Cryosurgery of normal and tumor tissue in the dorsal skin flap chamber: Part I--thermal response

[Therapeutic management of a kissing nevus of the eyelid]

Congenital divided melanocytic nevi of the upper and lower eyelid are rare pigmented changes of the eyelids. These processes are also known as "kissing nevi," "panda nevi," and "split ocular nevi," and were first described by Fuchs in 1919. About 120 cases have been described in the literature so far. Congenital melanocytic nevi are either present at birth (small nevi are already found in about 1% of neonates) or manifest predominantly during the first decade of life. These rare melanocytic changes of the eyelids should be controlled regularly, as malignant transformation can occur. The actual incidence of malignant transformation is highly variable in the literature, ranging from 2 to 40% depending on the duration of follow-up, with an average of 14% for the whole lifetime. Moreover, nevi of the eyelids may be considered cosmetically disturbing and cause functional problems. Therapeutic removal (dermabrasion, cryotherapy, laser therapy, and surgical excision with ophthalmoplastic reconstruction) is rarely medically indicated due to the low risk of malignant transformation. Removal can be performed in cases of secondary amblyopia in ptosis, compression of the lacrimal point, epiphora, or cosmetic desire. Treatment becomes necessary not only in case of suspicious manifestation or impairment of eyelid function, but it also helps to avoid possible bullying at school among children and is recommended at age 4 to 6 (before school age).

Cryoablation and Immunotherapy: An Enthralling Synergy for Cancer Treatment

As less invasive options for surgical tumor removal, minimally invasive ablative techniques have gained popularity. Several solid tumors are being treated with cryoablation, a non-heat-based ablation technique. Cryoablation data in comparison over time demonstrates better tumor response and faster recovery. Combining cryosurgery with other cancer therapies has been explored to improve the cancer-killing process. Cryoablation with the combination of immunotherapy, results in a robust and efficient attack on the cancer cells. This article focuses on investigating the ability of cryosurgery to create a strong antitumor response when combined with immunologic agents resulting in a synergetic effect. To achieve this objective, we combined cryosurgery with immunotherapy using Nivolumab and lpilimumab. Five clinical cases of lymph node, lung cancer, bone, and lung metastasis were followed and analyzed. In this series of patients, percutaneous cryoablation and addressing immunity agents were technically feasible. In the follow-ups, there appeared to be no radiological evidence of new tumor development.

Infrared thermal imaging controls freezing and warming in skin cryoablation

The purpose of this study was to assess the possibilities of intraoperative control of the current parameters of frozen biological tissues in the cryoablation area, including the instant location of primary necrosis isotherm, based on the dynamics of thermal fields on skin surface. Cryoablation of skin was performed in 30 rats with exposure durations of 0.5, 1 and 2 min. The contact cryoprobe actively cooled with liquid nitrogen was used. The dynamics of animal's skin thermal field during freeze/thaw cycle was quantitatively controlled by the original infrared camera with an extended range of measurable temperatures. The obtained by us ratio of the maximal diameters of primary necrosis and ice spots was 0.64 ± 0.03 for cryoexposure durations of 0.5 and 1 min. During thawing, a quasi-stable stage was observed both in the dynamics of ice spot diameters and their temperature distribution. The effect is presumably associated with structural rearrangements of ice in the frozen tissue volume. The results indicate that thermal imaging can be effectively used for quantitative control of freezing and warming of biological tissues in vivo, including current control of the position of necrotic and cryoscopic isotherms, distortion of their thermal symmetry, thermal response of other skin areas, etc.

Optimization of prostatic cryosurgery with multi-cryoprobe based on refrigerant flow

Cryosurgery is a promising novel minimally invasive surgical technique to eradicate carcinoma and non-carcinoma tissues by freezing. In this research, we applied a transient 3D two-phase refrigerant flow model inside the LN₂ boiling chamber as well as a bioheat transfer model inside the tissues to evaluate the optimized ablation outcome during prostatic cryosurgery. For the evaluation of the scenarios, a defect function was used that considers non-ablated target tissue (prostate/cancer tissue) as well as ablated healthy tissue, in which the ablated tissue was evaluated using a temperature threshold. Three different configurations using three LN₂ cryoprobes were analyzed during the modeling study, and the best configuration with the three LN₂ cryoprobes positioned isoscelesly was found. For this configuration, temperature distributions and temperature profiles at specific points within the tissue were investigated numerically. Owing to its low computational cost, the 3D coupled model has an advantage in accurate modeling cryosurgery for curing numerous diseases.

Cryosurgical Ablation of Renal Cell Carcinoma

BACKGROUND

Small renal masses are being commonly diagnosed incidentally in older patients. A partial nephrectomy is the first-line nephron sparing treatment option for these lesions. However, probe ablative therapy such as cryoablation is emerging as an alternative option for select patients requiring nephron sparing surgery.

