Preservation of Rat Aortic Tissue Transplant with Green Tea Polyphenols

Green tea polyphenols have recently attracted medical attention as bioactive agents with anticancer, antimicrobial, and antiviral effects. We discovered their new usage as preservative agents for tissue transplants. We preserved rat aortas in a DMEM solution containing polyphenols extracted from green tea leaves. The preserved aortas retained original structures and mechanical strength, and were devoid of any undesirable cell secretions for over a month under physiological conditions. In addition, aortas from Lewis rats preserved for a month and transplanted to allogenic ACI rats completely avoided rejection by the host, suggesting that the polyphenols have immunosuppressive actions on the aortic tissues. From these results, we conclude that polyphenol treatment of aortic tissue transplant can maintain its viability for extended periods of time either before or after transplantation, and the method can be applicable to other transplantation situations.

The Beneficial Effect of Carboxylated Poly-L-Lysine on Cryosurvival of Vitrified Early Stage Embryos

BACKGROUND

In the vitrification of embryos, dimethyl sulfoxide (DMSO) is one of the most effective cryoprotectant agents (CPAs), but cytotoxic effects of DMSO on embryos are well known. Carboxylated poly-L-lysine (CPLL) has been identified as an effective cryoprotectant of cultured cell lines and mammalian oocytes.

OBJECTIVE

To evaluate the efficacy and safety of CPLL as a CPA for developmental stage embryos.

MATERIALS AND METHODS

Mouse 8-cell embryos and blastocysts were vitrified with ethylene glycol (EG), DMSO/EG, or CPLL/EG and the developmental potency assessed in vitro.

RESULTS

In 8-cell embryos, there were no differences between the levels of survival and developmental progress into the blastocyst stage in each solution. At the blastocyst stage, the proportion of dead cells was significantly higher in the EG compared with other solutions. In contrast, there were no differences between the DMSO/EG and CPLL/EG.

CONCLUSION

These results indicate that CPLL can be used as a replacement for DMSO in the vitrification of mouse embryos.

52 EFFECT OF CARBOXYLATED POLY-L-LYSINE ON THE POST-THAW VIABILITY OF IN VITRO-PRODUCED BOVINE BLASTOCYST

Recently, there has been development of an antifreeze polyamino acid (carboxylated poly-l-lysine: PLL) as new cryoprotectants (CPA). This compound counts as amphoteric macromolecular cationic and anionic substituents (polyampholyte) by chemically modifying poly-lysine. In addition, PLL is highly safe and frequently used as a food additive in substitution for other CPA. Other common CPA have high toxicity and caused physiological damage. In vitro-produced blastocysts were randomly assigned into 3 groups: (1) vitrified embryos with PLL vitrification solution [PLL-vit-1: 15% PLL + 15% ethylene glycol (EG); PLL-vit-2: 30% PLL + 30% EG + 0.5 M sucrose], (2) vitrified embryos with Vajta et al. solution (Conv-vit-1: 7.5% dimethyl sulfoxide + 7.5% EG; Conv-vit-2: 16.5% dimethyl sulfoxide + 16.5% EG + 0.5 M sucrose), and (3) nonvitrified blastocysts (control). All embryos were frozen by droplet vitrification method. First, the PLL-vitrified embryos were exposed to 5, 10, and 15 min in the PLL-vit-1 and then putted for 30 to about 60 s in the PLL-vit-2. Then, we compared with each group regarding exposure time of Vit-1. Post-thaw survival rate of each exposure time did not significantly differ among the 3 groups (100 v. 100 v. 100%). However, hatching rate of the 10-min exposure group was higher than that of 5- and 15-min groups (75.0 v. 25.0 v. 66.7; P < 0.05). Therefore, we confirmed that exposure time of Vit-1 was exposed for a minimum of 10 min. The post-thawed survival rate of each vitrification method was not significantly different between PLL-vit and Conv-vit groups (97.7 v. 86.4%). The total cell numbers of blastocyst did not significantly differ among groups. However, the apoptotic cell numbers of blastocyst was significantly different between the control and Conv-vit groups (0.4 ± 0.6 v. 4.4 ± 3.9; P < 0.05) but was not different in control v. PLL-vit (0.4 ± 0.6 v. 2.1 ± 2.4) and Conv-vit v. PLL-vit (4.4 ± 3.9 v. 2.1 ± 2.4). In conclusion, PLL-vit for bovine blastocyst could reduce toxicity and osmotic shock and showed high efficiency on the quality of post-thawed bovine blastocysts compared with that of Conv-vit.This work was partly supported by a grant from the Next-Generation BioGreen 21 Program (No. PJ009587022014), IPET (Grant No. 112020-3), and a scholarship from the BK21 plus program. A-Na Ha, Kyeong-Lim Lee, and Md. Fakruzzaman were supported by BK21 plus fellowships at Gyeongsang National University, Republic of Korea.

Cryoprotection of fibroblasts by carboxylated poly-L-lysine upon repeated freeze/thaw cycles

The cryoprotection of carboxylated h-poly-L-lysine (COOH-PLL) was investigated on fibroblasts [L-929 cells and human dermal fibroblasts (HDFs)] during multiple freeze/thaw cycles. COOH-PLL was not toxic to two fibroblast cell types even at 25% (w/v) concentration, whereas dimethylsulphoxide (DMSO) was highly toxic over 3.13% (v/v). When L-929 cells were subjected to 5 freeze/thaw cycles, the media containing 7.5% (w/v) COOH-PLL maintained cell morphology and significantly suppressed growth inhibition as well as cell detachment (P < 0.05). The result was comparable to the media containing 10% (v/v) DMSO. For HDFs, COOH-PLL could effectively retain cell viability and proliferation against 3 freeze/thaw cycles. Cell viability of HDFs was decreased after 5 freeze/thaw cycles, but COOH-PLL exerted better cryoprotection. The cell type might account for the difference in the observations. The data demonstrated that COOH-PLL is a good cryoprotectant for mammalian cells against repeated freeze/thaw cycles, and may be used for cell preservation in fields of cell transplantation, tissue engineering and regenerative medicine.

