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Biomedical subjects

G M LaMuraglia

Publications and source records attributed to G M LaMuraglia.

At least 19 recordsLinked to original sources
PubMed2004

Evaluation of peripheral arterial occlusive disease and postsurgical viability using reflectance spectroscopy of skin.

HYPOTHESIS: Stress-induced changes in skin microcirculation allow staging of peripheral arterial vascular pathology using diffuse reflectance spectroscopy (DRS) of the skin. DESIGN AND METHODS: The changes in relative concentration of oxyhemoglobin and deoxyhemoglobin in the cutaneous microvasculature were assessed at rest, during limb elevation, dependency, and cuff-mediated reactive hyperemia for the forearm of 25 normal subjects and 105 feet of patients with peripheral arterial occlusive disease (PAOD) (normal=28, claudication=34, limb threatening ischemia=44). Thirty-four patients who had revascularization procedures were again evaluated within the first week postoperatively. RESULTS: Two measurements correlated with clinical staging: (1) the relative absorbance of oxyhemoglobin after 225 s of limb dependency and (2) the time to reach 50% of peak reactive hyperemia response (Spearman's rank: rs=0.625, P<0.001). Using these criteria alone, ischemic limbs were identified to a sensitivity of 69% and specificity of 95%. Significant post-revascularization improvement was identified in 14 of 34 patients' legs which had previously been classified as limb-threatening ischemia (n=14, W=105, P<0.001). CONCLUSIONS: These simple bedside evaluations of the superficial skin microvasculature allow staging of large vessel vascular insufficiency and may suggest and differentiate focal areas of tissue at risk for ulceration or necrosis.

Arterial Occlusive Diseases↗
PubMed2004

Characterization of the atherosclerotic carotid bifurcation using MRI, finite element modeling, and histology.

Atherogenesis is known to be associated with the stresses that act on or within the arterial wall. Still, the uneven distribution of atherosclerotic lesions and the impact of vessel remodeling on disease progression are poorly understood. A methodology is proposed to study the correlations between fluid dynamic parameters and histological markers of atherosclerosis. Trends suggested by preliminary data from four patients with advanced carotid bifurcation arterial disease are examined and compared to hypotheses in the literature. Four patients were scanned using MRI and ultrasound, and subsequently underwent carotid endarterectomy. For each patient. a geometric model and a numerical mesh were constructed from MR data, and velocity boundary conditions established. Computations yield values for average wall shear stress (WSS), maximum wall shear stress temporal gradient (WSSTG), and Oscillatory Shear Index (OSI). Following surgery, the excised plaques were sectioned, stained for smooth muscle cells (SMC), macrophages (M phi), lipid (LIP), and collagen (COL), and analyzed quantitatively. Correlations attempted between the various fluid dynamic variables and the biological markers were interesting but inconclusive. Tendencies of WSSTG and WSS to correlate negatively with M phi and LIP, and positively with COL and SMC, as well as tendencies of OSI to correlate positively with Mphi and LIP and negatively with COL and SMC, were observed. These trends agree with hypotheses in the literature, which are based on ex vivo and in vitro experimental studies.

Aged↗
PubMed2001

Laser-induced shock waves enhance sterilization of infected vascular prosthetic grafts.

