Rise in complications of acute otitis media during and after the COVID-19 pandemic.

PURPOSE: After the lifting of nonpharmaceutical interventions (NPIs) during the COVID-19 pandemic, clinical observation showed an increase in complications of acute otitis, followed by a rise in the number of mastoidectomies performed. The aim of this study was to record the number of mastoidectomies performed before, during and after the COVID-19 pandemic as an indicator for complications of acute otitis media. METHODS: Data were collected from a tertiary hospital in a university setting, as well as from four major public health insurance companies in Germany. The data of 24,824,763 German citizens during a period from 2014 until 2023 were analyzed. RESULTS: According to the data, during the COVID-19 pandemic, the number of mastoidectomies performed dropped by 54% for children aged 0-6 and by 62% for children aged 7-18. For adults, there were 30% fewer mastoidectomies performed between 2020 and 2022. After the lifting of most NPI's in the season from July 2022 to June 2023, there was a sharp increase in the number of mastoidectomies performed on patients of all ages. CONCLUSIONS: During the COVID-19 pandemic, a decrease in the number of mastoidectomies performed was seen, suggesting a lower incidence of complicated acute otitis, most likely linked to the general decrease of upper airway infections due to NPI's. In contrast, a sharp increase in the incidence of complicated otitis occurred after the hygiene measures were lifted. The current development causes a more frequent performance of mastoidectomies, thus entailing a change in the challenges for everyday clinical practice.

p16 overexpression identifies oncogenic high-risk HPV infection in non-oropharyngeal squamous cell carcinoma of the head and neck.

BACKGROUND: Human papillomavirus (HPV) is an increasing risk factor for cancer. HPV-associated oropharyngeal squamous cell carcinoma (OPSCC) is associated with a favorable outcome. Blockstaining for p16 is a surrogate marker for HPV+ OPSCC. In oral and laryngeal squamous cell carcinoma (OSCC/LSCC), the relevance of p16 immunohistochemistry, alone or in combination with other cell cycle-related proteins, to identify HPV-driven non-OPSCC is less well understood. METHODS: We stained for p16, pRb, cyclin D1, and p53 in 327 HNSCC. In 310 OPSCC, HPV-status was assessed by HPV DNA PCR. In 119 non-OPSCC, RNA in situ hybridization was additionally performed. HPV-status was correlated with staining patterns, p53 and clinical data. RESULTS: The OPSCC showed blockstaining for p16 in 36%, 8% were equivocal. Of these, HPV-testing was performed in 57%, and 53% were positive for HPV DNA. HPV-association correlated with absence of pRb and cyclin D1 and favorable outcome. In non-OPSCC, 18% showed p16-blockstaining, and 13% showed E6/E7 RNA. Six of seven HPV+ OSCC and 8/8 LSCC lost pRb and cyclin D1. Compared to HPV-negative counterparts, patients with HPV+ cancers had lower rates of alcohol consumption and keratinizing morphology. HPV-positive OSCC had a longer overall survival (p < 0.05). HPV subtype 16 was the most common. CONCLUSIONS: We conclude that HPV-positive non-OPSCC are associated with p16 overexpression and low levels of pRb and cyclin D1. High expression of pRb and cyclin D1 indicates HPV-negativity.

Identifying Predictive Biomarkers for Head and Neck Squamous Cell Carcinoma Response.

