Clinical thermofiltration: initial application

Extracorporeal LDL-Cholesterol Elimination in the Treatment of Severe Familial Hypercholesterolemia

The extracorporeal elimination of LDL-cholesterol could be performed using the classic non-selective centrifuge or membrane plasmapheresis. The modern methods are more selective and effective. The atherogenic particules are removed from plasma by active colon or capsula. The methods include: cascade filtration, imunoadsorbtion, heparin-induced precipitation of LDL, thermofiltration, dextran-induced precipitation of LDL and direct adsorption of lipids (DALI). The regular LDL-apheresis is the life-saving technique in the treatment of homozygous familial hypercholesterolaemia. It is used in heterozygous familial hypercholesterolaemia when the patients do not respond to diet and drugs therapy, too. The regular LDL-apheresis treatment may be followed by the decreased frequency of angina pain episodes, the reduction of ECG changes during the bicycle ergometry and significant disappearance of tendinous xantomas. Some prospective randomised studies has shown even in this group of patients, resistant to conventional treatment, a significant regression of atherosclerotic changes.

Removal and Recovery of Cholesterol in Thermofiltration

Thermofiltration, a system of membrane plasmapheresis for LDL apheresis, was applied to the treatment of hypercholesterolemic patients to assess its lipid lowering potential, clinical feasibility and post-treatment lipid recovery.

Plasma separated by a membrane separator was warmed above physiologic temperature, filtered with a plasma filter and returned to the patient on-line without requiring supplemental plasma product infusion. One calculated plasma volume was treated. Treatment schedules were weekly, biweekly or monthly. Patients treated by thermofiltration in this study were diagnosed as type II hypercholesterolemia. Reductions and sievings of high density lipoprotein (HDL) cholesterol and low density lipoprotein (LDL) cholesterol were evaluated. In addition, post-treatment solute recovery was assessed.

The reduction ratios of HDL cholesterol and LDL cholesterol were 0.31 ± 0.08 and 0.58 ± 0.08, respectively (mean ± S.D. of 7 patients). Sieving coefficients of the plasma filter for HDL cholesterol and LDL cholesterol were 0.62 ± 0.12 and 0.03 ± 0.02, respectively (mean ± S.D. of 32 treatments). Cholesterol reduction fitted well to a single pool model. HDL cholesterol recovered significantly faster than LDL cholesterol and LDL cholesterol recovery differed among individuals. For some patients total cholesterol and LDL cholesterol levels were lowered by the biweekly treatment while for others the weekly treatment was required. Significant removal of LDL cholesterol with sparing of HDL cholesterol was achieved without the requirement for plasma products.

VLDL/LDL acts as a drug carrier and regulates the transport and metabolism of drugs in the body

Only free drugs have been believed to be carried into tissues through active or passive transport. However, considering that lipoproteins function as carriers of serum lipids such as cholesterol and triglycerides, we hypothesized that lipoproteins can associate with certain drugs and mediate their transport into tissues in lipid-associated form. Here, in vitro and in vivo studies with low density lipoprotein receptor (LDLR)-overexpressing or -knockdown cells and wild-type or LDLR-mutant mice were used to show the association of various drugs with lipoproteins and the uptake of lipoprotein-associated drugs through a lipoprotein receptor-mediated process. In clinical studies, investigation of the effect of lipoprotein apheresis on serum drug concentrations in patients with familial hypercholesterolemia demonstrated that lipoprotein-mediated drug transport occurs in humans as well as in mice. These findings represent a new concept regarding the transport and metabolism of drugs in the body and suggest that the role of lipoprotein-mediated drug transport should be considered when developing effective and safe pharmacotherapies.

