Fibrinolytic nanocages dissolve clots in the tumor microenvironment, improving the distribution and therapeutic efficacy of anticancer drugs

Fibrin, one of the components of the extracellular matrix (ECM), acts as a transport barrier within the core of tumors by constricting the blood vessels and forming clots, leading to poor intratumoral distribution of anticancer drugs. Our group previously developed a microplasmin-based thrombolytic ferritin nanocage that efficiently targets and dissolves clots without causing systemic fibrinolysis or disrupting hemostatic clots. We hypothesized that the thrombolytic nanocage-mediated degradation of fibrin clots in the tumor ECM can lead to enhanced intratumoral drug delivery, especially for nanosized anticancer drugs. Fibrin clot deposition worsens after surgery and chemotherapy, further hindering drug delivery. Moreover, the risk of venous thromboembolism (VTE) also increases. Here, we used thrombolytic nanocages with multivalent clot-targeting peptides and fibrin degradation enzymes, such as microplasmin, to dissolve fibrin in the tumor microenvironment and named them fibrinolytic nanocages (FNCs). These FNCs target tumor clots specifically and effectively. FNCs efficiently dissolve fibrin clots inside of the tumor vessels, suggesting that they can mitigate the risk of VTE in cancer patients. Coadministration of FNC and doxorubicin led to improved chemotherapeutic activity in a syngeneic mouse melanoma model. Furthermore, the FNCs increased the distribution of Doxil/doxorubicin nanoparticles within mouse tumors. These results suggest that fibrinolytic cotherapy might help improve the therapeutic efficacy of anticancer nanomedicines. Thus, microplasmin-based fibrinolytic nanocages are promising candidates for this strategy due to their hemostatic safety and ability to home in on the tumor.

PROLONGATION OF CLEANSING DAMAGED TISSUES FROM DETRITUS USING EXOSOMES OF MULTIPOTENT STROMAL CELLS

Objective. To study the effect of exosomes of multipotent mesenchymal stromal cells (EMSCs) on soft tissues damaged during implantation of a metal screw into the bone. Methods. A defect (2 mm in diameter and 4 mm in depth) was created in the tibial proximal condyles of outbred rabbits. Metal screws were implanted into the defect by preliminary injection of saline (control, n=9 animals) or 19.2 μg of EMSCs per limb (experiment, n=10 rabbits). After 3, 7 and 10 days following the operation, the animals were taken out from the experiment; histological sections of soft tissues from the condyle surface, stained by hematoxylin and eosin were studied using light microscopy. Results. The use of water cooling in the process of introducing the metal implant into the tibial proximal condyle does not lead to complete removal of small bone fragments, which are subsequently either eliminated outward with wound discharge, or are destroyed and are subjected to lysis by macrophages. As a result of the EMSC effect on soft tissues near the site of damage, the activity of the postoperative inflammation reduces, leads to a slowdown in the resorption of hemorrhages, the elimination of fibrin clots, detritus and small bone fragments. Even on the 10^th day after using EMSCs in the postoperative wound a structureless detritus with a small number of infiltrating cells was present, as well as a significant number of multinucleated macrophages with fused cytoplasm, non-viable lysed striated muscle symplasts and bone fragments with a low degree of degradation. Conclusion. Suppression of inflammation by EMSCs delays the clearance of the postoperative wound, promotes the prolongation of the repair process and the attachment of the granulomatous component to the inflammation. The using EMSCs in the process of intraosseous implantation may be recommended only to control the activity of the inflammatory process and only after maximum preliminary cleansing of the postoperative wound from detritus, including non-viable muscle tissue and bone fragments. What this paper adds It has been firstly shown that after the experimental use of exosome of multipotent mesenchymal stromal cells to influence the regeneration of surgical trauma of soft tissues after intraosseous implantation, it is possible to reduce the activity of the inflammatory reaction, which leads to a slowdown of resorption of hemorrhages, elimination of fibrin clots, detritus and small bone fragments and, accordingly, prolongation of cleansing damaged tissue and delayed repair.

Predictive value of C-reactive protein for radiographic spinal progression in axial spondyloarthritis in dependence on genetic determinants of fibrin clot formation and fibrinolysis

ObjectiveGenetic determinants of fibrin clot formation and fibrinolysis have an impact on local and systemic inflammatory response. The aim of the present study was to assess whether coagulation-related genotypes affect the predictive value of C-reactive protein (CRP) in regards of radiographic spinal progression in axial spondyloarthritis (axSpA).MethodsTwo hundred and eight patients with axSpA from the German Spondyloarthritis Inception Cohort were characterised for genotypes of α-fibrinogen, β-fibrinogen (FGB) and γ-fibrinogen, factor XIII A-subunit (F13A) and α2-antiplasmin (A2AP). The relation between CRP levels and radiographic spinal progression defined as worsening of the modified Stoke Ankylosing Spondylitis Spinal Score (mSASSS) by ≥2 points over 2 years was assessed in dependence on the respective genetic background in logistic regression analyses.ResultsOverall, CRP was associated with mSASSS progression ≥2 points: time-averaged CRP ≥10 mg/L, OR: 3.32, 95% CI 1.35 to 8.13. After stratification for coagulation-related genotypes, CRP was strongly associated with mSASSS progression in individuals predisposed to form loose, fibrinolysis-susceptible fibrin clots (FGB rs1800790GG, OR: 6.86, 95% CI 2.08 to 22.6; A2AP 6Trp, OR: 5.86, 95% CI 1.63 to 21.0; F13A 34Leu, OR: 8.72, 95% CI 1.69 to 45.1), while in genotypes predisposing to stable fibrin clots, the association was absent or weak (FGB rs1800790A, OR: 0.83, 95% CI 0.14 to 4.84; A2AP 6Arg/Arg, OR: 1.47, 95% CI 0.35 to 6.19; F13A 34Val/Val, OR: 1.72, 95% CI 0.52 to 5.71).ConclusionsElevated CRP levels seem to be clearly associated with radiographic spinal progression only if patients are predisposed for loose fibrin clots with high susceptibility to fibrinolysis.