The 5-year survival rate for head and neck squamous cell carcinoma (HNSCC) is approximately 65%. In addition to radio-chemotherapy, immunotherapy is an approach in the treatment of advanced HNSCC. A better understanding of the immune context would allow personalized treatment by identifying patients who are best suited for different treatment options. In our discovery cohort, we evaluated the expression profiles of CMTM6, PD-L1, CTLA-4, and FOXP3 in 177 HNSCCs from Caucasian patients of all tumor stages and different treatment regimens, correlating marker expression in tumor and immune cells with outcomes. Patients with CMTM6high-expressing tumors had a longer overall survival regardless of treatment. This prognostic benefit of CMTM6 in HNSCC was validated in an independent cohort. Focusing on the in the discovery cohort (n = 177), a good predictive effect of CMTM6high expression was seen in patients receiving radiotherapy (p = 0.07; log rank), but not in others. CMTM6 correlated with PD-L1, CTLA-4 and FOXP3 positivity, with patients possessing CMTM6high/FOXP3high tumors showing the longest survival regardless of treatment. In chemotherapy-treated patients, PD-L1 positivity was associated with longer progression-free survival (p < 0.05). In the 27 patients who received immunotherapy, gene expression analysis revealed lower levels of CTLA-4 and FOXP3 with either partial or complete response to this treatment, while no effect was observed for CMTM6 or PD-L1. The combination of these immunomodulatory markers seems to be an interesting prognostic and predictive signature for HNSCC patients with the ability to optimize individualized treatments.

Head and Neck Cancer: A Study on the Complex Relationship between QoL and Swallowing Function.

Head and neck squamous cell carcinoma (HNSCC) is linked to significant morbidity, adversely affecting survival and functional capacity. Post-treatment challenges such as pain, dysphonia, and dysphagia are common, prompting increased attention in survivorship research. Quality of Life (QoL) questionnaires, especially the MD Anderson Dysphagia Inventory (MDADI), are prevalent outcome measures in clinical studies but often lack parallel objective swallowing function evaluations, leading to potential outcome discrepancies. This study aimed to illuminate the relationship between subjective QoL (EQ-5D-5L and MDADI) measures and objective swallowing function (evaluated via Fiberoptic Endoscopic Evaluation of Swallowing, FEES) in patients with HNSCC. The analysis revealed a notable discordance between objective measures of swallowing function, such as the Penetration-Aspiration Scale (PAS) and residue ratings in the vallecula or piriform sinus, and patients' subjective QoL assessments (p = 0.21). Despite the lack of correlation, swallowing-related QoL, as measured by the MDADI, was more indicative of disease severity than generic QoL assessments. Generic QoL scores did not demonstrate substantial variation between patients. In contrast, MDADI scores significantly declined with advancing tumor stage, multimodal therapy, and reliance on feeding tubes. However, the clinical significance of this finding was tempered by the less than 10-point difference in MDADI scores. The findings of this study underline the limitations of QoL measures as standalone assessments in patients with HNSCC, given their reliance on patient-perceived impairment. While subjective QoL is a crucial aspect of evaluating therapeutic success and patient-centric outcomes, it may fail to capture critical clinical details such as silent aspirations. Consequently, QoL assessments should be augmented by objective evaluations of swallowing function in clinical research and practice to ensure a holistic understanding of patient well-being and treatment impact.

Establishing safe high hydrostatic pressure devitalization thresholds for autologous head and neck cancer vaccination and reconstruction.

High hydrostatic pressure specifically devitalizes cells and tissues without major changes in their molecular structure. Hence, high hydrostatic pressure may enhance the development of whole-cell anti-tumor vaccines, representing tumor heterogeneity and thus (neo-) antigen diversity. Moreover, safe devitalization of tumor-infiltrated supporting tissue may facilitate reimplantation for functional reconstruction. However, precise high hydrostatic pressure thresholds for safe cancer cell killing are unknown. Here, we show that high hydrostatic pressure of at least 450 MPa is necessary to safely devitalize head and neck squamous cell cancer. A pressure of 300 MPa, which has been used frequently in cancer vaccine preparation, resulted in partial devitalization with 27% live cells in flow cytometry and 4% remaining autofluorescence in cell culture after one week. The remaining cells could form vital tumors in the chorioallantoic membrane assay. In contrast, 450 MPa killed all cells in vitro and prevented tumor outgrowth in ovo. The effectiveness of 450 MPa was attributed to the induction of DNA double-strand breaks, independent of apoptosis, autophagy, or methuosis. Furthermore, 450 MPa continued to induce immunogenic cell death. Our results demonstrate that 450 MPa of high hydrostatic pressure induces safe and sustained devitalization of head and neck cancer cells and tissues. Because of the heterogeneity in pressure resistance, we propose our approach as a starting point for determining the precise thresholds for other cancer entities. Further studies on head and neck cancer should focus on immunological co-cultures, combinations of immune checkpoint inhibition, and accurate anatomical reconstruction with pressure-treated autografts.

