Tissue Injury Research Articles

Open Soft Tissue Degloving Injuries of Lower Limbs Managed by a Staged Protocol Using Preserved Autologous Skin Graft

Background: Degloving soft tissue injuries (DSTIs) are defined as detachment of skin and its appendages from underlying muscle fascia. The present study aimed to assess the outcome of open circumferential DSTIs of lower limbs using a staged protocol by utilizing the stored skin graft harvested from degloved skin flaps. Methods: This retrospective study included 12 patients with open circumferential lower limb degloving injuries (Arnez types three and four), with a minimum final follow-up of two years. All the patients were treated using a staged protocol, which included harvesting skin grafts from the degloved skin flaps, followed by refrigerator storage of the graft and stay sutures for the flap. The refrigerator-stored graft was then used to cover the raw areas left after secondary debridement. Results: The mean wound area per patient that required skin grafting was 1082.9 ± 679.0 cm2 , and mean area of the wound covered by refrigerator-preserved skin graft per patient was 798.7 ± 350.0 cm2 . One patient needed a latissimus dorsi flap, and three patients with whole limb degloving had to undergo skin grafting for the remnant raw area harvested from the contralateral thigh. None of the patients ended up with amputation. Conclusion: Despite being rare, open DSTIs are very complex injuries with no definitive guidelines for management, especially Arnez type three and four injuries. The staged protocol presented in the present series potentially answers the dilemma. However, larger multi-centric trials are needed to study the outcome of the discussed staged protocol.

Neutrophil Reduction Attenuates the Severity of Lung Injury in the Early Phase of Pneumococcal Pneumonia in Mice.

Neutrophils are the first leukocytes to be recruited to sites of inflammation in response to chemotactic factors released by activated macrophages and pulmonary epithelial and endothelial cells in bacterial pneumonia, a common cause of acute respiratory distress syndrome (ARDS). Although neutrophilic inflammation facilitates the elimination of pathogens, neutrophils also may cause bystander tissue injury. Even though neutrophils in alveolar spaces is a key feature of acute lung injury and ARDS especially from pneumonia, their contribution to the pathogenesis of lung injury is uncertain. The goal of this study was to elucidate the role of neutrophils in a clinically relevant model of bacterial pneumonia. We investigated the effect of reducing neutrophils in a mouse model of pneumococcal pneumonia treated with antibiotics. Neutrophils were reduced with anti-Ly6G monoclonal antibody 24 hours before and immediately preceding infection. Mice were inoculated intranasally with Streptococcus pneumoniae and received ceftriaxone 12 hours after bacterial inoculation. Neutrophil reduction in mice treated with ceftriaxone attenuated hypoxemia, alveolar permeability, epithelial injury, pulmonary edema, and inflammatory biomarker release induced by bacterial pneumonia, even though bacterial loads in the distal air spaces of the lung were modestly increased as compared to antibiotic treatment alone. Thus, when appropriate antibiotics are administered, lung injury in the early phase of bacterial pneumonia is mediated in part by neutrophils. In the early phase of bacterial pneumonia, neutrophils contribute to the severity of lung injury, although they also participate in host defense.

Post-resolution macrophages shape long-term tissue immunity and integrity in a mouse model of pneumococcal pneumonia

Resolving inflammation is thought to return the affected tissue back to homoeostasis but recent evidence supports a non-linear model of resolution involving a phase of prolonged immune activity. Here we show that within days following resolution of Streptococcus pneumoniae-triggered lung inflammation, there is an influx of antigen specific lymphocytes with a memory and tissue-resident phenotype as well as macrophages bearing alveolar or interstitial phenotype. The transcriptome of these macrophages shows enrichment of genes associated with prostaglandin biosynthesis and genes that drive T cell chemotaxis and differentiation. Therapeutic depletion of post-resolution macrophages, inhibition of prostaglandin E2 (PGE2) synthesis or treatment with an EP4 antagonist, MF498, reduce numbers of lung CD4+/CD44+/CD62L+ and CD4+/CD44+/CD62L-/CD27+ T cells as well as their expression of the α-integrin, CD103. The T cells fail to reappear and reactivate upon secondary challenge for up to six weeks following primary infection. Concomitantly, EP4 antagonism through MF498 causes accumulation of lung macrophages and marked tissue fibrosis. Our study thus shows that PGE2 signalling, predominantly via EP4, plays an important role during the second wave of immune activity following resolution of inflammation. This secondary immune activation drives local tissue-resident T cell development while limiting tissue injury

Microglia, Trem2, and Neurodegeneration.