Peritoneal dialysis catheter dysfunction due to fibrin clots following treatment with tranexamic acid: a clinical case

Chronic kidney disease patients experience not only more frequent arterial and venous thrombosis but also hemorrhagic episodes. Tranexamic acid is an anti-fibrinolytic molecule that inhibits plasmin activation. It is used in hemorrhage cases (post-traumatic, gynecologic, or gastrointestinal bleeding). We report on an original case of tranexamic acid (Exacyl®) use in a peritoneal dialysis patient for gastrointestinal bleeding of unknown origin. The use of tranexamic acid led to the Tenckhoff catheter dysfunction because of fibrin clots in the dialysate. The emergence of fibrin clots a few days after the start of tranexamic acid treatment, which never occurred again after the end of the treatment, and the anti-fibrinolytic function of tranexamic acid favors this treatment’s role in fibrin clot occurrence.

Cell barrier function of resident peritoneal macrophages in post-operative adhesions

Post-operative adhesions are a leading cause of abdominal surgery-associated morbidity. Exposed fibrin clots on the damaged peritoneum, in which the mesothelial barrier is disrupted, readily adhere to surrounding tissues, resulting in adhesion formation. Here we show that resident F4/80HighCD206− peritoneal macrophages promptly accumulate on the lesion and form a ‘macrophage barrier’ to shield fibrin clots in place of the lost mesothelium in mice. Depletion of this macrophage subset or blockage of CD11b impairs the macrophage barrier and exacerbates adhesions. The macrophage barrier is usually insufficient to fully preclude the adhesion formation; however, it could be augmented by IL-4-based treatment or adoptive transfer of this macrophage subset, resulting in robust prevention of adhesions. By contrast, monocyte-derived recruited peritoneal macrophages are not involved in the macrophage barrier. These results highlight a previously unidentified cell barrier function of a specific macrophage subset, also proposing an innovative approach to prevent post-operative adhesions.

Incorporation of α2-Plasmin Inhibitor into Fibrin Clots and Its Association with the Clinical Outcome of Acute Ischemic Stroke Patients

Cross-linking of α2-plasmin inhibitor (α2-PI) to fibrin by activated factor XIII (FXIIIa) is essential for the inhibition of fibrinolysis. Little is known about the factors modifying α2-PI incorporation into the fibrin clot and whether the extent of incorporation has clinical consequences. Herein we calculated the extent of α2-PI incorporation by measuring α2-PI antigen levels from plasma and serum obtained after clotting the plasma by thrombin and Ca2+. The modifying effect of FXIII was studied by spiking of FXIII-A-deficient plasma with purified plasma FXIII. Fibrinogen, FXIII, α2-PI incorporation, in vitro clot-lysis, soluble fibroblast activation protein and α2-PI p.Arg6Trp polymorphism were measured from samples of 57 acute ischemic stroke patients obtained before thrombolysis and of 26 healthy controls. Increasing FXIII levels even at levels above the upper limit of normal increased α2-PI incorporation into the fibrin clot. α2-PI incorporation of controls and patients with good outcomes did not differ significantly (49.4 ± 4.6% vs. 47.4 ± 6.7%, p = 1.000), however it was significantly lower in patients suffering post-lysis intracranial hemorrhage (37.3 ± 14.0%, p = 0.004). In conclusion, increased FXIII levels resulted in elevated incorporation of α2-PI into fibrin clots. In stroke patients undergoing intravenous thrombolysis treatment, α2-PI incorporation shows an association with the outcome of therapy, particularly with thrombolysis-associated intracranial hemorrhage.

Use of Simvastatin, Fibrin Clots, and Their Combination to Improve Human Ovarian Tissue Grafting for Fertility Restoration After Anti-Cancer Therapy

Anticancer treatments, particularly chemotherapy, induce ovarian damage and loss of ovarian follicles. There are limited options for fertility restoration, one of which is pre-chemotherapy cryopreservation of ovarian tissue. Transplantation of frozen-thawed human ovarian tissue from cancer survivors has resulted in live-births. There is extensive follicular loss immediately after grafting, probably due to too slow graft revascularization. To avoid this problem, it is important to develop methods to improve ovarian tissue neovascularization. The study’s purpose was to investigate if treatment of murine hosts with simvastatin or/and embedding human ovarian tissue within fibrin clots can improve human ovarian tissue grafting (simvastatin and fibrin clots promote vascularization). There was a significantly higher number of follicles in group A (ungrafted control) than in group B (untreated tissue). Group C (simvastatin-treated hosts) had the highest levels of follicle atresia. Group C had significantly more proliferating follicles (Ki67-stained) than groups B and E (simvastatin-treated hosts and tissue embedded within fibrin clots), group D (tissue embedded within fibrin clots) had significantly more proliferating follicles (Ki67-stained) than group B. On immunofluorescence study, only groups D and E showed vascular structures that expressed both human and murine markers (mouse-specific platelet endothelial cell adhesion molecule, PECAM, and human-specific von Willebrand factor, vWF). Peripheral human vWF expression was significantly higher in group E than group B. Diffuse human vWF expression was significantly higher in groups A and E than groups B and C. When grafts were not embedded in fibrin, there was a significant loss of human vWF expression compared to groups A and E. This protocol may be tested to improve ovarian implantation in cancer survivors.