METHODS

The current literature regarding the management of small renal lesions with cryoablation was retrospectively reviewed. We selected six of the largest published series of renal cryoablation with a total of 320 patients. The diagnosis, staging, treatment options, mechanism, efficacy and morbidity associated with renal cryoablation were evaluated.

RESULTS

Renal cryoablation for localized small renal masses is well tolerated and associated with a low complication rate. The range of mean tumor size in our literature review series (320 patients) was 2.3 to 2.6 cm. After a range of mean follow-up of 5.9 to 72 months, including a series with a minimum of 5 years of follow-up, the cancer specific survival was 97% to 100% and overall patient survival was 82% to 90.2%.

CONCLUSIONS

Renal cryoablation, based on available clinical reports, appears to be a curative option for patients with small localized renal cell carcinomas (RCCs) who are unwilling or unable to undergo a partial nephrectomy. With encouraging intermediate oncological follow-up available, longer-term follow-up is needed to validate the use of cryoablation as a primary treatment option.

Evaluation of the cryosurgery for treatment of squamous cell carcinoma in cats

ABSTRACT The cryosurgery is a very useful therapy for the treatment of a variety of neoplastic and non-neoplastic processes. Nevertheless, it is still poorly described as an option for the treatment of specific cutaneous neoplasms, such as squamous cell carcinoma. The purpose of the present study was to analyze the clinical response of cryosurgery for the treatment of squamous cell carcinoma in cats. For this 13 squamous cell carcinoma lesions were selected in 11 cats, diagnosed through citopathological and/or histopathological examinations. The lesions were frozen using liquid nitrogen spray, and the evaluations were performed in the moment of freeze and approximately every 15 days until the wound was completely healed. The response of cryosurgery was considered complete with tumoral remission on 38.5% of the cats, and partial on 46.1%. The main complications included crusting and nostril stenosis. The presented results suggested that cryosurgery is effective and may be a viable option for the treatment of squamous cell carcinoma in cats. The effectiveness of the therapy; however, depends on the correct selection of the candidates for cryosurgery based on the lesion size, and the attendance to some criteria, such as the freezing time and post-operative care.

Review of the initial treatment and avoidance of scald injuries

Scald injuries, which describe burns to living tissue from hot liquids, are a very common injury that occur across geographical, social, economic, and national boundaries. Despite their ubiquitous nature, a complete understanding of the conditions which are required to cause scald burns is not yet available. In addition, clear guidance to medical practitioners is available through various guidelines however in actual situations, the extent of the burn is not fully known and this lack of knowledge complicates care. Here, a comprehensive review is made of the available knowledge of temperatures and scald durations which lead to skin-burn injuries. The range of volumes and liquid temperatures are typical of those found in heated consumer beverages. This review can help medical practitioners design initial treatment protocols and can be used by manufacturers of hot-liquid products to avoid the most severe burns. Next, within the context of this ability to quantify burn depths, a review of current burn treatment guidelines is given. Included in this review is a visual recognition of the extent of burns into the dermal layer as well as decision guidelines for selection of patients which would benefit from referral to a dedicated burn center. It is hoped that by bringing together both the quantified burn-depth information and current treatment guidelines, this review can be used as a resource for persons in the medical, manufacturing, beverage service, and other industries to reduce the human impact of scald injuries.

Disappearance of Renal Cysts Included in Ice Ball During Cryoablation of Renal-Cell Carcinoma: A Potential Therapy for Symptomatic Renal Cysts?

PURPOSE

To retrospectively evaluate the effect of cryoablation of renal-cell carcinoma on nearby renal cysts with the goal to investigate the potential for an alternative therapy to treat symptomatic renal cysts.

MATERIALS AND METHODS

The study population comprised 46 cysts (mean size, 12 mm; range, 5-43 mm) that were within or near the ice ball during cryoablation in 22 patients. Size change of each cyst was evaluated via enhanced CT or MR imaging before and 1, 3, 6, and 12 months after cryoablation. Forty-one cysts were also followed after 12 months. Variables including positional relationship between the cyst and the ice ball were evaluated via linear regression analysis using generalized estimating equation models to determine which factors affected cyst shrinkage rate at 12 months.

RESULTS

Fifteen, 12, and 19 cysts were completely included in, partially included in, or excluded from the ice ball, respectively. The overall shrinkage rate was 62%, and 57% of cysts (26 of 46) had disappeared at 12 months. Only the relationship between the cyst and the ice ball was significantly (P < .001) associated with cyst shrinkage rate. Cyst disappearance rates at 12 months were 100% (15 of 15), 67% (8 of 12), and 16% (3 of 19) for cysts completely included, partially included, and excluded from the ice ball, respectively. Among the 22 cysts that disappeared at 12 months and continued to be followed, none recurred after 12 months.

CONCLUSIONS

All renal cysts that were completely included in the ice ball disappeared after cryoablation, demonstrating the potential utility of cryoablation as an alternative therapy for symptomatic renal cysts.

