In vitro model systems for evaluation of smooth muscle cell response to cryoplasty

Comparison of tandem ureteral stents, cryoplasty, and cutting balloon ureteroplasty in treatment of refractory transplant ureteral strictures

The objective of study was to compare clinical outcome of cryoplasty, tandem stents, and cutting balloon ureteroplasty as "bailout procedures" to prevent surgical intervention or stent dependency in renal transplant patients with refractory ureteral stricture. All patients who underwent a bailout procedure from June 11, 2003, to August 8, 2015, at a single institution were reviewed retrospectively. Refractory ureteral stricture was defined as ureteral stenosis not responding to at least two prior percutaneous plain balloon ureteroplasties. Primary patency was defined as stable allograft function following the procedure with unobstructed urine outflow, not requiring indwelling ureteral stent, repeat ureteroplasty, or surgical revision. Sixty-one procedures were performed on 51 patients. Patients were followed up for a median of 286 days. Overall primary patency rate was 26.1%. Primary patency rate by method was 38.1%, 23.1%, and 14.3% after cryoplasty, tandem stent placement, and cutting balloon dilatation, respectively (P = .260). Primary patency rate was higher in early (<3 months post-transplant) ureteral strictures (35.7% vs 13.3%; P = .047). More complications identified in patients who had tandem ureteral stents (P = .00754). As some renal transplant patients may not be good operative candidates for ureteral revision, it would be reasonable to attempt one of these "bailout" interventions as long as the clinical team and patient are aware of overall low potential for achieving primary patency.

Drug-eluting balloon: design, technology and clinical aspects

A drug-eluting balloon is a non-stent technology in which the effective homogenous delivery of anti-proliferative drugs is processed by the vessel wall through an inflated balloon. This is done to restore luminal vascularity in order to treat atherosclerosis, in-stent restenosis and reduce the risk of late thrombosis without implanting a permanent foreign object. The balloon technology relies on the concept of targeted drug delivery, which helps in the rapid healing of the vessel wall and prevents the proliferation of smooth muscle cells. Several drug eluting devices in the form of coated balloons are currently in clinical use, namely DIOR^®, PACCOCATH^®, SeQuent^®Please and IN.PACT™. The device varies in terms of the material used for making the balloon, the coating techniques, the choice of coated drug and the release pattern of the drug at the site. This review gives an insight into the evolution, rationale and comparison of the marketed drug-eluting balloons. Here, different coating techniques have been analysed for the application and critical analysis of available DEB technologies, and a technical comparison has been done.

Endovascular techniques in limb salvage: cutting, cryo, brachy, and drug-eluting balloons

The complex pathophysiology response to injury of the lower-extremity arteries has prompted the development of several unique balloon technologies to overcome initial technical failures and short-term intimal hyperplasia. Cryoplasty alters the cellular and mechanical properties of the vessel wall during angioplasty. Cutting balloons incise the wall, preventing elastic recoil and allowing expansion of the lumen at a lower pressure, thus limiting barotrauma. Drug-eluting balloons actively transfer inhibitory compounds to the wall during the initial therapy, while brachytherapy balloons allow for localized delivery of radiation to inhibit the proliferative response seen after angioplasty. These platforms provide unique means to enhance immediate and short-term results and also reduce stent usage in the lower extremity.

Cryoplasty for peripheral arterial disease

BACKGROUND

Percutaneous balloon angioplasty is an endovascular technique for restoring blood flow through an artery that has become narrowed or blocked by atherosclerosis. Narrowing of the artery following angioplasty (restenosis) is the major cause of long-term failure. Cryoplasty offers a different approach to improving long-term angioplasty results. It combines the dilation force of balloon angioplasty with cooling of the vessel wall. This systematic review evaluated cryoplasty in peripheral arterial disease and provides focus for further research in the field. This is an update of a review first published in 2007.

OBJECTIVES

To assess the efficacy of, and complications associated with, cryoplasty for maintaining patency in the iliac, femoropopliteal and crural arteries in the short and medium term.

SEARCH METHODS

For this update the Cochrane Peripheral Vascular Diseases Group Trials Search Co-ordinator searched the Specialised Register (last searched October 2012) and CENTRAL (2012, Issue 10). Trial databases were searched for ongoing or unpublished studies. We also searched the reference lists of relevant articles.

SELECTION CRITERIA

All randomised controlled trials in which participants with peripheral arterial disease (PAD) of the lower limbs, or lower limb bypass graft stenoses, were randomised to cryoplasty with or without another procedure versus a procedure without cryoplasty were considered. This included trials where all participants received angioplasty and the randomisation was for cryoplasty versus no cryoplasty and trials where cryoplasty was used as an adjunct to conventional treatment (for example stenting) against a control.

