Distinct phases of cryogenic tissue damage in the cerebral cortex of wild-type and c-fos deficient mice

Tumor-Specific Immunoenhancing Effects after Local Cryoablation for Metastatic Bone Tumor in a Mouse Model

We investigated the abscopal effect after cryoablation (CA) on bone metastasis using a mouse model. Breast cancer cells were implanted in the bilateral tibiae of mice. The left tumor was treated locally with CA, and the right abscopal tumor (AT) was left untreated. The mice were divided into four groups based on the combination of CA and intraperitoneal administration of anti-PD-1 antibody (PD) as treatment interventions (Control, CA, PD, and CA + PD). The reduction ratio of the size of AT, the quantitative immune effects at enzyme-linked immunospot (ELISPOT) assay, and the intensity of infiltration of immune-related cells to AT were compared among the groups. CA alone showed a significant immunoenhancing effect on the volume change ratio of AT from day 0 to day 14 (Control-CA: p < 0.05), ELISPOT assay (Control-CA: p < 0.01), and CD4+ cell count in immunostaining (Control-CA: p < 0.05). CA alone showed no significant immunoenhancing effect on CD8+ and Foxp3+ cell counts in immunostaining, but the combination of CA and PD showed a significant immunoenhancing effect (Control-CA + PD: p < 0.01 [CD8, Foxp3]). The results suggested that the abscopal effect associated with the local cryotherapy of metastatic bone tumors was activated by CA and enhanced by its combination with PD.

The First Postlesion Minutes: An In Vivo Study of Extravasation and Perivascular Astrocytes Following Cerebral Lesions in Various Experimental Mouse Models

The immediate alterations following lesions cannot be investigated by using fixed tissues. Here, we employed two-photon microscopy to study the alterations to the permeability of blood-brain barrier and to glio-vascular connections in vivo during the first minutes following cortical lesions in mice. Four models were used: (1) cryogenic lesion, (2) photodisruption using laser pulses, (3) photothrombosis, and (4) bilateral carotid ligation. Sulforhodamine101 was used for supravital labeling of astrocytes and dextran-bound fluorescein isothiocyanate for the assessment of extravasation. Transgenic mice, in which the endothelium and astrocytes expressed a yellow fluorescent protein, were also used. Astrocytic labeling in vivo was verified with postmortem immunostaining against glial fibrillary acidic protein (GFAP). Summary of results: (1) the glio-vascular connections were stable in the intact brain with no sign of spontaneous dynamic attachment/detachment of glial end-feet; (2) only direct vascular damage (photodisruption or cryogenic) resulted in prompt extravasation; (3) even direct damage failed to provoke a prompt astroglial response. In conclusion, the results indicate that a detachment of the astrocytic end-feet does not precede the breakdown of blood-brain barrier following lesions. Whereas vasogenic edema develops immediately after the lesions, this is not the case with cytotoxic edemas. Time-lapse recordings and three-dimensional reconstructions are presented as supplemental materials.

Postmortem immunohistochemical alterations following cerebral lesions: A possible pathohistological importance of the β-dystroglycan immunoreactivity