Improved Cryosurgery by Use of Thermophysical and Inflammatory Adjuvants

In the present article, recent research efforts in our laboratory to improve cryosurgery by use of mechanistically derived adjuvants are reviewed. Our research has been focused on enhancing two freezing induced injury mechanisms - i) direct cell injury by use of thermophysical adjuvants, and ii) vascular injury by use of an inflammatory adjuvant. The thermophysical adjuvants are chemicals, usually salts, which can induce secondary crystallization, called eutectic solidification, in a cryolesion; thereby enhancing direct cell injury. The inflammatory adjuvant is a cytokine, tumor necrosis factor-alpha (TNF-α), which upregulates inflammation of microvasculature in tumors prior to freezing to promote vascular injury in the cryolesion. Even though the individual mechanism of injury enhancement within the cryolesion of each adjuvant requires further study, both adjuvants are envisioned to enlarge the complete killing zone so that the boundary of the cryolesion matches more closely with the edge of ice-ball. By bringing the edge of the cryolesion closer to the edge of iceball, the adjuvants hold promise for improvement of image guidance and outcome of cryosurgery.

NUMERICAL ANALYSIS OF TRIPLE LAYER SKIN TISSUE FREEZING USING NON-FOURIER HEAT CONDUCTION

The classical Fourier’s law assumes that the propagation speed of thermal disturbance is infinite, which is contradictory to physical reality. The living tissues are highly non-homogeneous and need a relaxation time to accumulate enough energy to transfer to the nearest element. This study proposes hyperbolic bio-heat model to study the freezing process in triple layer skin tissue with non-ideal property of skin tissue, metabolism and blood perfusion. The enthalpy formulation and finite difference method are used to solve the hyperbolic bio-heat model for triple layer skin tissue freezing. The effects of relaxation time for heat flux on temperature profile, liquidus and solidus interfaces are studied during the freezing of skin tissue. It is observed that the different values of relaxation time for heat flux have significant effect on temperature distribution, liquidus and solidus interfaces within the skin tissue.

Nanoparticle delivered vascular disrupting agents (VDAs): use of TNF-alpha conjugated gold nanoparticles for multimodal cancer therapy

Surgery, radiation and chemotherapy remain the mainstay of current cancer therapy. However, treatment failure persists due to the inability to achieve complete local control of the tumor and curtail metastatic spread. Vascular disrupting agents (VDAs) are a class of promising systemic agents that are known to synergistically enhance radiation, chemotherapy or thermal treatments of solid tumors. Unfortunately, there is still an unmet need for VDAs with more favorable safety profiles and fewer side effects. Recent work has demonstrated that conjugating VDAs to other molecules (polyethylene glycol, CNGRCG peptide) or nanoparticles (liposomes, gold) can reduce toxicity of one prominent VDA (tumor necrosis factor alpha, TNF-α). In this report, we show the potential of a gold conjugated TNF-α nanoparticle (NP-TNF) to improve multimodal cancer therapies with VDAs. In a dorsal skin fold and hindlimb murine xenograft model of prostate cancer, we found that NP-TNF disrupts endothelial barrier function and induces a significant increase in vascular permeability within the first 1-2 h followed by a dramatic 80% drop in perfusion 2-6 h after systemic administration. We also demonstrate that the tumor response to the nanoparticle can be verified using dynamic contrast-enhanced magnetic resonance imaging (MRI), a technique in clinical use. Additionally, multimodal treatment with thermal therapies at the perfusion nadir in the sub- and supraphysiological temperature regimes increases tumor volumetric destruction by over 60% and leads to significant tumor growth delays compared to thermal therapy alone. Lastly, NP-TNF was found to enhance thermal therapy in the absence of neutrophil recruitment, suggesting that immune/inflammatory regulation is not central to its power as part of a multimodal approach. Our data demonstrate the potential of nanoparticle-conjugated VDAs to significantly improve cancer therapy by preconditioning tumor vasculature to a secondary insult in a targeted manner. We anticipate our work to direct investigations into more potent tumor vasculature specific combinations of VDAs and nanoparticles with the goal of transitioning optimal regimens into clinical trials.

QUANTIFICATION AND THE UNDERLYING MECHANISM OF SKIN THERMAL DAMAGE: A REVIEW

Skin thermal damage is the most common thermal trauma in civilian and military communities. Besides, advances in laser, microwave, and similar technologies have led to recent developments of thermal treatments for diseases involving skin tissue aiming at inducing damage precisely within targeted tissue structures without affecting the surrounding healthy tissue. Pain sensation accompanying thermal damage is also a serious problem for burn patients. Therefore, it is of great importance to quantify the thermal damage in skin tissue. In this review, we detail the progress of the state-of-the-art mathematical models and experimental methods for the quantification of thermal damage (both heat damage and cold damage) and the general development of thermal treatments in tissue engineering. This could enable better understanding of the underlying mechanisms of skin thermal damage and the optimization of clinical thermal therapies.