Proteomic analysis of proteins eliminated by low-density lipoprotein apheresis

Low-density lipoprotein apheresis (LDL-A) treatment has been shown to decrease serum LDL cholesterol levels and prevent cardiovascular events in homozygous patients with familial hypercholesterolemia. Recently, LDL-A treatment has been suggested to have beneficial effects beyond the removal of LDL particles. In this study, to clarify the preventive effects of LDL-A treatment on atherosclerosis, the waste fluid from the adsorption columns was analyzed. The waste fluid of LDL adsorption columns was analyzed by two-dimensional electrophoresis followed by mass spectrometry. Serum concentrations of the newly identified proteins before and after LDL-A treatment were measured by enzyme-linked immunosorbent assay. We identified 48 kinds of proteins in the waste fluid of LDL adsorption columns, including coagulation factors, thrombogenic factors, complement factors, inflammatory factors and adhesion molecules. In addition to the proteins that were reported to be removed by LDL-A treatment, we newly identified several proteins that have some significant roles in the development of atherosclerosis, including vitronectin and apolipoprotein C-III (Apo C-III). The serum levels of vitronectin and Apo C-III decreased by 82.4% and 54.8%, respectively, after a single LDL-A treatment. While Apo C-III was removed with very low-density lipoprotein (VLDL) and LDL, vitronectin was removed without association with lipoproteins. The removal of proteins observed in the waste fluid has a certain impact on their serum levels, and this may be related to the efficacy of LDL-A treatment. Proteomic analysis of the waste fluid of LDL adsorption columns may provide a rational means of assessing the effects of LDL-A treatment.

Fibrinogen salvage during DF Thermo using Evaflux-5A plasma fractionators

DF Thermo, a modified form of double-filtration plasmapheresis (DFPP), has been used for the treatment of various indications such as arteriosclerosis obliterans (ASO). In case of ASO, fibrinogen is a substance to be removed by DFPP. On the other hand, plasmapheresis for chronic viral hepatitis C became an insurance covered treatment in Japan in April 2008. Since then DFPP has also become a treatment of chronic viral hepatitis C as an adjunctive therapy for the purpose of improving the effect of medication. Therefore, there has been a growing concern in recent years about patients' low fibrinogen levels due to DFPP treatment. With the aim of improving fibrinogen retention by DF Thermo, we examined by in vitro trial, the effects when recirculating the filtrate and elevating its temperature. The trial was conducted using bovine plasma, run through experimental circuits with the same configuration as the clinical setting of the One-Way method and DF Thermo method. The DF Thermo circuit contained a thermostat, on which the temperature was set to 40°C. Two One-Way method circuits were prepared with different temperature settings, i.e., 20°C and 40°C. With these three different conditions, variance of the fibrinogen retention under different temperatures and the implementation of recirculation were compared. Results show that the DF Thermo circuit tends to have enhanced the fibrinogen retention compared to the One-Way method 20°C and 40°C. The explanation is likely as follows: viscosity of plasma reduces when warmed, which in turn helps maintain the permeability of membrane, and the recirculation of the plasma helps prevent membrane fouling, thus more fibrinogen is retained in the DF Thermo method.

Role of lipid apheresis in changing times

During the last decades, LDL-apheresis was established as an extracorporeal treatment option for patients with severe heterozygous or homozygous familial hypercholesterolemia (FH) that is resistant to conventional treatment strategies such as diet, drugs, and changes in lifestyle. Nearly half a century ago, the first LDL-apheresis treatment was performed by plasma exchange in a child with homozygous FH. At the beginning of the 1970s, the clinical advantage of regular extracorporeal LDL-elimination was demonstrated in siblings suffering from homozygous FH. These findings encouraged researchers especially from Germany and Japan to develop extracorporeal devices to selectively eliminate LDL-cholesterol in the 1980s. Although the selectivity of the currently available LDL-apheresis devices is different, the efficacy of LDL-elimination during a single treatment is rather similar and ranges between 55 and 65 % of the pretreatment LDL plasma concentration.In the 1990s, the patients regularly treated by extracorporeal LDL-elimination, diet, and drugs were included in regression studies assessed by angiography. It was shown that the combined treatment with LDL-apheresis, diet, and drugs resulted in less progression of coronary lesions than drugs and/or diet alone. However, although a tendency was evident, results did not reach criteria for significance. During the last decade, apheresis registries were established to collect data on efficiency, safety, and clinical outcome of regular long-term LDL-apheresis. The evaluation of registry data will certainly permit further insights in the therapeutic benefit of this expensive and time-consuming therapeutic approach. Furthermore, the future of LDL-apheresis will depend upon the availability of highly efficient new drugs and molecular genetic approaches such as RNA silencing of the apoB gene, whereas the liver transplantation and gene therapy of the LDL-receptor deficiency will not replace LDL-apheresis in severe familial hypercholesterolemia in the near future.