Highly antibiotic-resistant Acinetobacter baumannii clinical isolates are killed by the green tea polyphenol (-)-epigallocatechin-3-gallate (EGCG)

Acinetobacter baumannii is an increasingly common cause of infection in intensive-care units throughout the world, and the occurrence of multiresistant A. baumannii is increasing. The aim of this study was to determine whether a highly purified polyphenol, (-)-epigallocatechin-3-gallate (EGCG), from green tea (Camellia sinesis), had antimicrobial effects against multiresistant clinical isolates of A. baumannii. Standard microplate assays were performed to determine the MIC of EGCG for 21 clinical isolates of A. baumannii. MICs ranged from 0.078 to 0.625 mg/mL, with MIC(50) and MIC(90) of 0.312 mg/mL and 0.625 mg/mL, respectively. All of the isolates of A. baumannii tested were killed by EGCG. In time-kill assays, EGCG resulted in a 3-log reduction in CFU/mL of A. baumannii after 5 h of incubation with the polyphenol. Synergy between the commonly used topical agent 5% mafenide acetate (Sulfamylon) and EGCG was noted for one clinical isolate, and partial synergy was noted for three other isolates. These findings demonstrate that EGCG is an effective bactericidal agent against antibiotic-resistant A. baumannii clinical strains in laboratory settings. EGCG has previously been shown to be safe, and therefore may be an attractive addition for the treatment of cutaneous A. baumannii infections where high concentrations of the drug can be applied to the wound surface.

Trypanosoma cruzi trans-sialidase inhibits human lymphocyte proliferation by nonapoptotic mechanisms: implications in pathogenesis and transplant immunology

Chiefly an intracellular parasite, Trypanosoma cruzi has a transient blood-borne stage (trypomastigote), the acute phase of Chagas' disease, during which surface trans-sialidase is expressed and shed by the parasite. It's immunosuppressive through the induction of apoptosis. Herein, we investigated the role of trans-sialidase as an immune modulator of allo- and xenoreactions. Trans-sialidase strongly inhibited human lymphocyte proliferation; a role for the interleukin-2 receptor CD25 was suggested by flow cytometry. These results may have implications both for the pathogenesis of Chagas' disease and for transplantation immunology.

Inhibition of allospecific response in pancreatic islet transplantation: the glycan approach

Host resistance has precluded clinical islet transplantation from becoming a consistent therapy for type I diabetic patients, mainly due to both specific and nonspecific processes. O-glycosylated proteins have a primary role in immunologic synapses. Therefore, we investigated the effects of a putative immunomodulatory effect of the cleavage of these molecules on islet allotransplantation.

METHODS

Murine islets were treated with O-sialoglycoprotein endopeptidase. Three endpoints were studied: (1) proliferation in allogeneic mixed islet mononuclear cell reactions using treated and control irradiated islets as stimulator cells of mononuclear cells; (2) expression of IA-d on monocytes using 48-hour transplants of treated versus control mouse islets into subcutaneous capsules; (3) posttransplant graft function in an in vivo model of islet allotransplantation. Treated and control islets were transplanted in diabetic mice treated daily with cyclosporine. Glycemia was monitored to determine diabetes reversion.

RESULTS

The allogeneic proliferative response was maximal when allogeneic mononuclear cells were mixed with control islets; it was significantly decreased with treated islets. Mean proliferative inhibition rate of treated vs. control was 62%. IA-d expression on monocytes was maximal in control islets. Reversion was significantly different for treated versus control islets with its duration varied from 3 to 7 days.

CONCLUSION

These results suggest that treatment of islets with O-sialoglycoprotein endopeptidase may modulate allogeneic immunologic reactions.

Protective effects of green tea polyphenol against reactive oxygen species-induced oxidative stress in cultured rat calvarial osteoblast

The injurious effects of reactive oxygen species on osteoblasts and the potential protective role played by green tea polyphenols (GtPP) were investigated using primarily cultured rat calvarial osteoblasts. Oxidative stress was induced in cultured osteoblasts, either by adding 100 mmol/L H2O2 or by the action of 40 U/L xanthine oxidase (XO) in the presence of xanthine (250 micromol/L). After incubation, the cellular viability, function and morphology were evaluated. Both treatments produced a significant reduction in osteoblast viability, as assessed by a two-colored fluorescence staining method combined with flow cytometric analysis and MTT assay. A significant reduction in the alkaline phosphatase activity was observed after H2O2 addition, whereas XO did not have the same effect. On the microscopic observations, the morphological changes and intracellular ultrastructural damages were remarkably induced by both treatments. The H2O2-induced alterations were prevented by pre-incubating the osteoblasts with 200 microg/ml GtPP for 1 h. When the oxidative stress was induced by XO, the cellular viability and morphology was also maintained at the same polyphenol concentration. These results demonstrate that GtPP can act as a biological antioxidant in a cell culture experimental model and protect cells from oxidative stress-induced toxicity.

Partial hemiarthroplasty for the treatment of osteonecrosis of the femoral head. An experimental study in the dog

The use of a composite osteochondral device for simulating partial hemiarthroplasty was examined. The device was composed of a polyvinyl alcohol hydrogel and a titanium fibre mesh, acting as artificial cartilage and as porous artificial bone, respectively. The titanium fibre mesh was designed to act as an interface material, allowing firm attachment to both the polyvinyl alcohol gel (through injection moulding) and the femoral joint surface (through bony ingrowth). We implanted 22 of these devices into canine femoral heads. Histological findings from the acetabular cartilage and synovial membrane, as well as the attachment of the prosthesis to bone, were examined up until one year after operation. No marked pathological changes were found and firm attachment of the device to the underlying bone was confirmed. The main potential application for this device is for partial surface replacement of the femoral head after osteonecrosis. Other applications could include articular resurfacing and the replacement of intervertebral discs.