Vascular disrupting agent arsenic trioxide enhances thermoradiotherapy of solid tumors

Our previous studies demonstrated arsenic trioxide- (ATO-) induced selective tumor vascular disruption and augmentation of thermal or radiotherapy effect against solid tumors. These results suggested that a trimodality approach of radiation, ATO, and local hyperthermia may have potent therapeutic efficacy against solid tumors. Here, we report the antitumor effect of hypofractionated radiation followed by ATO administration and local 42.5 °C hyperthermia and the effects of cisplatin and thermoradiotherapy. We found that the therapeutic efficacy of ATO-based thermoradiotherapy was equal or greater than that of cisplatin-based thermoradiotherapy, and marked evidence of in vivo apoptosis and tumor necrosis were observed in ATO-treated tumors. We conclude that ATO-based thermoradiotherapy is a powerful means to control tumor growth by using vascular disruption to augment the effects of thermal and radiation therapy.

Thermostability of biological systems: fundamentals, challenges, and quantification

This review examines the fundamentals and challenges in engineering/understanding the thermostability of biological systems over a wide temperature range (from the cryogenic to hyperthermic regimen). Applications of the bio-thermostability engineering to either destroy unwanted or stabilize useful biologicals for the treatment of diseases in modern medicine are first introduced. Studies on the biological responses to cryogenic and hyperthermic temperatures for the various applications are reviewed to understand the mechanism of thermal (both cryo and hyperthermic) injury and its quantification at the molecular, cellular and tissue/organ levels. Methods for quantifying the thermophysical processes of the various applications are then summarized accounting for the effect of blood perfusion, metabolism, water transport across cell plasma membrane, and phase transition (both equilibrium and non-equilibrium such as ice formation and glass transition) of water. The review concludes with a summary of the status quo and future perspectives in engineering the thermostability of biological systems.

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.

Intravital microscopy of tumor angiogenesis and regression in the dorsal skin fold chamber: mechanistic insights and preclinical testing of therapeutic strategies

Tumor angiogenesis is a major step in tumor progression to clinically symptomatic cancer and thus a potential target for cancer therapy. It is essential to understand the fundamental mechanisms of the angiogenic processes to provide a rational for testing inhibitory strategies for cancer treatment. The dorsal skin fold chamber provides a suitable (chronic) model for intravital microscopy to monitor the same tumor in time-lapse imaging series and in real-time functional analysis e.g., of blood flow. Adaptation of this model to several rodent species and tumor types has led to numerous physical and drug based therapy options. With modification of implantation techniques, motility and invasion of individual cells can be visualized, in addition to angiogenesis and microcirculation. Modern fluorescent techniques such as ex vivo labelling of specific cell populations and the introduction of stably fluorescent protein expressing cell lines further enhance the suitability of this technique. In addition, laser scanning and multiphoton microscopy in combination with genetically altered mouse strains and cell lines are making the DCSF even more attractive for mechanistic and interventional studies in cancer research. Here we review the preparation as well as the applications of the DCSF in tumor angiogenesis.

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.

The apparent critical isotherm for cryoinsult-induced osteonecrotic lesions in emu femoral heads

Cryoinsult-induced osteonecrosis (ON) in the emu femoral head provides a unique opportunity to systematically explore the pathogenesis of ON in an animal model that progresses to human-like femoral head collapse. Among the various characteristics of cryoinsult, the maximally cold temperature attained is one plausible determinant of tissue necrosis. To identify the critical isotherm required to induce development of ON in the cancellous bone of the emu femoral head, a thermal finite element (FE) model of intraoperative cryoinsults was developed. Thermal material property values of emu cancellous bone were estimated from FE simulations of cryoinsult to emu cadaver femora, by varying model properties until the FE-generated temperatures matched corresponding thermocouple measurements. The resulting FE model, with emu bone-specific thermal properties augmented to include blood flow effects, was then used to study intraoperatively performed in vivo cryoinsults. Comparisons of minimum temperatures attained at FE nodes corresponding to the three-dimensional histologically apparent boundary of the region of ON were made for six experimental cryoinsults. Series-wide, a critical isotherm of 3.5 degrees C best corresponded to the boundary of the osteonecrotic lesions.

Study on tumor microvasculature damage induced by alternate cooling and heating

Tumor vasculature damage induced by various thermal treatments has been studied in vivo via laser confocal microscopy. Murine mammary carcinoma 4T1 was implanted in the nude mice dorsal skin fold window chamber. The implanted tumor was treated by alternate cooling and heating. Results showed that the treatment was much more effective as compared with that of cooling or heating alone, especially in damaging the tumor vasculature. In general, tumor vascular response to thermal stimuli was heterogeneous. All the treatments of hyperthermia at 42 degrees C (for 1 h), alternate cooling at 1 degrees C and heating at 42 degrees C (for 1/2 h each) and that of -10 degrees C/42 degrees C (for 1/2 h each) enhanced liposome extravasation. Pre-cooling tumor at 1 degrees C preserved most of the vascular integrity but partially inhibited the effect of post-hyperthermia at 42 degrees C. On the other hand, cooling at -10 degrees C for 1/2 h before heating at 42 degrees C caused severe vessel damage. Histo-pathological analyses further confirmed the effect as rare tumor vessel recurrence and large necrotic tumor tissue areas shown on the 7th day after the treatment.

