Strategies to Overcome the Barrier of Ischemic Microenvironment in Cell Therapy of Cardiovascular Disease

The transplantation of various immune cell types are promising approaches for the treatment of ischemic cardiovascular disease including myocardial infarction (MI) and peripheral arterial disease (PAD). Major limitation of these so-called Advanced Therapy Medicinal Products (ATMPs) is the ischemic microenvironment affecting cell homeostasis and limiting the demanded effect of the transplanted cell products. Accordingly, different clinical and experimental strategies have been evolved to overcome these obstacles. Here, we give a short review of the different experimental and clinical strategies to solve these issues due to ischemic cardiovascular disease.

Improved Histological Evaluation of Vascularity around an Immunoisolation Device by Correlating Number of Vascular Profiles to Glucose Exchange

The aim of this study was to determine which vessels are important for the exchange of small molecules, such as glucose, from the microcirculation into an immunoisolation device. Reasonably, those vessels should be the ones of interest in histological evaluations. In a previous study, we examined the diffusion of glucose from the microcirculation into immunoisolation devices that had been implanted subcutaneously in rats for various times (i.e., 1, 2, and 4 weeks and 3 months). The glucose kinetic data were then correlated with the number of vascular profiles within 15 and 250 μm from the device. Significant correlations were found only at 250 μm. To examine the relation further between function and vascularization, we used the histological samples from the previous study and counted vascular profiles within various distances between 15 and 400 μm from the device. The number was then correlated with the already available glucose kinetic data. The highest correlations were found at 75 and 100 μm (p < 0.05). We therefore suggest that vascular profiles within 100 μm should be used when evaluating the vascularity of tissue surrounding an immunoisolation device. We also studied neovascularization asymmetries between the side of the membrane facing the skin and that facing the muscle. At 1 and 2 weeks about half of the devices were mainly vascularized on the side facing the skin, whereas the rest were equally vascularized on the two sides. At 3 months, all devices were well vascularized, and no striking vascularization asymmetries were seen.

Use of Repeating Dispensers to Increase the Efficiency of the Intramuscular Myogenic Cell Injection Procedure

Intramuscular myoblast transplantation in humans and nonhuman primates requires precise repetitive cell injections very close to each other. Performed with syringes operated manually throughout large regions, this procedure takes a lot of time, becoming tiring and thus imprecise. We tested two repetitive dispensers with Hamilton syringes as cell injection devices to facilitate this procedure. Monkeys received intramuscular allotransplantations of β-galactosidase-labeled myoblasts, using either a monosyringe or a multisyringe repeating dispenser. The monosyringe repeating dispenser allowed performing cell injections faster and easier than with a manually operated syringe. The multisyringe dispenser accelerated the procedure still more, but it was not ergonomic. Biopsies of the myoblast-injected sites 1 month later showed abundant β-galactosidase-positive myofibers, with the same density and morphological pattern observed following myoblast transplantation with a syringe operated manually. We recommend the monosyringe repeating dispenser for myoblast transplantation in skeletal muscles and maybe in the heart.

Novel Technique for Suspension Culture of Autologous Chondrocytes Improves Cell Proliferation and Tissue Architecture

We have developed a new and simple method of chondrocyte suspension culture using a spinner bottle with rotation of the matrices. We compared the characteristics of chondrocytes cultured by this method with those grown in standard monolayer cultures. We also determined the optimal nutritional medium for suspension cultures. Periosteum explants seeded with chondrocytes were grown in monolayer and suspension cultures under three conditions: in medium with no additive (control), with 10% fetal bovine serum (FBS), or with 10% autologous serum (AS). After culturing, the explants were harvested, processed for histology, and stained with hematoxylin-eosin or TUNEL, or immunostained for type I, II, and III collagen, and Ki-67 antigen. In monolayer cultures, the attachment of the chondrocytes to the periosteum was weak and the superficial layer consisted of fibrotic tissue and few nucleated cells. Collagen type II staining was strong, but types I and III were weak. Among the suspension cultures the AS group produced the thickest layer of chondrocytes with the fewest apoptotic cells. The superficial layer of cartilage in these cultures stained positive for type I and III collagen and Ki-67 antigen. Among the suspension cultures, total chondroitin and chondroitin-4 sulfate (C-4S) concentration was highest in the AS group, while prostaglandin E2 (PGE2) was highest in the FBS group. In summary, our new method of suspension culture of periosteal explants using rotational matrices combined with AS nutritional media was the most effective method for maintaining the bond between the chondrocyte layer and periosteum, as well as the production of type I and III collagen in the superficial layer.

Implantable Biohybrid Artificial Organs

Biohybrid artificial organs encompass all devices which substitute for an organ or tissue function and incorporate both synthetic materials and living cells. This review concerns implantable immunoisolation devices in which the tissue is protected from immune rejection by enclosure within a semipermeable membrane. Two critical areas are discussed in detail: (i) Device design and performance as it relates to maintenance of cell viability and function. Attention is focussed on oxygen supply limitation and how it is affected by tissue density and the development of materials that induce neovascularization at the host tissue-membrane interface; and (ii) Protection from immune rejection. Our current knowledge of the mechanisms that may be operative in immune rejection in the presence of a semipermeable membrane barrier is limited. Nonetheless, recent studies shed light on the role played by membrane properties in preventing immune rejection, and many studies demonstrate substantial progress towards clinically useful implantable immunoisolation devices.