The frequency of cerebrovascular injuries raises the importance of their immunohistological investigation in postmortem materials. Most injuries involve the impairment of the blood-brain barrier. The barrier is maintained by the glio-vascular connections which break up following injuries. Some immunohistochemical alterations may refer to the impairment of the gliovascular connections. Laminin and the components of the dystroglycan complex show characteristic immunohistochemical alterations following various experimental injuries (stab wound, cryogenic lesion, arterial occlusions): immunoreactivity of β-dystroglycan, α-dystrobrevin and aquaporin 4 disappeared while that of utrophin and laminin appeared along the vessels, whereas α-syntrophin visualized the reactive astrocytes but not the resting ones. The aims of the present study were to investigate whether these post-lesion alterations: (i) are reproducible with immersive fixation, which is used in postmortem histology; (ii) are resistant to a postmortem delay before fixation; and (iii) are to be attributed to a direct effect of the lesion, or are mediated by processes occurring only in the living brain. Three models were investigated: (i) following lesions, some brains were fixed by transcardial perfusion, others by immersion; (ii) following lesions, the animals were decapitated and stored at room temperature for 8 or 16 h before fixation; and (iii) the lesions were performed after decapitation. Cryogenic lesions were performed by applying a dry ice cooled copper rod to the brain surface of ketamine-xylazine anesthetized rats. The immunohistochemical reactions were performed on free-floating sections cut with vibratome. Both immunoperoxidase and immunofluorescence methods were used. The fixation method - perfusive or immersive - did not change the post-lesion phenomena investigated. The postmortem delay did not influence the β-dystroglycan immunoreactivity, that is its lack delineated the area of the lesion. However, in the case of the other substances, various lengths of postmortem delay rendered the immunohistochemistry uninterpretable. The results suggest β-dystroglycan immunostaining could be applied in the neuropathology to detect cerebrovascular impairments.

Correlation Between Extravasation and Alterations of Cerebrovascular Laminin and β-Dystroglycan Immunoreactivity Following Cryogenic Lesions in Rats

The blood-brain barrier becomes "leaky" following lesions. Former studies revealed that following lesions the immunoreactivity of cerebrovascular laminin becomes detectable whereas that of β-dystroglycan disappears. These alterations may be indicators of glio-vascular decoupling that may result in the impairment of the blood-brain-barrier. This study investigates correlation between the post-lesion extravasation and the above-mentioned immunohistochemical alterations. Following cryogenic lesions, the survival periods lasted 5, 10, 30 minutes, 1 or 12 hours, or 1 day. Some brains were fixed immediately post-lesion. Immunofluorescent reactions were performed in floating sections. The extravasation was detected with immunostaining for plasma fibronectin and rat immunoglobulins. When the survival period was 30 minutes or longer, the area of extravasation corresponded to the area of altered laminin and β-dystroglycan immunoreactivities. Following immediate fixation some laminin immunoreactivity was already detected. The extravasation seemed to precede this early appearance of laminin immunoreactivity. The β-dystroglycan immunoreactivity disappeared later. When the extravasation spread into the corpus callosum, vascular laminin immunoreactivity appeared but the β-dystroglycan immunoreactivity persisted. It seems that extravasation separates the glial and vascular basal laminae, which results in the appearance of laminin immunoreactivity. The disappearance of β-dystroglycan immunoreactivity is neither a condition nor an inevitable consequence of the 2 other phenomena.

Percutaneous image-guided cryoablation: current applications and results in the oncologic field

Percutaneous imaging-guided cryoablation (PICA) is a recently developed technique, which applies extreme hypothermia to destroy tumours under close imaging surveillance. It is minimally invasive, safe, repeatable, and does not interrupt or compromise other oncologic therapies. It presents several advantages over more established heat-based thermal ablation techniques (e.g. radiofrequency ablation; RFA) including intrinsic analgesic properties, superior monitoring capability on multi-modal imaging, ability to treat larger tumours, and preservation of tissue collagenous architecture. There has been a recent large increase in reports evaluating the utility of PICA in a wide range of patients and tumours, but systematic analysis of the literature is challenging due to the rapid pace of change and predominance of extensively heterogeneous level III studies. The precise onco-therapeutic role of PICA has not been established. This narrative review outlines the available evidence for PICA in a range of tumours. Current indications include curative therapy of small T1a renal tumours; curative/palliative therapy of small primary/secondary lung tumours where RFA is unsuitable; palliation of painful bone metastases; and urologic treatment of organ-confined prostate cancer. There is growing evidence to support its use for small hepatic tumours, and encouraging results have been obtained for breast tumours, extra-abdominal desmoid tumours, and management of higher-stage tumours and oligometastatic disease. However, the overall evidence base is weak, effectively restricting PICA to cases where standard therapy and RFA are unsuitable. As the technique and evidence continue to mature, the benefits of this emerging technique will hopefully become more widely available to cancer patients in the future.