Use of a fluorescently labeled poly-caspase inhibitor for in vivo detection of apoptosis related to vascular-targeting agent arsenic trioxide for cancer therapy

Arsenic trioxide (ATO, Trisenox) is a potent anti-vascular agent and significantly enhances hyperthermia and radiation response. To understand the mechanism of the anti-tumor effect in vivo we imaged the binding of a fluorescently-labeled poly-caspase inhibitor (FLIVO) in real time before and 3 h or 24 h after injection of 8 mg/kg ATO. FSaII tumors were grown in dorsal skin-fold window chambers or on the rear limb and we observed substantial poly-caspase binding associated with vascular damage induced by ATO treatment at 3 and 24 h after ATO injection. Flow cytometric analysis of cells dissociated from the imaged tumor confirmed cellular uptake and binding of the FLIVO probe. Apoptosis appears to be a major mode of cell death induced by ATO in the tumor and the use of fluorescently tagged caspase inhibitors to assess cell death in live animals appears feasible to monitor and/or confirm anti-tumor effects of therapy.

TNF-alpha-based accentuation in cryoinjury--dose, delivery, and response

Cryosurgery is a minimally invasive cancer treatment using cryogenic temperatures. Intraoperative monitoring of iceball growth is an advantage of the treatment. However, whereas the iceball can be easily visualized, destruction within the iceball is incomplete and the means to monitor the "kill zone" are urgently needed. Recently, we have shown the ability of tumor necrosis factor-alpha (TNF-alpha) to enhance destruction within an iceball. To avoid systemic toxicity, we delivered TNF-alpha selectively to the tumor by a gold nanoparticle of 30-nm diameter (CYT-6091) tagged with TNF-alpha and thiol-derivatized polyethylene glycol. Using a dorsal skin fold chamber (DSFC) in a nude mouse, both normal skin and human prostate carcinoma (LNCaP Pro 5) were pretreated with soluble TNF-alpha (topically or i.v.) or CYT-6091 (i.v.) and frozen after 4 h. The cryolesion was assessed after 3 days by comparing histologic necrosis with perfusion defects. Hind limb tumors were also treated by visibly encompassing the tumor with an iceball and assessing gross changes over time. A 5-mug dose of soluble TNF-alpha or CYT-6091 increased the temperature threshold of necrosis in the tumor in the DSFC from -14.0 +/- 1.6 degrees C (n = 6) to 0.9 +/- 1.5 degrees C (n = 6) and -1.5 +/- 3.7 degrees C (n = 6), respectively. In hind limb tumors, the same dose resulted in significant tumor shrinkage and remission in 2 of 8 (for soluble TNF-alpha) and in 3 of 8 (for CYT-6091). The nanoparticle alone group without TNF-alpha increased the temperature threshold of necrosis to -7.0 +/- 2.3 degrees C in the tumor in the DSFC and more shrinkage of the tumor in the hind limb when compared with cryo alone treatment. Systemic toxicity was noted in all soluble TNF-alpha groups but none with CYT-6091. These results suggest that it is possible to destroy all of a tumor within an iceball by preincubation with TNF-alpha and systemic toxicity can be avoided by CYT-6091.

Optical tissue window: a novel model for optimizing engraftment of intestinal stem cell organoids

BACKGROUND

Intestinal malabsorption disorders and short bowel syndrome lead to significant morbidity. We recently demonstrated that grafting of intestinal organoids can grow a bioengineered intestinal neomucosa and cure bile acid malabsorption in rats. Now we have developed a novel system that permits direct observation of intestinal organoids in vivo to optimize conditions for engraftment.

METHODS

Optical Windows were created in C57BL/6J mice by externalizing an omental pedicle into a dorsal skin flap chamber. Following creation of windows, 5000 intestinal organoids from green-fluorescent protein transgene (GFP)+ donor mice were seeded directly either on omentum or on polyglycolic acid (PGA) disks that had been placed on omentum at 1 or 5 days. Engraftment of green fluorescent cells was evaluated on postseeding days 1, 3, 5, 7, 10, 12, and 21 using fluorescence microscopy.