Electrostatic Endothelial Cell Seeding Technique for Small-Diameter (<6 MM) Vascular Prostheses: Feasibility Testing

Multiple studies have indicated the importance of surface charge in the adhesion of multiple cardiovascular cell lines including platelets and endothelial cells on the substrate materials (1,4,7-10,12-15). It is the purpose of this article to report a feasibility study conducted using an electrostatic endothelial cell seeding technique. The feasibility study was conducted using human umbilical vein endothelial cells (HUVEC), a static pool apparatus, a voltage source, and a parallel plate capacitor. The HUVEC concentration and seeding times were constant at 560,000 HUVEC/ml and 30 min, respectively. Scanning electron microscopy examination of the endothelial cell adhesion indicated that an induced temporary positive surface charge on e-PTFE graft material enhances the number and the maturation (flattening) of HUVECs adhered. The results indicated that the total number of endothelial cells adhered (70.9 mm2) was increased from 9198 ± 1194 HUVECs on the control (no induced surface charge) e-PTFE to 22,482 ± 4814 HUVECs (2.4 × control) on the maximum induced positive surface charge. The total number of cells in the flattened phase of adhesion increased from 837 ± 275 to 6785 ± 1012 HUVECs (8.1 ×) under identical conditions. Thus, the results of the feasibility study support the premise that electrostatic interaction is an important factor in both the endothelial cell adhesion and spreading processes and suggest that the electrostatic seeding technique may lead to an increased patency of small diameter (<6 mm) vascular prostheses.

Electrostatic Endothelial Cell Transplantation within Small-Diameter (<6 MM) Vascular Prostheses: A Prototype Apparatus and Procedure

This article presents a novel, clinically relevant electrostatic endothelial cell transplantation (seeding/sodding) device (U.S. & Foreign Patent Protections Pending) for small-diameter (<6 mm) vascular prostheses. The prototype apparatus was designed and built to tissue engineer 4.0 mm, I.D. GORE-TEX® (W.L. Gore & Associates, Inc.) standard wall graft segments varying in length from 4 to 12 cm. The prototype electrostatic endothelial cell transplantation apparatus is composed of an external and internal conductor, aluminum base, end supports, pillow blocks, filling apparatus, electric motor drive system, and a voltage source. The cylindrical capacitor arrangement of the device along with an electrical potential applied across the internal and external conductors creates the unique feature of this endothelial cell transplantation technique, an electric field within the cylindrical capacitor (within the graft lumen) which in turn induces a temporary positive surface charge on the graft (dielectric material) luminal surface. Multiple studies have shown that a positively charged substrate is more conducive to endothelial cell adhesion and morphological maturation (flattening) (1,2, 7,8,10,13-15). This induced positive surface charge dissipates immediately upon removal from the electrostatic endothelial cell transplantation device. Thus, after endothelial cell adhesion the graft luminal surface reverts back to its natural (nonthrombogenic) negative surface charge.

The Neointima Formed in Endothelial Cell Sodded ePTFE Vascular Grafts Results from Both Cellular-Hyperplasia and Extracellular-Hypertrophy

Endothelial cell transplantation onto polymeric vascular grafts results in the formation of a neointima. The formation of this neointima is often suggested to result from a chronic cellular hyperplasia where the terms intimal hyperplasia and intimal thickening are used interchangeably. While the formation of a midgraft neointima in sodded grafts involves a level of cell proliferation, the synthesis and deposition of extracellular matrix proteins is also a ubiquitous observation in these grafts. To assess the composition of midgraft neointima in sodded grafts, a morphometric method was developed to provide a differential quantitation of the cellular-hyperplastic and extracellular-hypertrophic elements of intimal thickening. The formed neointima on microvessel endothelial cell sodded and control (noncell-treated) ePTFE vascular grafts was quantified after 3, 12, and 52 wk of graft implantation in a canine carotid artery model. Midgraft sections of grafts were evaluated for both intimal thickness (IT) and cell density per unit volume and quantified using a PC-based image analysis program. Sodded grafts explanted at 3 wk exhibited an average neointimal cell density (3 × 109 cells/cm3; IT 30 μm) equivalent to cell densities observed in normal arterial media. After 12 wk the mean cell density approached a hyperplastic value (3.7 × 109 cells/cm3; IT 76 μm), while grafts explanted after 52 wk exhibited a mean cell density (2.8 × 109 cells/cm3; IT 30 μm) similar to 3-wk values. Control grafts that received no cells exhibited no midgraft cellular coverage. These results indicate that neointima formation in the midgraft region of sodded grafts occurred via mechanisms involving both a cellular hyperplasia and an extracellular hypertrophy. Differential responses occur presumably due to localized differences in cellular proliferation and cellular biosynthetic activity.

Experimental Hepatocyte Transplantation in Pigs

Technical issues of experimental hepatocyte transplantation in pigs, i.e., selection of animals, anesthesia, route of transplantation, and segment-specific transplantation have described.

Use of Thymidine Kinase Recombinant Adenovirus and Ganciclovir Mediated Mouse Liver Preconditioning for Hepatocyte Xenotransplantation

Hepatocyte transplantation is the best approach to maintain and propagate differentiated hepatocytes from different species. Host liver has to be adapted for transplanted hepatocytes productive engraftment and proliferation being required a chronic liver injury to eliminate host hepatocytes and provide a proliferative advantage to the transplanted hepatocytes. Most valuable mouse models for xenograft hepatocyte transplantation are based on genetically modified animals to cause a chronic liver damage and to limit host hepatocyte regeneration potential. We present a methodology that generates a chronic liver damage and can be applied to any host mouse strain and animal species based on the inoculation of a recombinant adenovirus to express herpes simplex thymidine kinase in host hepatocytes sensitizing them to ganciclovir treatment. This causes a prolonged liver damage that allows hepatocyte transplantation and generation of regenerative nodules in recipient mouse liver integrated by transplanted cells and host sinusoidal. Obtained chimeric animals maintain functional chimeric nodules for several weeks, ready to be used in any study.

Minimally Invasive Liver Preconditioning for Hepatocyte Transplantation in Rats

In the context of cell transplantation in the liver parenchyma, preconditioning is essential to enhance cell engraftment and liver repopulation. The authors have developed a minimally invasive technique of temporary portal embolization using an absorbable material, called reversible portal vein embolization. We hereby describe the method for isolating hepatocytes from a donor rat before transplanting hepatocytes after reversible portal vein embolization in the recipient.