GLP-1 improves neuropathology after murine cold lesion brain trauma

OBJECTIVES

In this study, we address a gap in knowledge regarding the therapeutic potential of acute treatment with a glucagon-like peptide-1 (GLP-1) receptor agonist after severe brain trauma. Moreover, it remains still unknown whether GLP-1 treatment activates the protective, anti-neurodegenerative cAMP response element binding protein (CREB) pathway in the brain in vivo, and whether activation leads to observable increases in protective, anti-neurodegenerative proteins. Finally, we report the first use of a highly sensitive in vivo imaging agent to assess reactive species generation after brain trauma.

METHODS

Severe trauma was induced with a stereotactic cryo-lesion in mice and thereafter treated with vehicle, liraglutide, or liraglutide + GLP-1 receptor antagonist. A therapeutic window was established and lesion size post-trauma was determined. Reactive oxygen species were visualized in vivo and quantified directly ex vivo. Hematological analysis was performed over time. Necrotic and apoptotic tone and neuroinflammation was assessed over time. CREB activation and CREB-regulated cytoprotective proteins were assessed over time.

RESULTS

Lira treatment reduced lesion size by ∼50% through the GLP-1 receptor. Reactive species generation was reduced by ∼40-60%. Necrotic and apoptotic tone maintained similar to sham in diseased animals with Lira treatment. Phosphorylation of CREB was markedly increased by Lira in a GLP-1 receptor-dependent manner. CREB-regulated cytoprotective and anti-neurodegenerative proteins increased with Lira-driven CREB activation.

INTERPRETATION

These results show that Lira has potent effects after experimental trauma in mice and thus should be considered a candidate for critical care intervention post-injury. Moreover, activation of CREB in the brain by Lira - described for the first time to be dependent on pathology - should be investigated further as a potential mechanism of action in neurodegenerative disorders.

Ablation technology for the surgical treatment of atrial fibrillation

The Cox maze procedure for the surgical treatment of atrial fibrillation has been simplified from its original cut-and-sew technique. Various energy sources now exist which create linear lines of ablation that can be used to replace the original incisions, greatly facilitating the surgical approach. This review article describes the anatomy of the atria that must be considered in choosing a successful energy source. Furthermore the device characteristics, safety profile, mechanism of tissue injury, and ability to create transmural lesions of the various energy sources that have been used in the Cox maze procedure, along with the strengths and weaknesses of each device is discussed.

Evaluation of a novel cryoablation system: in vitro testing of heat capacity and freezing temperatures

OBJECTIVE

Cryoablation has been used to ablate cardiac tissue for decades and has been shown to be able to replace incisions in the surgical treatment of atrial fibrillation. This in vitro study evaluates the performance of a novel cryoprobe and compares it with existing commercially available devices.

METHODS

A new malleable 10-cm aluminum cryoprobe was compared with a rigid 3.5-cm copper linear probe using in vitro testing to evaluate performances under different thermal loads and with different tissue thicknesses. Radial dimensions of ice formation were measured in each water bath by a high-precision laser 2 minutes after the onset of cooling. Probe-surface temperatures were recorded by thermocouples. Tissue temperature was measured at depths of 4 mm and 5 mm from the probe-tissue interface. Time to reach a tissue temperature of -20°C was recorded.

RESULTS

Ice formation increased significantly with lower water-bath temperatures (P < 0.001). Width and depth of ice formation were significantly less for the rigid linear probe (P < 0.012 and P < 0.001, respectively). There was no difference between the probes in the maximal negative temperature reached under different thermal loads or at different tissue depths. The malleable probe achieved significantly lower temperatures at the proximal compared with the distal end (-61.7°C vs -55.0°C, respectively; P < 0.001). A tissue temperature of -20°C was reached earlier at 4 mm than at 5 mm (P < 0.001) and was achieved significantly faster with the 3011 Maze Linear probe (P < 0.021).

