Chronic rejection remains the Achilles heel in vascularized composite allotransplantation. Animal models to specifically study chronic rejection in vascularized composite allotransplantation do not exist so far. However, there are established rat models to study chronic rejection in solid organ transplantation such as allogeneic transplantation between the rat strains Lewis and Fischer344. Thus, we initiated this study to investigate the applicability of hindlimb transplantation between these strains to imitate chronic rejection in vascularized composite allotransplantation and identify potential markers. Allogeneic hindlimb transplantation were performed between Lewis (recipient) and Fischer344 (donor) rats with either constant immunosuppression or a high dose immunosuppressive bolus only in case of acute skin rejections. Histology, immunohistochemistry, microarray and qPCR analysis were used to detect changes in skin and muscle at postoperative day 100. We were able to demonstrate significant intimal proliferation, infiltration of CD68 and CD4 positive cells, up-regulation of inflammatory cytokines and initiation of muscular fibrosis in the chronic rejection group. Microarray analysis and subsequent qPCR identified CXC ligands 9–11 as potential markers of chronic rejection. The Fischer344 to Lewis hindlimb transplantation model may represent a new option to study chronic rejection in vascularized composite allotransplantation in an experimental setting. CXC ligands 9–11 deserve further research to investigate their role as chronic rejection markers.

Background: Sarculator and Memorial Sloan Kettering Cancer Center (MSKCC) nomograms are freely available risk prediction scores for surgically treated patients with primary sarcomas. Due to the rarity of angiosarcomas, these scores have only been tested on small cohorts of angiosarcoma patients. In neither the original patient cohort upon which the Sarculator is based nor in subsequent studies was a distinction made between primary and secondary angiosarcomas, as the app is intended to be applied to primary sarcomas. Therefore, the objective of our investigation was to assess whether the Sarculator reveals a difference in prognosis and whether such differentiation aligns with actual clinical data. Patients and Methods: Thirty-one patients with primary or secondary soft tissue angiosarcoma, treated at our Sarcoma Center from 2001 to 2023, were included in the study. Actual survival rates were compared with nomogram-derived data for predicted 5-year survival (Sarculator), as well as 4-, 8- and 12-year sarcoma-specific death probabilities (MSKCC). Harrell’s c-index was utilized to assess predictive validity. Results: In total, 31 patients were analyzed. The actual overall 5-year survival was 22.57% with a predicted 5-year survival rate of 25.97%, and the concordance index was 0.726 for the entire cohort. The concordance index results from MSKCC for angiosarcoma patients were below 0.7 indicating limited predictive accuracy in this cohort, particularly when compared to Sarculator. Summary: Nomogram-based predictive models are valuable tools in clinical practice for rapidly assessing prognosis. They can streamline the decision-making process for adjuvant treatments and improve patient counselling especially in the treatment of rare and complicated tumor entities such as angiosarcomas.

Background: Angiosarcomas (ASs) are a heterogeneous subtype of soft tissue sarcomas. They can be subdivided into primary and secondary AS, with secondary AS being predominant, particularly those following radiotherapy. The aim of this study was first to analyze our patient cohort on a descriptive level and then to identify possible risk factors with regard to one and 5‐year survival using logistic regression. Methods: The study was designed as a retrospective, single‐center cohort study. All patients with histologically confirmed AS over 18 years of age were included in the study. Binary logistic regression was used for univariate analysis screening of continuous or dichotomous variables, respectively. For multivariate analysis, binary multivariate logistic regression was performed to assess independent associations between chosen variables and AS. Results: A total of 39 patients were included in this study. 14 (35.9%) had primary and 25 (64%) had secondary AS. Women were more frequently affected (76.9%) than men (23.1%). The 1‐year survival rate was 87.2%, and the 5‐year survival rate was 51.3%. In the logistic regression analyses, nicotine consumption and a history of carcinoma were identified as significant factors influencing the 1‐year survival rate. For the 5‐year survival rate, only breast cancer was found to be a significant influencing factor in the univariate analysis. Based on univariate logistic regression, all variables with a p value of < 0.1 were chosen to be included into multivariate analysis. The multivariate analysis showed diabetes mellitus ( p = 0.067) with an association to influence the 5‐year survival rate. Conclusions: We were able to show that the proportion of secondary ASs is predominant. These occur after radiation treatment of the breast. Diabetes mellitus may be associated with reduced 5‐year survival, although this finding did not reach statistical significance and requires further investigation. Due to its small sample size, this study should be regarded more as hypothesis‐generating.