Development of a Microforce Sensor and Its Array Platform for Robotic Cell Microinjection Force Measurement

Robot-assisted cell microinjection, which is precise and can enable a high throughput, is attracting interest from researchers. Conventional probe-type cell microforce sensors have some real-time injection force measurement limitations, which prevent their integration in a cell microinjection robot. In this paper, a novel supported-beam based cell micro-force sensor with a piezoelectric polyvinylidine fluoride film used as the sensing element is described, which was designed to solve the real-time force-sensing problem during a robotic microinjection manipulation, and theoretical mechanical and electrical models of the sensor function are derived. Furthermore, an array based cell-holding device with a trapezoidal microstructure is micro-fabricated, which serves to improve the force sensing speed and cell manipulation rates. Tests confirmed that the sensor showed good repeatability and a linearity of 1.82%. Finally, robot-assisted zebrafish embryo microinjection experiments were conducted. These results demonstrated the effectiveness of the sensor working with the robotic cell manipulation system. Moreover, the sensing structure, theoretical model, and fabrication method established in this study are not scale dependent. Smaller cells, e.g., mouse oocytes, could also be manipulated with this approach.

Asymmetric biodegradable microdevices for cell-borne drug delivery

Use of live cells as carriers for drug-laden particulate structures possesses unique advantages for drug delivery. In this work, we report on the development of a novel type of particulate structures called microdevices for cell-borne drug delivery. The microdevices were fabricated by soft lithography with a disklike shape. Each microdevice was composed of a layer of biodegradable thermoplastic such as poly(lactic-co-glycolic acid). One face of the thermoplastic layer was covalently grafted with a cell-adhesive polyelectrolyte such as poly-l-lysine. This asymmetric structure allowed the microdevices to bind to live cells through bulk mixing without causing cell aggregation. Moreover, the cell-microdevice complexes were largely stable, and the viability and proliferation ability of the cells were not affected by the microdevices over a week. In addition, sustained release of a mock drug from the microdevices was demonstrated. This type of microdevice promises to be clinically useful for sustained intravascular drug delivery.

Prevention of esophageal strictures after endoscopic submucosal dissection

Endoscopic mucosal resection (EMR) and endoscopic submucosal dissection (ESD) have recently been accepted as less invasive methods for treating patients with early esophageal cancers such as squamous cell carcinoma and dysplasia of Barrett’s esophagus. However, the large defects in the esophageal mucosa often cause severe esophageal strictures, which dramatically reduce the patient’s quality of life. Although preventive endoscopic balloon dilatation can reduce dysphagia and the frequency of dilatation, other approaches are necessary to prevent esophageal strictures after ESD. This review describes several strategies for preventing esophageal strictures after ESD, with a particular focus on anti-inflammatory and tissue engineering approaches. The local injection of triamcinolone acetonide and other systemic steroid therapies are frequently used to prevent esophageal strictures after ESD. Tissue engineering approaches for preventing esophageal strictures have recently been applied in basic research studies. Scaffolds with temporary stents have been applied in five cases, and this technique has been shown to be safe and is anticipated to prevent esophageal strictures. Fabricated autologous oral mucosal epithelial cell sheets to cover the defective mucosa similarly to how commercially available skin products fabricated from epidermal cells are used for skin defects or in cases of intractable ulcers. Fabricated autologous oral-mucosal-epithelial cell sheets have already been shown to be safe.

Robotic adherent cell injection for characterizing cell-cell communication

Compared to robotic injection of suspended cells (e.g., embryos and oocytes), fewer attempts were made to automate the injection of adherent cells (e.g., cancer cells and cardiomyocytes) due to their smaller size, highly irregular morphology, small thickness (a few micrometers thick), and large variations in thickness across cells. This paper presents a robotic system for automated microinjection of adherent cells. The system is embedded with several new capabilities: automatically locating micropipette tips; robustly detecting the contact of micropipette tip with cell culturing surface and directly with cell membrane; and precisely compensating for accumulative positioning errors. These new capabilities make it practical to perform adherent cell microinjection truly via computer mouse clicking in front of a computer monitor, on hundreds and thousands of cells per experiment (versus a few to tens of cells as state of the art). System operation speed, success rate, and cell viability rate were quantitatively evaluated based on robotic microinjection of over 4000 cells. This paper also reports the use of the new robotic system to perform cell-cell communication studies using large sample sizes. The gap junction function in a cardiac muscle cell line (HL-1 cells), for the first time, was quantified with the system.

Applications of tissue engineering in the genitourinary tract

Congenital abnormalities and acquired disorders can lead to organ damage or loss of tissue within the genitourinary tract. For reconstructive purposes, tissue-engineering efforts are currently underway for virtually every type of tissue and organ within the urinary tract. Tissue engineering incorporates the fields of cell transplantation, materials science and engineering for the purpose of creating functional replacement tissue. This article reviews some of the principles of tissue engineering and some of the applications of these principles to the genitourinary tract.

A naonoporous cell-therapy device with controllable biodegradation for long-term drug release

Herein we describe the development and implementation of a nanoporous cell-therapy device with controllable biodegradation. Dopamine-secreting PC12 cells were housed within newly formulated alginate-glutamine degradable polylysine (A-GD-PLL) microcapsules. The A-GD-PLL microcapsules provided a 3-D microenvironment for good spatial cell growth, viability and proliferation. The microcapsules were subsequently placed within a poly(ethylene glycol) (PEG)-coated poly(ε-caprolactone) (PCL) chamber covered with a PEG-grafted PCL nanoporous membrane formed by phase inversion. To enhance PC12 cell growth and to assist in controlled degradation of both the PC12 cells and the device construct, small PCL capsules containing neural growth factor (PCL-NGF) and a poly(lactic-co-glycolic acid) pellet containing glutamine (PLGA-GLN) were also placed within the PCL chamber. Release of NGF from the PCL-NGF capsules facilitated cell proliferation and viability, while the controlled release of GLN from the PLGA-GLN pellet resulted in A-GD-PLL microcapsule degradation and eventual PC12 cell death following a pre-specified period of time (4 weeks in this study). In vivo, our device was found to be well tolerated and we successfully demonstrated the controlled release of dopamine over a period of four weeks. This integrated biodegradable device holds great promise for the future treatment of a variety of diseases.