CONCLUSIONS

The new malleable probe achieved rapid freezing to clinically relevant levels in up to 5-mm-thick tissue. Both probes maintained their performance under a wide range of thermal loads.

Optical imaging of cell death in traumatic brain injury using a heat shock protein-90 alkylator

Traumatic brain injury is a major public health concern and is characterised by both apoptotic and necrotic cell death in the lesion. Anatomical imaging is usually used to assess traumatic brain injuries and there is a need for imaging modalities that provide complementary cellular information. We sought to non-invasively image cell death in a mouse model of traumatic brain injury using a near-infrared fluorescent conjugate of a synthetic heat shock protein-90 alkylator, 4-(N-(S-glutathionylacetyl) amino) phenylarsonous acid (GSAO). GSAO labels both apoptotic and necrotic cells coincident with loss of plasma membrane integrity. The optical GSAO specifically labelled apoptotic and necrotic cells in culture and did not accumulate in healthy organs or tissues in the living mouse body. The conjugate is a very effective imager of cell death in brain lesions. The optical GSAO was detected by fluorescence intensity and GSAO bound to dying/dead cells was detected from prolongation of the fluorescence lifetime. An optimal signal-to-background ratio was achieved as early as 3 h after injection of the probe and the signal intensity positively correlated with both lesion size and probe concentration. This optical GSAO offers a convenient and robust means to non-invasively image apoptotic and necrotic cell death in brain and other lesions.

Evaluation of a Novel Cryoablation System: In vitro Testing of Heat Capacity and Freezing Temperatures

Objective

Cryoablation has been used to ablate cardiac tissue for decades and has been shown to be able to replace incisions in the surgical treatment of atrial fibrillation. This in vitro study evaluates the performance of a novel cryoprobe and compares it with existing commercially available devices.

Methods

A new malleable 10-cm aluminum cryoprobe was compared with a rigid 3.5-cm copper linear probe using in vitro testing to evaluate performances under different thermal loads and with different tissue thicknesses. Radial dimensions of ice formation were measured in each water bath by a high-precision laser 2 minutes after the onset of cooling. Probe-surface temperatures were recorded by thermocouples. Tissue temperature was measured at depths of 4 mm and 5 mm from the probe-tissue interface. Time to reach a tissue temperature of −20°C was recorded.

Results

Ice formation increased significantly with lower water-bath temperatures (P < 0.001). Width and depth of ice formation were significantly less for the rigid linear probe (P < 0.012 and P < 0.001, respectively). There was no difference between the probes in the maximal negative temperature reached under different thermal loads or at different tissue depths. The malleable probe achieved significantly lower temperatures at the proximal compared with the distal end (–61.7°C vs −55.0°C, respectively; P < 0.001). A tissue temperature of −20°C was reached earlier at 4 mm than at 5 mm (P < 0.001) and was achieved significantly faster with the 3011 Maze Linear probe (P < 0.021).

Conclusions

The new malleable probe achieved rapid freezing to clinically relevant levels in up to 5-mm–thick tissue. Both probes maintained their performance under a wide range of thermal loads.

Current and future technology for minimally invasive ablation of renal cell carcinoma

Purpose of Review:

To provide an overview of the technologic advancements in the field of ablative therapy, focusing on the treatment of renal neoplasms.

Materials and Methods:

A MEDLINE search was performed using each specific ablative technique name as the search term. Articles written in the English language were selected for review. In cases of multiple reports by a single institution, the most recent report was utilized. Pertinent articles specific to the technologic advancement in ablative therapy were selected for review.

Recent Findings:

Intermediate-term oncologic outcomes of radiofrequency ablation (RFA) and cryoablation (CA) for the treatment of small renal masses are encouraging. For thermal therapies, molecular adjuvants to enhance cellular kill and local control have been developed. Improvements in microwave technology have allowed for reductions in antenna size and increases in ablation size. Laparoscopic high-intensity focused ultrasound (HIFU) probes have been developed to overcome the limitations of transcutaneous energy delivery, but HIFU remains experimental for the treatment of renal lesions. Irreversible electroporation (IRE), a novel nonthermal ablative technique, is currently undergoing clinical investigation in human subjects. Histotripsy causes mechanical destruction of targeted tissue and shows promise in treating renal and prostate pathology.

