a direct antioxidant and protective function. Second, mitochondria from both human WJ-MSCs and mouse BM-MSCs significantly increased fibroblast proliferation, though the magnitude of the effect depended on the dose of mitochondria delivered, underscoring that dosing will be a critical parameter in any future clinical protocol. Fibroblasts are the workhorses of wound repair, producing collagen and rebuilding the dermal matrix, so a cell-free treatment that simultaneously lowers oxidative damage and boosts their proliferation could be valuable for burns, chronic wounds, and radiation-injured skin.

The second stage moved from the dish to living animals. In a murine model of primary-intention wound healing, the researchers applied mitochondria isolated from mouse BM-MSCs directly to the wounds. Histological analysis showed enhanced early tissue repair, and the effects were comparable to those achieved by administering the intact stem cells themselves—a remarkable result, because it suggests that at least part of the regenerative benefit of mesenchymal stem cell therapy can be reproduced by their mitochondria alone, without the cells. This has profound implications. Live stem cell therapies face hurdles of manufacturing complexity, immune compatibility, tumorigenicity concerns, and regulatory scrutiny; mitochondria are simpler, cannot replicate on their own, and could in principle be standardized, stored, and dosed like a conventional biologic.

To confirm the findings in a species whose skin more closely resembles our own, the team repeated the experiment in pigs, applying mitochondria derived from human Wharton’s jelly MSCs to primary-intention wounds. The outcomes were measured with a wound healing index, histological assessment of tissue organization, and spatial quantification of Ki67, a protein marker of actively dividing cells. Treated wounds showed a higher wound healing index, improved organization of collagen-containing tissue, and increased Ki67 positivity in both the epidermal and dermal regions directly involved in repair. In other words, the transplanted mitochondria appeared to wake up the local proliferative response on both sides of the skin’s architecture, driving new cell generation precisely where the healing front was advancing.

Taken together, the study draws a translational line between a naturally occurring behavior of skin cells and a new class of cell-free regenerative medicine. On one end, melanocytes appear to act as mitochondrial donors to keratinocytes under ultraviolet stress, a contact-dependent rescue mechanism that may help explain how skin tolerates lifelong sun exposure. On the other end, mitochondria isolated from mesenchymal stromal cells can be manufactured, applied to wounded tissue, and shown to accelerate healing across two mammalian species. The authors argue that this establishes a coherent biological rationale for mitochondria-based therapies in dermatology and wound care. Much work remains—optimal dosing, delivery vehicles, immunological considerations, and eventual human trials—but the conceptual advance is clear: the mitochondria that power our cells may one day be prescribed like medicine, harvested from stem cells and delivered to the skin to quench oxidative damage and rebuild what injury has destroyed.

Subject of Research: Horizontal mitochondrial transfer and mitochondrial transplantation for protection against ultraviolet radiation-induced damage and enhancement of skin wound healing

Article Title: Horizontal mitochondrial transfer and mitochondrial transplantation in skin: protection against UVR-induced ROS damage and enhancement of cell proliferation and wound healing

Article References: Horizontal mitochondrial transfer and mitochondrial transplantation in skin: protection against UVR-induced ROS damage and enhancement of cell proliferation and wound healing. (n.d.). https://doi.org/10.1186/s12967-026-08801-y

Image Credits: AI Generated

DOI: 10.1186/s12967-026-08801-y

Keywords: mitochondria, horizontal mitochondrial transfer, mitochondrial transplantation, skin, ultraviolet radiation, reactive oxygen species, mesenchymal stem cells, wound healing, keratinocytes, melanocytes, fibroblasts, regenerative medicine

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