Microglia are a specialized type of neuroimmune cells that undergo morphological and molecular changes through multiple signaling pathways in response to pathological protein aggregates, neuronal death, tissue injury, or infections. Microglia express Trem2, which serves as a receptor for a multitude of ligands enhancing their phagocytic activity. Trem2 has emerged as a critical modulator of microglial activity, especially in many neurodegenerative disorders. Human TREM2 mutations are associated with an increased risk of developing Alzheimer disease (AD) and other neurodegenerative diseases. Trem2 plays dual roles in neuroinflammation and more specifically in disease-associated microglia. Most recent developments on the molecular mechanisms of Trem2, emphasizing its role in uptake and clearance of amyloid β (Aβ) aggregates and other tissue debris to help protect and preserve the brain, are encouraging. Although Trem2 normally stimulates defense mechanisms, its dysregulation can intensify inflammation, which poses major therapeutic challenges. Recent therapeutic approaches targeting Trem2 via agonistic antibodies and gene therapy methodologies present possible avenues for reducing the burden of neurodegenerative diseases. This review highlights the promise of Trem2 as a therapeutic target, especially for Aβ-associated AD, and calls for more mechanistic investigations to understand the context-specific role of microglial Trem2 in developing effective therapies against neurodegenerative diseases.

Enhanced hexanoyl glycol chitosan/tannic acid thermogels: Customizable physico-mechanical and biofunctional characteristics for biomedical applications

This study introduces HGC/TA thermogels, innovative thermosensitive hydrogels developed by integrating tannic acid (TA), a natural polyphenolic compound, into hexanoyl glycol chitosan (HGC). This unique formulation not only enhances the mechanical strength of the thermogels but also incorporates the beneficial physicochemical and biological properties of TA. Compared to conventional thermogels, including pure HGC variants, HGC/TA thermogels demonstrate significantly enhanced storage modulus and compressive strength, remarkable self-healing abilities, increased mucoadhesion, improved stability, and tunable degradation rates, all while being minimally cytotoxic. Moreover, these thermogels exhibit notable antioxidant properties, effectively counteracting free radicals, and display significant antibacterial activity against both Gram-negative E. coli and Gram-positive S. aureus. The ability to tailor the physico-mechanical and biological functions of HGC/TA thermogels by varying the TA concentration makes them highly versatile, marking them as ideal for diverse biomedical applications, particularly in wound care and tissue engineering.

Exosomes enriched by miR-429-3p derived from ITGB1 modified Telocytes alleviates hypoxia-induced pulmonary arterial hypertension through regulating Rac1 expression

BackgroundRecent studies have emphasized the critical role of Telocytes (TCs)-derived exosomes in organ tissue injury and repair. Our previous research showed a significant increase in ITGB1 within TCs. Pulmonary Arterial Hypertension (PAH) is marked by a loss of microvessel regeneration and progressive vascular remodeling. This study aims to investigate whether exosomes derived from ITGB1-modified TCs (ITGB1-Exo) could mitigate PAH.MethodsWe analyzed differentially expressed microRNAs (DEmiRs) in TCs using Affymetrix Genechip miRNA 4.0 arrays. Exosomes isolated from TC culture supernatants were verified through transmission electron microscopy and Nanoparticle Tracking Analysis. The impact of miR-429-3p-enriched exosomes (Exo-ITGB1) on hypoxia-induced pulmonary arterial smooth muscle cells (PASMCs) was evaluated using CCK-8, transwell assay, and inflammatory factor analysis. A four-week hypoxia-induced mouse model of PAH was constructed, and H&E staining, along with Immunofluorescence staining, were employed to assess PAH progression.ResultsForty-five miRNAs exhibited significant differential expression in TCs following ITGB1 knockdown. Mus-miR-429-3p, significantly upregulated in ITGB1-overexpressing TCs and in ITGB1-modified TC-derived exosomes, was selected for further investigation. Exo-ITGB1 notably inhibited the migration, proliferation, and inflammation of PASMCs by targeting Rac1. Overexpressing Rac1 partly counteracted Exo-ITGB1’s effects. In vivo administration of Exo-ITGB1 effectively reduced pulmonary vascular remodeling and inflammation.ConclusionsOur findings reveal that ITGB1-modified TC-derived exosomes exert anti-inflammatory effects and reverse vascular remodeling through the miR-429-3p/Rac1 axis. This provides potential therapeutic strategies for PAH treatment.Graphical 1. Identification of Differentially Expressed microRNAs (DEmiRs) in ITGB1 overexpressed TCs.2. Effects of Exo-ITGB1 or miR-429-3p on Hypoxia-Induced PASMCs in vitro.3. Exo-ITGB1 inhibits the hyper-proliferation and migration of PASMCs through regulating miR-429-3p/Rac1 axis in vitro.4. The therapeutic potential of Exo-ITGB1 in hypoxia-induced PAH model in vivo.