Summary:

Ablative techniques are commonly utilized in the primary treatment of urologic malignancies. The purpose of this review is to discuss technologic advances in ablative therapies with emphasis on the treatment of renal masses. RFA and CA show acceptable intermediate-term efficacy and technical refinement continues. Emerging technologies, including microwave thermotherapy, IRE, HIFU and histotripsy, are described with emphasis on the mechanism of cellular kill, energy delivery, and stage in clinical development.

Pre-conditioning cryosurgery: cellular and molecular mechanisms and dynamics of TNF-α enhanced cryotherapy in an in vivo prostate cancer model system

Cryosurgery is increasingly being used to treat prostate cancer; however, a major limitation is local recurrence of disease within the previously frozen tissue. We have recently demonstrated that tumor necrosis factor alpha (TNF-α), given 4h prior to cryosurgery can yield complete destruction of prostate cancer within a cryosurgical iceball. The present work continues the investigation of the cellular and molecular mechanisms and dynamics of TNF-α enhancement on cryosurgery. In vivo prostate tumor (LNCaP Pro 5) was grown in a dorsal skin fold chamber (DSFC) on a male nude mouse. Intravital imaging, thermography, and post-sacrifice histology and immunohistochemistry were used to assess iceball location and the ensuing biological effects after cryosurgery with and without TNF-α pre-treatment. Destruction was specifically measured by vascular stasis and by the size of histologic zones of injury (i.e., inflammatory infiltrate and necrosis). TNF-α induced vascular pre-conditioning events that peaked at 4h and diminished over several days. Early events (4-24 h) include upregulation of inflammatory markers (nuclear factor-κB (NFκB) and vascular cell adhesion molecule-1 (VCAM)) and caspase activity in the tumor prior to cryosurgery. TNF-α pre-conditioning resulted in recruitment of an augmented inflammatory infiltrate at day 3 post treatment vs. cryosurgery alone. Finally, pre-conditioning yielded enhanced cryosurgical destruction up to the iceball edge at days 1 and 3 vs. cryosurgery alone. Thus, TNF-α pre-conditioning enhances cryosurgical lesions by vascular mechanisms that lead to tumor cell injury via promotion of inflammation and leukocyte (esp. neutrophil) recruitment.

Adjuvant approaches to enhance cryosurgery

Molecular adjuvants can be used to enhance the natural destructive mechanisms of freezing within tissue. This review discusses their use in the growing field of combinatorial or adjuvant enhanced cryosurgery for a variety of disease conditions. Two important motivations for adjuvant use are: (1) increased control of the local disease in the area of freezing (i.e., reduced local recurrence of disease) and (2) reduced complications due to over-freezing into adjacent tissues (i.e., reduced normal functional tissue destruction near the treatment site). This review starts with a brief overview of cryosurgical technology including probes and cryogens and major mechanisms of cellular, vascular injury and possible immunological effects due to freeze-thaw treatment in vivo. The review then focuses on adjuvants to each of these mechanisms that make the tissue more sensitive to freeze-thaw injury. Four broad classes of adjuvants are discussed including: thermophysical agents (eutectic forming salts and amino acids), chemotherapuetics, vascular agents and immunomodulators. The key issues of selection, timing, dose and delivery of these adjuvants are then elaborated. Finally, work with a particularly promising vascular adjuvant, TNF-alpha, that shows the ability to destroy all cancer within a cryosurgical iceball is highlighted.