The role of autologous chondrocyte implantation in the treatment of symptomatic chondromalacia patellae

PURPOSE

Chondromalacia patella is a distinct clinical entity of abnormal softening of the articular cartilage of the patella, which results in chronic retropatellar pain. Its aetiology is still unclear but the process is thought to be a due to trauma to superficial chondrocytes resulting in a proteolytic enzymic breakdown of the matrix. Our aim was to assess the effectiveness of autologous chondrocyte implantation on patients with a proven symptomatic retropatellar lesion who had at least one failed conventional marrow-stimulating therapy.

METHODS

We performed chondrocyte implantation on 48 patients: 25 received autologous chondrocyte implantation with a type I/III membrane (ACI-C) method (Geistlich Biomaterials, Wolhusen, Switzerland), and 23 received the Matrix-assisted Chondrocyte Implantation (MACI) technique (Genzyme, Kastrup, Denmark).

RESULTS

Over a mean follow-up period of 40.3 months, there was a statistically significant improvement in subjective pain scoring using the visual analogue scale (VAS) and objective functional scores using the Modified Cincinnati Rating System (MCS) in both groups.

CONCLUSIONS

Chondromalacia patellae lesions responded well to chondrocyte implantation. Better results occurred with MACI than with ACI-C. Excellent and good results were achieved in 40% of ACI-C patients and 57% of MACI patients, but success of chondrocyte implantation was greater with medial/odd-facet lesions. Given that the MACI procedure is technically easier and less time consuming, we consider it to be useful for treating patients with symptomatic chondral defects secondary to chondromalacia patellae.

Cell microencapsulation: a potential tool for the treatment of neuronopathic lysosomal storage diseases

Lysosomal storage disorders (LSD) are monogenic diseases caused by the deficiency of different lysosomal enzymes that degrade complex substrates such as glycosaminoglycans, sphingolipids, and others. As a consequence there is multisystemic storage of these substrates. Most treatments for these disorders are based in the fact that most of these enzymes are soluble and can be internalized by adjacent cells via mannose-6-phosphate receptor. In that sense, these disorders are good candidates to be treated by somatic gene therapy based on cell microencapsulation. Here, we review the existing data about this approach focused on the LSD treatments, the advantages and limitations faced by these studies.

Feasibility of localized immunosuppression: 1. Exploratory studies with glucocorticoids in a biohybrid device designed for cell transplantation

Emerging biotechnologies, such as the use of biohybrid devices for cellular therapies, are showing increasing therapeutic promise for the treatment of various diseases, including type 1 diabetes mellitus. The functionality of such devices could be greatly enhanced if successful localized immunosuppression regimens could be established, since they would eliminate the many otherwise unavoidable side effects of currently used systemic immunosuppressive therapies. The existence of local immune privilege at some specialized tissues, such as the eye, CNS, or pregnant uterus, supports the feasibility of localized immunomodulation, and such an approach is particularly well-suited for cell transplant therapies where all transplanted tissue is localized within a device. Following the success of syngeneic transplantation in a subcutaneous prevascularized device as a bioartificial pancreas in a rodent model, we now report the first results of exploratory in vivo islet allograft studies in rats using locally delivered glucocorticoids (dexamethasone phosphate and the soft steroid loteprednol etabonate). Following in vitro assessments, in silico drug distribution models were used to establish tentative therapeutic dose ranges. Sustained local delivery was achieved via implantable osmotic mini-pumps through a central sprinkler, as well as with a sustained-delivery formulation for loteprednol etabonate using poly(D,L-lactic) acid (PLA) microspheres. Doses delivered locally were approximately hundred-fold smaller than those typically used in systemic treatments. While several solubility, stability, and implantation problems still remain to be addressed, both compounds showed promise in their ability to prolong graft survival after tapering of systemic immunosuppression, compared to control groups.

A biodegradable, immunoprotective, dual nanoporous capsule for cell-based therapies

To demonstrate the transplantation of drug-secreting cells with immunoprotection, a biodegradable delivery device combining two nanoporous capsules is developed using secretory alkaline phosphatase gene (SEAP) transfected mouse embryonic stem (mES) cells as a model system. The outer capsule is a poly (ethylene glycol) (PEG)-coated poly (epsilon-caprolactone) (PCL) chamber covered with a PEG grafted PCL nanoporous membrane made by phase inversion technique. SEAP gene transfected mES cells encapsulated in alginate-poly-L-lysine (AP) microcapsules are placed in the PCL capsule. Both nanoporous capsules showed good immunoprotection in the IgG solution. In microcapsules, mES cells could form a spheroid embryonic body (EB) and grow close to the microcapsule size. The secreted SEAP from encapsulated mES cells increased gradually to a maximum value before reaching a steady level, following the cell growth pattern in the microcapsule. Without microcapsules, mES cells only formed a monolayer in the large PCL capsule. The secreted SEAP release was very low. The integrated device showed a similar cell growth pattern to that in microcapsules alone, while the SEAP release rate could be regulated by the pore size of the large capsule. This integrated device can achieve multi-functionalities for cell-based therapy, i.e. a 3-D microenvironment provided by microcapsules for cell growth, superior immunoprotection and controllable release performance provided by the two nanoporous membranes, and good fibrosis prevention by PEG surface modification of the large capsule.