DATA COLLECTION AND ANALYSIS

Two review authors independently reviewed, assessed and selected trials, extracted data and assessed risk of bias.

MAIN RESULTS

Seven trials (six primary cryoplasty and one adjunctive cryoplasty trial) with a combined total of 478 patients were included in this review. The trials reported patency and restenosis either by participant, lesion or vessel location. Follow-up ranged from 30 days to three years.Target lesion patency measured at various time points in two primary cryoplasty trials showed no statistically significant difference between the treatment groups. The adjunctive cryoplasty study showed that cryoplasty was associated with improved patency only at six months (OR 5.37, 95% CI 1.09 to 26.49, n = 90).Restenosis measured per patient (two primary cryoplasty trials) showed no statistically significant difference between the treatments. Restenosis measured by lesion (two primary cryoplasty trials) showed a statistically significant difference only within 24 hours of the procedure (OR 0.08, 95% CI 0.04 to 0.18, n = 192) favouring cryoplasty.Need for re-intervention was not significantly different in primary cryoplasty trial participants (per participant: OR 0.27, 95% CI 0.05 to 1.52, n = 241, I(2) = 89%; per lesion: OR 0.59, 95% CI 0.06 to 5.69, n = 307, I(2) = 94%). The adjunctive cryoplasty trial did not report on need for intervention.Immediate success of procedure (within 24 hours) was not significantly different in primary cryoplasty trial participants (per participant: OR 1.63, 95% CI 0.14 to 19.55, n = 340, I(2) = 95%; per lesion: OR 1.81, 95% CI 0.19 to 17.36, n = 397, I(2) = 90%). The adjunctive cryoplasty trial reported 100% success.Limb loss, deaths from all causes and the risk of complications immediately after treatment showed no statistically significant differences between the treatments.

AUTHORS' CONCLUSIONS

The benefit of cryoplasty over conventional angioplasty cannot be established as the number of randomised controlled trials is small and their quality is not sufficiently high. The technical success and primary patency rates seen in these trials are inconsistent and do not necessarily suggest a future role for cryoplasty in the treatment of PAD, but they cannot be reliably interpreted. Currently there are insufficient data to support the routine use of cryoplasty over conventional balloon angioplasty in the treatment of PAD.

Cryoplasty versus conventional balloon angioplasty of the femoropopliteal artery in diabetic patients: long-term results from a prospective randomized single-center controlled trial

The purpose of this study was to investigate the immediate and long-term results of cryoplasty versus conventional balloon angioplasty in the femoropopliteal artery of diabetic patients. Fifty diabetic patients (41 men, mean age 68 years) were randomized to cryoplasty (group CRYO; 24 patients with 31 lesions) or conventional balloon angioplasty (group COBA; 26 patients with 34 lesions) of the femoropopliteal artery. Technical success was defined as <30% residual stenosis without any adjunctive stenting. Primary end points included technical success, primary patency, binary in-lesion restenosis (>50%), and freedom from target lesion recanalization. Cox proportional hazards regression analysis was performed to adjust for confounding factors of heterogeneity. In total, 61.3% (19 of 31) in group CRYO and 52.9% (18 of 34) in group COBA were de novo lesions. More than 70% of the lesions were Transatlantic Inter-Society Consensus (TASC) B and C in both groups, and 41.4% of the patients in group CRYO and 38.7% in group COBA suffered from critical limb ischemia. Immediate technical success rate was 58.0% in group CRYO versus 64.0% in group COBA (p = 0.29). According to 3-year Kaplan-Meier estimates, there were no significant differences with regard to patient survival (86.8% in group CRYO vs. 87.0% in group COBA, p = 0.54) and limb salvage (95.8 vs. 92.1% in groups CRYO and COBA, respectively, p = 0.60). There was a nonsignificant trend of increased binary restenosis in group CRYO (hazard ratio [HR] 1.3; 95% CI 0.6-2.6, p = 0.45). Primary patency was significantly lower in group CRYO compared with group COBA (HR 2.2; 95% CI 1.1-4.3, p = 0.02). Significantly more repeat intervention events because of recurrent symptoms were required in group CRYO (HR 2.5; 95% CI 1.2-5.3, p = 0.01). Cryoplasty was associated with lower primary patency and more clinically driven repeat procedures after long-term follow-up compared with conventional balloon angioplasty.