Experimental cryosurgery investigations in vivo

Cryosurgery is the use of freezing temperatures to elicit an ablative response in a targeted tissue. This review provides a global overview of experimentation in vivo which has been the basis of advancement of this widely applied therapeutic option. The cellular and tissue-related events that underlie the mechanisms of destruction, including direct cell injury (cryolysis), vascular stasis, apoptosis and necrosis, are described and are related to the optimal methods of technique of freezing to achieve efficacious therapy. In vivo experiments with major organs, including wound healing, the putative immunological response following thawing, and the use of cryoadjunctive strategies to enhance cancer cell sensitivity to freezing, are described.

Tumor necrosis factor-alpha-induced accentuation in cryoinjury: mechanisms in vitro and in vivo

Cryosurgical treatment of solid cancer can be greatly assisted by further translation of our finding that a cytokine adjuvant tumor necrosis factor-alpha (TNF-alpha) can achieve complete cancer destruction out to the intraoperatively imaged iceball edge (-0.5 degrees C) over the current clinical recommendation of reaching temperatures lower than -40 degrees C. The present study investigates the cellular and tissue level dose dependency and molecular mechanisms of TNF-alpha-induced enhancement in cryosurgical cancer destruction. Microvascular endothelial MVEC and human prostate cancer LNCaP Pro 5 (LNCaP) cells were frozen as monolayers in the presence of TNF-alpha. Normal skin and LNCaP tumor grown in a nude mouse model were also frozen at different TNF-alpha doses. Molecular mechanisms were investigated by using specific inhibitors to block nuclear factor-kappaB-mediated inflammatory or caspase-mediated apoptosis pathways. The amount of cryoinjury increased in a dose-dependent manner with TNF-alpha both in vitro and in vivo. MVEC were found to be more cryosensitive than LNCaP cells in both the presence and the absence of TNF-alpha. The augmentation in vivo was significantly greater than that in vitro, with complete cell death up to the iceball edge in tumor tissue at local TNF-alpha doses greater than 200 ng. The inhibition assays showed contrasting results with caspase-mediated apoptosis as the dominant mechanism in MVEC in vitro and nuclear factor-kappaB-mediated inflammatory mechanisms within the microvasculatures the dominant mechanism in vivo. These results suggest the involvement of endothelial-mediated injury and inflammation as the critical mechanisms in cryoinjury and the use of vascular-targeting molecules such as TNF-alpha to enhance tumor killing and achieve the clinical goal of complete cell death within an iceball.

Implanted Mouse Bone Marrow-Derived Cells Reconstruct Layered Smooth Muscle Structures in Injured Urinary Bladders

This study is a preliminary investigation to determine if bone marrow-derived cells, when implanted into freeze-injured urinary bladders, differentiate into smooth muscle cells and reconstruct smooth muscle layers. Bone marrow cells were harvested from femurs of male ICR mice and cultured in collagen-coated dishes for 7 days. After 5 days of culture, the cells were transfected with green fluorescent protein (GFP) genes for identification in recipient tissues. Three days prior to implantation, the posterior urinary bladder walls of female nude mice were injured with an iron bar refrigerated by dry ice. Seven days after the culture and 3 days after the injury, adherent, proliferating GFP-labeled bone marrow-derived cells (1.0 × 105 cells) were implanted into the injured regions. For controls, a cell-free solution was injected. At 14 days after implantation, the experimental urinary bladders were analyzed by histological, gene expression, and cystometric investigations. Just prior to implantation, the injured regions did not have any smooth muscle layers. After 14 days, the implanted cells surviving in the recipient tissues were detected with GFP antibody. The implanted regions had distinct smooth muscle layers composed of regenerated smooth muscle marker-positive cells. The implanted GFP-labeled cells differentiated into smooth muscle cells that formed into layers. The differentiated cells contacted each other within the implanted region as well as smooth muscle cells of the host. As a result, the reconstructed smooth muscle layers were integrated into the host tissues. Control mice injected with cell-free solution developed only few smooth muscle cells and no layers. Cystometric investigations showed that mice with implanted the cells developed bladder contractions similar to normal mice, whereas control mice did not. In summary, mouse bone marrow-derived cells can reconstruct layered smooth muscle structures in injured bladders to remediate urinary dysfunction.