RESULTS

An initial group had seeding onto omentum (n = 5) or biopolymer disks (n = 5) on postoperative day 1. After 7 days, there was mucosal cell engraftment onto omental tissue and biopolymers. GFP+ organoids engrafted significantly better when seeded onto biopolymers compared to omentum (P < 0.05). In a second study with increased sample size (n = 24) up to day 12, all four groups demonstrated adherence and growth. However, GFP+ organoids seeded onto delayed PGA biopolymer demonstrated significantly better engraftment (P < 0.05).

CONCLUSIONS

This novel system allows continuous in vivo observation of engrafted cells that are seeded on externalized omentum. The use of PGA mesh biopolymer may improve engraftment of intestinal organoids.

Analysis of thermal stress in cryosurgery of kidneys

In this study, the thermal stress distribution in cryosurgery of kidney was investigated using a multiphysics finite element model developed in ANSYS (V8.1). The thermal portion of the model was verified using experimental data and the mechanics portion of the model (elastic) was verified using classic analytical solutions. Temperature dependent thermal and mechanical properties were used in the model. Moreover, the model accounts for thermal expansion due to both thermal expansion in single phase and volumetric expansion associated with phase change of tissue water to ice. For a clinical cylindrical cryoprobe inserted into the renal cortex from the top-middle renal capsule, it was found that the thermal stress distributions along the radial position are very different at different depths from the top renal capsule. The thermal stress is much higher at both ends than in the middle of the cryoprobe surface. It was found that there might be more tissue next to the top renal capsule than other region undergoing microcrack formation or plastic deformation. Furthermore, it was found that macrocrack formation is more likely to occur in tissue adjacent to the cryoprobe surface (especially on the sharp point tip) and during the thawing phase of cryosurgery. It was further found that the volumetric expansion associated with phase change induced much higher thermal stress than thermal expansion in a single phase and might therefore be the main cause of the frequently observed crack formation shortly after initiation of thawing in cryosurgery. Because the thermal stress adjacent to the cryoprobe is much higher than the yield stress of frozen renal tissue, a plastic stress model is required for better modeling of the thermal stress distribution in cryosurgery of kidney in future. However the computational effort will then be drastically increased due to the strong nonlinear nature of the plastic model and more experimental studies are indispensable for better understanding of the mechanical behavior of frozen tissue in cryosurgery.

A Cryoinjury Model Using Engineered Tissue Equivalents for Cryosurgical Applications

Cryosurgery is emerging as a promising treatment modality for various cancers, but there are still challenges to be addressed to improve its efficacy. Two primary challenges are determining thermal injury thresholds for various types of cell/tissue, and understanding of the mechanisms of freezing induced cell/tissue injury within a cryolesion. To address these challenges, various model systems ranging from cell suspensions to three-dimensional in vivo tissues have been developed and used. However, these models are either oversimplifications of in vivo tissues or difficult to control and extract precise experimental conditions from. Therefore, a more readily controllable model system with tissue-like characteristics is needed. In this study, a cryoinjury model was developed using tissue engineering technology, and the capabilities of the model were demonstrated. Engineered tissue equivalents (TEs) were constructed by seeding and culturing cells in a type I collagen matrix. Two different cell lines were used in this study, AT-1 rat prostate tumor cells and LNCaP human prostate cancer cells. The constructed TEs underwent a freeze/thaw cycle imitating in vivo cryosurgery. Thermal conditions within TEs during freeze/thaw cycles were characterized, and the responses of TEs to these thermal conditions including freezing induced cellular injury and extracellular matrix damage were investigated at three different time points. The results illustrate the feasibility to establish thermal thresholds of cryoinjury for different cell/tissue types using the presently developed model, and its potential capabilities to study cell death mechanisms, cell proliferation or migration, and extracellular matrix structural damage after a freeze/thaw cycle.

Pre-treatment inflammation induced by TNF-α augments cryosurgical injury on human prostate cancer

Vascular injury is a major mechanism of cryosurgical destruction. The extent of vascular injury may be affected by the addition of molecular adjuvants. This study, in addition to determining the injury mechanism in the LNCaP Pro 5 human prostate cancer subline grown in a nude mouse, examined the effect of cytokine TNF-alpha on cryosurgery of an in vivo microvascular preparation (Dorsal Skin Flap Chamber). A comparison of injury data to a thermal model indicated that the minimum temperature after moderate cooling, thawing, and hold time required for causing necrosis was 3.5+/-6.9 degrees C in TNF-alpha-treated LNCaP Pro 5 tumor tissue (n=4) and -9.8+/-5.8 degrees C in TNF-alpha-treated normal skin of the nude mouse (n=4). Compared to tissues without TNF-alpha treatment, where the minimum temperature required for causing necrosis was -16.5+/-4.3 degrees C in LNCaP Pro 5 tumor tissue (n=8) and -24.4+/-7.0 degrees C in normal skin of the nude mouse (n=9), the results indicate the local use of TNF-alpha can dramatically increase the threshold temperature of cryo-destruction by more than 10 degrees C (p <0.01). These findings were consistent with the hypothesis that vascular-mediated injury is responsible for defining the edge of the cryolesion in microvascular-perfused tissue, and therefore pre-induced inflammation can augment cryoinjury. The local use of TNF-alpha to pre-inflame prostate cancer promises to increase both the ability of freezing to destroy cancer as well as improve the ability of ultrasound or other iceball-monitoring techniques to predict the outcome of the treatment.