Intracranial stereotaxic cannulation for development of orthotopic glioblastoma allograft in Sprague-Dawley rats and histoimmunopathological characterization of the brain tumor

Glioblastoma is the most common brain tumor that causes significant mortality annually. Limitations of the current therapeutic regimens warrant development of new techniques and treatment strategies in orthotopic animal model for better management of this devastating brain cancer. There are only a few experimental orthotopic models of glioblastoma for pre-clinical testing. In the present investigation, we successfully implanted rat C6 cells via intracranial stereotaxic cannulation in adult Sprague-Dawley rats for development and histoimmunopathological characterization of an advanced orthotopic glioblastoma allograft model, which could be useful for investigating the course of glioblastoma development as well as for testing efficacy of new therapeutic agents. The orthotopic glioblastoma allograft was generated by intracerebral injection of rat C6 cells through a guide-cannula system and after 21 post-inoculation days the brain tumor was characterized by histoimmunopathological experiments. Histological staining and immunofluorescent labelings for TERT, VEGF, Bcl-2, survivin, XIAP, and GFAP revealed the distinct characteristics of glioblastoma in C6 allograft, which could be useful as a target for treatment with emerging new therapeutic agents. Our investigation indicated the successful development of intracranial cannulated orthotopic glioblastoma allograft in adult Sprague-Dawley rats, making it as a useful animal model of glioblastoma for pre-clinical evaluation of various therapeutic strategies for the management of glioblastoma.

Transplantation of cultured human keratinocytes in single cell suspension: a comparative in vitro study of different application techniques

Transplantation of autologous cultured keratinocytes in single cell suspension is useful in the treatment of burns. The reduced time needed for culture, and the fact that keratinocytes in suspension can be transported from the laboratory to the patient in small vials, thus reducing the costs involved and be stored (frozen) in the clinic for transplantation when the wound surfaces are ready, makes it appealing. We found few published data in the literature about actual cell survival after transplantation of keratinocytes in single cell suspension and so did a comparative in vitro study, considering commonly used application techniques. Human primary keratinocytes were transplanted in vitro in a standard manner using different techniques. Keratinocytes were counted before and after transplantation, were subsequently allowed to proliferate, and counted again on days 4, 8, and 14 by vital staining. Cell survival varied, ranging from 47 to >90%, depending on the technique. However, the proliferation assays showed that the differences in numbers diminished after 8 days of culture. Our findings indicate that a great number of cells die during transplantation but that this effect is diminished if cells are allowed to proliferate in an optimal milieu. A burned patient's wounds cannot be regarded as the optimal milieu, and using less harsh methods of transplantation may increase the take rate and wound closing properties of autologous keratinocytes transplanted in a single cell suspension.

Biomedical interfaces: titanium surface technology for implants and cell carriers

Titanium and its alloys have become key materials for biomedical applications, mainly owing to their compatibility with human tissues and their mechanical strength. Effects of surface topography on cell and tissue response have been investigated extensively in the past, while (bio)chemical surface modification and its combination with designed topographies have remained largely unexplored. The following report describes some of the strategies used or intended to modify titanium surfaces, based on biological principles, with a focus on ultrathin biomimetic adlayers. One of the visions behind such approaches is to achieve improved healing and integration responses after implantation for patients, especially for those suffering from deficiencies, for example, diabetes or osteoporosis, two diseases that have increased drastically in our society during the last century.

Microfabricated airflow nozzle for microencapsulation of living cells into 150 micrometer microcapsules

Microencapsulation of genetically engineered cells has attracted much attention as an alternative nonviral strategy to gene therapy. Though smaller microcapsules (i.e. less than 300 microm) theoretically have various advantages, technical limitations made it difficult to prove this notion. We have developed a novel microfabricated device, namely a micro-airflow-nozzle (MAN), to produce 100 to 300 microm alginate microcapsules with a narrow size distribution. The MAN is composed of a nozzle with a 60 microm internal diameter for an alginate solution channel and airflow channels next to the nozzle. An alginate solution extruded through the nozzle was sheared by the airflow. The resulting alginate droplets fell directly into a CaCl2 solution, and calcium alginate beads were formed. The device enabled us to successfully encapsulate living cells into 150 microm microcapsules, as well as control microcapsule size by simply changing the airflow rate. The encapsulated cells had a higher growth rate and greater secretion activity of marker protein in 150 microm microcapsules compared to larger microcapsules prepared by conventional methods because of their high diffusion efficiency and effective scaffold surface area. The advantages of smaller microcapsules offer new prospects for the advancement of microencapsulation technology.

Multilayer nanoencapsulation. New approach for immune protection of human pancreatic islets

Immune protection of artificial tissue by means of pancreatic islet microencapsulation is a very ambitious new approach to avoid life-long immune suppression. But the success in the utilization of the alginate-beads with incorporated islets is unfortunately limited. Some of the problems cannot be solved by a two-component system, so polymer encapsulation of the microbeads was tested to improve the properties. In the present paper a pure nanoencapsulation multilayer approach was tested in order to reduce the size of the capsule and possibly apply in the future a multilayer capsule with individual properties in each layer or region of the capsule. Different polycations were attached in a self-assembly process. The advantage in using the surface charge of islets as binding site for the polyions is the guarantee of complete coverage after the second layer. Release of insulin was determined to characterize the function of the islets after encapsulation as well as the permeability of the capsule. Fluorescence microscopy was used to visualize the polyelectrolyte layers. Finally by means of an immune assay, the protection capability of the capsule was proved. In these first measurements the encapsulation with a multilayer nanocapsule was shown to be a possible alternative to the more space-consuming and random islet-trapping microencapsulation.

Instrumentation and Technique for Delivery of Tissue Explants to the Subretinal Space

PURPOSE

The controlled orientation of subretinal or intraretinal delivery of delicate tissue sheets is a critical problem in retinal transplantation research.

METHODS

A surgical device (explant injector) was designed and built for the controlled delivery of tissue explants into the subretinal or intraretinal space via a vitrectomy approach. The technical feasibility was demonstrated in enucleated porcine eyes.

RESULTS

Using negative pressure, the injector allows for the fixation of an explant, such as a monolayer of cells cultured on a collagen membrane, on the carrier platform. The sheet can then be placed safely without loss of orientation in the subretinal space.

CONCLUSIONS

With the aid of the explant injector, it is possible to deliver an explant with the proper orientation to a precise location in the subretinal space.