Vascular endothelial-derived SPARCL1 exacerbates viral pneumonia through pro-inflammatory macrophage activation

Inflammation induced by lung infection is a double-edged sword, moderating both anti-viral and immune pathogenesis effects; the mechanism of the latter is not fully understood. Previous studies suggest the vasculature is involved in tissue injury. Here, we report that expression of Sparcl1, a secreted matricellular protein, is upregulated in pulmonary capillary endothelial cells (EC) during influenza-induced lung injury. Endothelial overexpression of SPARCL1 promotes detrimental lung inflammation, with SPARCL1 inducing ‘M1-like’ macrophages and related pro-inflammatory cytokines, while SPARCL1 deletion alleviates these effects. Mechanistically, SPARCL1 functions through TLR4 on macrophages in vitro, while TLR4 inhibition in vivo ameliorates excessive inflammation caused by endothelial Sparcl1 overexpression. Finally, SPARCL1 expression is increased in lung ECs from COVID-19 patients when compared with healthy donors, while fatal COVID-19 correlates with higher circulating SPARCL1 protein levels in the plasma. Our results thus implicate SPARCL1 as a potential prognosis biomarker for deadly COVID-19 pneumonia and as a therapeutic target for taming hyperinflammation in pneumonia.

The bioengineering application of hyaluronic acid in tissue regeneration and repair

The multifaceted role of hyaluronic acid (HA) across diverse biomedical disciplines underscores its versatility in tissue regeneration and repair. HA hydrogels employ different crosslinking including chemical (chitosan, collagen), photo- initiation (riboflavin, LAP), enzymatic (HRP/H2O2), and physical interactions (hydrogen bonds, metal coordination). In biophysics and biochemistry, HA's signaling pathways, primarily through CD44 and RHAMM receptors, modulate cell behavior (cell migration; internalization of HA), inflammation, and wound healing. Particularly, smaller HA fragments stimulate inflammatory responses through toll-like receptors, impacting macrophages and cytokine expression. HA's implications in oncology highlight its involvement in tumor progression, metastasis, and treatment. Elevated HA in tumor stroma impacts apoptosis resistance and promotes tumor growth, presenting potential therapeutic targets to halt tumor progression. In orthopedics, HA's presence in synovial fluid aids in osteoarthritis management, as its supplementation alleviates pain, enhances synovial fluid's viscoelastic properties, and promotes cartilage integrity. In ophthalmology, HA's application in dry eye syndrome addresses symptoms by moisturizing the eyes, replenishing tear film deficiencies, and facilitating wound healing. Intravitreal injections and hydrogel-based systems offer versatile approaches for drug delivery and vitreous humor replacement. For skin regeneration and wound healing, HA hydrogel dressings exhibit exceptional properties by promoting moist wound healing and facilitating tissue repair. Integration of advanced regenerative tools like stem cells and solubilized amnion membranes into HA-based systems accelerates wound closure and tissue recovery. Overall, HA's unique properties and interactions render it a promising candidate across diverse biomedical domains, showcasing immense potentials in tissue regeneration and therapeutic interventions. Nevertheless, many detailed cellular and molecular mechanisms of HA and its applications remain unexplored and warrant further investigation.

Exploring the Progress of Hyaluronic Acid Hydrogels: Synthesis, Characteristics, and Wide-Ranging Applications.