BACKGROUND AND OBJECTIVE: Bacteria that cause infection of vascular prosthetic grafts produce an exopolysaccharide matrix known as biofilm. Growth in biofilms protects the bacteria from leukocytes, antibodies and antimicrobial drugs. Laser-generated shock waves (SW) can disrupt biofilms and increase drug penetration. This study investigates the possibility of increasing antibiotic delivery and sterilization of vascular prosthetic graft. STUDY DESIGN/MATERIALS AND METHODS: Strains of Staphylococcus epidermidis and S. aureus were isolated from infected prosthetic grafts obtained directly from patients. Dacron grafts were inoculated with the isolated bacteria, which were allowed to form adherent bacterial colonies. The colonized grafts underwent the following treatments: (a) antibiotic (vancomycin) alone; (b) antibiotic and SW (c) saline only; and (d) saline and SW. Six hours after treatment, the grafts were sonicated, the effluent was cultured and the colony forming units (CFU) were counted. RESULTS: CFU recovered from control grafts colonized by S. epidermidis were comparable: saline, 3.05 x 10(8) and saline+SW 3.31 x 10(8). The number of S. epidermidis CFU diminished to 7.61 x 10(6) after antibiotic treatment but the combined antibiotic+SW treatment synergistically decreased CFU number to 1.27 x 10(4) (P<0.001). S. aureus showed a higher susceptibility to the antibiotic: 2.26 x 10(6) CFU; antibiotic +SW treatment also had an incremental effect: 8.27 x 10(4) CFU (P<0.001). CONCLUSIONS: This study demonstrates that laser-generated shock waves have no effects alone, but can enhance the effectiveness of antibiotics against bacteria associated with prosthetic vascular graft biofilms, suggesting that this treatment may be of value as adjunctive therapy for prosthetic graft infections.

Anti-Bacterial Agents↗
PubMed2001

Clinical potential of photodynamic therapy in cardiovascular disorders.

Atherosclerosis and intimal hyperplasia remain obstacles for surgeons to overcome following vascular reconstructions. Even with all of the technical improvements that have occurred in the past several decades, long term patency following intervention is hindered by these inherent adverse developments. Today, the use of light is seen as a potential treatment modality in vascular surgery. Photodynamic therapy (PDT) has been used in the treatment of cancer, and because of its continued success in vascular experimental models it is now being tested in clinical trials for vascular diseases. PDT offers the surgeon many advantages, and it may have unlimited uses in the clinical setting. Is PDT the ultimate treatment modality for the cardiovascular surgeon and will it help to overcome the inherent failures associated with vascular reconstructions? It may be too early to answer these questions, but with the current successes demonstrated by PDT, there is a need for further testing in clinical trials. In the near future, PDT may be used clinically as a treatment modality to inhibit restenosis and intimal hyperplasia following surgical intervention.

Animals↗
PubMed2000

Photodynamic therapy generates a matrix barrier to invasive vascular cell migration.

Photodynamic therapy (PDT) inhibits experimental intimal hyperplasia. PDT results in complete vascular wall cell eradication with subsequent adventitia but minimal media repopulation. This study was designed to test the hypothesis that PDT alters the vascular wall matrix thereby inhibiting invasive cell migration, and as such, provides an important barrier mechanism to favorably alter the vascular injury response. Untreated smooth muscle cells (SMCs) and fibroblasts were seeded on control and PDT-treated (100 J/cm(2); photosensitizer was chloroaluminum-sulfonated phthalocyanine, 5 microg/mL) 3-dimensional collagen matrix gels. Invasive cell migration was temporally quantified by calibrated microscopy. Zymography and ELISA assessed SMC matrix metalloproteinase levels. Molecular changes of gel proteins and their susceptibility to collagenase were analyzed by SDS-PAGE and Western blot. Limited pepsin digestion and histology were used to assess the in vivo relevance of the model, using an established rat carotid artery model at 1 and 4 weeks after balloon injury and PDT. PDT of 3-dimensional matrix of gels led to a 52% reduction of invasive SMCs and to a 59% reduction of fibroblast migration (P<0.001) but did not significantly affect secretion of matrix metalloproteinases. PDT induced collagen matrix changes, including cross-linking, which resulted in resistance to protease digestion. PDT led to a durable 45% reduction in pepsin digestion susceptibility of treated arteries (P<0.001) and inhibition of periadventitial cell migration into the media. These data suggest that PDT of matrix gels generates a barrier to invasive cellular migration. This newly identified effect on matrix proteins underscores its pleiotropic actions on the vessel wall, and as such, PDT may be of considerable potential therapeutic value to inhibit restenosis.