Tissue-engineered pancreatic islets: culturing rat islets in the chitosan sponge

Subcutaneous islet transplantation has become an attractive modality. With development of tissue-engineering techniques, it is possible to rectify the disadvantage of poor blood supply in the subcutaneous site by reconstruction of the capillary network. According to reports, the Chitosan sponge (CS) could be used for reconstruction of in vitro capillary-like network and could be used in artificial skin equivalent. In this study, we cultured the islets in CS for future application. CSs, having 200-500 microm pore size, were prepared by freeze-drying method. Rat islets were isolated from the pancreas of Lewis rats (10 weeks old, 280-300 g, male) by collagenase digestion followed by discontinuous dextran gradient centrifugation method. Each 20 islets were seeded equally into the CSs and were cultured for 62 days with various culture media such as RPMI-1640, Dulbecco's modified Eagle's medium (DMEM), and Eagle's MEM. They contained 10% fetal bovine serum (FBS) and 5 ml/L antibiotic-antimycotic mixed stock solution in the culture dishes. Insulin concentration both inside and outside of the islet-seeded CS was measured during culture. Changes in the morphology of islets were also observed in this study. Freshly isolated islets had a loose appearance with an irregular border, and most were seen as a single islet. Occasionally a cluster, consisting of 2-4 islets ranging mainly from 150 to 250 microm in diameter, was observed. Islets cultured in the CSs in different culture media retained initial morphology, which had well-delineated smooth borders for at least 53 days. The insulin release behavior of islets cultured in the CS showed constant secretory capacities for 49 days. After that they exhibited a rapid and definitive decline from the initial insulin release. Until this stage, insulin concentration in the CS was well maintained. The properties were dependent on culture medium used and insulin diffusion released from islets. This experiment is a new study model for establishment of islet culture in a three-dimensional matrix. Also extension of this observation will provide new insights for islet transplantation at the subcutaneous site by a tissue-engineering approach.

Long-term implantation test and tumorigenicity of polyvinyl alcohol hydrogel plates

Two types of flat plates made from a polyvinyl alcohol (PVA) hydrogel with a water content of 80 and 20 (PVA-H80, PVA-H20), 20 x 10 x 1 mm in size, were subcutaneously implanted into each of 50 young, male Wistar rats. As a control, a sham operation was done on another set of 50 rats (Sham Op group). The shape and transparency of the PVA hydrogel were unchanged for up to 24 months. Tumors arose in 14 rats from the PVA-H80 group. In the PVA-H20 group, tumors appeared in 15 rats. The average tumor latency was 598 +/- 109 days in the PVA-H80 and 637 +/- 94 days in the PVA-H20. There was no difference in tumor incidence between the PVA-H20 and PVA-H80 groups (p < 0.05). In the Sham Op group, no malignant tumors appeared. Histopathologically, the tumors induced by hydrogel plates were malignant tumors resembling fibrosarcoma or malignant fibrous histiocytoma. This indicates that PVA hydrogel implants also induce solid state carcinogenesis at a similarly high rate to medical grade hydrophobic material reported in a previous study.

Culture of porcine hepatocytes: the dogma of exogenous matrix revisited

The use of exogenous matrices has been described as an essential component in securing the viability and functionality of hepatocytes in vitro whether cultured for extracorporeal devices or cell transplantation. Here we report on the in vitro culture of porcine hepatocytes in polystyrene tissue-culture flasks without exogenous matrices showing adequate attachment and viability. Cell proliferation was evidenced by uptake of 5-bromo-2'-deoxyuridine, with peaks at Days 2 (19.7 +/- 8.5%), 15 (20.8 +/- 3.3%), and 35 (21.4 +/- 0.3%). Detoxification capacity was assessed by determination of monoethylglycinexylidide, a product of lidocaine metabolism (highest value 156.5 +/- 10.1 ng/ml at Day 4), and by diazepam clearance (maximum clearance 66.2% at Day 6). Diazepam metabolite levels were highest at Day 4 both for temazepam and oxazepam (6.5 +/- 0.1 and 0.10 +/- 0.01, respectively). These results suggest that the need for an exogenous matrix to achieve sustained proliferative activity and differentiated hepatocyte function should not necessarily be considered a sine qua non condition.

Long-term preservation of rat pancreatic islets under physiological conditions

In this study, we found that islet cells treated with polyphenol could be preserved for over 2 months under physiological conditions retaining their original function and maintaining their spherical shapes without any insulin secretion. When islets were treated at higher concentration than 250 microg ml(-1), these islets could retain their compact spherical shape over 65 days whereas non-treated islets were scattered ease to break within 2 weeks. The secretional capacity from treated islets in the initial stage is also lower than untreated islets. However, in the case of untreated islets, insulin release rapidly lowered with the progress in the culture time and secretion completely disappeared after 9 days. On the contrary, islets treated with polyphenol (250 microg ml(-1)) in RPMI culture medium showed significant enhancement of insulin secretion on 40th day. The secretional capacity of islets was greatly dependent on the treating concentration. Polyphenol treatment may be a useful method for preservation of mammalian islet cells. By changing the concentration of polyphenol, it is possible to control the preservation duration and insulin secretion of islets.

[Kidney and pancreas transplantation: initial experience at a single transplant center in Argentina]

After more than 10,000 cases reported all over the world until 1998, simultaneous kidney and pancreas transplantation has become a safe clinical practice, and it may probably represent the best treatment available for diabetic patients in end-stage renal disease. Here we present our results after 12 cadaveric pancreas transplants (8 whole organ, and 4 islet transplants), performed on insulin-dependent diabetic patients. Eleven of these patients received a kidney simultaneously, and one of them required a kidney retransplantation. All vascularised pancreatic grafts were positioned intraperitoneally, anastomosed to the iliac vessels, and bladder drained. One year patient, whole pancreas, and kidney survival rates were 86%, 86% and 71%, respectively. All of these patients remain insulin and dialysis-free, the longest for 37 months. Islets for transplantation were obtained from single cadaveric donors. Fresh, unpurified cells were transplanted intraperitoneally by laparoscopy (equivalent islet yields: 3 x 10(5), 4 x 10(5), 1 x 10(6) and 5 x 10(5)). None of the islet recipients resulted insulin-independent but they all reduced daily requirements in about 40%, with better metabolic control (mean HbA1c pretransplant 9.4 +/- 1.8, vs 7.9 +/- 1.6 posttransplant). One kidney graft was lost due to venous thrombosis. Simultaneous kidney and pancreas transplantation offers the diabetic patient in end-stage renal disease a chance of independence both from dialysis and exogenous insulin. Whole pancreas transplantation has better functional outcome than islet transplantation. Nevertheless, for those diabetic patients who do not meet the criteria to receive a vascularised graft, pancreatic cells may still improve carbohydrate metabolism with minor surgical risk.