This comprehensive review delves into the world of hyaluronic acid (HA) hydrogels, exploring their creation, characteristics, research methodologies, and uses. HA hydrogels stand out among natural polysaccharides due to their distinct features. Their exceptional biocompatibility makes them a top choice for diverse biomedical purposes, with a great ability to coexist harmoniously with living cells and tissues. Furthermore, their biodegradability permits their gradual breakdown by bodily enzymes, enabling the creation of temporary frameworks for tissue engineering endeavors. Additionally, since HA is a vital component of the extracellular matrix (ECM) in numerous tissues, HA hydrogels can replicate the ECM's structure and functions. This mimicry is pivotal in tissue engineering applications by providing an ideal setting for cellular growth and maturation. Various cross-linking techniques like chemical, physical, enzymatic, and hybrid methods impact the mechanical strength, swelling capacity, and degradation speed of the hydrogels. Assessment tools such as rheological analysis, electron microscopy, spectroscopy, swelling tests, and degradation studies are employed to examine their attributes. HA-based hydrogels feature prominently in tissue engineering, drug distribution, wound recovery, ophthalmology, and cartilage mending. Crafting HA hydrogels enables the production of biomaterials with sought-after qualities, offering avenues for advancements in the realm of biomedicine.

O15 Transcriptomic profiling reveals regulators of dermal fibroblast state switching

Abstract Introduction and aims Fibroblasts, the major cell population in connective tissue, are the guardians of the extracellular matrix homeostasis. In adult tissue they exist in a quiescent state that can persist for years, but upon tissue injury, they become rapidly activated and re-enter the cell cycle, followed by deposition and reorganization of the dermal matrix. The fundamental mechanism by which fibroblasts can maintain quiescence and be primed for prompt activation is currently unknown. Deregulations of this process in the skin and other organs is associated with several pathologies including fibrosis or chronic wounds. Notably, rapid fibroblast state switching is also observed during skin development, where a tightly controlled change from a highly proliferative state to a quiescent state promotes extracellular matrix deposition and maturation of the dermal architecture. Understanding the shared mechanisms and differences between development and wound healing will help in the development of tissue regenerative therapies. Methods Using dermal development as a model for fibroblast state switching, we integrated several single-cell RNA-Seq and assay for transposase-accessible chromatin-Seq datasets of whole skin during embryonic and postnatal growth. Our novel integrated multiomics single-cell dataset can recapitulate skin developmental changes observed in vivo and reveal the major regulatory networks. Results We identified the activating protein (AP)-1 member cJun as the key regulator of fibroblast state switching in skin development and wound repair. Mechanistically, in quiescent adult fibroblasts cJun is highly transcribed, but the protein is constantly ubiquitinated and degraded, priming fibroblasts for rapid activation when needed. Upon injury cJun ubiquitination is reduced, allowing an accumulation of cJun leading to a change in AP-1 dimer composition at the chromatin level, inhibiting fibroblast quiescence and promoting proliferation and activation. Conclusions In normal wounds cJun accumulation is inhibited during the advanced (remodelling) wounding phase; however, chronic wounds and fibrotic disease conditions show a continuous and pathological cJun stabilization, which can be targeted through pharmacological intervention.

P17 Dissection of the molecular and cellular heterogeneity of dermal fibroblasts in skin fibrosis

Abstract Introduction and aims Skin fibrosis, a common fibrotic condition that currently has no specific treatments or cures, is caused by persistent activation of skin fibroblasts after tissue injury that Results in excessive scarring, can cause severe disability and seriously affect morbidity. This study aims to uncover the specific fibroblast subsets and molecular pathways that are integral to this sustained fibroblast activation using a bleomycin-induced skin fibrosis mouse model that accurately recapitulates the human disease. Methods We have successfully shown that 2 weeks (early) and 4 weeks (advanced) of bleomycin injections Results in an increasing severity of skin fibrosis characteristics. Following this treatment, we performed single-cell RNA sequencing (scRNA-Seq) using control, early and advanced fibrotic tissue and identified fibroblast subclusters and specific gene signatures that are altered across the time course and may play a role in the fibrotic phenotype we observe. The use of advanced scRNA-Seq analysis techniques such as SCENIC and regulon analysis has allowed us to further characterize the changes in fibroblast states during fibrosis. Results Our scRNA-Seq data show a loss of fibroblast heterogeneity alongside the emergence of two main subclusters with distinct gene signatures in the advanced fibrotic state. While proliferation is minimal, RNA velocity analysis indicates that the increase in cell count is due to the convergence of neighbouring fibroblast subclusters. The pronounced profibrotic gene expression point to its key role in driving skin fibrosis and we are now exploring the therapeutic potential of chemically or genetically targeting this subcluster. Conclusions Our novel skin fibrosis time course scRNA-Seq dataset allows us to compare the cellular and molecular changes in early and advanced fibrotic lesions in order to identify the key fibroblast subpopulations, molecular regulators and connective tissue alterations promoting fibrotic tissue repair. Our findings will support the development of new fibroblast-targeted fibrosis therapies in skin and potentially in other organs.