Different behaviour of implanted stem cells in intact and lesioned forebrain cortices

Cell-replacement therapy promises a useful tool to regenerate compromised brain tissue, but the interaction between grafted cells and host tissues is not well understood. In these studies, the fates of neuroectodermal stem cells were compared in 'healthy' or damaged mouse forebrains. One-cell derived, fluorescent GFP-4C neural stem cells were implanted into normal and cold-lesioned mouse cortices. The fates of implanted cells were followed by histological and immunocytochemical assays for a 55-day postimplantation period. Cells were recultivated from lesioned cortices and characterized by cell cycle parameters, chromosome numbers, immunocytochemical markers and in vitro inducibility. Their intracerebral fates were checked upon re-implanting into 'healthy' mouse brain cortices. GFP-4C cells, giving rise to neurones and astrocytes upon in vitro induction, failed to differentiate in either normal or lesioned cortical tissues. The rate of proliferation and the length of the survival, however, depended on the host environment, markedly. In intact cortices, implanted cells formed compact, isolated aggregates and their survival did not exceed 4 weeks. In compromised cortices, GFP-4C cells survived longer than 8 weeks and repopulated the decayed region. The morphology, viability, immunocytochemical properties, in vitro inducibility and chromosome number of cells recultivated from lesioned cortices were identical to those of the master cells. Long-term survival and repopulating capability were due to signals present in the lesioned, but missing from the intact cortical environment. The results underline the importance of host environment in the fate determination of grafted cells and emphasize the need to understand the 'roles' of recipient tissues for potential cell-replacement methodologies.

Mouse brains deficient in neuronal PDGF receptor-beta develop normally but are vulnerable to injury

Platelet-derived growth factors (PDGFs) and PDGF receptors (PDGFRs) are widely expressed in the mammalian CNS, though their functional significance remains unclear. The corresponding null-knockout mutations are lethal. Here, we developed novel mutant mice in which the gene encoding the beta subunit of PDGFR (PDGFR-beta) was genetically deleted in CNS neurons to elucidate the role of PDGFR-beta, particularly in the post-natal stage. Our mutant mice reached adulthood without apparent anatomical defects. In the mutant brain, immunohistochemical analyses showed that PDGFR-beta detected in neurons and in the cells in the subventricular zone of the lateral ventricle in wild-type mice was depleted, but PDGFR-beta detected in blood vessels remained unaffected. The cerebral damage after cryogenic injury was severely exacerbated in the mutants compared with controls. Furthermore, TdT-mediated dUTP-biotin nick end labeling (TUNEL)-positive neuronal cell death and lesion formation in the cerebral hemisphere were extensively exacerbated in our mutant mice after direct injection of NMDA without altered NMDA receptor expression. Our results clearly demonstrate that PDGFR-beta expressed in neurons protects them from cryogenic injury and NMDA-induced excitotoxicity.

In vivo cryochemotherapy of a human lung cancer model

Cryotherapy, an efficient technique to destroy tumour cells, is sometimes applied locally as a palliative treatment in lung cancers. It can be performed in combination with chemotherapy. Our aims were to determine in vivo: (1) the effects of cryochemotherapy in a human lung adenocarcinoma, (2) if it presents a benefit compared to the separate treatments and (3) if cryotherapy allows a tumour retention of the drug. Cells from the A549 cell line were xenografted into SCID mice. Tumours were treated by cryotherapy, chemotherapy (injection of Vinorelbine: Navelbine) or both and were studied morphologically at variable time points. Apoptosis was analysed by immunohistochemical staining of cleaved caspase-3 and by TUNEL. Intratumour Navelbine concentration was assessed by high performance liquid chromatography. Necrosis was important 2 h after cryochemotherapy (45% of the tumour surface) and at the later time points. Expression of cleaved caspase-3 was not significantly different from that of untreated tumours, except at the time point of 2 h where it was maximal (58%). Navelbine concentration was more important in tumours treated by chemotherapy than in tumours treated by cryochemotherapy, demonstrating that in our model, the benefit of the association observed 2h after treatment was not due to a concentration-dependent effect.

