mTORC1 Inhibitor Rapamycin Inhibits Growth of Cerebral Cavernous Malformation in Adult Mice.

BACKGROUND: Cerebral cavernous malformations (CCMs) are vascular malformations that frequently cause stroke. CCMs arise due to loss of function in one of the genes that encode the CCM complex, a negative regulator of MEKK3-KLF2/4 signaling in vascular endothelial cells. Gain-of-function mutations in PIK3CA (encoding the enzymatic subunit of the PI3K (phosphoinositide 3-kinase) pathway associated with cell growth) synergize with CCM gene loss-of-function to generate rapidly growing lesions. METHODS: We recently developed a model of CCM formation that closely reproduces key events in human CCM formation through inducible CCM loss-of-function and PIK3CA gain-of-function in mature mice. In the present study, we use this model to test the ability of rapamycin, a clinically approved inhibitor of the PI3K effector mTORC1, to treat rapidly growing CCMs. RESULTS: We show that both intraperitoneal and oral administration of rapamycin arrests CCM growth, reduces perilesional iron deposition, and improves vascular perfusion within CCMs. CONCLUSIONS: Our findings further establish this adult CCM model as a valuable preclinical model and support clinical testing of rapamycin to treat rapidly growing human CCMs.

PIK3CA and CCM mutations fuel cavernomas through a cancer-like mechanism.

Vascular malformations are thought to be monogenic disorders that result in dysregulated growth of blood vessels. In the brain, cerebral cavernous malformations (CCMs) arise owing to inactivation of the endothelial CCM protein complex, which is required to dampen the activity of the kinase MEKK31-4. Environmental factors can explain differences in the natural history of CCMs between individuals5, but why single CCMs often exhibit sudden, rapid growth, culminating in strokes or seizures, is unknown. Here we show that growth of CCMs requires increased signalling through the phosphatidylinositol-3-kinase (PI3K)-mTOR pathway as well as loss of function of the CCM complex. We identify somatic gain-of-function mutations in PIK3CA and loss-of-function mutations in the CCM complex in the same cells in a majority of human CCMs. Using mouse models, we show that growth of CCMs requires both PI3K gain of function and CCM loss of function in endothelial cells, and that both CCM loss of function and increased expression of the transcription factor KLF4 (a downstream effector of MEKK3) augment mTOR signalling in endothelial cells. Consistent with these findings, the mTORC1 inhibitor rapamycin effectively blocks the formation of CCMs in mouse models. We establish a three-hit mechanism analogous to cancer, in which aggressive vascular malformations arise through the loss of vascular 'suppressor genes' that constrain vessel growth and gain of a vascular 'oncogene' that stimulates excess vessel growth. These findings suggest that aggressive CCMs could be treated using clinically approved mTORC1 inhibitors.

Penetrating Spinal Column Injuries (pSI): An Institutional Experience with 100 Consecutive Cases in an Urban Trauma Center.

BACKGROUND: Gunshot wound (GSW) injuries are among the leading causes of penetrating spinal column injury (pSI). Patients with pSI often have concurrent polytrauma that complicates management. METHODS: We retrospectively reviewed charts between January 2012 to June 2018 at an urban Level 1 trauma center and analyzed bracing and surgical indications, antibiotic and magnetic resonance imaging (MRI) use, and patient outcomes. RESULTS: We identified 100 patients with pSI with an average age of 27.2 (range, 15-58) years. Five patients had knife injuries and 95 suffered GSW. Polytrauma occurred in 90% of patients with an average of 3.39 bullets per patient (range, 1-23). Fourteen patients underwent either decompressive surgery (n = 8) or decompression and fusion (n = 6). Thirty-five patients were externally braced. A total of 43% of patients presented as American Spinal Injury Association-A compared with 26% who were intact. Although 14 patients received prophylactic antibiotics for retained bullets or durotomies, only 2 patients had postoperative wound infections and 4 had extraspinal infections from retained bullets. All inpatient mortalities (n = 5) were patients with cervical pSI. Thirteen patients with GSW obtained MRI scans without complications. Among our cohort, only 65 patients had follow-up with a median follow-up period of 1.25 (range, 1-60) months. CONCLUSIONS: Management of pSI in urban trauma centers is complex, as these victims routinely have polytrauma that takes precedence. Indications for surgical intervention are narrow and secondary to surgery for polytrauma. External bracing may be overutilized. The efficacy of prophylactic antibiotics remains unclear. MRI can contribute valuable information but is limited by uncertainty regarding bullet compatibility. Lack of follow-up limits the study of this population.

