Intracranial microcapsule chemotherapy delivery for the localized treatment of rodent metastatic breast adenocarcinoma in the brain.

Metastases represent the most common brain tumors in adults. Surgical resection alone results in 45% recurrence and is usually accompanied by radiation and chemotherapy. Adequate chemotherapy delivery to the CNS is hindered by the blood-brain barrier. Efforts at delivering chemotherapy locally to gliomas have shown modest increases in survival, likely limited by the infiltrative nature of the tumor. Temozolomide (TMZ) is first-line treatment for gliomas and recurrent brain metastases. Doxorubicin (DOX) is used in treating many types of breast cancer, although its use is limited by severe cardiac toxicity. Intracranially implanted DOX and TMZ microcapsules are compared with systemic administration of the same treatments in a rodent model of breast adenocarcinoma brain metastases. Outcomes were animal survival, quantified drug exposure, and distribution of cleaved caspase 3. Intracranial delivery of TMZ and systemic DOX administration prolong survival more than intracranial DOX or systemic TMZ. Intracranial TMZ generates the more robust induction of apoptotic pathways. We postulate that these differences may be explained by distribution profiles of each drug when administered intracranially: TMZ displays a broader distribution profile than DOX. These microcapsule devices provide a safe, reliable vehicle for intracranial chemotherapy delivery and have the capacity to be efficacious and superior to systemic delivery of chemotherapy. Future work should include strategies to improve the distribution profile. These findings also have broader implications in localized drug delivery to all tissue, because the efficacy of a drug will always be limited by its ability to diffuse into surrounding tissue past its delivery source.

Etiology and management of hyponatremia in neurosurgical patients.

Hyponatremia is the most common electrolyte disorder encountered in neurosurgical patients. The aggressive treatment of hyponatremia in this group is critical, as hyponatremia can lead to mental status changes, seizures, vasospasm, cerebral edema, and even death. When it occurs, it represents a failure of one of several homeostatic mechanisms that tightly regulate serum sodium. In these patients, hyponatremia is most commonly due to the syndrome of inappropriate antidiuretic hormone (SIADH) or cerebral salt wasting (CSW). It can be problematic to differentiate between these 2 as they share key features, including low serum sodium, low serum osmolality, a higher urine osmolality than serum osmolality, and an elevated urinary sodium concentration. Furthermore, distinctions between CSW and SIADH, namely extracellular fluid (ECF) volume and total sodium balance, are often difficult to establish. Syndrome of inappropriate antidiuretic hormone is characterized by a volume-expanded state, whereas CSW is characterized by a volume-contracted state. Determining the exact cause remains a clinical imperative as the treatment for each is different. The rate at which serum sodium is corrected must be attended to, as rapid shifts in serum sodium pose potential risk of cerebral pontine myelinolysis.

Role of pre- and intraoperative imaging and neuronavigation in neurosurgery.

Advances in neuroimaging acquisition, computing and image processing have enabled neurosurgeons to use radiological imaging to guide both preoperative planning and intraoperative guidance. In preoperative planning, imaging may be used to evaluate surgical risks, choose the best method of intervention and select the safest surgical approach. Neuronavigation may be useful in designing the surgical flap and alerting the surgeon of surrounding anatomy. Finally, intraoperative imaging may be used to define brain shift associated with the resection of intracranial lesions, assist in more complete lesion resection, and monitor for certain intraoperative complications. In the following review, we briefly examine the history of neuroradiology for neurosurgery, neuronavigation and intraoperative imaging and trace their advances to current systems in use. We will also highlight new experimental applications of neuroimaging that are currently being refined.

Inflammation in stroke and focal cerebral ischemia.