Morphologic study and syntheses of type I collagen and fibronectin of human periodontal ligament cells cultured on poly(ethylene-co-vinyl alcohol) (EVA) with collagen immobilization

The purpose of this study was to regenerate the human periodontal ligament (PDL) around dental implants by using a hybrid structure of cells with materials, such as PDL cells + collagen + poly(ethylene-co-vinyl alcohol) (EVA) on titanium implant. Human PDL cells were cultured on the EVA surface coated with type I collagen and the cell adhesion and extension were investigated. Furthermore, collagen type I and fibronectin syntheses were analyzed. The serum free culture was also tried, to investigate the role of collagen in detail. The results showed that: 1. Satisfactory adhesion, extension, and proliferation of the PDL cells on the EVA films coated with collagen were observed, but were not good without collagen. 2. Immunostaining of cultured PDL cells revealed the syntheses of type I collagen, when cultured on the EVA coated with collagen or conventional culture dish, though fibronectin synthesis was observed even in the EVA without collagen. 3. Only PDL cells on the EVA coated with collagen proliferated well in the absence of serum. These results indicate that our novel implant material (EVA coated with collagen) provides a possibility of PDL regeneration on dental implants.

Type I atelocollagen grafting onto ozone-treated polyurethane films: cell attachment, proliferation, and collagen synthesis

An approach is presented for the graft copolymerization of type I atelocollagen onto the surface of polyurethane (PU) films treated with ozone. Through inducing oxidization to modify PU surface by ozone, peroxide groups are easily generated on the surface. Those peroxides are broken by redox-polymerization, and provide active species which initiate graft polymerization by reacting with amines in the collagen molecules. The ozone oxidation time and voltage could readily control the amount of peroxide production. The surface density of generated peroxides on PU surface was determined by iodide method. The maximum concentration of peroxide was about 10.20 x 10(-8)mol/cm(2) when ozone oxidation was performed at 60 V for 30 min. After the reaction of PU by ozone oxidation, type I atelocollagen was graft-copolymerized onto the PU film. All the physical measurements on the collagen-grafted surface indicated that the PU surface was effectively covered with type I atelocollagen. The interaction of the collagen-grafted PU surface with fibroblasts could be greatly enhanced by the surface graft polymerization with type I atelocollagen. Attachment and proliferation of fibroblasts on the grafted type I atelocollagen were significantly enhanced, and it is assumed that the atelocollagen matrix supported the initial attachment and growth of cells. In the early stage of proliferation, collagen synthesis in fibroblasts was not activated and remained at a relatively low level due to the grafted type I atelocollagen, increasing only with fibroblast differentiation.

Biodegradable poly (lactic acid) microspheres for drug delivery systems

In connection with aim of maximizing the bio-availability of conventional drugs with minimum side-effects, new drug delivery systems (DDS) continue to attracted much attention. The controlled or sustained release of drugs represents one such approach, and in this regard report upon a study of DDS using biodegradable polymers which include poly (lactic acid) (PLA), poly (glycolic acid), and their copolymers (PLGA). Much attention is being paid to the controlled release of bio-active agents from microcapsules and microspheres made of biodegradable polymers, such as lactic acid homopolymers, as well as copolymers of glycolic acid. (11-21) Microcapsules or microspheres are injectable and able to provide pre-programmed durations of action, offering several advantages over the conventional dosage forms. This article reviews the results of a work program conducted in collaboration with a medical doctor upon DDS using biodegradable microspheres, such as PLA and PLGA.

Biodegradable scleral implant for controlled intraocular delivery of betamethasone phosphate

We evaluated nail-like, biodegradable scleral implants as a controlled intraocular delivery system of betamethasone phosphate (BP) for the treatment of chronic uveitis using pigmented rabbits. The scleral implants, which contained 10% and 25% of BP (weight 8.5 mg; length 5 mm), were made of poly (D,L-lactide-co-glycolide) (PLGA). In vivo release and retinal toxicity after implantation were also studied in pigmented rabbits. The in vitro release studies demonstrated the 10% and 25% BP-loaded scleral implants released BP in a biphasic release pattern for at least 1 month. The BP concentrations in the vitreous and the retina/choroid after application of scleral implants in pigmented rabbit eyes stayed within the concentration range capable of suppressing inflammatory responses for over 1 month. The BP concentration was greater in the retina/choroid than in the vitreous throughout the study. No substantial toxic reactions in the retina were observed by electroretinography. Our findings suggest that the BP-loaded scleral implant may be a promising device for treatment of chronic uveitis.

Management of a high-output postoperative enterocutaneous fistula with a vacuum sealing method and continuous enteral nutrition

A postoperative enterocutaneous fistula is one of the most complex medical problems. Its treatment may become long-lasting, wearisome, and its outcome often is disappointing. Here, we describe the use of a novel device to treat a 67-year-old patient with a postoperative, high-output enterocutaneous fistula. A semipermeable barrier was created over the fistula by vacuum packing a synthetic, hydrophobic polymer covered with a self-adherent surgical sheet. To set up the system, we constructed a vacuum chamber equipped with precision instruments that supplied subatmospheric pressures between 350 and 450 mm Hg. The intestinal content was, thus, kept inside the lumen, restoring bowel transit and physiology. The fistula output was immediately reduced from a median of 800 ml/day (range, 400-1,600 ml/day), to a median of 10 ml/day (range, 0-250 ml/day), which was readily collected by the apparatus. Oral feeding was reinitiated while both parenteral nutrition and octreotide were withdrawn. No septic complications occurred, and the perifistular skin stayed protected from irritating intestinal effluents. Both the fistula orifice and the wound defect fully healed after 50 days of treatment. We believe this method may serve as a useful tool to treat selected cases of high-output enterocutaneous fistulas without the need for octreotide or parenteral nutrition.

Polyacrylonitrile membrane interposition between a xenograft and a patient in fulminant liver failure: the concept of xenohemodiafiltration in clinical practice

Fulminant hepatic failure is an important cause of morbidity and mortality in intensive care units. Conventional therapies are not sufficiently effective. Liver transplantation may be life saving, but a "bridge therapy" is needed until transplantation is performed. Hepatic extracorporeal xenohemodiafiltration (XHDF) is aimed at the transitory support of a patient with fulminant hepatic failure. The first clinical case of XHDF is presented. The system consisted of cross-circulation between a porcine liver and a patient with fulminant liver failure through a polyacrylonitrile membrane. The procedure lasted for 5 hours and produced hemodynamic, biochemical, and metabolic improvements. Intracranial pressure decreased from 34 to 5 cm H2O, serum ammonia fell from 673 to 370 ng/dl, lactic acid from 11 to 5.3 mmol/L, and bilirubin from 7.4 to 2.5 mg/dl. Hemodynamic values were maintained stable throughout the procedure. The patient was able to undergo transplantation and remains alive 11 months later. XHDF is a clinical experimental method that can constitute an alternative clinical therapy to support patients with fulminant hepatic failure until an organ is available for transplantation.