Novel Treatment of Cerebral Vasospasm Using Solitaire Stent Retriever-Assisted Angioplasty: Case Series.

BACKGROUND: Endovascular procedures such as intraarterial (IA) vasodilator injection and balloon angioplasty are used to treat medically refractory cerebral vasospasm. The effects of IA therapy may be short lived and thus require multiple treatments. Balloon angioplasty also has limitations including transient occlusion of the spastic blood vessel, possible endothelial injury, and limited access to proximal vessels. We aim to demonstrate a novel technique using a stent retriever for the management of medically refractory vasospasm, especially in distal vessels. Compared with balloon angioplasty, stent retrievers provide a passive, self-limiting expansion of blood vessels. Other benefits over balloon angioplasty include 1) ability to simultaneously inject IA vasodilators, 2) limited contact and damage to vessel wall, 3) nonocclusive expansion, and 4) technical ease. METHODS: Fourteen blood vessels from 6 patients with symptomatic vasospasm after subarachnoid hemorrhage were identified. We injected 5 mg of IA vasodilator medication into the vasospastic segments without radiographic improvement in vessel diameter and blood flow. The stent retriever was deployed for 2-5 minutes in each vasospastic segment. RESULTS: Distal anterior and posterior circulation segments were easily accessible with the stent retriever system. It resulted in improved vessel diameter and blood flow with subsequent improvement in neurologic examination. All patients demonstrated radiographic resolution of vasospasm. No procedural-related complications were noted. CONCLUSIONS: We demonstrate the safety and efficacy of a novel technique for the treatment of medically refractory cerebral vasospasm using stent retriever angioplasty in distal vessels. Stent angioplasty can be used as an additional tool in the management of subarachnoid hemorrhage-induced cerebral vasospasm.

Laparoscopy assisted ventriculoperitoneal shunt placement in children.

BACKGROUND: Placement of ventriculoperitoneal shunts (VPS) can be challenging in children with previous VPS, previous abdominal surgery, or complex abdominal pathology. Laparoscopy can help identify intra-abdominal adhesions and determine the optimal site for insertion of the distal VPS catheter. We analyzed the feasibility and safety of laparoscopy assisted VPS placement (lapVPS) in children. METHODS: A retrospective review from January/2015 to December/2018 was performed. Laparoscopy was performed via a 5 mm trans-umbilical port. Once the optimal entry site was identified, the distal end of the VPS was inserted by Seldinger technique under direct laparoscopic guidance. RESULTS: One hundred ten lapVPS procedures were reviewed. Median age was 1 (IQR 0.3-9.37) year. Fifty-five (50%) patients were <1 year, and 15 (13.6%) were ≤28 days old. The mean age of the neonates was 14.7 (SD 7.6, range 4-28) days, and the mean weight was 3 (SD 0.39, range 2.4-3.7) kg. Thirty-one (28.2%) lapVPS were initial VPS placements, whereas 79 (71.8%) were subsequent VPS placements. Thirty-nine (35.5%) patients had a history of abdominal surgery or complex abdominal pathology. Median operative time was 36 (IQR 28-56) minutes. One hundred seven (97.3%) patients underwent successful lapVPS. Two (1.8%) patients underwent diagnostic laparoscopy, and lapVPS was deemed infeasible due to intraabdominal adhesions. One (0.9%) patient had an intestinal perforation from trocar placement. Three patients developed 5 postoperative complications that required a reoperation. CONCLUSION: Laparoscopy is a valuable tool to assess the suitability of the peritoneal cavity to accommodate a VPS. LapVPS is safe and can be performed in children of all ages. LEVEL OF EVIDENCE: Level IV.

Near-Infrared Optical Contrast of Skull Base Tumors During Endoscopic Endonasal Surgery.