Continuous intraoperative perfusion monitoring of free microvascular anastomosed fasciocutaneous flaps using remote photoplethysmography.

Flap loss through limited perfusion remains a major complication in reconstructive surgery. Continuous monitoring of perfusion will facilitate early detection of insufficient perfusion. Remote or imaging photoplethysmography (rPPG/iPPG) as a non-contact, non-ionizing, and non-invasive monitoring technique provides objective and reproducible information on physiological parameters. The aim of this study is to establish rPPG for intra- and postoperative monitoring of flap perfusion in patients undergoing reconstruction with free fasciocutaneous flaps (FFCF). We developed a monitoring algorithm for flap perfusion, which was evaluated in 15 patients. For 14 patients, ischemia of the FFCF in the forearm and successful reperfusion of the implanted FFCF was quantified based on the local signal. One FFCF showed no perfusion after reperfusion and devitalized in the course. Intraoperative monitoring of perfusion with rPPG provides objective and reproducible results. Therefore, rPPG is a promising technology for standard flap perfusion monitoring on low costs without the need for additional monitoring devices.

The Dorsal Skinfold Chamber as a New Tympanic Membrane Wound Healing Model: Intravital Insights into the Pathophysiology of Epithelialized Wounds.

BACKGROUND: Tympanic membrane perforations (TMPs) are a common complication of trauma and infection. Persisting perforations result from the unique location of the tympanic membrane. The wound is surrounded by air of the middle ear and the external auditory canal. The inadequate wound bed, growth factor, and blood supply lead to circular epithelialization of the perforation's edge and premature interruption of defect closure. Orthotopic animal models use mechanical or chemical tympanic membrane laceration to identify bioactive wound dressings and overcome premature epithelialization. However, all orthotopic models essentially lack repetitive visualization of the biomaterial-wound interface. Therefore, recent progress in 3D printing of customized wound dressings has not yet been transferred to the unique wound setup of the TMP. Here, we present a novel application for the mice dorsal skinfold chamber (DSC) with an epithelialized full-thickness defect as TMP model. METHODS: A circular 2-mm defect was cut into the extended dorsal skinfold using a biopsy punch. The skinfold was either perforated through both skin layers without prior preparation or perforated on 1 side, following resection of the opposing skin layer. In both groups, the wound was sealed with a coverslip or left unclosed (n = 4). All animals were examined for epithelialization of the edge (histology), size of the perforation (planimetry), neovascularization (repetitive intravital fluorescence microscopy), and inflammation (immunohistology). RESULTS: The edge of the perforation was overgrown by the cornified squamous epithelium in all pre-parations. Reduction in the perforation's size was enhanced by application of a coverslip. Microsurgical preparation before biopsy punch perforation and sealing with a coverslip enabled repetitive high-quality intravital fluorescence microscopy. However, spontaneous reduction of the perforation occurred frequently. Therefore, the direct biopsy punch perforation without microsurgical preparation was favorable: spontaneous reduction did not occur throughout 21 days. Moreover, the visualization of the neovascularization was sufficient in intravital microscopy. CONCLUSIONS: The DSC full-thickness defect is a valuable supplement to orthotopic TMP models. Repetitive intravital microscopy of the epithelialized edge enables investigation of the underlying pathophysiology during the transition from the inflammation to the proliferation phase of wound healing. Using established analysis procedures, the present model provides an effective platform for the screening of bioactive materials and transferring progress in tissue engineering to the special conditions of tympanic membrane wound healing.

