Vascular analysis as a proxy for mechanostransduction response in an isogenic, irradiated murine model of mandibular distraction osteogenesis

Blood Supply of Early Lung Adenocarcinomas in Mice and the Tumor-supplying Vessel Relationship: A Micro-CT Angiography Study

This study aimed to investigate the blood supply of early lung adenocarcinomas in mice and the relationship between tumors and their supplying vessels by using micro-CT. An early lung adenocarcinoma model was established in 10 female mice with subcutaneous injections of a 1-methyl-3-nitro-1-nitrosoguanidine solution. Micro-CT pulmonary and bronchial arteriography were performed to demonstrate the blood supply of early lung adenocarcinomas, especially the tumor-vessel relationships, and the findings were correlated with the pathology results. The quantitative and texture changes in the tumor-supplying vessels were analyzed. Micro-CT showed that the pulmonary artery was densely distributed in and around tumors in 141 (84%) of 167 early lung adenocarcinomas, the bronchial artery was not related to tumors, and there were four patterns of tumor-pulmonary artery relationships that correlated well with pathologic findings. Quantitative and texture analyses showed that the tumor size had positive correlations with vessel volume (VV), VV fraction (VVF), vessel thickness (VT), vessel number (VN), inverse difference moment, long run emphasis, gray level nonuniformity (GLN), and run length nonuniformity (RLN) and negative correlations with vessel separation (VS), inertia, and short run emphasis (SRE); the size of the solid component had positive correlations with VV, VVF, VT, VN, GLN, and RLN and negative correlations with VS, cluster shade, and SRE. This study concluded that early lung adenocarcinomas are mainly supplied by the pulmonary arteries in mice, and micro-CT angiography can clearly demonstrate the morphologic changes of pulmonary arteries and their relationships with tumors.

Is Distraction Osteogenesis of the Irradiated Craniofacial Skeleton Contraindicated?

BACKGROUND

Craniofacial distraction osteogenesis (DO) is a common treatment modality today. Despite its numerous advantages, however, concerns have been expressed regarding the use of DO in the irradiated setting.

METHODS

A systematic review was performed to identify all published reports of patients who underwent DO of the irradiated craniofacial skeleton. The following parameters were of particular interest: postoperative complications, specifically, insufficient bone formation, fracture, and hardware exposure (intraoral and cutaneous), as well as the need for additional bone grafting.

RESULTS

The initial search retrieved a total of 183 articles of which 20 articles (38 patients) met predetermined inclusion criteria. The most common site of distraction was the mandible (76.3%). The median radiation dose was 50.7 Gy (range, 30-70 Gy). Bone defects ranged from 30 to 80 mm (median, 42.5 mm). Complications were encountered in 19 patients (50%), with insufficient bone formation being most common (9 patients; 23%). The overall incidence of complications was not significantly associated with radiation dosage (P = 0.79). The remaining procedural and demographic variables also failed to meet statistical significance when compared against the overall complication rate (P = 0.27-0.97).

CONCLUSION

The complication rate associated with craniofacial DO of the irradiated skeleton does not appear to be substantially higher than what is reported for DO in the nonirradiated setting. As such, patients should be offered this treatment modality, particularly in light of the fact, that it offers the option to decrease patient morbidity as well as treatment complexity.

Clinical Use of Deferoxamine in Distraction Osteogenesis of Irradiated Bone

The deleterious effects of radiotherapy, including hypovascularity and hypocellularity, have made distraction of irradiated bones challenging. Animal studies, however, have demonstrated adjunctive measures such as the administration of deferoxamine to significantly improve bone regeneration across irradiated distraction gaps. In this report, the authors demonstrate, for the first time, enhanced bone formation following deferoxamine application in a patient following distraction of a previously irradiated maxilla. Computed tomography imaging of the pterygomaxillary buttress on the side of administration revealed significantly increased bone area and density relative to the contralateral buttress. This is the first presentation of clinical deferoxamine use to promote bone formation following irradiated bone distraction and highlights the promise for this adjunctive measure to make outcomes after distraction of irradiated bone more reliable.