Animals↗
PubMed2000

Photodynamic therapy induces apoptosis in intimal hyperplastic arteries.

Photodynamic therapy (PDT) generates free radicals through the absorption of light by photosensitizers. PDT shows promise in the treatment of intimal hyperplasia, which contributes to restenosis, by completely eradicating cells in the vessel wall. This study investigates the mechanisms of PDT-induced cell death. PDT, using the photosensitizer chloroaluminum-sulfonated phthalocyanine (1 mg/kg) and laser light (lambda = 675 nm) 100 J/cm(2) was administered to rat carotid arteries after balloon injury-induced intimal hyperplasia. Apoptosis was determined by cell morphology with light microscopy and transmission electron microscopy, DNA cleavage by terminal dUTP nick-end labeling staining, and nucleosomal fragmentation (ladder pattern) by DNA agarose gel electrophoresis. Four hours after PDT, apoptosis was observed in vascular cells, as evidenced by terminal dUTP nick-end labeling staining and transmission electron microscopy. Within 24 hours no cells were present in the neointima and media. Immunofluorescence using an alpha-smooth muscle cell actin antibody confirmed the disappearance of all neointimal and medial cells within 24 hours. No inflammatory cell infiltrate was observed during this time frame. Apoptosis was sharply confined to the PDT treatment field. These data demonstrate that vascular PDT induces apoptosis as a mechanism of rapid, complete, and precise cell eradication in the artery wall. These findings and the lack of inflammatory reaction provide the basis for understanding and developing PDT for a successful clinical application in the treatment of hyperplastic conditions such as restenosis.

Actins↗
PubMed2000

The reduction of the allogenic transfusion requirement in aortic surgery with a hemoglobin-based solution.

OBJECTIVE: Because of allogenic red blood cell (RBC) availability and infection problems, novel alternatives, including hemoglobin-based oxygen-carrying solutions (HBOC), are being explored to minimize the perioperative requirement of RBC transfusions. This study evaluated HBOC-201, a room-temperature stable, polymerized, bovine-HBOC, as a substitute for allogenic RBC transfusion in patients undergoing elective infrarenal aortic operations. METHODS: In a single blind, multicenter trial, 72 patients were prospectively randomized two-to-one to HBOC (n = 48) or allogenic RBC (n = 24) at the time of the first transfusion decision, either during or after elective infrarenal aortic reconstruction. Patients randomized to the HBOC group received 60 g of HBOC for the initial transfusion and had the option to receive three more doses (30 g each) within 96 hours. In this group, any further blood requirement was met with allogenic RBCs. Patients randomized to the allogenic RBC group received only standard RBC transfusions. The efficacy analysis was a means of assessing the ability of HBOC to eliminate the requirement for any allogenic RBC transfusions from the time of randomization through 28 days. Safety was evaluated by means of standard clinical trial methods. RESULTS: The two treatment groups were comparable for all baseline characteristics. Although all patients in the allogenic RBC group required at least one allogenic RBC transfusion, 13 of 48 patients (27%; 95% CI, 15% to 42%) in the HBOC group did not require any allogenic RBC transfusions. The only significant changes documented were a 15% increase in mean arterial pressure and a three-fold peak increase in serum urea nitrogen concentration after HBOC. The complications were similar in both groups, with no allergic reactions. There were two perioperative deaths (8%) in the allogenic RBC group and three perioperative deaths (6%) in the HBOC group (P = 1.0). CONCLUSION: HBOC significantly eliminated the need for any allogenic RBC transfusion in 27% of patients undergoing infrarenal aortic reconstruction, but did not reduce the median allogenic RBC requirement. HBOC transfusion was well tolerated and did not influence morbidity or mortality rates.

Adult↗
PubMed1999

Surgical renal artery reconstruction without contrast arteriography: the role of clinical profiling and magnetic resonance angiography.