Freeze-thaw induced biomechanical changes in arteries: role of collagen matrix and smooth muscle cells

Applications involving freeze-thaw, such as cryoplasty or cryopreservation can significantly alter artery biomechanics including an increase in physiological elastic modulus. Since artery biomechanics plays a significant role in hemodynamics, it is important to understand the mechanisms underlying these changes to be able to help control the biomechanical outcome post-treatments. Understanding of these mechanisms requires investigation of the freeze-thaw effect on arterial components (collagen, smooth muscle cells or SMCs), as well as the components' contribution to the overall artery biomechanics. To do this, isolated fresh swine arteries were subjected to thermal (freeze-thaw to -20 degrees C for 2 min or hyperthermia to 43 degrees C for 2 h) and osmotic (0.1-0.2 M mannitol) treatments; these treatments preferentially altered either the collagen matrix (hydration/stability) or smooth muscle cells (SMCs), respectively. Tissue dehydration, thermal stability and SMC functional changes were assessed from bulk weight measurements, analyses of the thermal denaturation profiles using Fourier transform infrared (FTIR) spectroscopy and in vitro arterial contraction/relaxation responses to norepinephrine (NE) and acetylcholine (AC), respectively. Additionally, Second Harmonic Generation (SHG) microscopy was performed on fresh and frozen-thawed arteries to directly visualize the changes in collagen matrix following freeze-thaw. Finally, the overall artery biomechanics was studied by assessing responses to uniaxial tensile testing. Freeze-thaw of arteries caused: (a) tissue dehydration (15% weight reduction), (b) increase in thermal stability (approximately 6.4 degrees C increase in denaturation onset temperature), (c) altered matrix arrangement observed using SHG and d) complete SMC destruction. While hyperthermia treatment also caused complete SMC destruction, no tissue dehydration was observed. On the other hand, while 0.2 M mannitol treatment significantly increased the thermal stability (approximately 4.8 degrees C increase in denaturation onset), 0.1 M mannitol treatment did not result in any significant change. Both 0.1 and 0.2 M treatments caused no change in SMC function. Finally, freeze-thaw (506+/-159 kPa), hyperthermia (268+/-132 kPa) and 0.2 M mannitol (304+/-125 kPa) treatments all caused significant increase in the physiological elastic modulus (Eartery) compared to control (185+/-92 kPa) with the freeze-thaw resulting in the highest modulus. These studies suggest that changes in collagen matrix arrangement due to dehydration as well as SMC destruction occurring during freeze-thaw are important mechanisms of freeze-thaw induced biomechanical changes.

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.

Freezing-induced fluid-matrix interaction in poroelastic material

Freezing of biological tissue is emerging in various biomedical applications. The success of these applications requires precise control of the tissue functionality, which is closely associated with the microstructure of the extracellular matrix (ECM). In the present study, the spatiotemporal effects of freezing on the ECM were experimentally and theoretically investigated by approximating biological tissue as a poroelastic material saturated with interstitial fluid. The experiments with type I collagen gel showed that its matrix underwent two distinct levels of structural changes due to freezing: enlarged pore structure of the matrix and increased collagen fibril diameters. The extent of these changes was augmented as the freezing temperature was lowered. The theoretical model suggested that the interstitial fluid might be transported toward the unfrozen region from the phase change interface due to the volumetric expansion associated with the water-ice phase change, and the transported fluid could interact with the matrix and enlarge its pore structure. The model also illustrated the effects of matrix structural properties on this interaction including initial porosity, hydraulic conductivity, and elastic modulus. These results imply that an identical macroscopic freezing protocol may result in different microstructural alterations of poroelastic materials depending on the structural properties of the matrix. This may be relevant to understanding the tissue-type dependent outcomes of cryomedicine applications and be useful in designing cryomedicine applications for a wide variety of tissues.

Membrane hydration correlates to cellular biophysics during freezing in mammalian cells

Cell survival during freezing applications in biomedicine is highly correlated to the temperature history and its dependent cellular biophysical events of dehydration and intracellular ice formation (IIF). Although cell membranes are known to play a significant role in cell injury, a clear correlation between the membrane state and the surrounding intracellular and extracellular water is still lacking. We previously showed that lipid hydration in LNCaP tumor cells is related to cellular dehydration. The goal of this study is to build upon this work by correlating both the phase state of the membrane and the surrounding water to cellular biophysical events in three different mammalian cell types: human prostate tumor cells (LNCaP), human dermal fibroblasts (HDF), and porcine smooth muscle cells (SMC) using Fourier Transform Infrared spectroscopy (FTIR). Variable cooling rates were achieved by controlling the degree of supercooling prior to ice nucleation (-3 degrees C and -10 degrees C) while the sample was cooled at a set rate of 2 degrees C/min. Membranes displayed a highly cooperative phase transition under dehydrating conditions (i.e. NT=-3 degrees C), which was not observed under IIF conditions (NT=-10 degrees C). Spectral analysis showed a consistently greater amount of ice formation during dehydrating vs. IIF conditions in all cell types. This is hypothesized to be due to the extreme loss of membrane hydration in dehydrating cells that is manifested as excess water available for phase change. Interestingly, changes in residual membrane conformational disorder correlate strongly with cellular volumetric decreases as assessed by cryomicroscopy. A strong correlation was also found between the activation energies for freezing induced lyotropic membrane phase change determined using FTIR and the water transport measured by cryomicroscopy. Reduced lipid hydration under dehydration freezing conditions is suggested as one of the likely causes of what has been termed as "solution effects" injury in cryobiology.