BACKGROUND: Near-infrared (NIR) tumor contrast is achieved through the "second-window ICG" technique, which relies on passive accumulation of high doses of indocyanine green (ICG) in neoplasms via the enhanced permeability and retention effect. OBJECTIVE: To report early results and potential challenges associated with the application of second-window ICG technique in endonasal endoscopic, ventral skull-base surgery, and to determine potential predictors of NIR signal-to-background ratio (SBR) using endoscopic techniques. METHODS: Pituitary adenoma (n = 8), craniopharyngioma (n = 3), and chordoma (n = 4) patients received systemic infusions of ICG (5 mg/kg) approximately 24 h before surgery. Dual-channel endoscopy with visible light and NIR overlay were photodocumented and analyzed post hoc. RESULTS: All tumors (adenoma, craniopharyngioma, chordoma) demonstrated NIR positivity and fluoresced with an average SBR of 3.9 ± 0.8, 4.1 ± 1.7, and 2.1 ± 0.6, respectively. Contrast-enhanced T1 signal intensity proved to be the single best predictor of observed SBR (P = .0003). For pituitary adenomas, the sensitivity, specificity, positive predictive value, and negative predictive value of NIR-guided identification of tumor was 100%, 20%, 71%, and 100%, respectively. CONCLUSION: In this preliminary study of a small set of patients, we demonstrate that second-window ICG can provide NIR optical tumor contrast in 3 types of ventral skull-base tumors. Chordomas demonstrated the weakest NIR signal, suggesting limited utility in those patients. Both nonfunctional and functional pituitary adenomas appear to accumulate ICG, but utility for margin detection for the adenomas is limited by low specificity. Craniopharyngiomas with third ventricular extension appear to be a particularly promising target given the clean brain parenchyma background and strong SBR.

Single-molecule imaging of Hedgehog pathway protein Smoothened in primary cilia reveals binding events regulated by Patched1.

Accumulation of the signaling protein Smoothened (Smo) in the membrane of primary cilia is an essential step in Hedgehog (Hh) signal transduction, yet the molecular mechanisms of Smo movement and localization are poorly understood. Using ultrasensitive single-molecule tracking with high spatial/temporal precision (30 nm/10 ms), we discovered that binding events disrupt the primarily diffusive movement of Smo in cilia at an array of sites near the base. The affinity of Smo for these binding sites was modulated by the Hh pathway activation state. Activation, by either a ligand or genetic loss of the negatively acting Hh receptor Patched-1 (Ptch), reduced the affinity and frequency of Smo binding at the base. Our findings quantify activation-dependent changes in Smo dynamics in cilia and highlight a previously unknown step in Hh pathway activation.

Engineered knottin peptide enables noninvasive optical imaging of intracranial medulloblastoma.

Central nervous system tumors carry grave clinical prognoses due to limited effectiveness of surgical resection, radiation, and chemotherapy. Thus, improved strategies for brain tumor visualization and targeted treatment are critically needed. We demonstrate that mouse cerebellar medulloblastoma (MB) can be targeted and illuminated with a fluorescent, engineered cystine knot (knottin) peptide that binds with high affinity to αvß3, αvß5, and α5ß1 integrin receptors. This integrin-binding knottin peptide, denoted EETI 2.5F, was evaluated as a molecular imaging probe in both orthotopic and genetic models of MB. Following tail vein injection, fluorescence arising from dye-conjugated EETI 2.5F was localized to the tumor compared with the normal surrounding brain tissue, as measured by optical imaging. The imaging signal intensity correlated with tumor volume. Due to its unique ability to bind to α5ß1 integrin, EETI 2.5F showed superior in vivo and ex vivo brain tumor imaging contrast compared with other engineered integrin-binding knottin peptides and with c(RGDfK), a well-studied integrin-binding peptidomimetic. Next, EETI 2.5F was fused to an antibody fragment crystallizable (Fc) domain (EETI 2.5F-Fc) to determine if a larger integrin-binding protein could also target intracranial brain tumors. EETI 2.5F-Fc, conjugated to a fluorescent dye, illuminated MB following i.v. injection and was able to distribute throughout the tumor parenchyma. In contrast, brain tumor imaging signals were not detected in mice injected with EETI 2.5F proteins containing a scrambled integrin-binding sequence, demonstrating the importance of target specificity. These results highlight the potential of using EETI 2.5F and EETI 2.5-Fc as targeted molecular probes for brain tumor imaging.