LDL-apheresis: technical and clinical aspects

The prognosis of patients suffering from severe hyperlipidemia, sometimes combined with elevated lipoprotein (a) levels, and coronary heart disease refractory to diet and lipid-lowering drugs is poor. For such patients, regular treatment with low-density lipoprotein (LDL) apheresis is the therapeutic option. Today, there are five different LDL-apheresis systems available: cascade filtration or lipid filtration, immunoadsorption, heparin-induced LDL precipitation, dextran sulfate LDL adsorption, and the LDL hemoperfusion. There is a strong correlation between hyperlipidemia and atherosclerosis. Besides the elimination of other risk factors, in severe hyperlipidemia therapeutic strategies should focus on a drastic reduction of serum lipoproteins. Despite maximum conventional therapy with a combination of different kinds of lipid-lowering drugs, sometimes the goal of therapy cannot be reached. Hence, in such patients, treatment with LDL-apheresis is indicated. Technical and clinical aspects of these five different LDL-apheresis methods are shown here. There were no significant differences with respect to or concerning all cholesterols, or triglycerides observed. With respect to elevated lipoprotein (a) levels, however, the immunoadsorption method seems to be most effective. The different published data clearly demonstrate that treatment with LDL-apheresis in patients suffering from severe hyperlipidemia refractory to maximum conservative therapy is effective and safe in long-term application.

Combination of therapeutic apheresis and therapeutic ventricular assistance for end-stage heart failure patients

Dilated cardiomyopathy is a cardiac disease of unknown origin which is characterized by the gradual development of cardiac failure associated with four-chamber dilatation of the heart. Heart transplantation has been considered as the last resort for this disease. However, some patients who received support with a ventricular assist device (VAD) as a bridge-to-transplantation and then recovered without transplantation have been reported. This new concept of treating heart failure is termed bridge-to-recovery. A VAD can inhibit the heart failure compensatory mechanisms by extreme ventricular unloading. Also, heart failure is a complex neurohormonal/autocrine-paracrine syndrome, and these mechanisms consecutively lead to inflammatory response by proinflammatory cytokines; interleukin-1 alpha (IL-1 alpha), interleukin-1 beta (IL-1 beta), interleukin-2 (IL-2), interleukin-6 (IL-6), and tumor necrosis factor-alpha (TNF-alpha). Furthermore, the existence of anti-beta1-adrenoceptor autoantibodies (A-beta1-AABs) in a patient with dilated cardiomyopathy has been reported. These proinflammatory cytokines and this antibody accelerate a ventricular remodeling and a contractile dysfunction over the long term. Apheresis can also inhibit the vicious cycle in heart failure by removing the factors that are produced by activated neurohormonal/autocrine-paracrine compensatory mechanisms. Therefore, we propose that the combined therapies, therapeutic VAD and therapeutic apheresis, will provide a prominent outcome for a patient who is suffering from end-stage heart failure.

Comparison of two filter combinations for low-density lipoprotein apheresis by membrane differential filtration: a prospective crossover controlled clinical study

Membrane differential filtration is an accepted procedure for the extracorporeal removal of low-density lipoprotein (LDL). Reduction rates largely depend on the nature of the membranes and are ideally evaluated in a crossover study design. Four patients who had been treated by LDL apheresis for at least 6 months were included. Six consecutive weekly sessions (40 ml plasma/kg body weight) were scheduled per system (Plasmacure PS06/Evaflux Eval 5A [Kuraray] versus Plasmaflo OP05W/Cascadeflo AC1770 [Asahi]). Laboratory measurements indicated reductions of plasma concentrations for fibrinogen (37% [Kuraray] versus 44% [Asahi]), IgG (15% versus 20%), IgA (24% versus 28%), IgM (63% versus 53%), and total protein (11% versus 16%). Total cholesterol was eliminated by 52% versus 49%, LDL by 67% versus 66%, triglycerides by 56% versus 41%, and high-density lipoprotein by 10% versus 20%. Three therapies employing the Asahi filter combination were terminated prematurely due to saturation of the plasma fractionator. In conclusion, despite similar physical properties, the membranes differ significantly concerning selectivity and sensitivity to saturation.