Cryoplasty for peripheral vascular disease

BACKGROUND

In the UK, symptomatic peripheral arterial disease (PAD) occurs in 5 to 7% of people over the age of 55 years. Cryoplasty offers a new approach by combining the dilation force of balloon angioplasty with the delivery of cold thermal energy to the vessel wall. Cryoplasty is thought to provoke apoptosis rather than necrosis in the arterial smooth muscle cells and thus has the theoretical advantage of reduced myointimal hyperplasia in long-term patency. As it is an emerging therapy, safety and efficacy questions remain. This systematic review evaluates the treatment and provide focus for further research in the field.

OBJECTIVES

To assess the efficacy of, and complications associated with, cryoplasty for maintaining patency in the iliac or infrainguinal arteries.

SEARCH STRATEGY

We searched the Specialized Register of the Cochrane Peripheral Vascular Diseases Group (inception to August 2007), the Cochrane Central Register of Controlled Trials (CENTRAL) in The Cochrane Library 2007, Issue 3, along with MEDLINE (1966 to August 2007) and EMBASE (1980 to August 2007).

SELECTION CRITERIA

Trials in which patients with peripheral arterial disease (PAD) of the iliac or infrainguinal arteries were randomised to cryoplasty with or without another procedure versus a procedure without cryoplasty. This includes trials where all patients receive angioplasty and the randomisation is for cryoplasty versus none.

DATA COLLECTION AND ANALYSIS

Studies identified for potential inclusion were independently assessed for inclusion by at least two authors, with excluded trials arbitrated by the third author. As no randomised controlled trials of cryoplasty were found, no statistical analyses were performed.

MAIN RESULTS

No randomised controlled trials of cryoplasty were identified.

AUTHORS' CONCLUSIONS

The benefit of cryoplasty over conventional angioplasty has not been established as no randomised controlled trials exist to properly evaluate this method. Technical success and primary patency rates seen in the prospective series are encouraging and may suggest a future role for cryoplasty in the treatment of PAD, but cannot be reliably interpreted due to the nature of the studies.

Early endothelial and haematological response to cryoplasty compared with balloon angioplasty of the superficial femoral artery – a pilot study

The purpose of the present study was to assess the course of adhesion molecules (intercellular adhesion molecule (ICAM), vascular cell adhesion molecule (VCAM), e-selectin, p-selectin and monocyte chemoatlractant protein 1 (MCP-1)), growth factors (transforming growth factor beta (TGFbeta) and basic fibroblast growth factor (bFGF)) and the cytokine tumour necrosis factor alpha (TNFalpha) after both angioplasty and cryoplasty. Recently cryoplasty has been suggested as a new method to oppose neointimal hyperplasia resulting in restenosis formation. While in vitro models have shown that the application of cryothermal energy to the endothelium during angioplasty leads to apoptosis induction and reduced proliferation rates, no human in vivo proof for an inhibition of neointimal hyperplasia exists. For restenosis initiation adhesion molecules, growth factors and cytokines play an important role. One possibility to investigate the endothelial response to angioplasty is the measurement of the soluble forms of adhesion molecules, growth factors and cytokines that are released into the circulation after denuding the vessel wall. In the present study we assessed the distribution pattern of the soluble forms of e-selectin, p-selectin, ICAM, VCAM, MCP-1, TGFbeta, bFGF and TNFalpha after angiography, angioplasty and cryoplasty of the femoropopliteal artery in the early course of 4 weeks in 29 patients with peripheral arterial occlusive disease. During the 4 weeks after intervention levels of e-selectin, ICAM, VCAM and MCP-1 increased after both angioplasty and cryoplasty. The course of the screened biomarkers was similar between angioplasty and cryoplasty. P-selectin and TGFbeta both decreased after cryoplasty, but not significantly. The present results show that the release of adhesion molecules, growth factors and cytokines is similar between balloon angioplasty and cryoplasty.