Surface modification of poly(ethylene-co-vinyl alcohol) (EVA). Part I. Introduction of carboxyl groups and immobilization of collagen

To enhance the surface biocompatibility of poly(ethylene-co-vinyl alcohol) (EVA) and high-density polyethylene (HDPE), carboxyl groups were introduced by ozone exposure. Type I collagen was immobilized onto the surface through polyion complexing. The carboxyl groups on the EVA were characterized by electron spectroscopy for chemical analysis and neutralization. The amounts of the carboxylic group and collagen increased with increases in time and temperature of exposure. Water-soluble fragments were produced by ozone exposure to EVA, and they acted as collagen crosslinkers. The differences in charge distribution of carboxyl groups affected the amount of collagen immobilization. Graft polymerization of acrylic acid was also carried out onto EVA and HDPE surfaces. The amount of collagen immobilized by graft polymerization was much higher than that by ozone exposure despite the introduction of almost the same amounts of carboxylic groups. It was suggested that the negative charge distribution influences the amount of collagen immobilized onto films.

Development of artificial articular cartilage

Attempts have been made to develop an artificial articular cartilage on the basis of a new viewpoint of joint biomechanics in which the lubrication and load-bearing mechanisms of natural and artificial joints are compared. Polyvinyl alcohol hydrogel (PVA-H), 'a rubber-like gel', was investigated as an artificial articular cartilage and the mechanical properties of this gel were improved through a new synthetic process. In this article the biocompatibility and various mechanical properties of the new improved PVA-H is reported from the perspective of its usefulness as an artificial articular cartilage. As regards lubrication, the changes in thickness and fluid pressure of the gap formed between a glass plate and the specimen under loading were measured and it was found that PVA-H had a thicker fluid film under higher pressures than polyethylene (PE) did. The momentary stress transmitted through the specimen revealed that PVA-H had a lower peak stress and a longer duration of sustained stress than PE, suggesting a better damping effect. The wear factor of PVA-H was approximately five times that of PE. Histological studies of the articular cartilage and synovial membranes around PVA-H implanted for 8-52 weeks showed neither inflammation nor degenerative changes. The artificial articular cartilage made from PVA-H could be attached to the underlying bone using a composite osteochondral device made from titanium fibre mesh. In the second phase of this work, the damage to the tibial articular surface after replacement of the femoral surface in dogs was studied. Pairs of implants made of alumina, titanium or PVA-H on titanium fibre mesh were inserted into the femoral condyles. The two hard materials caused marked pathological changes in the articular cartilage and menisci, but the hydrogel composite replacement caused minimal damage. The composite osteochondral device became rapidly attached to host bone by ingrowth into the supporting mesh. The clinical implications of the possible use of this material in articular resurfacing and joint replacement are discussed.

In vivo evaluation of 2-cyanoacrylates as surgical adhesives

To evaluate 2-cyanoacrylates as surgical adhesives, the bond strength in vivo as well as the tissue reaction was investigated using methyl-, ethyl-, isobutyl-, and ethoxyethyl-2-cyanoacrylate. In addition, their set time and spreading on blood were studied. When the 2-cyanoacrylates were applied to an incised site of rabbit skin, they could maintain the skin closure without suturing during the first week and the bond strength increased during the second week. Significant inflammatory response was observed around the subcutaneous tissue glued with methyl- and ethoxyethyl-2-cyanoacrylate and persisted for approximately one week. All the 2-cyanoacrylate polymers were absorbed and the tissues treated were healed two weeks after the operation. There was a mild inflammatory reaction in the tissue treated with ethyl- and isobutyl-2-cyanoacrylate, and their polymers still remained at the wound site at the second week postoperatively. The disappearance rate of the 2-cyanoacrylate polymers was roughly in proportion to the inflammatory tissue response. Ethoxyethyl-2-cyanoacrylate spread more broadly on tissues than the other 2-cyanoacrylates, while its set time was shorter than that of methyl- and ethyl-2-cyanoacrylates.

Biodegradation and tumorigenicity of implanted plates made from a copolymer of epsilon-caprolactone and L-lactide in rat

Flat plates made from a copolymer of epsilon-caprolactone and L-lactide (P-CL-LA) [50:50 (w/w), molecular weight 1.62 x 10(5); 20 x 10 x 1 mm size] were subcutaneously implanted into 50 young, male Wistar rats (P-CL-LA group). After 24 months the plates had become a mass of small pieces, which were concentrated in an area of 3 x 2 x 1 mm. For comparison, 50 rats were implanted with medical-grade polyethylene plates (PE group) while another set of 50 rats was subjected to the same operation but without an implant (Sham Op group). Tumors arose in 25 rats from the P-CL-LA group: 24 were malignant mesenchymal tumors at the implant sites. In the PE group, tumors appeared in 16 rats (14 at the implant sites and two ectopically). The average tumor latency was 578+/-84 days in the P-CL-LA group and 452+/-102 days in the PE group. There was no difference in tumor incidence between the P-CL-LA and PE groups (p < 0.05). In the Sham Op group, two malignant tumors appeared over 2 years. Pathologically, these induced tumors arose from the inflammatory cells surrounding the degrading fragments of P-CL-LA within the tissue capsule. This indicates that relatively slowly degrading material can induce malignant tumors at a similarly high rate to nonabsorbable medical grade PE, at least in this animal model.

Experimental and clinical evaluation of cisplatin-containing microspheres as intraperitoneal chemotherapy for ovarian cancer

BACKGROUND

We aimed to evaluate the in vitro and in vivo effects of poly [L-lactic acid] microsphere containing cisplatin (CDDP-MS) for intraperitoneal (i.p.) chemotherapy for ovarian cancer.

METHODS

We initially examined the in vitro and in vivo profile of cisplatin release from the CDDP-MS, then this drug delivery system was evaluated in 15 patients.

