Direct comparison of endothelial cell and smooth muscle cell response to supercooling and rewarming

Cryoplasty for Canine Iliac Artery Stenosis and its Impact on Expression of TIMP-2 and MMP-2

Objective:

This study was performed to observe the effects of cryoplasty on canine iliac artery stenosis and the expression of tissue inhibition of matrix metalloproteinase 2 (TIMP-2) and matrix metalloproteinase 2 (MMP-2).

Methods:

We produced a reliable canine model to mimic the atherosclerotic stenosis in the iliac artery by suturing the artery followed by vessel ligation to create an injury to intimal and medial walls. Sixteen mongrel dogs with iliac artery stenosis were randomized to conventional balloon angioplasty (n = 8) or cryoplasty (n = 8).

Results:

Four weeks posttreatment, the cryoplasty group with less collagen fibers and smooth muscle demonstrated significantly larger luminal diameter of iliac artery compared to the balloon angioplasty group ( P < .001). Expression of TIMP-2 significantly increased and expression of MMP-2 significantly reduced in iliac artery of the cryoplasty group compared to conventional balloon angioplasty.

Conclusion:

Our study suggests cryoplasty might increase the expression of TIMP-2 and decrease the expression of MMP-2, thereby inhibiting vascular hyperplasia and collagen fibers synthesis of the stenotic vessels.

The sensitivity of human mesenchymal stem cells to vibration and cold storage conditions representative of cold transportation

In the current study, the mechanical and hypothermic damage induced by vibration and cold storage on human mesenchymal stem cells (hMSCs) stored at 2-8°C was quantified by measuring the total cell number and cell viability after exposure to vibration at 50 Hz (peak acceleration 140 m s(-2) and peak displacement 1.4 mm), 25 Hz (peak acceleration 140 m s(-2), peak displacement 5.7 mm), 10 Hz (peak acceleration 20 m s(-2), peak displacement 5.1 mm) and cold storage for several durations. To quantify the viability of the cells, in addition to the trypan blue exclusion method, the combination of annexin V-FITC and propidium iodide was applied to understand the mode of cell death. Cell granularity and a panel of cell surface markers for stemness, including CD29, CD44, CD105 and CD166, were also evaluated for each condition. It was found that hMSCs were sensitive to vibration at 25 Hz, with moderate effects at 50 Hz and no effects at 10 Hz. Vibration at 25 Hz also increased CD29 and CD44 expression. The study further showed that cold storage alone caused a decrease in cell viability, especially after 48 h, and also increased CD29 and CD44 and attenuated CD105 expressions. Cell death would most likely be the consequence of membrane rupture, owing to necrosis induced by cold storage. The sensitivity of cells to different vibrations within the mechanical system is due to a combined effect of displacement and acceleration, and hMSCs with a longer cold storage duration were more susceptible to vibration damage, indicating a coupling between the effects of vibration and cold storage.

Lower extremity limb salvage with cryoplasty: a single-center cohort study

Endovascular techniques have been playing an increasing role in managing lower extremity chronic critical limb ischemia (CLI) in patients considered poor or non-candidates for surgical revascularization secondary to co-morbidities such as coronary artery disease, uncontrolled hypertension, diabetes mellitus or inadequate conduit. This study reviews our recent clinical experience in the treatment of peripheral artery disease solely using cryoplasty. A retrospective cohort study was performed. The cohort consisted of 88 patients who underwent lower extremity revascularization utilizing cryoplasty between December 2003 and August 2007. Indications for intervention included poor wound healing after forefoot amputation or persistent ulceration of the foot, disabling claudication and rest pain. Kaplan–Meier analysis was performed to assess salvage rates. One hundred twenty-six lesions were treated in 88 patients. Technical success rate was 97%. Limb salvage rates were 75 and 63% for patients with critical limbs ischemia after one and three years, respectively. A history of smoking was associated with a threefold increased risk of limb loss. In conclusion, endovascular management of lower extremity lesions with cryoplasty is an emerging and viable paradigm in the treatment of CLI in an attempt to preserve limbs and avoid major amputations.

Effects of medium and hypothermic temperatures on preservation of isolated porcine testis cells

The effects of medium and hypothermic temperatures on testis cells were investigated to develop a strategy for their short-term preservation. Testes from 1-week-old piglets were enzymatically dissociated for cell isolation. In Experiment 1, testis cells were stored at either room (RT) or refrigeration (RG) temperature for 6 days in one of 13 different media. Live cell recovery was assayed daily using trypan blue exclusion. In Experiment 2, three media at RG were selected for immunocytochemical and in vitro culture studies. Live cell recovery was also assayed daily for 6 days using both trypan blue exclusion and a fluorochrome assay kit. For all media tested, significantly or numerically more live cells were maintained at RG than RT. On preservation Day 3 at RG (cell isolation day as Day 0), 20% FBS-Leibovitz resulted in the highest live cell recovery (89.5 + or - 1.7%) and DPBS in the lowest (60.3 + or - 1.9%). On Day 6 at RG, 20% FBS- Leibovitz also resulted in the best preservation efficiency with 80.9 + or - 1.8% of Day 0 live cells recovered. There was no difference in live cell recovery detected by the two viability assays. After preservation, the proportion of gonocytes did not change, whereas that of Sertoli and peritubular cells increased and decreased, respectively. After 6 days of hypothermic preservation, testis cells showed similar culture potential to fresh cells. These results show that testis cells can be preserved for 6 days under hypothermic conditions with a live cell recovery of more than 80% and after-storage viability of 88%.