Olfactory ensheathing glial co-grafts improve functional recovery in rats with 6-OHDA lesions

Olfactory ensheathing cells (OEC) transplanted to the site of a spinal cord injury can promote axonal sparing/regeneration and functional recovery. The purpose of this study was to investigate if OEC enhance the effects of grafted dopamine-neuron-rich ventral mesencephalic tissue (VM) in a rodent model of Parkinson's disease. We co-grafted VM with either OEC or astrocytes derived from the same olfactory bulbs as the OEC to rats with a unilateral 6-hydroxydopamine lesion of the nigrostriatal system. Co-grafting fetal VM with OEC, but not with astrocytes enhanced dopamine cell survival, striatal reinnervation and functional recovery of amphetamine- and apomorphine-induced rotational behaviour compared with grafting embryonic VM alone. Grafting OEC or astrocytes alone had no effects. Intriguingly, only in the presence of OEC co-grafts, did dopamine neurons extend strikingly long neurites that reached peripheral striatal compartments. Comparable results were observed in a co-culture system where OEC promoted dopamine cell survival and neurite elongation through a mechanism involving both releasable factors and direct contact. Cell type analysis of fetal VM grafts suggested that dopamine neurons of the substantia nigra rather than of the ventral tegmental area were increased in the presence of OEC co-grafts. We conclude that the addition of OEC enhances efficacy of grafted immature dopamine neurons in a rat Parkinson's disease model.

Autologous olfactory ensheathing cell transplantation in human spinal cord injury

Olfactory ensheathing cells transplanted into the injured spinal cord in animals promote regeneration and remyelination of descending motor pathways through the site of injury and the return of motor functions. In a single-blind, Phase I clinical trial, we aimed to test the feasibility and safety of transplantation of autologous olfactory ensheathing cells into the injured spinal cord in human paraplegia. Participants were three male paraplegics, 18-55 years of age, with stable, complete thoracic injuries 6-32 months previously, with stable spinal column, no implanted prostheses, and no syrinx. Olfactory ensheathing cells were grown and purified in vitro from nasal biopsies and injected into the region of damaged spinal cord. The trial design includes a matched injury group as a control for the assessors, who are blind to treatment status. Assessments, made before transplantation and at regular intervals subsequently, include MRI, medical, neurological and psychosocial assessments, and standard American Spinal Injury Association and Functional Independence Measure assessments. One year after cell implantation, there were no medical, surgical or other complications to indicate that the procedure is unsafe. There is no evidence of spinal cord damage nor of cyst, syrinx or tumour formation. There was no neuropathic pain reported by the participants, no change in psychosocial status and no evidence of deterioration in neurological status. Participants will be followed for 3 years to confirm long-term safety and to compare neurological, functional and psychosocial outcomes with the control group. We conclude transplantation of autologous olfactory ensheathing cells into the injured spinal cord is feasible and is safe up to one year post-implantation.

Development of mammalian cell-enclosing subsieve-size agarose capsules (<100μm) for cell therapy

Agarose capsules were prepared using a droplet breakup method in a coflowing stream. Subsieve-size capsules 76+/-9 microm in diameter were obtained by extruding 4 wt% agarose solution from a needle (300 microm inner diameter) at a velocity of 1.2 cm/s into an ambient liquid paraffin flow of 20.8 cm/s. Increasing the flow rate of the liquid paraffin and decreasing that of the agarose solution resulted in a decreased resultant capsule diameter. Reduction in diameter from several hundred micrometers to subsieve-size (<100 microm) enhanced molecular exchange and mechanical stability. Measurements based on the percentage of intact mitochondria in the cells demonstrated that the viability of the enclosed cells was independent of capsule diameter. No significant difference was observed between the viabilities of cells enclosed in capsules with diameters of 79+/-8 and 351+/-41 microm (p=0.43). Compared with cells seeded in a tissue culture dish, the cells enclosed in the subsieve-size capsules showed 89.2% viability.

Closed-chest cell injections into mouse myocardium guided by high-resolution echocardiography

The mouse is an important model for the development of therapeutic stem cell/bone marrow cell implantation to treat ischemic myocardium. However, its small heart size hampers accurate implantation into the left ventricular (LV) wall. Precise injections have required surgical visualization of the heart, which is subject to complications and is impractical for delayed or repeated injections. Furthermore, the thickness of the myocardium is comparable to the length of a needle bevel, so surgical exposure does not prevent inadvertent injection into the LV cavity. We describe the use of high-resolution echocardiography to guide nonsurgical injections accurately into the mouse myocardial wall. We optimized this system by using a mixture of ultrasound contrast and fluorescent microspheres injected into the myocardium, which enabled us to interpret the ultrasound image of the needle during injection. Quantitative dye injection studies demonstrated that guided closed-chest injections and open-chest injections deliver comparable amounts of injectate to the myocardium. We successfully used this system in a mouse myocardial infarction model to target the injection of labeled cells to a region adjacent to the infarct. Intentional injection of tracer into the LV cavity resulted in a small accumulation in the myocardium, suggesting that non-guided cell injections into mouse hearts may appear to be successful even if the majority of the injectate is lost in the chamber. The use of this system will allow more precise cellular implantation into the mouse myocardium by accurately guiding injections to desired locations, confirming successful implantation of cells, in a clinically relevant time frame.

Mammalian cell delivery via aerosol deposition

The objective of this study was to test the hypothesis that bovine dermal fibroblasts can survive aerosol delivery via an airbrush with mean cell survival rates greater than 50%. This technology has great implications for burn and other wound therapies, for delivery of genetically altered cells in gene therapies, and for tissue engineering with tissue scaffolds. Bovine dermal fibroblasts were suspended at a concentration of 200,000 cells/mL in Hank's Balanced Salt Solution, and delivered into six-well tissue culture plates using a Badger 100G airbrush. Cells were delivered through three nozzle diameters (312, 484, and 746 microm) at five different air pressures (41, 55, 69, 96, and 124 kPa). Nine repetitions were performed for each treatment group, and cell viability was measured using trypan blue exclusion assay. Mean cell viability ranged from 37 to 94%, and depended on the combination of nozzle diameter and delivery pressure (p < 0.0001). Linear regression analysis was used to develop a stochastic model of cell delivery viability as a function of nozzle diameter and delivery air pressure. This study demonstrates the feasibility of using an airbrush to deliver viable cells in an aerosol to a substrate.