Fibrosarcomas represent a rare but highly aggressive tumor entity among soft tissue tumors. Due to its rarity, questions regarding its development and pathophysiology remain unclear. The chorioallantoic membrane (CAM) assay represents an easily available method to investigate tumors on a growth membrane, live and in ovo. The following study was established to test whether the growth of fibrosarcoma spheroids on the CAM was possible and to critically review their applicability for downstream investigations. The shells of fertilized chicken eggs were opened and the previously prepared HT1080 cell spheroids (50,000, 75,000, and 100,000 cells per spheroid) were applied to the CAM. After 7 days, tumors were examined for size, weight, and vascularization. After 7 days, 80 of 163 chicken eggs showed sufficient tumor growth. Of these 80 eggs with confirmed tumor growth, 32 (40%) were from the 50,000 spheroid group, 18 (22.5%) were from the 75,000 spheroid group, and 30 (37.5%) were from the 100,000 spheroid group. The 100,000-cell spheroid group exhibited the highest weights, with a mean of 110.7 mg, as well as tumor size expansion. This cell number also showed the highest vascularization rates. Tumor growth of fibrosarcoma spheroids could successfully be initiated on the CAM. Consequently, the CAM assay presents a good base for future studies involving human fibrosarcoma cell spheroids.

Posttraumatic lymphedema is a frequent yet underrecognized complication of severe limb trauma and fractures. Although chronic inflammation is known to impair bone repair, it is entirely unknown whether lymphatic dysfunction itself affects skeletal regeneration. To date, no clinical or experimental data exist that directly link lymphedema to impaired bone healing. Using a validated rat model including both male and female animals, tibial bone defects were created with or without concomitant lymphatic vessel disruption. Bone regeneration was assessed by histology (aniline blue), Osteocalcin immunohistochemistry, and high-resolution micro-computed tomography (μCT). Mechanistic analyses included markers of osteoblast differentiation (RUNX2), remodeling-associated signaling (RANKL), endothelial/angiogenesis-associated signaling (PECAM-1), and cellular proliferation (PCNA), and multiplex Luminex-based cytokine and chemokine profiling. Posttraumatic lymphedema significantly impaired bone regeneration, evidenced by reduced osteoid formation, diminished Osteocalcin expression, and lower bone volume fraction on μCT (p = 0.0246). The PTL phenotype was associated with reduced osteoblast differentiation (RUNX2↓, p = 0.0038), reduced RANKL expression, consistent with altered remodeling-associated signaling (p = 0.0002), and decreased PECAM-1 expression (p = 0.0026), while PCNA expression remained unchanged. Luminex analysis revealed a distinct proinflammatory and chemotactic signature characterized by elevated TNF-α, IL-6, IL-12p70, MIP-1α, RANTES, MCP-1, and MIP-2.. This cytokine and chemokine upregulation occurred in both lymphedema groups – regardless of whether a bone defect was present – whereas animals with isolated bone defects showed only minimal inflammatory activation. This study provides experimental evidence that posttraumatic lymphedema is associated with impaired bone regeneration. The PTL phenotype was accompanied by a sustained proinflammatory and chemotactic microenvironment, reduced osteoblast differentiation, altered remodeling-associated signaling, and reduced PECAM-1 expression. These findings identify a previously unrecognized association between posttraumatic lymphatic dysfunction and skeletal repair and provide a basis for further mechanistic investigation.

Introduction: Vascular compromise after free anterolateral thigh (ALT) flap reconstruction is a time‐critical event and may result in total flap loss despite re‐exploration. Although earlier re‐exploration is associated with improved salvage, this relationship is often simplified by arbitrary thresholds, and internally validated prediction models remain scarce. We aimed to quantify this relationship and assess the additional predictive value of systemic factors beyond timing. Methods: This retrospective single‐center cohort study included all free ALT flaps for post‐traumatic extremity reconstruction between 2005 and 2020 that underwent re‐exploration for suspected vascular compromise on postoperative day (POD) 0–4. The primary endpoint was flap salvage at POD 5. Intraoperative findings were compared between salvaged and failed flaps. Univariable logistic regression examined the association between POD and salvage, followed by a multivariable model with prespecified covariates. Restricted cubic splines assessed nonlinearity, and 1000 bootstrap resamples were used to obtain optimism‐corrected estimates of discrimination and calibration. Results: Among 222 ALT flaps, 58 (26.1%) required re‐exploration; 33 (56.9%) were salvaged and 25 (43.1%) failed. Salvage rates were 90.0%, 51.7%, 37.5%, 57.1%, and 50.0% for re‐exploration on POD 0–4, respectively. Arterial and venous compromise were more frequent in failed flaps, without significant differences. Salvage probability crossed the 50% threshold between POD 1 and POD 2. Spline modeling demonstrated significant nonlinearity, with a steeper decline during the first two PODs followed by a relative plateau (LRT p = 0.037). Most systemic variables added little predictive information. Apparent discrimination was moderate (AUC 0.714), and optimism‐corrected performance was modest (AUC 0.622; calibration slope 0.69). Conclusion: Salvage probability declined in a biologically plausible, continuous, and nonlinear manner with increasing POD of re‐exploration, with a steeper decline at earlier time points, although salvage remained possible later. Timing appeared to be the principal determinant of salvage, while systemic variables added limited predictive value.