Historical perspectives of hybrid hepatic assist devices: tissue sourcing, immunoisolation, and clinical trial

A hybrid hepatic assist device using canine liver tissues was developed and clinically applied 38 years ago. However, for many years practical hybrid hepatic assist devices were not clinically introduced owing to the many difficulties encountered in employing cultured hepatocytes. These problems include: (1) maintenance of viable cultured cells, (2) maintenance of normal hepatocyte function with these cells, (3) elimination of toxic substances generated by non-viable cultured and/or stored cells, (4) elimination of immunological factors generated by cultured cells and by the patient, and (5) difficulties of the biocompatible immunological barrier for cells against the patient. Fortunately, recent progress in apheresis and biomaterial technologies enable us to isolate cultured cells immunologically and yet maintain effective metabolic functions for the patient. These technologies generate an immunological barrier of a hybrid hepatic assist device for the patients. Proper adsorption columns developed for apheresis procedures enable us to remove the toxic substances released by non-viable cells. Recent development of oxygen-carrying macromolecules enable us to provide sufficient oxygen supply to the cultured cells and to maintain their normal cellular function, not only during the cultured period of time, but also during their actual clinical application. Together with the advancement of cell culture technologies, including the proper cultured environments and cellular seeding environments, these technologies, primarily developed for therapeutic apheresis, should be able to provide more effective and safe hybrid artificial organs.

Membrane processes for plasma separation and plasma fractionation: guiding principles for clinical use

The use of membranes in blood processing range from the use of large-pore structures for filtration of blood for the removal of large particles (>20 microm transfusion filters) to membranes for the dialysis of blood for the removal of low molecular weight solutes in the treatment of renal failure. Within the past 20 years, membranes have been applied in the separation of plasma from whole blood. Compared to centrifugal plasma separation membrane, plasma separation is preferred when used with online plasma fractionation since the plasma is free of cells. In addition, membranes have also been applied in the online treatment of plasma for the selective removal of macromolecules in selected disease states obviating the need for plasma replacement products. The membranes used for plasma separation and fractionation may be distinguished from conventional dialysis membranes and high-flux membranes used in hemofiltration by their very high or select passage of plasma proteins. Membrane techniques are simple and safe to apply and can be competitive to other plasma separation and treatment technologies.

Current topics on low-density lipoprotein apheresis

The prognosis of patients suffering from severe hyperlipidemia, sometimes combined with elevated lipoprotein (a) (Lp[a]) levels, and coronary heart disease (CHD) refractory to diet and lipid-lowering drugs is poor. For such patients, regular treatment with low-density lipoprotein (LDL) apheresis is the therapeutic option. Today, there are four different LDL-apheresis systems available: immunoadsorption, heparin-induced extracorporeal LDL/fibrinogen precipitation, dextran sulfate LDL-adsorption, and LDL-hemoperfusion. Despite substantial progress in diagnostics, drug therapy, and cardiosurgical procedures, atherosclerosis with myocardial infarction, stroke, and peripheral cellular disease still maintains its position at the top of morbidity and mortality statistics in industrialized nations. Established risk factors widely accepted are smoking, arterial hypertension, diabetes mellitus, and central obesity. Furthermore, there is a strong correlation between hyperlipidemia and atherosclerosis. Besides the elimination of other risk factors, in severe hyperlipidemia (HLP) therapeutic strategies should focus on a drastic reduction of serum lipoproteins. Despite maximum conventional therapy with a combination of different kinds of lipid-lowering drugs, however, sometimes the goal of therapy cannot be reached. Mostly, the prognosis of patients suffering from severe HLP, sometimes combined with elevated Lp(a) levels and CHD refractory to diet and lipid-lowering drugs is poor. Hence, in such patients, treatment with LDL-apheresis can be useful. Regarding the different LDL-apheresis systems used, there were no significant differences with respect to the clinical outcome or concerning total cholesterol, LDL, high-density lipoprotein, or triglyceride concentrations. With respect to elevated Lp(a) levels, however, the immunoadsorption method seems to be the most effective. The published data clearly demonstrate that treatment with LDL-apheresis in patients suffering from severe hyperlipidemia refractory to maximum conservative therapy is effective and safe in long-term application.