RESULTS

The in vitro study showed that cisplatin was released constantly over a 3-week period. Rats in the CDDP-MS group had a significantly lower peak serum concentration of platinum compared with rats in the aqueous cisplatin solution (CDDP-S) group; the serum concentration of platinum showed a gradual decline. The ascitic fluid concentration of platinum also gradually decreased in the CDDP-MS group. We treated 15 patients with recurrent ovarian cancer with CDDP-MS containing 200 mg of cisplatin (n = 5) or CDDP-S containing 100 mg of cisplatin (n = 10) administered i.p. The peak serum and ascites concentrations of platinum were lower immediately after administration of CDDP-MS than after administration of CDDP-S, but increased over time in the CDDP-MS group, reflecting the slow-release effect of CDDP-MS. Grade 1 to 2 leukopenia and/or neutropenia occurred in 2 of 5 patients. No thrombocytopenia or renal or neurologic toxicity was observed;

CONCLUSION

These findings indicate that the i.p. administration of CDDP-MS increased the dose intensity of cisplatin and appeared to be safe and effective for the treatment of ovarian cancer.

Occlusive effects of lactic acid-glycolic acid copolymer membrane on gingival fibroblasts in vitro

The cell occlusive effects on human gingival fibroblasts of degradable lactic acid-glycolic acid copolymer membranes (noncoated membranes) and membranes coated with a sucrose ester of fatty acid (coated membranes) were studied and compared with those of expanded polytetrafluoroethylene (e-PTFE) membranes. The membranes were immersed in a culture medium periodically for 21 days and interposed into a chemotaxis chamber, and the fibroblasts then were cultured in the chamber for another 7 days. The passage rate of cells through the membranes was calculated and the change in surface structure of each membrane after immersion for 28 days was observed by an environmental scanning electron microscope. The passage rate of coated membranes (3.4+/-2.2%) was significantly lower than that of noncoated (25.7+/-5.1%) at the 28th day whereas the passage rate of e-PTFE membranes was 0.8-1.5%. Many pores were observed on the noncoated membranes before immersion while the coating material covered most of the pores on the coated membranes. The average pore size of the noncoated membranes was larger than that of the coated membranes at day 28. The structure of the e-PTFE membranes underwent no change. The passage rate of the coated membranes was not different from the e-PTFE membranes, suggesting an effect that might be useful for a guided tissue regeneration procedure.

Synthesis of polylactides with different molecular weights

The synthesis of poly(lactic acid) through polycondensation of the lactic acid monomer gave weight average molecular weights (Mw) lower than 1.6 x 10(4), whereas ring-opening polymerization of lactides in bulk at 130 degrees C for 72 h using stannous octoate as catalyst in the concentration range from 0.003 to 0.8 wt% produced polylactides with viscosity average molecular weight (Mv) ranging from 2 x 10(4) to 6.8 x 10(5). The monomer conversion and Mv showed a maximum at a catalyst concentration around 0.05 wt%. The monomer conversion and Mv increased almost linearly with polymerization time up to a monomer conversion of 80%, but both the conversion and Mv decreased after passing through a maximum, when the polymerization reaction was allowed to proceed for longer periods of time. This time dependence was pronounced at higher polymerization temperatures. The decrease in Mv at prolonged polymerization and higher polymerization temperatures was attributed to thermal depolymerization of resultant polylactides, but no significant optical rotation of poly(L-lactide) was noticed.

Polyacrylonitrile membrane interposition between a xenograft and an animal in fulminant liver failure. The concept of xenohemodiafiltration

In fulminant liver failure (FLF) there is need for support as a bridge to liver transplantation. Based on the concepts of hemofiltration and xenotransplantation, the authors present a model of liver support in FLF. The authors performed a portacaval shunt and ligature of the hepatic artery in 12 pigs. In six pigs (Group A) continuous hemofiltration through a polyacrylonitrile membrane was performed. Six isolated dog's livers were catheterized through the portal vein and perfused with autologous erythrocytes, albumin, and electrolytes in a closed circuit. With the use of the auxiliary liver, the circuit was connected to one of the lateral outlets of the hemofilter, while the other lateral outlet was connected to the portal vein through the pump. Thus, a polyacrylonitrile exchange membrane was created between the blood of the pig with FLF and the auxiliary liver's circulation. In Group B (controls), six pigs were connected directly to the auxiliary liver through a pump. In Group A, the auxiliary liver worked for 8 hr, without evidence of macroscopic or histologic damage. Lactic acid and ammonia levels improved: lactic acid, 8.2 +/- 6 mmol/L to 1.6 +/- 1 mmol/L; ammonia 487 +/- 110 micrograms/dl to 117 +/- 13 micrograms/dl, p < 0.1. The lidocaine clearing (MEGX) test results remained at functional levels (> 90 ng/ml) at the end of the perfusion. In Group B, the perfusion was discontinued at 60 +/- 15 min because of evidence of necrosis of the auxiliary liver. Lactic acid levels increased from 8.19 +/- 1.1 mmol/L to 13 +/- 4 mmol/L, ammonia levels remained high (390 +/- 15 micrograms/dl to 480 +/- 80 micrograms/dl), and the MEGX test results showed levels below functional activity by the end of the perfusion (45 +/- 30 ng/ml). The authors conclude that the concept of xenohemodiafiltration based on the interposition of a polyacrylonitrile membrane between a xenograft and an animal in FLF is adequate to support functions of detoxification and could be used in the future in the support of patient with FLF.

New biodegradable oligoesters for pharmaceutical application

Tartaric acid, malic acid, and glyceric acid were copolycondensed with glycolic acid at various molar ratios in feed to quickly synthesize biodegradable oligoesters. They were likely to have a moderately cross-linked structure with relatively low molecular weights and hydrophilic groups on the chains. In addition to macroscopic gels which were insoluble in any solvents, we could obtain the oligoesters which were insoluble in water but soluble in N,N-dimethylformamide. The degradation rate of the oligoesters was higher than that of lactic acid (LA) oligomers having molecular weights of a few thousands. On the contrary, their glass transition and flow temperatures were much higher than those of LA oligomers, indicating that their handling during the preparation of drug delivery dosage forms was much improved. The formulation of microspheres containing drugs from the oligoesters revealed that they were useful as biodegradable matrices having high degradation rates.