Treatment of Ureterointestinal Anastomotic Strictures by Diathermal or Cryoplastic Dilatation

BACKGROUND

Ureterointestinal anastomotic strictures (UAS) complicate 10-15% of surgeries for urinary diversion and are the main cause of deterioration in renal function. Treatments are surgical revision, management with autostatic stent, balloon dilatation, endoscopic incision, and percutaneous transrenal diathermy (Acucise). A new option is cryoplastic dilatation (Polar-Cath).

PURPOSE

To assess the feasibility, complications, and preliminary results of UAS treatment using the Acucise and Polar-Cath systems.

METHODS

Nineteen UAS, diagnosed by ultrasonography or computed tomography and sequential renal scintigraphy, occurred in 15 cancer patients after radical cystectomy and urinary diversion. Fifteen were managed with balloon diathermy and 4 by balloon cryoplasty in a three-stage procedure--percutaneous nephrostomy, diathermal or cryoplastic dilatation, and transnephrostomic control with nephrostomy removal--each separated by 15 days. All patients gave written informed consent.

RESULTS

Dilatations were successful in all cases. The procedure is simple and rapid (about 45 min) under fluoroscopic control and sedation. Procedural complications occurred in 1 (5%) patient with UAS after Wallace II uretero-ileocutaneostomy: a common iliac artery lesion was induced by diathermal dilatation, evident subsequently, and required surgical repair. Patency with balloon diathermy was good, with two restenoses developing over 12 months (range 1-22) of follow-up. With balloon cryoplastic dilatation, one restenosis developed in the short term; follow-up is too brief to assess the long-term efficacy.

CONCLUSION

Our short-term results with diathermal and cryoplastic dilatation to resolve UAS are good. If supported by longer follow-up, the techniques may be considered as first-choice approaches to UAS. Surgery should be reserved for cases in which this minimally invasive technique fails.

Biothermal Modeling of Post-Cryoplasty Atheroscelerosis in Restenotic Patients

Atherosclerosis is a leading cause of heart diseases and mortality around the world. Recently, cryoplasty has emerged as a potential alternative method to treat arterial atherosclerosis. Finite element heat transfer and mass transfer models are developed using ANSYS in this study. The model analyzes the heat transfer within the atherosclerotic plaque and arterial wall during the cryoplasty procedure. The model is useful in predicting the transient temperature through the diseased wall tissues. The results may be used to decide required treatment procedure to effectively freeze the plaque with minimal damage to the healthy arterial tissues. Finally, the model investigates the parameters that may effect temperature distribution within the tissues during the ablative procedure.

Cryoplasty for Arterial Restenosis

OBJECTIVE

A prospective follow-up study of patients with arterial restenosis undergoing cryoplasty.

MATERIALS & METHODS

Between May 2004 and June 2005, 10 patients with restenosis following ilio-femoral endovascular treatment underwent twelve cryoplasty procedures. All patients had had at least one previous episode of stenosis treated by conventional endovascular methods and had suffered further restenosis. The indications for treatment were grafts at risk (n=5) and symptomatic in-stent restenosis (n=5). Two patients underwent re-cryoplasty. Cryoplasty was performed in accordance with manufacturer's instructions using 6-8mm balloons. All patients had Doppler ultrasound evaluation at 1, 3, 6 and 12 months.

RESULTS

All procedures had angiographically successful immediate outcome with <30% residual stenosis. Non flow limiting dissection was evident in two cases. In six procedures (50%), restenosis was evident within 6 months post-procedure, whilst in the other six, there was progressive restenosis appearing between 6-12 months. Five cryoplasty procedures have needed endovascular re-intervention due to symptomatic high-grade restenosis and a sixth is awaiting surgery.

CONCLUSION

Cryoplasty is of no value in patients with restenosis in the iliofemoral segment with half the procedures failing within six months and all of them within the first year. Evidence to support the use of cryoplasty in the peripheral arterial restenotic lesions is lacking.

Superficial femoral artery: current treatment options

Treatment of the superficial femoral artery (SFA) has been among the least effective of all endovascular procedures in terms of long-term patency. The relatively small vessel lumen, in conjunction with a high plaque burden, slow flow, and a high frequency of primary occlusions, contributes to a considerable rate of acute technical failures. Because of these technical limitations a much effort has been made during the past years. This manuscript should summarize the hopes and limitations of different approaches such as brachytherapy, cutting balloons, stents and stent grafts, drug-eluting stents, and drug-coated balloons.

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.