Lipid apheresis: from a heroic treatment to routine clinical practice

Lipid apheresis has developed from a heroic treatment into a routine clinical therapy and currently is the major indication for performing extracorporeal plasma therapy. Whereas it was once reserved for patients with homozygous familial hypercholesterolemia, today it has a place in the secondary prevention of severe coronary heart disease when low-density lipoprotein (LDL)-cholesterol level exceeds 150 mg/dl, despite conservative treatment, in any type of primary hypercholesterolemia. Unselective plasma exchange has been replaced by a variety of selective procedures. The efficacy of the treatment can be maximized by combining LDL apheresis with the use of cholesterol synthesis enzyme inhibitors. Clinical studies have shown that drastic cholesterol reduction can result in regression of coronary atherosclerosis as well as in reduced cardiac morbidity and mortality. Technical progress comprises improved selectivity, online regeneration of adsorbers, and LDL adsorption from whole blood. Recently, a new LDL hemoperfusion procedure was successfully tested in a clinical pilot study; blood is passed directly over a lipid sorbent without prior plasma separation. If this system is demonstrated to be safe and effective in clinical Phase III trials, a further qualitative step in the rapid development of LDL apheresis will have made.

State of the art of lipid apheresis

Currently, 5 different lipid apheresis procedures are available for routine clinical treatment of hypercholesterolemic patients. Unselective plasma exchange is a technically simple extracorporeal circuit, but albumin substitution fluid must be used and there is no high-density lipoprotein (HDL) recovery. Semiselective double filtration with improved size selectivity because of a small-pore secondary filter combines good elimination of low-density lipoprotein (LDL), lipoprotein (a) (Lp[a]), and fibrinogen with adequate HDL recovery; modifications such as thermofiltration, predilution/backflush, or pulsatile flow have been proposed for the improvement of this system. Three highly selective procedures are based on immunologic or electrostatic interactions: immunoadsorption using anti-low-density lipoprotein (LDL) antibodies, chemoadsorption onto dextran sulfate, and heparin-induced LDL precipitation (HELP) apheresis. The features of each system are discussed critically. Lastly, two new developments, Lp(a) immunoadsorption and LDL hemoperfusion using a polyacrylate LDL adsorber compatible with whole blood, are described.

Evaluation of double filtration plasmapheresis, thermofiltration, and low-density lipoprotein adsorptive methods by crossover test in the treatment of familial hypercholesterolemia patients

A comparative assessment has been made regarding efficacy and safety of the double filtration plasmapheresis (DFPP), thermofiltration (TFPP), and low-density lipoprotein (LDL) adsorptive (PA) methods by making a crossover test on heterozygous familial hypercholesterolemia patients. Treatments by DFPP, TFPP (secondary membrane Evalux 5A), and PA (Liposorber LA-40) were carried out 5 times each, with a 2-week interval, in 5 patients with heterozygous familial hypercholesterolemia. The same plasma separator (Plasmacure PS-60, polysulfone) was used in all cases, and the volume of plasma processed was set at 4 L. High removal rates were obtained of total cholesterol, LDL cholesterol, triglycerides TG, and apolipoprotein B (apoB) by all three methods, and no differences were observed. Lipoprotein (a), apoA-2, apoC-3, fibrinogen, and immunoglobulin M (IgM) showed significantly high removal rates by the DFPP and TFPP methods compared with the PA method. The sieving coefficient of albumin and high-density lipoprotein (HDL) cholesterol at 2 and 4 L of plasma processed exhibited high permeabilities using all three methods. Supplementing albumin was not necessary. An increase of the transmembrane pressure was observed in 1 case treated by DFPP but was not observed when using the TFPP or PA method. No changes were observed in serum interleukin 1beta (IL-1beta) or tumor necrosis factor-alpha (TNF-alpha) before and after treatment by any of the three methods. No remarkable side effects were observed using either the DFPP or TFPP method. The DFPP and TFPP methods showed efficacy and safety that was not inferior to the PA method in conventional LDL apheresis, and the dead-end method of the filter operation without the discarding of plasma was shown to be possible.