Functional Outcomes and Quality of Life after Cochlear Implantation in Patients with Long-Term Deafness.

Background: Hearing-related quality of life (QoL) after cochlear implantation (CI) is as important as audiological performance. We evaluated the functional results and QoL after CI in a heterogeneous patient cohort with emphasis on patients with long-term deafness (>10 years). Methods: Twenty-eight patients (n = 32 implanted ears, within n = 12 long-term deaf ears) implanted with a mid-scala electrode array were included in this retrospective mono-centric cohort study. Speech intelligibility for monosyllables (SIM), speech reception thresholds (SRT50) and QoL with Nijmegen Cochlear Implant Questionnaire (NCIQ) were registered. Correlation of SIM and QoL was analyzed. Results: SIM and SRT50 improved significantly 12 months postoperatively up to 54.8 ± 29.1% and 49.3 ± 9.6 dB SPL, respectively. SIM progressively improved up to 1 year, but some early-deafened, late implanted patients developed speech understanding several years after implantation. The global and all subdomain QoL scores increased significantly up to 12 months postoperatively and we found a correlation of SIM and global QoL score at 12 months postoperatively. Several patients of the "poor performer" (SIM < 40%) group reported high improvement of hearing-related QoL. Conclusions: Cochlear implantation provides a benefit in hearing-related QoL, even in some patients with low postoperative speech intelligibility results. Consequently, hearing-related QoL scores should be routinely used as outcome measure beside standard speech understanding tests, as well. Further studies with a prospective multi-centric design are needed to identify factors influencing post-implantation functional results and QoL in the patient group of long-term deafness.

Relatives Experience More Psychological Distress Due to COVID-19 Pandemic-Related Visitation Restrictions Than In-Patients.

Background: The COVID-19 pandemic led to visiting restrictions (VRs) of patients in hospitals. Social contacts between patients' relatives play an important role in convalescence. Isolation may cause new psychological comorbidity. The present study investigated the psychological distress of VR in in-patients and their relatives. Methods: From April 1, 2020 to May 20, 2020, 313 in-patients (≥14 years) of the University Medical Center Rostock were interviewed by questionnaires and 51 relatives by phone. Subjective psychological distress was assessed by a distress thermometer [0 (not at all)-100 (extreme)]. The study also investigated stressors due to VR, psychological distress in dependence on demographic or disease-related data, currently used communication channels and desired alternatives and support. Results: Relatives were more psychologically distressed by VR than in-patients (59 ± 34 vs. 38 ± 30, p = 0.002). Loss of direct physical contact and facial expressions/gestures resulted in the most distress. Psychological distress due to VR was independent of demographics and indicates small positive correlations with the severity of physical restriction and the general psychological distress of in-patients. The most frequent ways of communication were via phone and social media. Frequently requested alternatives for patients were other interlocutors and free phone/tablet use, for relatives visiting rooms with partitions. Conclusion: VRs are a stressor for patients and their relatives. The establishment of visiting rooms with partitions and the free use of phones/tablets could reduce the additional distress.

3D-printed lightweight dorsal skin fold chambers from PEEK reduce chamber-related animal distress.

The dorsal skinfold chamber is one of the most important in vivo models for repetitive longitudinal assessment of microcirculation and inflammation. This study aimed to refine this model by introducing a new lightweight chamber made from polyetheretherketone (PEEK). Body weight, burrowing activity, distress, faecal corticosterone metabolites and the tilting angle of the chambers were analysed in mice carrying either a standard titanium chamber or a PEEK chamber. Data was obtained before chamber preparation and over a postoperative period of three weeks. In the early postoperative phase, reduced body weight and increased faecal corticosterone metabolites were found in mice with titanium chambers. Chamber tilting and tilting-related complications were reduced in mice with PEEK chambers. The distress score was significantly increased in both groups after chamber preparation, but only returned to preoperative values in mice with PEEK chambers. In summary, we have shown that light chambers reduce animal distress and may extend the maximum dorsal skinfold chamber observation time. Chambers made of PEEK are particularly suitable for this purpose: They are autoclavable, sufficiently stable to withstand rodent bites, inexpensive, and widely available through 3D printing.