PURPOSE: Contrast arteriography is the accepted gold standard for diagnosis and treatment planning in patients with atherosclerotic renovascular disease (RVD). In this study, the results of a selective policy of surgical renal artery reconstruction (RAR) with magnetic resonance angiography (MRA) as the sole preoperative imaging modality are reviewed. METHODS: From May 1993 to May 1998, 25 patients underwent RAR after clinical evaluation, and aortic/renal MRA performed with a gadolinium-enhanced and 3-dimensional phase contrast technique. Clinical presentations suggested severe RVD in all patients and included poorly controlled hypertension (16 patients), hospitalization for hypertensive crises and/or acute pulmonary edema (13), and deterioration of renal function within one year of operation (15). Thirteen patients had associated aortic pathologic conditions (12 aneurysms, 1 aortoiliac occlusive disease), and eight of these patients also underwent noncontrast computed tomography scans. Significant renal dysfunction (serum creatinine level, >/=2.0 mg/dL) was present in all but 4 patients with 14 of 25 patients having extreme (creatinine level, >/=3.0 mg/dL) dysfunction. RESULTS: Hemodynamically significant RVD in the main renal artery was verified at operation in 37 of 38 reconstructed main renal arteries (24/25 patients). A single accessory renal artery was missed by MRA. RAR was comprehensive (bilateral or unilateral to a single-functioning kidney) in 21 of 25 patients and consisted of hepatorenal bypass graft (3 patients), combined aortic and RAR (13 patients), isolated transaortic endarterectomy (8 patients), and aortorenal bypass graft (1 patient). Early improvement in both hypertension control and/or renal function was noted in 21 of 25 patients without operative deaths or postoperative renal failure. Sustained favorable functional results at follow-up, ranging from 5 months to 4 years, were noted in 19 of 25 patients. CONCLUSION: MRA is an adequate preoperative imaging modality in selected patients before RAR. This strategy is best applied in circumstances where the clinical presentation suggests hemodynamically significant bilateral RVD and/or in patients at substantial risk of complications from contrast angiography.

Angiography↗
PubMed1999

Photodynamic therapy inhibits the injury-induced fibrotic response of vascular smooth muscle cells.

OBJECTIVES: excessive deposition of extracellular matrix (ECM) proteins plays a key role in the intervention-related vascular fibroproliferative response, resulting in intimal hyperplasia (IH). Cytokines, such as platelet-derived growth factor (PDGF), released after vascular injury and deposited in the ECM, are known to stimulate production of matrix proteins. Photodynamic therapy (PDT), the combination of light and a photosensitive dye to produce free radicals, is a novel approach to inhibit experimental IH by the local eradication of smooth-muscle cells (SMC) and alteration of ECM. This in vitro study examined whether PDT can inhibit the fibrotic response of vascular SMC. MATERIALS AND METHODS: the effect of PDT on important pro-fibrotic factors was determined by performing PDT of isolated ECM, injured SMC and pure PDGF. SMC production of collagen was monitored by cellular [3H]-proline incorporation. RESULTS: untreated SMC seeded on ECM demonstrated an increase of 50% in collagen production ( p <0.0001) as compared to SMC on an empty plate. This increase was also seen when SMC was incubated with the conditioned media of mechanically injured SMC, or pure PDGF. However, after PDT of ECM, injured SMC or PDGF, there was an inhibition of 40% ( p <0.05) in SMC-collagen production. CONCLUSIONS: these findings indicate that PDT can interfere with factors that lead to the vascular fibrotic response. In this way, PDT, with its cytotoxic and extracellular effects, can promote healing of the vessel wall without the stimulus of fibrosis that can lead to restenosis.