Low-density lipoprotein removal methods by membranes and future perspectives

Since the application by Thompson et al. in 1975 of plasma exchange for the treatment of 2 patients with familial hyperlipidemia, plasma purification techniques for selective low-density lipoprotein (LDL) removal (i.e., LDL apheresis) have been developed and adopted for the management of this disease. Thermofiltration is one of the LDL apheresis systems that utilizes membrane techniques developed by Nose and Malchesky's group in 1985. This article reviews its rationale, in vitro studies, animal studies, and clinical investigation. Thermofiltration effectively and selectively removes LDL cholesterol while retaining in the plasma physiologically important macromolecules such as albumin and high-density lipoprotein (HDL) cholesterol. Based on the global view of the treatment of atherosclerosis by LDL apheresis, membrane techniques are as effective, safe, and simpler to apply than other methods. Additionally, these methods are effective for the removal of lipoprotein (a) and fibrinogen; thus, they can address the needs in these application areas.

5th WAA Congress therapeutic artificial organs, 10 years after

In 1983, more than 10 years ago, the concept of therapeutic artificial organs was proposed by this author. Currently developments of various types of immunomodulation technologies are well established, and therapeutic artificial organs for the treatment of autoimmunodiseases have become a well-accepted concept. It is this author's opinion that if we utilize apheresis technologies properly we should be able to prevent the aging process of mankind. Physical youth, and perhaps mental youth, can be achieved by apheresis technologies. However, in order to maintain youth and enjoy a high quality of life, it is essential to maintain a strong will to live. In this paper a new type of an artificial organ is proposed. This antiaging artificial organ is named "Juzo," the organ for a longer life, in Japanese, by this author.

An effective LDL removal filter for the treatment of hyperlipidemia

On-line membrane plasma fractionation techniques have made semiselective removal of pathological macromolecules practical. However, several problems such as cryogel formation exist when the procedure is performed at ambient temperature. Cryogel formation takes place when heparinized plasma is cooled below 35 degrees C and when it tends to occlude the pore structure of the secondary filter membrane resulting in a poor molecular cut off of the macromolecular filter. Thermofiltration is one of the on-line plasma fractionation techniques used when warming plasma from 37 to 42 degrees C to prevent cryogel formation. Thermofiltration enhanced the performance of the lipofilter (Kuraray 4A) and demonstrated better molecular cut off between low density lipoprotein (LDL) cholesterol and high density lipoprotein (HDL) cholesterol than double filtration plasmapheresis (DFPP). An improved lipofilter (Kuraray 5A) has been developed and has shown better molecular cut off between LDL cholesterol and HDL cholesterol than the 4A filter. However, cryogel formation still occurred even using the 5A filter during the DFPP procedure. Thermofiltration maintains the performance of the secondary filter by preventing cryogel formation. Further studies are required to evaluate the enhanced performance of the 5A filter by thermofiltration.

Nonbiological liver support: historic overview

An effective hepatic assist system could serve as a bridge to transplantation or to treat acute or chronic hepatic failure. Early nonbiological approaches focused on the removal of low molecular weight toxins by dialysis or hemoperfusion, such as over charcoals or resins. This approach led to clinical trials that showed varying degrees of success. Introduction of more porous membranes and blood separation technologies stimulated the development of plasma exchange, on-line plasma fractionation technologies with sorbents and membranes, and other schemes of sorbent-blood interactions based on the principles of dialysis and hemofiltration with sorbent perfusion. Although detoxification of blood has improved the prognosis for acute liver failure, key issues of when to initiate treatment and by which method need to be resolved. In chronic liver disease, blood detoxification can be applied in patients intractable to conventional therapies and for some awaiting transplantation to relieve disease symptoms such as pruritus, jaundice, elevated bile acids, hyperbilirubinemia, endotoxemia, and hypercholesterolemia. Although biological support is considered the ideal, nonbiological techniques can be useful because hepatocytes possess a regenerative capacity and temporary support is helpful. Available nonbiological liver support technologies can substitute for select liver functions in acute and chronic disease.