Degradation of high molecular weight poly(L-lactide) in alkaline medium

To study the effect of molecular weight and morphology on hydrolytic degradation, four poly(L-lactide)s (PLLAs) with average molecular weight of 3.0 x 10(5), 4.5 x 10(5), 6.5 x 10(5) and 3 x 10(6) were used. PLLA films with different morphologies were obtained by solution casting. Degradation of the films was performed at 37 degrees C in 0.01 N NaOH solution and this alkaline hydrolysis seemed to simulate well the real case while offering significant acceleration of the degradation process. Diverse microscopy techniques (light, polarizing and scanning electron) were used to study the surface change of morphology and erosion of the PLLA films. Swelling was visualized by scanning electron microscopy, particularly on the spherulites, which were eroded from the centre by hydrolysis. In the case of highly amorphous film, crystallization took place as degradation proceeded. The reduction in transparency of PLLA films, measured by a spectrophotometer at 570 nm, was ascribed to the increased density of spherulites. Differential scanning calorimetry revealed that the crystallinity of PLLA increased with degradation time, in accordance with accelerated spherulite formation.

Clinical evaluation of uniaxially oriented poly-L-lactide rod for fixation of experimental femoral diaphyseal fracture in immature cats

Transverse diaphyseal fractures of the femur were experimentally made in immature cats, and were fixed by an intramedullary pinning technique using an uniaxially oriented poly-L-lactide (PLLA) rod, a biodegradable polymer. The healing process was evaluated radiographically and histologically. Formation of bony callus was completed in 8 weeks, and cortical bony union followed. The remodeling process was then observed form 12 to 16 weeks. The healing process was almost the same as when a metallic implant was used. Abundant periosteal callus formation may be attributable to the lower elasticity of the PLLA rod compared with metallic implants. Since no other abnormalities such as growth deformities were detected, it was concluded that the combined use of a uniaxially oriented PLLA rod and an external splint is clinically useful for the repair of diaphyseal fractures in immature cats.

Scleral plug of biodegradable polymers for controlled drug release in the vitreous

We designed a new device, a scleral plug, that releases drugs into the vitreous after being implanted and fixed at the pars plana. Use of the plug for provision of doxorubicin hydrochloride was evaluated in rabbits. The scleral plug (8.5 mg) was made of poly(lactic-glycolic acid) (molecular weight, 40,000 daltons) containing 1% doxorubicin. Vitreous concentrations of doxorubicin were measured after the implantation. In vitro studies showed that the plug released 26% of the drug during 4 weeks. In vivo studies demonstrated that the concentration in the vitreous humor was maintained at a therapeutic range for longer than 4 weeks. No substantial toxic reactions were observed by electroretinographic and histopathologic evaluations. Our findings suggested that a scleral plug made of biodegradable polymers is a promising device for a controlled drug-release system in the vitreous.

Bioabsorbable struts made from poly-L-lactide and their application for treatment of chest deformity

Poly-L-lactide, a polymer of lactic acid, shows slow degradation in living tissue. Poly-L-lactide plate of high molecular weight maintains more than 90% of its initial mechanical properties for more than 3 months after implantation. Using struts made from poly-L-lactide plate, we performed chest wall reconstruction in 56 patients: for postoperative chronic sternal dehiscence in 23 and sternal elevation for pectus excavatum in 33 cases. The postoperative external appearances of the anterior chest were improved in comparison with the preoperative state in all cases. The internal features were evaluated by computed tomographic scan. Neither postoperative wound infection nor respiratory complication was observed, and no tendency for regression of the anterior chest occurred in any of the patients. In 3 of 56 cases (5.4%; one in the sternal dehiscence group and two in the pectus excavatum group), it was necessary to remove part of the strut because of overgrowth of granulation tissue around the implanted material after 4, 12, and 13 postoperative months, respectively. In the pectus excavatum group, the computed tomographic evaluations showed that poly-L-lactide strut maintained sufficient strength to support the thoracic wall 5 months after implantation. These findings suggest that the bioabsorbable poly-L-lactide strut is a promising material for surgical treatment of chest deformity.

Effect of polylactic acid on osteoinduction of demineralized bone: preliminary study of the usefulness of polylactic acid as a carrier of bone morphogenetic protein

To evaluate the usefulness of polylactic acid (PLA), a bioabsorbable and plastic polymer, as a carrier of bone morphogenetic protein (BMP), a preliminary study has been carried out to investigate any negative effect of PLA on osteoinduction of demineralized bone (DB). PLA (10,600 mol. wt) was mixed with DB particles (1-1.5 mm square) prepared from rat femurs and laid subcutaneously on the intercostal muscle of 4-week-old Wistar rats. The PLA/DB pellets were harvested at 2, 4, 8 and 24 weeks after the operation, and prepared for light microscopic examination. Histological examination revealed cartilage formation at 2 weeks and new bone formation at 4 weeks. Extensive bone and marrow formation were observed at 24 weeks. PLA was gradually absorbed and completely disappeared at 24 weeks to be replaced by connective tissue. These results demonstrate that PLA does not have a negative influence on the osteoinductive activity and that PLA could well be a promising bioabsorbable carrier of BMP.

Tumorigenicity of poly-L-lactide (PLLA) plates compared with medical-grade polyethylene

Poly-L-lactide (PLLA) plates, 20 x 10 x 1 mm in size, with flat surfaces, were implanted into 50 young male Wistar rats subcutaneously, and the incidence of tumors for 2 years under specific pathogen-free (SPF) conditions was evaluated. Tumors arose in 22 rats (at the implant sites in 20, and distant from the implantation site in 2). As a control, plates of medical-grade polyethylene of the same shape were implanted into 50 rats. Tumors appeared in 23 of these rats (21 at the sites of the plates, and 2 ectopically). In 30 rats given sham operations, no tumors appeared in the 2 year observation period. Histologically, all the tumors were mesenchymal malignant tumors resembling fibrosarcoma or malignant fibrous histocytoma (MFH) in humans. In 6 of the PLLA tumors and 3 of the PE tumors, bone formation was observed. There was no significant difference between the incidence of tumors caused by PLLA plates and that of tumors caused by medical-grade polyethylene plates. Macroscopically, PLLA plates retained their initial shape for 2 years. Scanning electron microscopy revealed small holes on the surfaces of the plates, and their molecular weight was reduced to 8% of the initial value.

