Demeclocycline as a contrast agent for detecting brain neoplasms using confocal microscopy

Terahertz dielectric spectroscopy and solid immersion microscopy of ex vivo glioma model 101.8: brain tissue heterogeneity

Terahertz (THz) technology holds strong potential for the intraoperative label-free diagnosis of brain gliomas, aimed at ensuring their gross-total resection. Nevertheless, it is still far from clinical applications due to the limited knowledge about the THz-wave-brain tissue interactions. In this work, rat glioma model 101.8 was studied ex vivo using both the THz pulsed spectroscopy and the 0.15λ-resolution THz solid immersion microscopy (λ is a free-space wavelength). The considered homograft model mimics glioblastoma, possesses heterogeneous character, unclear margins, and microvascularity. Using the THz spectroscopy, effective THz optical properties of brain tissues were studied, as averaged within the diffraction-limited beam spot. Thus measured THz optical properties revealed a persistent difference between intact tissues and a tumor, along with fluctuations of the tissue response over the rat brain. The observed THz microscopic images showed heterogeneous character of brain tissues at the scale posed by the THz wavelengths, which is due to the distinct response of white and gray matters, the presence of different neurovascular structures, as well as due to the necrotic debris and hemorrhage in a tumor. Such heterogeneities might significantly complicate delineation of tumor margins during the intraoperative THz neurodiagnosis. The presented results for the first time pose the problem of studying the inhomogeneity of brain tissues that causes scattering of THz waves, as well as the urgent need to use the radiation transfer theory for describing the THz-wave - tissue interactions.

Confocal Laser Microscopy in Neurosurgery: State of the Art of Actual Clinical Applications

Achievement of complete resections is of utmost importance in brain tumor surgery, due to the established correlation among extent of resection and postoperative survival. Various tools have recently been included in current clinical practice aiming to more complete resections, such as neuronavigation and fluorescent-aided techniques, histopathological analysis still remains the gold-standard for diagnosis, with frozen section as the most used, rapid and precise intraoperative histopathological method that permits an intraoperative differential diagnosis. Unfortunately, due to the various limitations linked to this technique, it is still unsatisfactorily for obtaining real-time intraoperative diagnosis. Confocal laser technology has been recently suggested as a promising method to obtain near real-time intraoperative histological data in neurosurgery, due to its established use in other non-neurosurgical fields. Still far to be widely implemented in current neurosurgical clinical practice, this technology was initially studied in preclinical experiences confirming its utility in identifying brain tumors, microvasculature and tumor margins. Hence, ex vivo and in vivo clinical studies evaluated the possibility with this technology of identifying and classifying brain neoplasms, discerning between normal and pathologic tissue, showing very promising results. This systematic review has the main objective of presenting a state-of-the-art summary on actual clinical applications of confocal laser imaging in neurosurgical practice.

Demeclocycline Reduces the Growth of Human Brain Tumor-Initiating Cells: Direct Activity and Through Monocytes

Myeloid cells that infiltrate into brain tumors are deactivated or exploited by the tumor cells. We previously demonstrated that compromised microglia, monocytes, and macrophages in malignant gliomas could be reactivated by amphotericin-B to contain the growth of brain tumorinitiating cells (BTICs). We identified meclocycline as another activator of microglia, so we sought to test whether its better-tolerated derivative, demeclocycline, also stimulates monocytes to restrict BTIC growth. Monocytes were selected for study as they would be exposed to demeclocycline in the circulation prior to entry into brain tumors to become macrophages. We found that demeclocycline increased the activity of monocytes in culture, as determined by tumor necrosis factor-α production and chemotactic capacity. The conditioned medium of demeclocycline-stimulated monocytes attenuated the growth of BTICs generated from human glioblastoma resections, as evaluated using neurosphere and alamarBlue assays, and cell counts. Demeclocycline also had direct effects in reducing BTIC growth. A global gene expression screen identified several genes, such as DNA damage inducible transcript 4, frizzled class receptor 5 and reactive oxygen species modulator 1, as potential regulators of demeclocycline-mediated BTIC growth reduction. Amongst several tetracycline derivatives, only demeclocycline directly reduced BTIC growth. In summary, we have identified demeclocycline as a novel inhibitor of the growth of BTICs, through direct effect and through indirect stimulation of monocytes. Demeclocycline is a candidate to reactivate compromised immune cells to improve the prognosis of patients with gliomas.

Fluorescence Image-Guided Surgery - a Perspective on Contrast Agent Development

In the past several decades, a number of novel fluorescence image-guided surgery (FGS) contrast agents have been under development, with many in clinical translation and undergoing clinical trials. In this review, we have identified and summarized the contrast agents currently undergoing clinical translation. In total, 39 novel FGS contrast agents are being studied in 85 clinical trials. Four FGS contrast agents are currently being studied in phase III clinical trials and are poised to reach FDA approval within the next two to three years. Among all novel FGS contrast agents, a wide variety of probe types, targeting mechanisms, and fluorescence properties exists. Clinically available FGS imaging systems have been developed for FDA approved FGS contrast agents, and thus further clinical development is required to yield FGS imaging systems tuned for the variety of contrast agents in the clinical pipeline. Additionally, study of current FGS contrast agents for additional disease types and development of anatomy specific contrast agents is required to provide surgeons FGS tools for all surgical specialties and associated comorbidities. The work reviewed here represents a significant effort from many groups and further development of this promising technology will have an enormous impact on surgical outcomes across all specialties.