No evidence for feedback inhibition of hepatic apolipoprotein B (apo B) production after extracorporeal low density lipoprotein precipitation as determined by [1-13C]leucine infusion in normal volunteers

To determine the impact of an acute reduction of the circulating mass of apolipoprotein B (apo B) on apo B metabolism we studied six healthy male volunteers before (day 0), 1 day after (day 2), and 7 days after (day 8) an LDL apheresis treatment which reduced apo B mass by 59%. Appearance of newly synthesized apo B in plasma VLDL and LDL was studied using a primed-constant infusion of [1-13C]-leucine. VLDL apo B pool size and fractional VLDL apo B production rate calculated using a one-compartment model were similar on all 3 study days. Absolute VLDL apo B production was not statistically different throughout the study (19.7 +/- 12.3, 19.5 +/- 7.5, 29.1 +/- 17.7 mg kg-1 day-1). LDL apo B fractional production rate was increased on day 2 (0.38 +/- 0.17, 0.68 +/- 0.08, 0.37 +/- 0.06 pools day-1 on days 0, 2, and 8; P < 0.01). Absolute LDL apo B production, however, remained constant throughout the study (10.8 +/- 3.3, 11.0 +/- 1.9, 10.8 +/- 3.1 mg kg-1 day-1). We conclude that in healthy male volunteers acute reduction of the circulating apo B mass by LDL apheresis does not affect apo B metabolism significantly.

Selective removal of cholesterol by plasmapheresis and the progression of atherosclerosis

There is a strong correlation of plasma cholesterol levels with the risk of coronary heart diseases as shown by epidemiologic studies. This study was undertaken to evaluate the effect of plasma cholesterol lowering on the progression of atherosclerosis in the homozygous Watanabe heritable hyperlipidemic (WHHL) rabbit. The effect of cholesterol lowering, which was accomplished by thermofiltration (on-line plasma separation with plasma filtration at 39 degrees C) was evaluated by comparison between treated and untreated control groups. Thermofiltration reduced significantly the mean plasma level of total cholesterol (284 vs. 655 mg/dl, P = 0.0005) and the percent aortic area occupied by atherosclerotic plaque (15.0 vs. 44.2%, P = 0.0003). The total lipid and cholesterol contents in the aortas in the treated group were also significantly lower than those in the control group. Microscopically, thickness measurements of the lesions showed that the mean thickness of the fibrous cap and the ratio of the thickness of the intima to that of the media were smaller for the treated group than the control group. This study demonstrated the slowing or stopping of the progression of atherosclerosis by lowering the plasma total cholesterol level in WHHL rabbits.

Adsorption treatment in hyperlipidemia

Clinical LDL- adsorption has made overwhelming progress in recent years. Thus, immunoadsorption with polyclonal anti-LDL-antibodies and chemoadsorption using the dextransulfate system have been applied successfully for selective LDL-removal in routine clinical plasma treatment of hypercholesterolemic patients suffering from coronary artery disease. Clinical pilot studies showed good results using immunoadsorption with anti-LDL-F(ab)-columns. Promising laboratory results have been achieved using immunoadsorption with monoclonal LDL-antibodies, polyacrylate/fractogel and macroporous cellulose. While these systems need a primary separation step for cells and plasma, the integrated plasma separation/adsorption device and the LDL-hemoperfusion module using E 280590 can even treat whole blood. Thus, these systems hold a great promise for the future.

Artificial liver. State of the art

If an effective hepatic assist system existed, it could serve as a bridge to transplantation. Most of the patients waiting for liver transplantation have chronic liver insufficiency but are not in hepatic coma. Various hepatic assist systems have been used to salvage patients with acute liver insufficiency. Most attempts have been disappointing. The methods used have included plasma exchange, plasma adsorption, double filtration, cryofiltration, thermofiltration, the combination of plasma exchange and amino acid hemodialysis, and others. For patients with chronic liver disease with moderate liver function impairment and limited to one or only a few areas of metabolic abnormality, a hepatic assist might allow the life of the patient to be maintained temporarily. The application of hepatic assist methods for chronic liver disease patients treated at the Cleveland Clinic has been encouraging. One of the patients who suffered from sclerosing cholangitis has maintained a near-normal life for almost five years by 170 plasma treatments. This is in spite of the fact that, at the onset of treatment, the patient was nearly comatose. Unfortunately, this patient did not wish to receive a liver transplantation. Based upon this experience, the concept of a bridge to transplantation approach to hepatic assist devices appears feasible. In addition, it is speculated that hepatic assistance during the early recovery stage of liver transplantation and during mild episodes of rejection may be useful.