Computer simulation of prostate cryoablation--fast and accurate approximation of the exact solution

OBJECTIVE

Cryosurgery is a minimally invasive cancer treatment that uses liquid nitrogen or supercooled argon to freeze and destroy tumors. To achieve complete ablation of the prostate, we have developed a computer program that can determine treatment effects by calculating iceball formation. This is based on a three-dimensional (3D) model of the patient's prostate constructed from ultrasound images. The program predicts the best set of cryoablation parameters and cryoprobe spatial positions, then displays these parameters in graphical or numerical form. The objective of this work was to improve our prostate cryoablation modeling software by making its partial differential equation (PDE) solver more accurate and faster.

MATERIALS AND METHODS

CryoSim, our software package, accepts a set of acquired and processed 3D ultrasound images of the prostate, then models heat diffusion using numerical approximations of the heat equation.

RESULTS

We describe the latest version of the CryoSim software, which models cryoablation therapy. Solving the problems of low spatial resolution (now down to a fraction of a millimeter, as compared to 5 mm in the old version) and modeling cryosurgery in a short time (down to few minutes versus hours) provides a platform for proper planning of cryosurgery and a tool for the training of surgeons.

CONCLUSION

Changes in the PDE solver algorithm produce more accurate results, leading to an improved visualization of the iceball, with a precision of a few mm and a significant decrease in computation time.

Intralesional cryotherapy for enhancing the involution of hypertrophic scars and keloids

Although therapeutic management of hypertrophic scars and keloids using contact or spray cryosurgery has yielded significant improvement or complete regression of hypertrophic scars and keloids, it requires one to 20 treatment sessions. This study was designed to assess the clinical safety and efficacy of an intralesional needle cryoprobe method in the treatment of hypertrophic scars and keloids. Ten patients, ranging in age from 3 to 54 years, with a total of 12 hypertrophic scars and keloids of more than 6 months duration and of diverse causes, were included in this study. The 18-month trial evaluated volume reduction of the hypertrophic scars and keloids after a single session of intralesional cryotherapy. Objective (hardness and color) and subjective (pain/tenderness and itchiness/discomfort) parameters were examined on a scale of 0 to 3 (low score was better). Pretreatment and posttreatment histomorphometric studies of the collagen fibers included spectral picrosirius red polarization and fast Fourier transformation orientation index. A specially designed cryo-needle was inserted into the long axis of the hypertrophic scars and keloids so as to maximize the volume of the hypertrophic scars and keloids to be frozen. The cryo-needle was connected by an adaptor to a cryogun filled with liquid nitrogen, which was introduced into the cryoprobe, thereby freezing the hypertrophic scars and keloids. After the hypertrophic scars and keloids were completely frozen, the cryoprobe defrosted and was withdrawn. An average of 51.4 percent of scar volume reduction was achieved after one session of intralesional cryosurgery treatment (average preoperative hypertrophic scars and keloids volume, 1.82 +/- 0.33; average posttreatment volume, 0.95 +/- 0.21; p < 0.0022). Significant alleviation of objective and subjective clinical symptoms was documented. Mild pain or discomfort during and after the procedure was easily managed. Only mild local edema and epidermolysis, followed by a short reepithelialization period, were evident. During the 18-month follow-up period, there was no evidence of bleeding, infection, adverse effects, recurrence, or permanent depigmentation. The histomorphometric analysis demonstrated rejuvenation of the treated scars (i.e., parallelization) and a more organized architecture of the collagen fibers compared with the pretreated scars. This study demonstrated the increased efficacy of this method as a result of increased freezing area of deep scar material compared with that obtained with contact/spray probes. As a result, fewer treatment cycles are needed. Because the reepithelialization period is short, treatment intervals, if any, can be shortened to 2 to 3 weeks. This intralesional cryoneedle method is simple to operate and safe to use, it necessitates less postoperative care of the wound, and it can easily be added to any preexisting cryosurgical unit.

The cryobiology of cryosurgical injury

Cryosurgery, or tissue destruction by controlled freezing, has been investigated as a possible alternative to surgical intervention in the treatment of many diseases. This technique, which is under the larger category of thermal therapy, has its origins in the 1800s when advanced carcinomas of the breast and uterine cervix were treated with iced saline solutions. Since those early times, this technique has been used routinely to treat malignancies on the surface of the body (ie, dermatologic tumors) and has gained some acceptance as a clinical tool for the management of internal malignancies, including carcinoma of the prostate and kidney. The main advantages of the technique are the potential for less invasiveness and lower morbidity compared with surgical excision. The study of the destructive process of freezing is the focus of this article and is divided into 2 main areas: (1) understanding the mechanism by which freezing destroys tissue, and (2) understanding the thermal history that causes tissue destruction. The term "thermal history," as used in this article, will mean the time-temperature history experienced by the tissue during a thermal insult.