The effects of freezing versus supercooling on vascular cells: implications for balloon cryoplasty

PURPOSE

To investigate the effects of supercooling, a phase whereby cells are below 0 degrees C but still in a liquid state, and freezing, the phase when cells become solid, of vascular cells in culture.

MATERIALS AND METHODS

Bovine aortic endothelial cells and smooth muscle cells were supercooled to -10 degrees C with or without freezing for 3, 30, or 60 seconds and then rewarmed to 37 degrees C for 24 hours. Viability was assessed by means of trypan blue exclusion, and apoptosis was assessed with the TUNEL (terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling) assay.

RESULTS

Viability of smooth muscle cells decreased 49% after freezing versus supercooling (P< .05). Endothelial cells maintained greater viability rates. A 19.5% smooth muscle cell apoptotic rate was observed after freezing, whereas smooth muscle cell supercooling yielded rates of only 11% (P< .05). A 4.17% endothelial cell apoptotic rate was observed after freezing, whereas supercooled endothelial cells yielded a 1.76% rate (P< .05).

CONCLUSIONS

Freezing results in decreased viability and increased apoptosis compared to supercooling in both cell lines. Smooth muscle cells appear more susceptible to freezing. The biologic effects of freezing on vascular cells may elucidate the mechanisms behind the enhanced patency after cryoplasty of atherosclerotic lesions.

Delineation of the chemomechanosensory regulation of gastrin secretion using pure rodent G cells

BACKGROUND & AIMS

Gastrin is a key regulator of gastric acid secretion. We aimed to isolate pure G cells to identify the mechanistic basis of luminal- and strain-mediated regulation.

METHODS

Using gradient centrifugation and fluorescence-activated cell sorting, rat G cells were prepared and luminal, neural, hormonal, and mechanical activation of secretion and signaling pathways studied.

RESULTS

Pure G-cell preparations (>97%) were isolated. Reverse-transcription polymerase chain reaction identified neural, hormonal, bacterial, and luminal G protein-coupled receptors, and immunostaining visualized specific sweet/bitter receptors and the tastant-associated G protein alpha-gustducin. Gastrin release was stimulated by forskolin (adenosine 3',5'-cyclic monophosphate [cAMP] inducer, 10 micromol/L; >3-fold), potentiated by 3-isobutyl-1-methylxanthine (IBMX; phosphodiesterase type 5 inhibitor and adenosine antagonist, 10 micromol/L) and phorbol myristate acetate (phorbol ester, 10 micromol/L), and inhibited by H-89 (protein kinase A inhibitor, 10 micromol/L), PD98059 (MEK1 inhibitor, 0.1 micromol/L), and wortmannin (phosphatidylinositol 3-kinase inhibitor, 1 nmol/L). Gastrin release was stimulated by neuronal G protein-coupled receptor ligands, pituitary adenylate cyclase-activating protein (20 pmol/L, >8-fold) and bombesin (0.1 micromol/L, 8-fold) through cAMP signaling. The tastants sucralose, glucose, caffeine, denatonium, and the vanilloid receptor activator capsaicin all stimulated secretion (>3-fold), as did bacterial lipopolysaccharides Salmonella enteritidis (0.24 nmol/L, 5-fold) greater than Helicobacter pylori (0.57 micromol/L, 3-fold). Secretion was associated with elevated cAMP levels (approximately 2-fold) and could be inhibited by H-89 and PD98059 and potentiated by IBMX and cholera toxin (250 microg/mL). Bacterially mediated secretion also involved activation of nuclear factor kappaB and the c-Jun-N-terminal kinase pathway. Mechanical strain stimulated (2-fold to 8-fold) gastrin release, and decreasing pH from 7.4 to 5.5 inhibited release. The adenosine receptor 2B antagonist MRS1754 inhibited mechanically induced gastrin release.

CONCLUSIONS

G cells are luminal sampling chemomechanosensory cells whose secretion is regulated by neural, hormonal, luminal, and mechanical factors through protein kinase A activation, cAMP signaling, and mitogen-activated protein kinase phosphorylation.

Synergistic effect of cool/thaw cycles on vascular cells in an in vitro model of cryoplasty

PURPOSE

Cryoplasty combines mechanical dilation with supercooling of the vessel and has shown encouraging preliminary results in the management of atherosclerotic lesions. However, the mechanisms of action and the optimum inflation regimen are still not well established. This study investigates the effects of single and dual supercooling and rewarming cycles on the survival responses of smooth muscle cells (SMCs) and endothelial cells (ECs).

MATERIALS AND METHODS

Bovine aortic SMCs and ECs were cultured separately in six-well plates with medium supplemented with 10% fetal bovine serum. In the one-cycle treatment group, the cells were supercooled for 60 seconds to -10 degrees C and then rewarmed rapidly in a water bath at 37 degrees C for another 60 seconds. Two-cycle treatment was done by supercooling and rewarming the cells twice. The samples were then put into an incubator at 37 degrees C for 0, 6, 12, and 24 hours. Terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling was used to measure apoptosis and phospho-Akt immunohistochemistry and immunoblot analysis were employed to assess activation of Akt.

RESULTS

A significant increase of apoptotic cells was observed in the two-cycle procedure versus the one-cycle procedure. In both groups, there were more apoptotic SMCs than ECs. Akt activation was higher in ECs by a factor of three compared with SMCs (P < .05).

CONCLUSIONS

The higher apoptotic rate and the absence of Akt activation of SMCs versus controls in both treatment groups may imply the potential of a lower restenosis rate, especially after two cycles of supercooling and rewarming. Further in vivo and clinical investigations are needed to confirm results of the in vitro testing.