Analysis of Variance↗
PubMed1999

Different effects of photodynamic therapy and gamma-irradiation on vascular smooth muscle cells and matrix : implications for inhibiting restenosis.

gamma-Irradiation (gamma-RT) and photodynamic therapy (PDT) are known to inhibit intimal hyperplasia. The common mechanism is that both modalities produce free radicals, but unlike gamma-RT, PDT generates them through the absorption of light by photosensitizers. The purpose of this in vitro study was to assess the differences that PDT and gamma-RT have on the fibroproliferative response after vascular injury by comparing their effects on vascular smooth muscle cells (SMCs) and on the extracellular matrix (ECM). Mitochondrial activity (tetrazolium salt), proliferation ([(3)H]thymidine incorporation), and the mechanisms of cell death (terminal deoxynucleotidyl transferase-mediated dUTP biotin nick end labeling [TUNEL] staining) were used to assess differences between PDT (100 J/cm(2)) and gamma-RT (10 or 20 Gy) on SMC injury. The different effects on bioregulatory molecules were investigated by quantitating the proliferation of SMCs cultured with conditioned medium and on treated ECM. PDT of SMCs reduced proliferation and mitochondrial activity (0.5+/-0.75% and 1.7+/-4.25%, respectively, P<0.0001), whereas gamma-RT of SMCs decreased cell proliferation but did not affect metabolic activity. Stimulation with calf serum of gamma-RT-treated SMCs did not affect proliferation but increased mitochondrial enzyme activity (160+/-11%, P<0.0005). The conditioned medium, derived from PDT- but not gamma-RT-treated SMCs, did not stimulate effector SMC proliferation compared with gamma-RT-treated SMCs (16+/-4.1% versus 80+/-16.8%, P<0.0001). Apoptosis was the principle cytotoxic mechanism after PDT, whereas gamma-RT cells were growth arrested but viable. PDT of the ECM reduced effector SMC proliferation compared with controls and gamma-RT cells (18+/-6.5% versus 100+/-17.7% and 84+/-8.9%, respectively, P<0.0001). These data suggest that gamma-RT and PDT may inhibit restenosis but by different mechanisms. The effects of PDT are more diverse and may result in improved outcome while avoiding the teratogenic exposure due to ionizing irradiation.

Animals↗
PubMed1999

Significance of dosimetry in photodynamic therapy of injured arteries: classification of biological responses.

With conflicting results in the literature on the ability of photodynamic therapy (PDT) to inhibit intimal hyperplasia (IH), the present study systematically investigated the effects of drug and light dosimetry on the biologic responses in the artery wall. The rat common carotid artery was balloon-injured and pressurized with benzoporphyrin-derivative monoacid ring (BPD). Then, PDT was performed with an external laser at different fluences and the biologic responses of the artery wall were histologically examined at 24 h and at 2 weeks. Photodynamic therapy effects on injured arteries can be classified into four stages: low-dose PDT using 0.5 microgram/mL BPD at 50 J/cm2 (stage I) resulted in incomplete cell eradication and significant IH at 2 weeks. Irradiation with 100 J/cm2 at the same BPD concentration (stage II) completely eradicated the cells in the artery wall at 24 h but still led to IH at 2 weeks. However, 25 micrograms/mL BPD at 100 J/cm2 (stage III) resulted in total cell eradication at 24 h and inhibition of IH at 2 weeks. In contrast, high-dose PDT with 25 micrograms/mL BPD and 200 J/cm2 (stage IV) led to thrombus development and vascular occlusion at 24 h. These data, demonstrating the different stages of PDT effects on injured arteries, emphasize the critical importance of appropriate PDT dosimetry for the effective inhibition of IH.

Animals↗
PubMed1998

Photodynamic therapy with local photosensitizer delivery inhibits experimental intimal hyperplasia.