Preclinical Head and Neck Squamous Cell Carcinoma Models for Combined Targeted Therapy Approaches.

This study aimed to refine combined targeted approaches on well-characterized, low-passage tumor models. Upon in vivo xenografting in immunodeficient mice, three cell lines from locally advanced or metastatic HNSCC were established. Following quality control and basic characterization, drug response was examined after therapy with 5-FU, Cisplatin, and cyclin-dependent kinase inhibitors (abemaciclib, THZ1). Our cell lines showed different in vitro growth kinetics, morphology, invasive potential, and radiosensitivity. All cell lines were sensitive to 5-FU, Cisplatin, and THZ1. One cell line (HNSCC48 P0 M1) was sensitive to abemaciclib. Here, Cyto-FISH revealed a partial CDKN2a deletion, which resulted from a R58* mutation. Moreover, this cell line demonstrated chromosome 12 polysomy, accompanied by an increase in CDK4-specific copy numbers. In HNSCC16 P1 M1, we likewise identified polysomy-associated CDK4-gains. Although not sensitive to abemaciclib per se, the cell line showed a G1-arrest, an increased number of acidic organelles, and a swollen structure. Notably, intrinsic resistance was conquered by Cisplatin because of cMYC and IDO-1 downregulation. Additionally, this Cisplatin-CDKI combination induced HLA-ABC and PD-L1 upregulation, which may enhance immunogenicity. Performing functional and molecular analysis on patient-individual HNSCC-models, we identified CDK4-gains as a biomarker for abemaciclib response prediction and describe an approach to conquer intrinsic CDKI resistance.

Magnetically Controlled Growing Rods Graduation: Deformity Control with High Complication Rate.

STUDY DESIGN: A multicenter retrospective review of consecutive series of patients. OBJECTIVE: Long-term experience with using the magnetically controlled growing rods (MCGR) to treat patients with deformity in the growing spine to the conclusion of treatment with posterior spine fusion. SUMMARY OF BACKGROUND DATA: MCGR treatment for growing spine gained popularity with paucity of long-term follow up data. We hypothesized that final fusion might be more effective in bringing additional correction of the spine deformity after treatment with MCGR than that reported after traditional growing rods (TGR) due to less scarring and auto-fusion. METHODS: Retrospective review of 47 patients with varied etiology, treated between 2011 and 2017 which graduated treatment were followed in five academic medical centers for average of 50 months (range, 10-88). RESULTS: The initial mean coronal deformity of 69.6° (95% CI 65-74) was corrected to 40° (95% CI 36-40) immediately after the MCGR implantation but progressed to 52.8° (95% CI 46-59) prior to the final surgery (P < 0.01). Nevertheless, thoracic spine growth (T1-T12 height) improved from 187.3 mm (95% CI 179-195) following index surgery to 208.9 mm (95% CI 199-218) prior to final fusion (P < 0.01). Significant correction and spinal length were obtained at final fusion, but metallosis was a frequent observation (47%, 22/47). The average growth rate was 0.5 mm/month (95% CI 0.3-0.6). The overall complication rate within our cohort was 66% (31/47) with 45% (21/47) of unplanned returns to the operating theater. 32% (15/47) of the patients had an implant related complication. Unplanned surgery was highly correlated with thoracic kyphosis greater than 40° (OR 5.42 95% CI 1.3-23). CONCLUSION: Treatment of growing spine deformities with MCGR provides adequate control of spine deformity it is comparable to previously published data about TGR. The overall high complications rate over time and specifically implant related complications.Level of Evidence: 4.

Establishment and characterization of patient-derived head and neck cancer models from surgical specimens and endoscopic biopsies.