Cryosurgery of normal and tumor tissue in the dorsal skin flap chamber: Part II--injury response

It has been hypothesized that vascular injury may be an important mechanism of cryosurgical destruction in addition to direct cellular destruction. In this study we report correlation of tissue and vascular injury after cryosurgery to the temperature history during cryosurgery in an in vivo microvascular preparation. The dorsal skin flap chamber implanted in the Copenhagen rat, was chosen as the cryosurgical model. Cryosurgery was performed in the chamber on either normal skin or tumor tissue propagated from an AT-1 Dunning rat prostate tumor, as described in a companion paper (Hoffmann and Bischof, 2001). The vasculature was then viewed at 3 and 7 days after cryoinjury under brightfield and FITC-labeled dextran contrast enhancement to assess the vascular injury. The results showed that there was complete destruction of the vasculature in the center of the lesion and a gradual return to normal patency moving radially outward. Histologic examination showed a band of inflammation near the edge of a large necrotic region at both 3 and 7 days after cryosurgery. The area of vascular injury observed with FITC-labeled dextran quantitatively corresponded to the area of necrosis observed in histologic section, and the size of the lesion for tumor and normal tissue was similar at 3 days post cryosurgery. At 7 days after cryosurgery, the lesion was smaller for both tissues, with the normal tissue lesion being much smaller than the tumor tissue lesion. A comparison of experimental injury data to the thermal model validated in a companion paper (Hoffmann and Bischof 2001) suggested that the minimum temperature required for causing necrosis was -15.6 +/- 4.3 degrees C in tumor tissue and -19.0 +/- 4.4 degrees C in normal tissue. The other thermal parameters manifested at the edge of the lesion included a cooling rate of approximately 28 degrees C/min, 0 hold time, and a approximately 9 degrees C/min thawing rate. The conditions at the edge of the lesion are much less severe than the thermal conditions required for direct cellular destruction of AT-1 cells and tissues in vitro. These results are consistent with the hypothesis that vascular-mediated injury is responsible for the majority of injury at the edge of the frozen region in microvascular perfused tissue.

Microscopic and calorimetric assessment of freezing processes in uterine fibroid tumor tissue

The use of cryosurgery in the treatment of uterine fibroids is emerging as a possible treatment modality. The two known mechanisms of direct cell injury during the tissue freezing process are linked to intracellular ice formation and cellular dehydration. These processes have not been quantified within uterine fibroid tumor tissue. This study reports the use of a combination of freeze-substitution microscopy and differential scanning calorimetry (DSC) to quantify freeze-induced dehydration within uterine fibroid tumor tissue. Stereological analysis of histological tumor sections was used to obtain the initial cellular volume (V(o)) or the Krogh model dimensions (deltaX, the distance between the microvascular channels = 15.5 microm, r(vo), the initial radius of the extracellular space = 4.8 micro m, and L, the axial length of the Krogh cylinder = 19.1 microm), the interstitial volume ( approximately 23%), and the vascular volume ( approximately 7%) of the fibroid tumor tissue. A Boyle-van't Hoff plot was then constructed by examining freeze-substituted micrographs of "equilibrium"-cooled tissue slices to obtain the osmotically inactive cell volume, V(b) = 0.47V(o). The high interstitial volume precludes the use of freeze-substitution microscopy data to quantify freeze-induced dehydration. Therefore, a DSC technique, which does not suffer from this artifact, was used to obtain the water transport data. A model of water transport was fit to the calorimetric data at 5 and 20 degrees C/min to obtain the "combined best fit" membrane permeability parameters of the embedded fibroid tumor cells, assuming either a Krogh cylinder geometry, L(pg) = 0.92 x 10(-13) m(3)/Ns (0.55 microm/min atm) and E(Lp) = 129.3 kJ/mol (30.9 kcal/mol), or a spherical cell geometry (cell diameter = 18.3 microm), L(pg) = 0.45 x 10(-13) m(3)/Ns (0.27 microm/min atm) and E(Lp) = 110.5 kJ/mol (26.4 kcal/mol). In addition, numerical simulations were performed to generate conservative estimates, in the absence of ice nucleation between -5 and -30 degrees C, of intracellular ice volume in the tumor tissue at various cooling rates typical of those experienced during cryosurgery (< or =100 degrees C/min). With this assumption, the Krogh model simulations showed that the fibroid tumor tissue cells cooled at rates < or = 50 degrees C/min are essentially dehydrated; however, at rates >50 degrees C/min the amount of water trapped within the tissue cells increases rapidly with increasing cooling rate, suggesting the formation of intracellular ice.