BACKGROUND: Photodynamic therapy (PDT), the light activation of photosensitizer dyes for the production of free radicals, effectively inhibits experimental intimal hyperplasia with systemic administration of the photosensitizer. The local application of the photosensitizer directly into a vascular lesion to avoid systemic side effects and tightly control dose administration has theoretical appeal. The aim of this study was to quantify serum and arterial tissue uptake after site-specific photosensitizer delivery and, following PDT, determine its effectiveness at inhibiting intimal hyperplasia. STUDY DESIGN/MATERIALS AND METHODS: The rat common carotid artery was balloon-injured, pressurized at 400 mm Hg for 2 minutes with the photosensitizer dye benzoporphyrin-derivative (BPD), and irradiated with 690 nm laser light at a fluence of 100 J/cm2. Control animals were pressurized with saline only, or received no additional treatment than balloon-injury. RESULTS: Pressurization with BPD resulted in complete penetration of the intima and media and was associated with relatively high tissue, but almost no detectable serum BPD concentrations. No skin photosensitization or other systemic side effects were observed with photosensitizer administration. After 9 days, PDT-treated arteries displayed a significantly lower number of smooth muscle cells in the arterial wall than balloon-injured (P < 0.001) or saline-pressurized arteries (P < 0.0002), and no intimal hyperplasia. At 21 days, IH after PDT was significantly reduced as compared with balloon-injured (P < 0.0004), or saline-pressurized arteries (P < 0.003) with no arterial dilatation. CONCLUSIONS: Site-specific delivery of liposomal BPD followed by PDT represents a safe method to treat arteries, and may be effectively used in vivo to inhibit the development of intimal hyperplasia.

Animals↗
PubMed1998

Initial experience with endovascular aneurysm repair: comparison of early results with outcome of conventional open repair.

PURPOSE: To determine the safety, effectiveness, and problems encountered with endovascular repair of abdominal aortic aneurysm (AAA). Initial experience with endoluminal stent grafts was examined and compared with outcome for a matched concurrent control group undergoing conventional operative repair of AAA. METHODS: Over a 3-year period, 30 patients underwent attempts at endovascular repair of infrarenal AAA. Of the 28 (93%) successfully implanted endografts, 8 were tube endografts, 8 bifurcated grafts, and 12 aortouniiliac grafts combined with femorofemoral bypass. Most of the procedures were performed in the past year because the availability of bifurcated and aortoiliac endografts markedly expanded the percentage of patients with AAA who might be treated with endoluminal methods. The follow-up period ranged from 1 to 44 months, with a mean value of 11 months. RESULTS: Endovascular procedures demonstrated significant advantages with respect to reduced blood loss (408 versus 1287 ml), use of an intensive care unit (0.1 versus 1.75 days), length of hospitalization (3.9 versus 10.3 days), and quicker recovery (11 versus 47 days). Although the total number of postoperative complications was identical for the two groups, the nature of the complications differed considerably. Local and vascular complications characteristic of endovascular repair could frequently be corrected at the time of the procedure and tended to be less severe than systemic or remote complications, which predominated among the open surgical repair group. On an intent-to-treat basis, 23 (77%) of the 30 AAAs were successfully managed with endoluminal repair. The seven (23%) failures were attributable to two immediate conversions caused by access problems, three persistent endoleaks, one late conversion caused by AAA expansion, and one late rupture. CONCLUSIONS: Although less definitive than those for conventional operations, these early results suggest that endovascular AAA repair offers considerable benefits for appropriate patients. The results justify continued application of this method of AAA repair, particularly in the treatment of older persons at high risk.

Aged↗
PubMed1998

Telemedicine in vascular surgery: feasibility of digital imaging for remote management of wounds.