BACKGROUND: Head and neck squamous cell carcinoma (HNSCC) is heterogeneous in etiology, phenotype and biology. Patient-derived xenografts (PDX) maintain morphology and molecular profiling of the original tumors and have become a standard "Avatar" model for human cancer research. However, restricted availability of tumor samples hindered the widespread use of PDX. Most PDX-projects include only surgical specimens because reliable engraftment from biopsies is missing. Therefore, sample collection is limited and excludes recurrent and metastatic, non-resectable cancer from preclinical models as well as future personalized medicine. METHODS: This study compares the PDX-take rate, -growth, histopathology, and molecular characteristics of endoscopic specimens with surgical specimens. HNSCC samples (n = 55) were collected ad hoc, fresh frozen and implanted into NOD.Cg-PrkdcscidIl2rgtm1Wjl/SzJ mice. RESULTS: Engraftment was successful in both sample types. However, engraftment rate was lower (21 vs. 52%) and growth delayed (11.2 vs. 6.7 weeks) for endoscopic biopsies. Following engraftment, growth kinetic was similar. Comparisons of primary tumors and corresponding PDX models confirmed preservation of histomorphology (HE histology) and molecular profile (Illumina Cancer Hotspot Panel) of the patients' tumors. Accompanying flow cytometry on primary tumor specimens revealed a heterogeneous tumor microenvironment among individual cases and identified M2-like macrophages as positive predictors for engraftment. Vice versa, a high PD-L1 expression (combined positive score on tumor/immune cells) predicted PDX rejection. CONCLUSION: Including biopsy samples from locally advanced or metastatic lesions from patients with non-surgical treatment strategies, increases the availability of PDX for basic and translational research. This facilitates (pre-) clinical studies for individual response prediction based on immunological biomarkers.

Experimental Models to Study Skin Wound Healing with a Focus on Angiogenesis.

A large number of models are now available for the investigation of skin wound healing. These can be used to study the processes that take place in a phase-specific manner under both physiological and pathological conditions. Most models focus on wound closure, which is a crucial parameter for wound healing. However, vascular supply plays an equally important role and corresponding models for selective or parallel investigation of microcirculation regeneration and angiogenesis are also described. In this review article, we therefore focus on the different levels of investigation of skin wound healing (in vivo to in virtuo) and the investigation of angiogenesis and its parameters.

Cyclin-dependent kinase inhibitors in head and neck cancer and glioblastoma-backbone or add-on in immune-oncology?

Cyclin-dependent kinases (CDK) control the cell cycle and play a crucial role in oncogenesis. Pharmacologic inhibition of CDK has contributed to the recent clinical approval of dual CDK4/6 inhibitors for the treatment of breast and small cell lung cancer. While the anticancer cell effects of CDK inhibitors are well-established, preclinical and early clinical studies describe additional mechanisms of action such as chemo- and radiosensitization or immune stimulation. The latter offers great potential to incorporate CDK inhibitors in immune-based treatments. However, dosing schedules and accurate timing of each combination partner need to be respected to prevent immune escape and resistance. In this review, we provide a detailed summary of CDK inhibitors in the two solid cancer types head and neck cancer and glioblastoma multiforme; it describes the molecular mechanisms of response vs. resistance and covers strategies to avoid resistance by the combination of immunotherapy or targeted therapy.

Activation of the Kynurenine Pathway in Human Malignancies Can Be Suppressed by the Cyclin-Dependent Kinase Inhibitor Dinaciclib.