Healing Effect of Hydroalcoholic Extracts of Thymbra Spicata and Ferulago Angulata on Second-degree Burn Wounds in Rats

Objective: Burns can be physically and mentally painful, making them one of the worst experiences. In this study, hydroalcoholic extracts of Thymbra spicata and Ferulago angulata were investigated as treatments for second-degree burns in male Wistar rats. Methods: To create the burn wounds, a circular metal tool with a diameter of 2 cm was used, followed by treatment with prepared ointments including Ferulago angulata (1%), Thymbra spicata (1%), Thymbra spicata plus Ferulago angulata (1%), and Adib derm ointment. The wound area was measured and the wound tissue was examined histopathologically on days 1, 7, 14, and 21 in each group. The ointments were applied every day for 21 days to determine the wound healing rate. Results: The experiment showed that on the sixth and eleventh days, the groups treated with a combination of Ferulago angulata and Thymbra spicata, and Ferulago angulata alone, demonstrated significant reductions in wound area. According to histopathology, both Ferulago angulata alone and in combination with Thymbra spicata significantly improved the inflammatory condition, epithelialization process, fibroplasia, arrangement, and density of collagen fibers when compared to the other groups. Conclusion: The study showed that Ferulago angulata extract, either on its own or in combination with Thymbra spicata extract, has significant healing and restorative effects on seconddegree burn wounds in animal models.

Baicalein alleviates cisplatin-induced acute kidney injury by inhibiting ALOX12-dependent ferroptosis

BackgroundIn acute kidney injury (AKI), ferroptosis is the main mechanism of cell death in the renal tubular epithelium. Baicalein, a traditional Chinese medicine monomer, plays a protective role in various kidney diseases; however, the effect of baicalein on ferroptosis in AKI still needs further exploration. PurposeIn this study, we explored the role of baicalein and its specific mechanism in mediating ferroptosis in cisplatin-induced AKI. MethodsWe used a cisplatin-induced AKI model to study the effects of baicalein on renal tissue and tubular epithelial cell injury. The effects of baicalein on tubular epithelial cell ferroptosis were detected in cisplatin-induced AKI and further verified by folic acid-induced AKI. The Swiss Target Prediction online database was used to predict the possible mechanism by which baicalein regulates ferroptosis, and the specific target proteins were further verified. Molecular docking and SPR were used to further determine the binding potential of baicalein to the target protein. Finally, RNA interference (RNAi) technology and enzymatic inhibition were used to determine whether baicalein regulates ferroptosis through target proteins. ResultsBaicalein alleviated cisplatin- and folic acid-induced renal dysfunction and pathological damage and improved cisplatin-induced HK2 cell injury. Mechanistically, baicalein reduced the expression of 12-lipoxygenase (ALOX12), which inhibits phospholipid peroxidation and ferroptosis in AKI. Molecular docking and SPR demonstrated direct binding between baicalein and ALOX12. Finally, we found that silencing ALOX12 had a regulatory effect similar to that of baicalein. Comparable results were also obtained with the ALOX12 inhibitor ML355. ConclusionThis was the first study to confirm that baicalein regulates ferroptosis both in vitro and in vivo in cisplatin-induced AKI and to verify the regulatory effect of baicalein in folic acid-induced AKI. Our results reveal the critical role of ALOX12 in kidney damage and ferroptosis caused by cisplatin and emphasize the regulatory effect of baicalein on renal tubular epithelial cell ferroptosis mediated by ALOX12. Baicalein is an effective drug for treating AKI, and ALOX12 is a potential drug target.

