RESUMEN
Microbubble activation with focused ultrasound (FUS) facilitates the noninvasive and spatially-targeted delivery of systemically administered therapeutics across the blood-brain barrier (BBB). FUS also augments the penetration of nanoscale therapeutics through brain tissue; however, this secondary effect has not been leveraged. Here, 1 MHz FUS sequences that increase the volume of transfected brain tissue after convection-enhanced delivery of gene-vector "brain-penetrating" nanoparticles were first identified. Next, FUS preconditioning is applied prior to trans-BBB nanoparticle delivery, yielding up to a fivefold increase in subsequent transgene expression. Magnetic resonance imaging (MRI) analyses of tissue temperature and Ktrans confirm that augmented transfection occurs through modulation of parenchymal tissue with FUS. FUS preconditioning represents a simple and effective strategy for markedly improving the efficacy of gene vector nanoparticles in the central nervous system.
Asunto(s)
Sistemas de Liberación de Medicamentos/métodos , Nanopartículas/química , Ondas Ultrasónicas , Animales , Barrera Hematoencefálica/diagnóstico por imagen , Barrera Hematoencefálica/metabolismo , Sistema Nervioso Central/diagnóstico por imagen , Sistema Nervioso Central/metabolismo , Imagen por Resonancia Magnética , Microburbujas , TemperaturaRESUMEN
Background: Focused ultrasound (FUS) activation of microbubbles (MBs) for blood-brain (BBB) and blood-tumor barrier (BTB) opening permits targeted therapeutic delivery. While the effects of FUS+MBs mediated BBB opening have been investigated for normal brain tissue, no such studies exist for intracranial tumors. As this technology advances into clinical immunotherapy trials, it will be crucial to understand how FUS+MBs modulates the tumor immune microenvironment. Methods and Results: Bulk RNA sequencing revealed that FUS+MBs BTB/BBB opening (1 MHz, 0.5 MPa peak-negative pressure) of intracranial B16F1cOVA tumors increases the expression of genes related to proinflammatory cytokine and chemokine signaling, pattern recognition receptor signaling, and antigen processing and presentation. Flow cytometry revealed increased maturation (i.e. CD86) of dendritic cells (DCs) in the meninges and altered antigen loading of DCs in both the tumor and meninges. For DCs in tumor draining lymph nodes, FUS+MBs had no effect on maturation and elicited only a trend towards increased presentation of tumor-derived peptide by MHC. Neither tumor endothelial cell adhesion molecule expression nor homing of activated T cells was affected by FUS+MBs. Conclusion: FUS+MBs-mediated BTB/BBB opening elicits signatures of inflammation; however, the response is mild, transient, and unlikely to elicit a systemic response independent of administration of immune adjuvants.
Asunto(s)
Neoplasias Encefálicas/terapia , Células Dendríticas/metabolismo , Melanoma Experimental/terapia , Ovalbúmina/inmunología , Terapia por Ultrasonido/métodos , Animales , Barrera Hematoencefálica , Neoplasias Encefálicas/genética , Neoplasias Encefálicas/inmunología , Regulación Neoplásica de la Expresión Génica , Masculino , Melanoma Experimental/genética , Melanoma Experimental/inmunología , Ratones , Microburbujas , Análisis de Secuencia de ARN , Microambiente Tumoral , Ensayos Antitumor por Modelo de XenoinjertoRESUMEN
The delivery of systemically administered gene therapies to brain tumors is exceptionally difficult because of the blood-brain barrier (BBB) and blood-tumor barrier (BTB). In addition, the adhesive and nanoporous tumor extracellular matrix hinders therapeutic dispersion. We first developed the use of magnetic resonance image (MRI)-guided focused ultrasound (FUS) and microbubbles as a platform approach for transfecting brain tumors by targeting the delivery of systemically administered "brain-penetrating" nanoparticle (BPN) gene vectors across the BTB/BBB. Next, using an MRI-based transport analysis, we determined that after FUS-mediated BTB/BBB opening, mean interstitial flow velocity magnitude doubled, with "per voxel" flow directions changing by an average of ~70° to 80°. Last, we observed that FUS-mediated BTB/BBB opening increased the dispersion of directly injected BPNs through tumor tissue by >100%. We conclude that FUS-mediated BTB/BBB opening yields markedly augmented interstitial tumor flow that, in turn, plays a critical role in enhancing BPN transport through tumor tissue.
Asunto(s)
Neoplasias Encefálicas , Nanopartículas , Barrera Hematoencefálica , Encéfalo/diagnóstico por imagen , Neoplasias Encefálicas/tratamiento farmacológico , Sistemas de Liberación de Medicamentos/métodos , Humanos , Imagen por Resonancia Magnética/métodos , Microburbujas , TransfecciónRESUMEN
Non-invasive drug and gene delivery to the brain to treat central nervous system pathologies has long been inhibited by the blood-brain barrier. The activation of microbubbles with focused ultrasound has emerged as a promising non-invasive approach to circumvent this obstacle, by transiently disrupting the blood-brain barrier and permitting passage of systemically administered therapeutics into the tissue. Clinical trials are underway to evaluate the safety of this technique; however, concerns remain regarding the potential for the treatment to induce sterile inflammation or petechiae. In this issue of Theranostics, Jones et al.[1] address these concerns through the development of an advanced three-dimensional imaging system for monitoring acoustic emissions from oscillating microbubbles. When subharmonic emissions are detected with this system, focused ultrasound pressure is reduced by 50% for the remainder of the treatment. This serves to transiently open the blood-brain barrier without generating adverse effects. While the ideal configuration of the transducer array for treatment and monitoring still presents an area for further optimization, the approach indicates that the acoustic signature of microbubble behavior within the skull can be used to ensure safe and effective blood-brain barrier opening using focused ultrasound.
Asunto(s)
Barrera Hematoencefálica , Microburbujas , Encéfalo , Imagenología Tridimensional , UltrasonografíaRESUMEN
Immunotherapy is rapidly emerging as the cornerstone for the treatment of several forms of metastatic cancer, as well as for a host of other pathologies. Meanwhile, several new high-profile studies have uncovered remarkable linkages between the central nervous and immune systems. With these recent developments, harnessing the immune system for the treatment of brain pathologies is a promising strategy. Here, we contend that MR image-guided focused ultrasound (FUS) represents a noninvasive approach that will allow for favorable therapeutic immunomodulation in the setting of the central nervous system. One obstacle to effective immunotherapeutic drug delivery to the brain is the blood brain barrier (BBB), which refers to the specialized structure of brain capillaries that prevents transport of most therapeutics from the blood into brain tissue. When applied in the presence of circulating microbubbles, FUS can safely and transiently open the BBB to facilitate the delivery of immunotherapeutic agents into the brain parenchyma. Furthermore, it has been demonstrated that physical perturbations of the tissue microenvironment via FUS can modulate immune response in both normal and diseased tissue. In this review article, we provide an overview of FUS energy regimens and corresponding tissue bioeffects, followed by a review of the literature pertaining to FUS for therapeutic antibody delivery in normal brain and preclinical models of brain disease. We provide an overview of studies that demonstrate FUS-mediated immune modulation in both the brain and peripheral settings. Finally, we provide remarks on challenges facing FUS immunotherapy and opportunities for future expansion in this area.