Poly(vinyl alcohol) hydrogels as soft contact lens material

A new type of soft contact lens was developed from the poly(vinyl alcohol) (PVA) hydrogel prepared by a low temperature crystallization technique using a water-dimethyl sulfoxide mixed solvent. The PVA contact lens materials had a water content of 78% and a tensile strength of 50 kg/cm2, five times as strong as that of commercial poly(2-hydroxyethyl methacrylate) soft contact lens. The amount of proteins adsorbed to the PVA soft hydrogel material was half to one thirtieth of that of conventional soft contact lenses. Histological and scanning electron microscopic observation of rabbit eyes which had worn the PVA soft contact lens for 12 weeks showed no difference in corneal epithelium and cell arrangement in the corneal epithelium from the non-wearing eyes.

Pharmacologic effects of cisplatin microspheres on peritoneal carcinomatosis in rodents

BACKGROUND

A new drug-delivery formulation of cisplatin, whereby cisplatin was incorporated in lactic acid oligomer microspheres (CDDP-MS), has been developed in dosage form for peritoneal carcinomatosis and has been designed to release 70% of the incorporated cisplatin slowly during a period of 3 weeks. In this study, its pharmacologic effects were examined in rodents.

METHODS

CDDP-MS was tested to determine (1) tissue distribution of cisplatin after intraperitoneal administration of cisplatin at 3.0 mg/kg body weight to rats, (2) acute toxicity in mice when injected intraperitoneally, and (3) therapeutic effects on peritoneal carcinomatosis induced by transplantable M5076 tumors in mice.

RESULTS

These experiments revealed the following: (1) CDDP-MS resulted in a higher cisplatin concentration in tissues adjacent to the peritoneum for a longer period, and the concentration of cisplatin measured in the rest of the body was lower than that delivered by the cisplatin aqueous solution; (2) the 50% lethal dose value, determined by the Litchfield-Wilcoxon method, was 23.8 mg/kg body weight in CDDP-MS in terms of cisplatin, whereas in the cisplatin aqueous solution it was 13.5 mg/kg body weight; (3) CDDP-MS enhanced therapeutic effects when compared with the same toxicity dosage of cisplatin aqueous solution.

CONCLUSIONS

Intraperitoneal CDDP-MS releases cisplatin into the peritoneal cavity for a long time, and it results in less systemic toxicity and greater therapeutic effects on peritoneal carcinomatosis than does cisplatin aqueous solution.

In vitro and in vivo studies on bioabsorbable ultra-high-strength poly(L-lactide) rods

Ultra-high-strength poly(L-lactide) (PLLA) rods were fabricated using a drawing technique. Rods with a diameter of 3.2 mm and a draw ratio of 2.5:1 showed initial bending strength and modulus values of 240 MPa and 13 GPa, respectively. The purpose of this study was to investigate the in vitro and in vivo degradation of PLLA rods with a draw ratio of 2.5:1. The greater the rod diameter, the longer the bending strength was maintained in phosphate buffered saline at 37 degrees C. The bending strength retention of rods (diam. 3.2 mm) implanted in the subcutis of rabbits was almost equal to that of rods in the in vitro study, while those rods implanted in the medullary cavity of rabbit femora showed a slightly lower bending strength retention. Molecular weight was reduced to the greatest extent in the medullary cavity, followed by in the subcutis and in vitro. The weight of PLLA rods in the medullary cavity was reduced by 22% at 52 weeks and by 70% at 78 weeks after implantation. Histologically, no inflammatory or foreign body reaction was observed in the medullary cavity for 52 weeks. The drawn PLLA rods maintained a bending strength exceeding that of human cortical bone in the medullary canal for a period of 8 weeks, suggesting that the drawn PLLA rods may be useful in the repair of fractured human bones.

Injectable microspheres with controlled drug release for glaucoma filtering surgery

The authors evaluated the effects of biodegradable poly (lactic acid) microspheres that provided the controlled release of the antimetabolic agent adriamycin (ADR) to prevent post surgical fibrosis after glaucoma filtering surgery. Fifty six eyes of 28 rabbits underwent posterior lip sclerotomy and received a 0.2 ml subconjunctival injection that contained microspheres 90 degrees from the filtering site immediately after surgery. Microspheres containing ADR (100 or 200 micrograms) were randomly administered to one eye. The fellow eyes served as controls and received microspheres without the drug. Intraocular pressure in the eyes treated with the microspheres that contained the drug was significantly lower than that in the control eyes from days 7-12 in the 100 micrograms group and from days 6-16 in the 200 micrograms group (P < .05). Eyes that received ADR had a significantly longer patent filtering bleb compared with the control eyes (P < .05). No corneal complications were observed in the eyes treated with 100 micrograms of ADR and the control eyes. Peripheral corneal opacities (25%) and epithelial erosion (17%) were observed in the eyes that received the 200 micrograms dose, but the cornea returned to normal after 4 wk. These results suggest that controlled-drug-release microspheres with an antimetabolic agent may be promising for preventing fibrosis after surgery.

Biodegradable microspheres containing adriamycin in the treatment of proliferative vitreoretinopathy

The use of biodegradable polymer microspheres containing adriamycin for the treatment of proliferative vitreoretinopathy (PVR) in an experimental rabbit model was investigated. A single injection of microspheres containing 10 micrograms of adriamycin effectively decreased traction retinal detachment to 10% (n = 10), whereas 50% of eyes injected with blank microspheres (n = 10) developed retinal detachment (P < 0.05). A single injection of microspheres, containing 3 micrograms of adriamycin, did not suppress retinal detachment. Electroretinographic and histologic studies confirmed that the 10 micrograms injection of adriamycin in microspheres was not toxic to the retina, although the injection of the same amount of free adriamycin caused retinal necrosis and detachment. Thus, microspheres containing adriamycin hold promise as a new treatment modality for PVR.

Controlled cisplatin delivery system using poly(D,L-lactic acid)

Cisplatin (CDDP)-containing poly(D,L-lactic acid) microspheres (CDDP-MS) and beads (CDDP-B) with an average molecular weight of the oligomer of 1.2 x 10(4) and 4% CDDP loading were prepared. In Tris buffer, 95% of CDDP disappeared from CDDP-MS within 3 d. In vitro and in vivo, CDDP-B released CDDP for 30-57 d, and for 21-42 d, respectively. The other CDDP-B with an average oligomer molecular weight of 9.6 x 10(3) with 5% lactic acid monomers, that contained 4% CDDP, showed a two-phase CDDP release pattern and CDDP disappeared within 41 d in vitro, and within 21 d in vivo. Histologically, tissue necrosis surrounding the CDDP-B was not severe.