Cryosurgery--a putative approach to molecular-based optimization

Cryosurgery must be performed in a manner that produces a predictable response in an appropriate volume of tissue. In present-day clinical practice, that goal is not always achieved. Concerns with cryosurgical techniques in cancer therapy focus in part on the incidence of recurrent disease in the treated site, which is commonly approximately 20-40% in metastatic liver tumors, and prostate cancers. Whether the cause of this failure is disease-based or technique related, cryosurgery for cancer commonly needs the support of adjunctive therapy in the form of anti-cancer drugs or radiotherapy to increase the rate of cell death in the peripheral zone of the therapeutic lesion where cell survival is in balance for several days post-treatment. Recent evidence has identified a third mechanism of cell death associated with cryosurgery. This mechanism, apoptosis or gene regulated cell death, is additive with both the direct ice-related cell damage that occurs during the operative freeze-thaw intervals and coagulative necrosis that occurs over days post-treatment. In this manuscript we discuss, through a combination of literature review and new data, the combined roles of these distinct modes of cell death in a prostate and colorectal cancer. Data are presented suggesting that sub-freezing temperatures, when sequentially applied with low dose chemotherapy, may provide improved cancer cell death in the freeze zone periphery. Since the mechanism of action of most common chemotherapeutic agents is to initiate apoptosis in cancer cells, the observation that sub-freezing exposures yields a similar effect provides a possible route toward molecular-based procedural optimization to improve therapeutic outcome.

Identification of brain tissue necrosis by MRI: validation by histomorphometry

The volume of an experimental necrotic lesion of the cortex expands up to 400% of its initial size within the first 24 h after the insult. Lesion expansion, a clinically well known phenomenon, is often accompanied by perifocal brain edema and consequently difficult to image and to analyze by magnetic resonance imaging (MRI). Therefore we aimed to validate a T(2)-weighted spin echo sequence upon its ability to distinguish necrotic from edematous brain tissue. Male Sprague-Dawley rats (n = 5 per group) were subjected to a cortical freezing lesion leading to immediate tissue necrosis with subsequent perifocal vasogenic brain edema. Immediately and 4, 12, and 24 h after the lesion the maximal area of necrosis was quantified longitudinally by coronal T(2)-weighted spin echo MRI-scans. After the last scan, animals were sacrificed for direct comparison of the lesion area obtained by MRI and histomorphometry. In parallel groups of animals, lesion expansion was quantified by histology. The acquired T(2)-maps clearly distinguish the cortical necrosis from perifocal edema and healthy brain. Focal freezing led to a cortical lesion of 5.24 +/- 0.36 mm(2) immediately after trauma (0 h; 100%) which expanded progressively to a maximum of 6.82 +/- 0.34 mm(2) after 24 h (131%; *p < 0.01 vs. 0 h). Lesion expansion quantified by histology was almost identical (132% within 24 h). Histological assessment resulted in smaller absolute lesion areas compared to MRI, most likely due to shrinking during tissue processing (4.72 +/- 0.26 mm(2) vs. 6.82 +/- 0.34 mm(2), p < 0.01). The current study shows that necrotic brain tissue can be distinguished from surrounding brain edema by T(2)-mapping. The technique is sensitive enough to detect small changes in necrosis expansion in vivo as validated by histology. The presented technique may be a useful future tool for the non-invasive identification of necrotic brain tissue following brain injury (e. g., from trauma or ischemia).

The blood-brain barrier and cerebral angiogenesis: lessons from the cold-injury model

Brain injury is associated with an initial blood-brain barrier (BBB) breakdown, which can be life threatening. A second phase of BBB breakdown accompanies the angiogenesis occurring at the lesion margins. Studies of the molecular mechanisms involved in these processes are essential to determine targets for therapeutic intervention, as well as the time periods during which therapeutic intervention could ameliorate brain damage and thus improve the clinical outcome.