PURPOSE: Telemedicine coupled with digital photography could potentially improve the quality of outpatient wound care and decrease medical cost by allowing home care nurses to electronically transmit images of patients' wounds to treating surgeons. To determine the feasibility of this technology, we compared bedside wound examination by onsite surgeons with viewing digital images of wounds by remote surgeons. METHODS: Over 6 weeks, 38 wounds in 24 inpatients were photographed with a Kodak DC50 digital camera (resolution 756 x 504 pixels/in2). Agreements regarding wound description (edema, erythema, cellulitis, necrosis, gangrene, ischemia, and granulation) and wound management (presence of healing problems, need for emergent evaluation, need for antibiotics, and need for hospitalization) were calculated among onsite surgeons and between onsite and remote surgeons. Sensitivity and specificity of remote wound diagnosis compared with bedside examination were calculated. Potential correlates of agreement, level of surgical training, certainty of diagnosis, and wound type were evaluated by multivariate analysis. RESULTS: Agreement between onsite and remote surgeons (66% to 95% for wound description and 64% to 95% for wound management) matched agreement among onsite surgeons (64% to 85% for wound description and 63% to 91% for wound management). Moreover, when onsite agreement was low (i.e., 64% for erythema) agreement between onsite and remote surgeons was similarly low (i.e., 66% for erythema). Sensitivity of remote diagnosis ranged from 78% (gangrene) to 98% (presence of wound healing problem), whereas specificity ranged from 27% (erythema) to 100% (ischemia). Agreement was influenced by wound type (p < 0.01) but not by certainty of diagnosis (p > 0.01) or level of surgical training (p > 0.01). CONCLUSIONS: Wound evaluation on the basis of viewing digital images is comparable with standard wound examination and renders similar diagnoses and treatment in the majority of cases. Digital imaging for remote wound management is feasible and holds significant promise for improving outpatient vascular wound care.

Amputation, Surgical↗
PubMed1998

Importance of the treatment field for the application of vascular photodynamic therapy to inhibit intimal hyperplasia.

Intimal hyperplasia (IH) plays a dominant role in the development of restenosis. In previous studies, photodynamic therapy (PDT) prevented IH induced by segmental balloon injury of the rat carotid. The critical elements required to control IH effectively with this technique are not fully understood. This study assessed the importance of the treatment field by studying the repair process of injured vessels, in which the PDT-treatment field did not target the entire injured area. The entire rat common carotid artery was balloon-injured to induce IH, whereas only the cervical segment below the bifurcation was subjected to PDT by external light irradiation after administration of the photosensitizer chloroaluminum sulfonated phthalocyanine. Light irradiation of injured arteries without photosensitizer served as control for PDT, and PDT of uninjured arteries was included as a control group for the balloon injury. Histologic characterization of the repair process was sequentially assessed. Balloon-injured arteries without PDT displayed rapid IH development with a peak at 2 weeks. Photodynamic therapy of balloon-injured arteries resulted in complete local depletion of medial smooth muscle cells (SMC), which was associated with a lack of IH until 2 weeks. However, at 4 and 16 weeks there was significant IH in PDT-treated arteries despite a lack of medial SMC repopulation. A wave of IH progression over the acellular media was observed in these arteries, migrating from the injured non-PDT-treated area. The PDT of uninjured arteries did not result in IH and was also associated with a persistent acellular media. Delayed IH development after PDT of injured vessels can result from IH progression from an injured site not included in the treatment field. This also indicated that the source of cells developing the intimal hyperplasia lesion can originate from an area remote from the lesion. Together with previous results and the determination that PDT itself does not induce IH, it can be reasoned that inclusion of the whole injured artery or a section of an uninjured margin in the treatment field is essential for effective PDT prevention of IH.

Angioplasty, Balloon↗
PubMed1997

Photodynamic therapy inactivates cell-associated basic fibroblast growth factor: a silent way of vascular smooth muscle cell eradication.