Multimodal quantitative imaging of brain cancer in cultured cells

Fluorescence emission, polarization and subcellular localization of methylene blue (MB) were studied in four cancerous and two normal human brain cell lines. Fluorescence emission and polarization images were acquired and analyzed. The co-localization of MB with mitochondria, lysosomes and nuclei of the cells was evaluated. Glioblastoma cells exhibited significantly higher MB fluorescence polarization compared to normal astrocytes. Preferential accumulation of MB in mitochondria of glioblastoma cells may explain higher fluorescence polarization values in cancer cells as compared to normal. These findings may lead to the development of a quantitative method for the detection of brain cancer in single cells.

Confocal scanning microscopy provides rapid, detailed intraoperative histological assessment of brain neoplasms: Experience with 106 cases

OBJECTIVES

Frozen section histological analysis is currently the mainstay for intraprocedural tissue diagnosis during the resection of intracranial neoplasms and for evaluating tumor margins. However, frozen sections are time-consuming and often do not reveal the histological features needed for final diagnosis when compared with permanent sections. Confocal scanning microscopy (CSM) with certain stains may be a valuable technology that can add rapid and detailed histological assessment advantage for the neurosurgical operating room. This study describes potential advantages of CSM imaging of fresh human brain tumor tissues labeled with acriflavine (AF), acridine orange (AO), cresyl violet (CV), methylene blue (MB), and indocyanine green (ICG) within the neurosurgical operating room facility.

PATIENTS AND METHODS

Acute slices from orthotopic human intracranial neoplasms were incubated with AF/AO and CV solutions for 10 s and 1 min respectively. Staining was also attempted with MB and ICG. Samples were imaged using a bench-top CSM system. Histopathologic features of corresponding CSM and permanent hematoxylin and eosin images were reviewed for each case.

RESULTS

Of 106 cases, 30 were meningiomas, 19 gliomas, 13 pituitary adenomas, 9 metastases, 6 schwannomas, 4 ependymomas, and 25 other pathologies. CSM using rapid fluorophores (AF, AO, CV) revealed striking microvascular, cellular and subcellular structures that correlated with conventional histology. By rapidly staining and optically sectioning freshly resected tissue, images were generated for intraoperative consultations in less than one minute. With this technique, an entire resected tissue sample was imaged and digitally stored for tele-pathology and archiving.

CONCLUSION

CSM of fresh human brain tumor tissue provides clinically meaningful and rapid histopathological assessment much faster than frozen section. With appropriate stains, including specific cellular structure or antibody staining, CSM could improve the timeliness of intraoperative decision-making, and the neurosurgical-pathology workflow during resection of human brain tumors, ultimately improving patient care.

Oncologic Procedures Amenable to Fluorescence-guided Surgery

OBJECTIVE

Although fluorescence imaging is being applied to a wide range of cancers, it remains unclear which disease populations will benefit greatest. Therefore, we review the potential of this technology to improve outcomes in surgical oncology with attention to the various surgical procedures while exploring trial endpoints that may be optimal for each tumor type.

BACKGROUND

For many tumors, primary treatment is surgical resection with negative margins, which corresponds to improved survival and a reduction in subsequent adjuvant therapies. Despite unfavorable effect on patient outcomes, margin positivity rate has not changed significantly over the years. Thus, patients often experience high rates of re-excision, radical resections, and overtreatment. However, fluorescence-guided surgery (FGS) has brought forth new light by allowing detection of subclinical disease not readily visible with the naked eye.

METHODS

We performed a systematic review of clinicatrials.gov using search terms "fluorescence," "image-guided surgery," and "near-infrared imaging" to identify trials utilizing FGS for those received on or before May 2016.

INCLUSION CRITERIA

fluorescence surgery for tumor debulking, wide local excision, whole-organ resection, and peritoneal metastases.

EXCLUSION CRITERIA

fluorescence in situ hybridization, fluorescence imaging for lymph node mapping, nonmalignant lesions, nonsurgical purposes, or image guidance without fluorescence.

RESULTS

Initial search produced 844 entries, which was narrowed down to 68 trials. Review of literature and clinical trials identified 3 primary resection methods for utilizing FGS: (1) debulking, (2) wide local excision, and (3) whole organ excision.

CONCLUSIONS

The use of FGS as a surgical guide enhancement has the potential to improve survival and quality of life outcomes for patients. And, as the number of clinical trials rise each year, it is apparent that FGS has great potential for a broad range of clinical applications.

Fluorescence depth estimation from wide-field optical imaging data for guiding brain tumor resection: a multi-inclusion phantom study

Studies have shown that fluorescent agents demarcate tumor from surrounding brain tissue and offer intraoperative guidance during resection. However, visualization of fluorescence signal from tumor below the surgical surface or through the appearance of blood in the surgical field is challenging. We have previously described red light imaging techniques for estimating fluorescent depths in turbid media. In this study, we evaluate these methods over a broader range of fluorophore concentrations, and investigate the ability to resolve multiple fluorescent emissions in the same plane or at different depths along the axis of imaging. A tungsten halogen lamp is used as a broadband white light source for reflectance imaging. Fluorescence from Alexa Fluor 647 is excited with a 635 nm diode laser. Reflectance and fluorescence spectral data are gathered between 670 and 720 nm with the use of a liquid crystal tunable filter and recorded on a sCMOS camera. Results show that two fluorescent emissions can be resolved within 2 mm if they are in the same plane or within 3 mm if they are at different depths along the axis of imaging up to 6 mm below the surface.