Bone marrow stem cells assuage radiation-induced damage in a murine model of distraction osteogenesis: A histomorphometric evaluation

The purpose of this study is to determine if intraoperatively placed bone marrow stem cells (BMSCs) will permit successful osteocyte and mature bone regeneration in an isogenic murine model of distraction osteogenesis (DO) following radiation therapy (XRT). Lewis rats were split into three groups, DO only (Control), XRT followed by DO (xDO) and XRT followed by DO with intraoperatively placed BMSCs (xDO-BMSC). Coronal sections from the distraction site were obtained, stained and analyzed via statistical analysis with analysis of variance (ANOVA) and subsequent Tukey or Games-Howell post-hoc tests. Comparison of the xDO-BMSC and xDO groups demonstrated significantly improved osteocyte count (87.15 ± 10.19 vs. 67.88 ± 15.38, P = 0.00), and empty lacunae number (2.18 ± 0.79 vs 12.34 ± 6.61, P = 0.00). Quantitative analysis revealed a significant decrease in immature osteoid volume relative to total volume (P = 0.00) and improved the ratio of mature woven bone to immature osteoid (P = 0.02) in the xDO-BMSC compared with the xDO group. No significant differences were found between the Control and xDO-BMSC groups. In an isogenic murine model of DO, BMSC therapy assuaged XRT-induced cellular depletion, resulting in a significant improvement in histological and histomorphometric outcomes.

Prophylactic amifostine prevents a pathologic vascular response in a murine model of expander-based breast reconstruction

BACKGROUND

Although expander-based breast reconstruction is the most commonly used method of reconstruction worldwide, it continues to be plagued with complication rates as high as 60% when radiotherapy is implemented. We hypothesized that quantitative measures of radiotherapy-induced vascular injury can be mitigated by utilizing amifostine in a murine model of expander-based breast reconstruction.

METHODS

30 rats were divided into three groups: expander placement (Control), expander placement followed by radiotherapy (XRT), and expander placement followed by radiotherapy with amifostine (AMF/XRT). All groups underwent placement of a sub-latissimus tissue expander. After a 45 day recovery period, all groups underwent vascular perfusion and micro-CT analysis.

RESULTS

Micro-CT analysis was used to calculate vessel volume fraction (VVF), vessel number (VN), and vessel separation (VSp). A significant increase in VN was seen in the XRT group as compared to the Control (p = 0.021) and the AMF/XRT (p = 0.027). There was no difference between Control and AMF/XRT (p = 0.862). VVF was significantly higher in XRT than either Control (p = 0.043) and AMF/XRT (p = 0.040), however no difference was seen between Control and AMF/XRT (p = 0.980). VSp of XRT was smaller when compared to both Control and AMF/XRT specimens (p = 0.05 and p = 0.048, respectively), and no difference was seen between Control and AMF/XRT (p = 0.339).

CONCLUSIONS

Amifostine administered prior to radiotherapy preserved vascular metrics similar to those of non-radiated specimens. Elevated vascularity demonstrated within the XRT group was not seen in either the Control or AMF/XRT groups. These results indicate that amifostine protects soft tissue in our model from a radiotherapy-induced pathologic vascular response.

A Histomorphometric Analysis of Radiation Damage in an Isogenic Murine Model of Distraction Osteogenesis

PURPOSE

The devastation radiation therapy (XRT) causes to endogenous tissue in patients with head and neck cancer can be a prohibitive obstacle in reconstruction of the mandible, demanding a better understanding of XRT-induced damage and options for reconstruction. This study investigated the cellular damage caused by radiation in an isogenic murine model of mandibular distraction osteogenesis (DO). The authors posited that radiation would result in fewer osteocytes, with increased empty lacunae and immature osteoid.

MATERIALS AND METHODS

Twenty Lewis rats were randomly assigned to a DO group (n = 10) or a XRT/DO group (n = 10). These groups underwent an osteotomy and mandibular DO across a 5.1-mm gap. XRT was administered to the XRT/DO group at a fractionated human equivalent dose of 35 Gy before surgery. Animals were sacrificed on postoperative day 40 and mandibles were harvested and sectioned for histologic analysis.

RESULTS

Bone that underwent radiation showed a significantly decreased osteocyte count and complementary increase in empty lacunae compared with non-XRT bone (P = .019 and P = .000). In addition, XRT bone exhibited increased immature osteoid and decreased mature woven bone compared with nonradiated bone (P = .001 and P = .003, respectively). Furthermore, analysis of the ratio of immature osteoid to woven bone volume exhibited a significant increase in the XRT bone, further showing the devastating damage from XRT (P = .001).

CONCLUSION

These results clearly show the cellular diminution that occurs as a result of radiation. This foundational study provides the groundwork on which to investigate cellular therapies in an immuno-privileged model of mandibular DO.