OBJECTIVE: Procedurally related vascular injury results in a smooth muscle cell (SMC) proliferative response which is in part initiated by SMC release of mitogens, including basic fibroblast growth factor (bFGF). This injury-induced proliferative response is believed to be a key event in intimal hyperplasia development. Photodynamic therapy (PDT), a novel approach found to be effective in inhibiting experimental intimal hyperplasia, produces cytotoxic free radicals resulting in localized SMC eradication. However, this form of SMC injury does not induce an inflammatory or proliferative response in the vessel wall. This study investigated whether PDT-generated free radicals could inactivate cell-associated bFGF normally released with cell injury. METHODS: PDT of bovine SMC was performed in vitro with the photosensitizer CASPc (5 micrograms/ml) and 675 nm laser light using three different fluences: 10, 50, and 100 J/cm2. After PDT, SMC viability was determined with the tetrazolium salt (MTT) assay and cell-associated bFGF was quantitated by ELISA. A SMC mitogenesis assay was utilized to detect cell-associated bFGF activity released with SMC injury. RESULTS: In a dose-dependent manner, PDT-generated free radicals reduced cell-associated bFGF levels. After PDT with 100 J/cm2, cell-associated bFGF content was reduced by 88% (P < 0.0002). Of special interest was the finding that PDT with 10 J/cm2 significantly (P < 0.0002) reduced cell viability to around 50%, without affecting cellular bFGF levels. Consequently, a higher PDT dose (100 J/cm2) was needed to significantly (P < 0.001) inhibit the SMC mitogenic response associated with SMC injury. CONCLUSION: These results provide a mechanism to explain how, unlike mechanical or other forms of SMC injury, optimal doses of PDT can locally eradicate medial vascular SMC without resulting in a bFGF-induced initiation of cell proliferation.

Animals↗
PubMed1997

Photodynamic therapy inhibits transforming growth factor beta activity associated with vascular smooth muscle cell injury.

PURPOSE: The multifunctional cytokine, transforming growth factor beta 1 (TGF-beta), plays an important role in the development of injury-associated intimal hyperplasia (IH). Strategies to suppress local TGF-beta activity may have a clinical potential to prevent restenosis caused by IH. Photodynamic therapy (PDT) involves the local generation of cytotoxic free radicals by light activation of photosensitizer dyes and has been shown to inhibit experimental IH. This study investigated whether PDT-generated free radicals can affect TGF-beta activity in a biologic system using vascular smooth muscle cells (SMCs). METHODS: The release and activation of TGF-beta by injured SMCs in culture was compared between mechanical injury and PDT. Mechanical injury was induced with a rubber policeman, and PDT was performed with the photosensitizer chloroaluminum sulfonated phthalocyanine (5 micrograms/ml) and 675 nm laser light at subtherapeutic 10 J/cm2 and the in vivo therapeutic dose of 100 J/cm2. Cell viability was assessed by the tetrazolium salt conversion assay, and active and total (active + latent) TGF-beta was determined by enzyme-linked immunosorbent assay in the conditioned media of SMCs 24 hours after treatment. Functional TGF-beta activity was assessed by inhibition of endothelial cell mitogenesis. RESULTS: Both forms of injury severely reduced (p < 0.0005) SMC viability to less than 15%. In untreated SMC conditioned media, only 14.5% of the total TGF-beta was active (27.7 +/- 8.7 pg per 1 x 10(5) cells). However, after mechanical injury and PDT with 10 J/cm2, there was a significant increase (p < 0.02) in active TGF-beta (60.1 +/- 10.1 pg and 48.6 +/- 21.0 pg, respectively), despite a total reduction of approximately 50%. In contrast to this result, PDT with 100 J/cm2 did not result in increased levels of active TGF-beta (8.1 +/- 3.5 pg), despite having similar levels of total TGF-beta. Consequently, the conditioned media of SMCs that had 100 J/cm2 PDT did not inhibit endothelial cell mitogenesis as compared with the conditioned media of SMCs with mechanical injury and 10 J/cm2 PDT (p < 0.0002). CONCLUSIONS: This report describes two novel findings: (1) injury to SMCs in vitro induces the conversion of biologically latent TGF-beta to active TGF-beta; and (2) the therapeutic PDT dose interferes with this injury activation process. This study substantiates the concept of local cytokine inhibition by PDT in a biologic system and provides new insights into the mechanisms of PDT-mediated inhibition of experimental IH.

Aluminum↗