BACKGROUND: A growing number of recent investigations have established a critical role for leukocytes in propagating tissue damage after ischemia and reperfusion in stroke. Experimental data obtained from animal models of middle cerebral artery occlusion implicate inflammatory cell adhesion molecules, chemokines, and cytokines in the pathogenesis of this ischemic damage. METHODS: Data from recent animal and human studies were reviewed to demonstrate that inflammatory events occurring at the blood-endothelium interface of the cerebral capillaries underlie the resultant ischemic tissue damage. RESULTS: After arterial occlusion, the up-regulated expression of cytokines including IL-1, and IL-6 act upon the vascular endothelium to increase the expression of intercellular adhesion molecule-1, P-selectin, and E-selectin, which promote leukocyte adherence and accumulation. Integrins then serve to structurally modify the basal lamina and extracellular matrix. These inflammatory signals then promote leukocyte transmigration across the endothelium and mediate inflammatory cascades leading to further cerebral infarction. CONCLUSIONS: Inflammatory interactions that occur at the blood-endothelium interface, involving cytokines, adhesion molecules, chemokines and leukocytes, are critical to the pathogenesis of tissue damage in cerebral infarction. Exploring these pathophysiological mechanisms underlying ischemic tissue damage may direct rational drug design in the therapeutic treatment of stroke.

Pharmacogenomics-based RNA interference nanodelivery: focus on solid malignant tumors.

INTRODUCTION: RNA interference represents one of the most promising strategies in fighting disease. However, small RNA interference faces substantial challenges for in vivo application due to the inherent instability of the RNA interference molecule. Among the nonviral gene delivery carriers, nanoparticles have attracted interest due to their success in various model systems. Nanomaterials have unique properties compared to conventional bulk materials that may be applicable in this setting. The nanoparticle complex carrying small interference RNA can undergo surface modification to achieve targeted modification for tissue-specific delivery. However, toxicity issues of the delivery systems need to be addressed and they require a pharmacogenomic profile of their own. AREAS COVERED: The authors review pharmacogenomics, toxicogenomics, nanoparticle-based drug delivery, and small interference RNA, with a focus on how logically engineered nanoparticle delivery systems can be used for personalized medicine in malignant tumors. EXPERT OPINION: Pharmacogenomics may be helpful in addressing possible individualized drug response for both the gene silencing capability of the delivered siRNA and the nanoparticle drug delivery system as both complete and distinct units. This may be done by assessing variations in gene expressions and single nucleotide polymorphisms. Patient profiling may be key as patient noncompliance due to toxicity plays a major role in treatment failure.

Intracranial microcapsule drug delivery device for the treatment of an experimental gliosarcoma model.

Controlled-release drug delivery systems are capable of treating debilitating diseases, including cancer. Brain cancer, in particular glioblastoma multiforme (GBM), is an extremely invasive cancer with a dismal prognosis. The use of drugs capable of crossing the blood-brain barrier has shown modest prolongation in patient survival, but not without unsatisfactory systemic, dose-limiting toxicity. Among the reasons for this improvement include a better understanding of the challenges of delivery of effective agents directly to the brain tumor site. The combination of carmustine delivered by biodegradable polyanhydride wafers (Gliadel(®)), with the systemic alkylating agent, temozolomide, allows much higher effective doses of the drug while minimizing the systemic toxicity. We have previously shown that locally delivering these two drugs leads to further improvement in survival in experimental models. We postulated that microcapsule devices capable of releasing temozolomide would increase the therapeutic capability of this approach. A biocompatible drug delivery microcapsule device for the intracranial delivery of temozolomide is described. Drug release profiles from these microcapsules can be modulated based on the physical chemistry of the drug and the dimensions of the release orifices in these devices. The drug released from the microcapsules in these experiments was the clinically utilized chemotherapeutic agent, temozolomide. In vitro studies were performed in order to test the function, reliability, and drug release kinetics of the devices. The efficacy of the temozolomide-filled microcapsules was tested in an intracranial experimental rodent gliosarcoma model. Immunohistochemical analysis of tissue for evidence of DNA strand breaks via terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay was performed. The experimental release curves showed mass flow rates of 36 µg/h for single-orifice devices and an 88 µg/h mass flow rate for multiple-orifice devices loaded with temozolomide. In vivo efficacy results showed that localized intracranial delivery of temozolomide from microcapsule devices was capable of prolonging animal survival and may offer a novel form of treatment for brain tumors.