A cell encapsulation device for studying soluble factor release from cells transplanted in the rat brain

The transplantation of a variety of naturally occurring and genetically modified cell types has been shown to be an effective experimental method to achieve sustained delivery of therapeutic molecules to specific target areas in the brain. To acquire a better understanding of dosing, implant mechanism of action, and how certain cell types affect remodeling of central nervous system (CNS) tissue, a refillable cell encapsulation device was developed for introducing cells into the brain while keeping them physically isolated from contact with brain tissue with a semipermeable membrane. The stereotactically placed device consists of a hollow fiber membrane (HFM), a polyurethane grommet with watertight cap that snaps into a precisely drilled hole in the rat skull, and a removable cell-containing insert. The cell-containing insert can be introduced or removed in a time-dependent manner to study the influence of soluble factors released from transplanted cells. The study describes the device design and validates its utility using a well-established cell transplantation model of Parkinson's disease.

A comparative study of three different biomaterials in the engineering of skeletal muscle using a rat animal model

Defects caused by traumatic or postsurgical loss of muscle mass may result in severe impairments of the functionality of skeletal muscle. Tissue engineering represents a possible approach to replace the lost or defective muscle. The aim of this study was to compare the suitability of three different biomaterials as scaffolds for rat myoblasts, using a new animal model. PKH26-fluorescent-stained cultured rat myoblasts were either seeded onto polyglycolic acid meshes or, alternatively, suspended in alginate or in hyaluronic acid-hydrogels. In each of the eight Fisher CDF-344 rats, four capsule pouches were induced by subcutaneous implantation of four silicone sheets. After two weeks the silicone sheets were removed and myoblast-biomaterial-constructs were implanted in the preformed capsules. Specimens were harvested after four weeks and examined histologically by H&E-staining and fluorescence microscopy. All capsules were well-vascularized. Implanted myoblasts fused by forming multinucleated myotubes. This study demonstrates that myoblasts seeded onto different biomaterials can be successfully transplanted into preformed highly vascularized capsule pouches. Our animal model has paved the way for studies of myoblast-biomaterial transplantations into an ectopic non-muscular environment.

Photo-crosslinkable microcapsules formed by polyelectrolyte copolymer and modified collagen for rat hepatocyte encapsulation

New anionic polyelectrolyte tetra-copolymers with photo-crosslinkable 4-(4-methoxycinnamoyl)phenyl methacrylate monomer in addition to a HEMA-MMA-MAA ter-copolymer system were synthesized. The tetra-copolymers were used to form photo-crosslinkable microcapsules with modified collagen by complex coacervation for rat hepatocytes encapsulation. The hepatocytes were encapsulated within a two-layered membrane comprising of modified collagen as the inner core and an outer photo-crosslinkable copolymer shell. Upon photo-crosslinking of the microcapsules with UV-Vis light irradiation, the mechanical strength and chemical stability of the microcapsules, and the cellular functions of the encapsulated hepatocytes were enhanced. Particularly, the mechanical stability of the microcapsules was dramatically strengthened. The new photo-crosslinkable tetra-copolymer formulation described in this article has opened a way to the development of hepatocyte microencapsulation technology for bioartifical liver assist device.

Percutaneous endoscopic cellular transplantation into the lower lumbar spinal cord

OBJECTIVE

To explore the feasibility of performing percutaneous endoscopic cellular transplantation into the lumbar spinal cord of pigs to create intramedullary cellular trails.

METHODS

The lumbar subarachnoid space was accessed using a 10-gauge needle inserted between L5 and L6. A 12.5-French flexible introducer sheath was fed over the needle into the subarachnoid space. A 3.2-mm-diameter flexible, steerable endoscope was then directed intradurally through the sheath. The thecal space was distended by saline infusion. A microcatheter with an attached needle then was advanced through the working channel into the dorsal surface of the lumbar spinal cord. Five microliters of Hoechst-labeled fibroblasts were injected while the catheter was withdrawn slowly to create a trail of cells within the spinal cord. The spinal canal then was perfused with fixative. The injected spinal cord segment was removed and studied histologically. Endoscopic video was analyzed offline.

RESULTS

The endoscope could be navigated under visual guidance. The sacral and lumbar rootlets, the spinal cord, and associated vessels were visualized. In fixed sagittal sections, a linear trail of fluorescent fibroblasts could be seen within the lumbar spinal cord in each specimen.

CONCLUSION

Percutaneous endoscopic cellular injection may be useful for cellular transplantation, may reduce surgical and anesthetic time, may be compatible with local anesthesia, may eliminate the need to disrupt spinal instrumentation and bone grafts, and may allow greater flexibility in the respective timing of spinal fixation and cellular transplantation after spinal cord injury. This is the first report of the use of endoscopic intraspinal cellular transplantation.

A model for intratumoural chemotherapy in the rat brain

To achieve the best reproducibility in rat brain tumour models several injection techniques have been used. Although stereotactic cell injections have proved to be effective and reliable, they are expensive and time consuming. A new permanently implanted device is presented here. It allows precise cell delivery for best tumour reproducibility, and it can be left in place for future injections at the exact same location, such as intratumoural chemotherapy. A Teflon tube was mounted on a disc, inserted into the rat brain and sealed to the skull. The device was tested in two rat strains (Wistar and New Zealand Nude rats) with two different glioma cell lines (9L and C6). Rats were treated with placebo to determine if repeated treatments had an effect on the device placement, or if device-related morbidity was induced. Analysis of brain sections showed that the device path was always within the tumour. The device never moved or came off the scalp. Both Wistar rats and NZ nude rats tolerated the device well. No morbidity or mortality was observed, regardless of the presence of the device; no infections were seen. Biocompatible, non-irritating and well tolerated, such a device can be used for reproducible tumour cell injections and repeated intralesional delivery of drugs.