Mathematical Models of Wound Healing and Tissue Regeneration: Insights with Numerical Solution

Understanding and forecasting the dynamics of wound healing processes heavily relies on mathematical modeling. Researchers can understand the complicated connections between cells, tissues, and biochemical components involved in wound healing by using mathematical equations and computational simulations. One such mathematical model that has seeks the interest of researchers in exploring wound healing phenomenon is Fisher’s equation. In the present work, the equation is solved using differential quadrature method with trigonometric tension B-spline (TTBs) basis function. The obtained results are compared with the results obtained from earlier studies and the results are presented in form of tables and figures. The implementation of the particle swarm optimization algorithm has removes the dilemma of unknown parameter involvement in the TTBs and hence resulted in a novel technique to find the numerical results.

Tissue Regeneration and Remodeling in Rat Models after Application of Hypericum perforatum L. Extract-Loaded Bigels.

The wound-healing effect of St. John's Wort (SJW) is mainly attributed to hyperforin (HP), but its low stability restricts its topical administration. This study investigates how "free" HP-rich SJW extract (incorporated into a bigel; B/SJW) and extract "protected" by nanostructured lipid carriers (also included in a biphasic semisolid; B/NLC-SJW) affect tissue regeneration in a rat skin excision wound model. Wound diameter, histological changes, and tissue gene expression levels of fibronectin (Fn), matrix metalloproteinase 8 (MMP8), and tumor necrosis factor-alpha (TNF-α) were employed to quantify the healing progress. A significant wound size reduction was achieved after applying both extract-containing semisolids, but after a 21-day application period, the smallest wound size was observed in the B/NLC-SJW-treated animals. However, the inflammatory response was affected more favorably by the bigel containing the "free" SJW extract, as evidenced by histological studies. Moreover, after the application of B/SJW, the expression of Fn, MMP8, and TNF-α was significantly higher than in the positive control. In conclusion, both bigel formulations exhibited beneficial effects on wound healing in rat skin, but B/SJW affected skin restoration processes in a comprehensive and more efficient way.

Identifying p56lck SH2 Domain Inhibitors Using Molecular Docking and In Silico Scaffold Hopping

Bacterial infections are the second-leading cause of death, globally. The prevalence of antibacterial resistance has kept the demand strong for the development of new and potent drug candidates. It has been demonstrated that Src protein tyrosine kinases (TKs) play an important role in the regulation of inflammatory responses to tissue injury, which can trigger the onset of several severe diseases. We carried out a search for novel Src protein TK inhibitors, commencing from reported highly potent anti-bacterial compounds obtained using the Mannich reaction, using a combination of e-pharmacophore modeling, virtual screening, ensemble docking, and core hopping. The top-scoring compounds from ligand-based virtual screening were modified using protein structure-based design approaches, and their binding to the Src homology-2 domain of p56lck TK was predicted using ensemble molecular docking. We have prepared a database of 202 small molecules and have identified six novel top hits that can be subjected to further investigation. We have also performed in silico ADMET property prediction for the hit compounds. This combined computer-aided drug design approach can serve as a starting point for identifying novel TK inhibitors that could be further subjected to in vitro studies and validation of antimicrobial activity.

End-ischemic pharmacological cocktail treatment to mitigate rewarming/reperfusion injury

Increasing shortage of donor organs leads to the acceptance of less than optimal grafts for transplantation, up to and including organs donated after circulatory standstill of the donor.Therefore, protective strategies and pharmacological interventions destined to reduce ischemia induced tissue injury are considered a worthwhile focus of research.The present study evaluates the potential of a multidrug pharmacological approach as single flush at the end of static preservation to protect the liver from reperfusion injury.Livers were retrieved from male Wistar rats 20 min after cardiac standstill. The organs were cold stored for 18 h, flushed with 20 ml of saline, kept at room temperature for 20 min, and reperfused at 37 °C with oxygenated Williams E solution. In half of the cases, the flush solution was supplemented with a cocktail containing metformin, bucladesine and cyclosporin A.Upon reperfusion, treated livers disclosed a massive mitigation of hepatic release of alanine aminotransferase and aspartate aminotransferase, along with a significant approximately 50 % reduction of radical mediated lipid peroxidation, caspase activation and release of TNF-alpha.Even after preceding cold preservation, a pharmacological cocktail given as single flush is capable to mitigate manifestations of reperfusion injury in the present model.

Osteochondroprogenitor cells and neutrophils expressing p21 and senescence markers modulate fracture repair.