Indoleamine 2,3-dioxygenase (IDO) and tryptophan 2,3-dioxygenase (TDO2) are the key enzymes of tryptophan (TRP) metabolism in the kynurenine pathway (KP). Both enzymes function as indicators of immunosuppression and poor survival in cancer patients. Direct or indirect targeting of either of these substances seems thus reasonable to improve therapy options for patients. In this study, glioblastoma multiforme (GBM) as well as head and neck squamous cell carcinomas (HNSCC) were examined because of their different mechanisms of spontaneous and treatment-induced immune escape. Effects on gene expression and protein levels were examined. Accompanying assessment of TRP metabolites from treated GBM cell culture supernatants was conducted. Our results show a heterogeneous and inversely correlated expression profile of TRP-metabolizing genes among GBM and HNSCC cells, with low, but inducible IDO1 expression upon IFNγ treatment. TDO2 expression was higher in GBM cells, while genes encoding kynurenine aminotransferases were mainly confined to HNSCC cells. These data indicate that the KP is active in both entities, with however different enzymes involved in TRP catabolism. Upon treatment with Temozolomide, the standard of care for GBM patients, IDO1 was upregulated. Comparable, although less pronounced effects were seen in HNSCC upon Cetuximab and conventional drugs (i.e., 5-fluorouracil, Gemcitabine). Here, IDO1 and additional genes of the KP (KYAT1, KYAT2, and KMO) were induced. Vice versa, the novel yet experimental cyclin-dependent kinase inhibitor Dinaciclib suppressed KP in both entities. Our comprehensive data imply inhibition of the TRP catabolism by Dinaciclib, while conventional chemotherapeutics tend to activate this pathway. These data point to limitations of conventional therapy and highlight the potential of targeted therapies to interfere with the cells' metabolism more than anticipated.

Intravital Microscopy and Thrombus Induction in the Earlobe of a Hairless Mouse.

Thrombotic complications of vascular diseases are one leading cause of morbidity and mortality in industrial nations. Due to the complex interactions between cellular and non-cellular blood components during thrombus formation, reliable studies of the physiology and pathophysiology of thrombosis can only be performed in vivo. Therefore, this article presents an ear model in hairless mice and focuses on the in vivo analysis of microcirculation, thrombus formation, and thrombus evolution. By using intravital fluorescence microscopy and the intravenous (iv) application of the respective fluorescent dyes, a repetitive analysis of microcirculation in the auricle can easily be performed, without the need for surgical preparation. Furthermore, this model can be adapted for in vivo studies of different issues, including wound healing, reperfusion injury, or angiogenesis. In summary, the ear of hairless mice is an ideal model for the in vivo study of skin microcirculation in physiological or pathophysiological conditions and for the evaluation of its reaction to different systemic or topical treatments.

Differential effects of endogenous, phyto and synthetic cannabinoids on thrombogenesis and platelet activity.

This study analysed the impact of anandamide, cannabidiol (CBD), and WIN55,212-2 on platelet activity and thrombogenesis for the first time. The effects of the cannabinoids on venular thrombosis were studied in the ear of hairless mice. Cannabinoid treatment was performed either once or repetitive by a once-daily administration for three days. To assess the role of cyclooxygenase metabolites in the putative action of anandamide, in vivo studies likewise included a combined administration of anandamide with indomethacin. In vitro, the effect of the cannabinoids on human platelet activation was studied by means of P-selectin expression using flow cytometry. Platelets were analysed under resting or thrombin receptor activating peptide (TRAP)-stimulated conditions, both after cannabinoid treatment alone and after TRAP stimulation and subsequent cannabinoid exposure. Finally, platelet count was assessed after treatment with high concentrations of anandamide. Anandamide, but not CBD and WIN55,212-2, significantly accelerated thrombus growth after one-time treatment as compared to vehicle control. Co-administration with indomethacin neutralized this effect. However, thrombogenesis was not altered by repeated treatment with the cannabinoids. In vitro, anandamide was shown to elicit a concentration-dependent activation of resting human platelets. However, at higher concentrations anandamide reduced the response to TRAP activation associated with a decrease of platelet count. CBD and WIN55,212-2 neither increased nor reduced activation of platelets. Acute exposure to anandamide elicits a cyclooxygenase-dependent prothrombotic effect in vivo. Anandamide seems to affect human platelet activation by a concentration-dependent toxic effect. By contrast, CBD and WIN55,212-2 were not associated with induction of thrombosis or activation of platelets. © 2016 BioFactors, 42(6):581-590, 2016.