Overview: techniques and indications of LDL-apheresis

In recent years, LDL-apheresis has emerged to be an efficient treatment of hyperlipidemia in patients who do not respond sufficiently to diet and lipid lowering drugs. A survey of LDL lowering extracorporeal procedures is presented. Among them, to date 5 procedures have been used clinically on a routine basis: unselective plasma exchange, semi-selective double filtration (including its modifications like thermofiltration and predilution/backflush) and three highly selective LDL-apheresis systems: LDL-adsorption on dextran sulfate coated cellulose beads or anti-apoprotein B-linked sepharose and heparin induced extracorporeal LDL and fibrinogen precipitation (the so-called HELP system). Advantages, limitations and special indications of these commercially available systems are discussed. If atherosclerosis can really be made regress by drastic reduction of elevated serum cholesterol levels as indicated by recent publications, lipid apheresis will no doubt play a major role in attaining this goal.

Thermofiltration in hypercholesterolemia treatment: analysis of removal and posttreatment cholesterol recovery

Thermofiltration, a system of membrane plasmapheresis for LDL apheresis, is used to treat patients with refractory hyperlipidemia. In this system, the separated plasma is warmed to or above physiologic temperature, filtered with a membrane filter, and returned to the patient on-line. Plasma infusion products are not required. In this study one calculated plasma volume was treated weekly, biweekly, or monthly in patients classified as type II hypercholesterolemic. Reduction and sieving of lipoproteins were evaluated. The reduction ratios of high-density lipoprotein cholesterol (HDLc) and low-density lipoprotein cholesterol (LDLc) were 0.30 +/- 0.06 and 0.58 +/- 0.05, respectively (mean +/- S.D.). Sieving coefficients of the plasma filter for HDLc and LDLc were 0.62 +/- 0.12 and 0.03 +/- 0.02, respectively (mean +/- S.D. of 31 treatments). To evaluate the posttreatment recovery the apparent fractional catabolic rates (FCRa) for total cholesterol and LDLc were calculated. FCRa was 0.151 +/- 0.06 and 0.148 +/- 0.06 day-1 for total cholesterol and LDLc, respectively. The ratio of the posttreatment concentration on the seventh day to the concentration immediately pretreatment was found to be significantly higher for HDLc than for LDLc, 0.92 +/- 0.8 vs. 0.77 +/- 0.1 (mean +/- S.D.), due to faster HDLc recovery. The ratio of LDLc/HDLc was lowered for up to 2 weeks after the treatments.

Removal of apolipoprotein B from dog whole blood by ex vivo hemoadsorption on antibody-agarose beads

Antibody columns for hemoperfusion were prepared by filling 300-ml polycarbonate canisters with 2% agarose gel beads having attached goat antibodies directed toward apolipoprotein B (apo B), the major apoprotein of low and very low density lipoproteins. Blood was withdrawn from the left external jugular vein of dogs, regionally treated with anticoagulant citrate dextrose solution A, pumped through the antibody column, and returned to the right external jugular vein. Immunoreactive apo B decreased by 81% during passage of blood over the column. Adverse effects were not observed during four weekly hour-long perfusions with blank columns (agarose beads without antibody attached) followed by four weekly perfusions with antibody columns. The columns were disinfected and stored in 1 M acetic acid and reused weekly in each animal. Recovery of platelets and white blood cells over the columns was 90 and 102%, respectively, with no significant differences between blank columns and antibody-containing columns. Complement was not consumed during the hemoadsorption procedure. Hemoadsorption on antibody-agarose columns is a promising potential method for removing toxic molecules and cells from whole blood.

Selective removal of low density lipoproteins (LDL) by precipitation at low pH: first clinical application of the HELP system

The first clinical application of a new extracorporeal procedure (HELP) for the selective elimination of low-density lipoproteins by heparin precipitation at acid pH is described. Plasma, obtained by filtration of whole blood through a 0.2 mu filter, is continuously mixed with an equal volume of an acetate buffer (pH 4.85) containing heparin. After removal of the precipitated heparin complex by filtration, excess heparin is adsorbed to a specially developed filter and the clear plasma filtrate is subject to bicarbonate dialysis/ultrafiltration to restore physiologic pH and remove excess fluid. The calculated efficiency for the elimination of low-density lipoproteins from plasma by HELP is 100% and is therefore comparable to conventional plasmapheresis. The HELP system shows a high degree of specificity with over 80% of total protein being returned to the patient. Over 130 treatment procedures have now been performed. Patient compliance and acceptance have been excellent and no major complications have been observed.