Cells expressing features of senescence, including upregulation of p21 and p16, appear transiently following tissue injury, yet the properties of these cells or how they contrast with age-induced senescent cells remains unclear. Here, we used skeletal injury as a model and identified the rapid appearance following fracture of p21+ cells expressing senescence markers, mainly as osteochondroprogenitors (OCHs) and neutrophils. Targeted genetic clearance of p21+ cells suppressed senescence-associated signatures within the fracture callus and accelerated fracture healing. By contrast, p21+ cell clearance did not alter bone loss due to aging; conversely, p16+ cell clearance, known to alleviate skeletal aging, did not affect fracture healing. Following fracture, p21+ neutrophils were enriched in signaling pathways known to induce paracrine stromal senescence, while p21+ OCHs were highly enriched in senescence-associated secretory phenotype factors known to impair bone formation. Further analysis revealed an injury-specific stem cell-like OCH subset that was p21+ and highly inflammatory, with a similar inflammatory mesenchymal population (fibro-adipogenic progenitors) evident following muscle injury. Thus, intercommunicating senescent-like neutrophils and mesenchymal progenitor cells were key regulators of tissue repair in bone and potentially across tissues. Moreover, our findings established contextual roles of p21+ vs p16+ senescent/senescent-like cells that may be leveraged for therapeutic opportunities.

Langerhans Cells in Sentinel Lymph Nodes from Melanoma Patients.

Langerhans cells (LCs) are professional Dendritic Cells (DCs) involved in immunoregulatory functions. At the skin level, LCs are immature. In response to tissue injuries, they migrate to regional Lymph Nodes (LNs), reaching a full maturation state. Then, they become effective antigen-presenting cells (APCs) that induce anti-cancer responses. Notably, melanoma patients present several DC alterations in the Sentinel Lymph Node (SLN), where primary antitumoral immunity is generated. LCs are the most represented DCs subset in melanoma SLNs and are expected to play a key role in the anti-melanoma response. With this paper, we aim to review the current knowledge and future perspectives regarding LCs and melanoma. A systematic review was carried out according to the PRISMA statement using the PubMed (MEDLINE) library from January 2004 to January 2024, searching for original studies discussing LC in melanoma. The final synthesis included 15 articles. Several papers revealed significant LCs-melanoma interactions. Melanoma immune escape mechanisms include SLN LC alterations, favoring LN metastasis arrival/homing and melanoma proliferation. The SLN LCs of melanoma patients are defective but not irreversibly, and their function may be restored by appropriate stimuli. Thus, LCs represent a promising target for future immunotherapeutic strategies and cancer vaccines.

Co-Delivery of Recombinant Super-Affinity VEGF and PDGF-BB Accelerates Diabetic Wound Healing by Improving Angiogenesis, Arteriogenesis and Blood Flow

Abstract Background Diabetic ulcers are characterized by local ischemia, usually without macroangiopathy. We have previously found that the combination of VEGF and PDGF-BB in a fibrin matrix is effective in stimulating arterial growth to diabetic wounds. Aims We developed modified forms of VEGF and PDGF-BB to bear super-affinity for the extracellular matrix (SA-VP), in order to decorate the wound tissue without the need for a biomaterial. We investigated the dose-dependent effects on local blood flow and wound healing, by applying the treatment either to the healthy tissue around the wound or to the damaged wound bed. Methods Full thickness wounds were created on the dorsal skin of diabetic (db/db) mice. SA-VP or saline were applied to the wound bed or divided into 4 injections around the wound edge. Wound closure and blood flow were measured on days 4 and 8 after treatment and tissues were harvested for histology on day 8. Data were analysed by Anova with Tukey’s post-hoc test for multiple comparisons. Results Wound healing was improved dose-dependently by SA-VP by both delivery routes. Histologically, angiogenic areas and total amount of angiogenesis were significantly increased by the highest SA-VP dose, again independent of delivery route (p = 0.034). However, the total amount of recruited arterioles was significantly increased only in the healthy tissue around the wound and only by intradermal injections of SA-VP (p = 0.008). In agreement with the arteriogenic effect, the blood flow at day 4 was significantly increased only by injections of the highest SA-VP dose around the wound (p = 0.018). Conclusion SA-VP treatment significantly accelerates wound healing in a diabetic murine model with a clear dose-dependent effect. Targeting the undamaged tissue around the wound by injections induces more effective arteriogenesis. However, direct treatment of the wound bed is equally effective for healing. These results support further development for a potential clinical use.