Behavior of Human Dermal Fibroblasts in Three-Dimensional Fibrin Clots: Dependence on Fibrinogen and Thrombin Concentration

Fibrin sealant products are used in hemostasis and tissue sealing, and potentially as a cell delivery vehicle. In this study, fibrin sealant was evaluated as a delivery vehicle for human dermal fibroblasts. Fibroblast proliferation and migration were assessed in various dilutions of fibrin sealant by changing the fibrinogen and thrombin concentration. Fibroblasts proliferated well within three-dimensional (3-D) fibrin clots consisting of fibrinogen (5-17 mg/mL) and thrombin (1-167 U/mL). These fibroblasts also retained good morphology and growth characteristics after migrating out of the 3-D fibrin clots. Furthermore, using Western blot and fluorescence-activated cell-sorting analysis, we found that the expression of growth factors and interleukins in the entire fibroblast-fibrin construct was dependent on the fibrin sealant formulation. For example, in a formulation in which fibroblasts showed modest proliferation and migration, interleukin 8 was secreted to a lesser extent than in a formulation that supported robust proliferation and migration. To our knowledge, this is the first time that it has been shown that modifying the concentration of fibrinogen and thrombin affects fibroblast behavior within formed 3-D fibrin clots. In addition, some of these formulations present an ideal delivery vehicle for fibroblasts that could be used for the treatment of chronic wounds.

A Novel Injectable Approach for Cartilage Formation in Vivo Using PLG Microspheres

This study documents the use of biodegradable poly(lactide-co-glycolide) (PLG) microspheres as a novel, injectable scaffold for cartilage tissue engineering. Chondrocytes were delivered via injection to the subcutaneous space of athymic mice in the presence and absence of PLG microspheres. Tissue formation was evaluated up to 8 weeks post-injection. Progressive cartilage formation was observed in samples containing microspheres. The presence of microspheres increased the quantity of tissue formed, the amount of glycosaminoglycan that accumulated, and the uniformity of type II collagen deposition. Microsphere composition influenced the growth of the tissue engineered cartilage. Higher molecular weight PLG resulted in a larger mass of cartilage formed and a higher content of proteoglycans. Microspheres comprised PLG with methyl ester end groups yielded increased tissue mass and matrix accumulation, but did not display homogenous matrix deposition. The microencapsulation of Mg(OH)2 had negative effects on tissue mass and matrix accumulation. Matrix accumulation, cell number, and tissue mass were unchanged by microsphere size, but larger microspheres increased the frequency of central necrosis in implants. The data herein reflect the promising utility of an injectable PLG-chondrocyte system for tissue engineering applications.

Development of a Plasma-Polymerized Surface Suitable for the Transplantation of Keratinocyte–Melanocyte Cocultures for Patients with Vitiligo

The purpose of this study was to develop a convenient methodology for the coculture of autologous melanocytes and keratinocytes for grafting of patients with vitiligo. While grafting of pure melanocytes may achieve repigmentation, the inclusion of keratinocytes ensures rapid reepithelialization. Previously we have used confluent sheets of keratinocytes (with melanocytes present) to transfer cells. However, we found that as the keratinocyte density increased, melanocyte number and function were downregulated. Accordingly in this study we explored combinations of three culture surfaces and three media, seeking to achieve subconfluent culture of primary keratinocytes with a reasonable density of melanocytes, using cells immediately after isolation from skin. For this in vitro study, the surfaces studied were uncoated glass coverslips, and glass coverslips coated with collagen I or a nitrogen-containing plasma polymer. The results show that both the substrate surface and the medium composition influence the proliferation and survival of melanocytes. Keratinocytes and melanocytes could be successfully cocultured on a chemically defined plasma polymer substrate using a serum-free medium.

Retroviral packaging cells encapsulated in TheraCyte immunoisolation devices enable long-term in vivo gene delivery

The method of delivering a therapeutic gene into a patient is still one of the major obstacles towards successful human gene therapy. Here we describe a novel gene delivery approach using TheraCyte immunoisolation devices. Retroviral vector producing cells, derived from the avian retrovirus spleen necrosis virus, SNV, were encapsulated in TheraCyte devices and tested for the release of retroviral vectors. In vitro experiments show that such devices release infectious retroviral vectors into the tissue culture medium for up to 4 months. When such devices were implanted subcutaneously in SCID mice, infectious virus was released into the blood stream. There, the vectors were transported to and infected tumors, which had been induced by subcutaneous injection of tissue culture cells. Thus, this novel concept of a continuous, long-term gene delivery may constitute an attractive approach for future in vivo human gene therapy.

Autologous cardiomyocyte transplantation using a biodegradable polymer scaffold

BACKGROUND

To achieve a more reliable way of transplanting cardiomyocytes, we conducted an autologous cardiomyocyte transplantation using a biodegradable scaffold, instead of a syringe injection, as a vehicle for transporting cells in an ovine myocardial infarction model.

MATERIALS AND METHODS

A myocardial infarction was created in sheep using sequential ligation of the homonymous artery and its diagonal branch. Autologous cardiomyocytes from the right ventricular infundibulum were cultured and seeded onto a biodegradable polymer scaffold. Three months after creating myocardial infarction, the two animals were re-anesthetized and cardiomyocyte-seeded scaffolds were implanted in the infarcted area. The animals were kept alive for a further month, and then sacrificed for postmortem heart examinations. Light microscopic analysis and an immunohistochemical study for myoglobin were performed.

RESULTS

On postmortem gross examinations, the polymer scaffolds were visible in the background of well-demarcated thin-walled anteroseptal myocardial infarcts. Microscopic analysis showed abundant myoglobin-stained cells between the fiber strands of the polymer scaffolds. However, there is a possibility that some of these cells might have been giant cells reacting to foreign material.

CONCLUSION

The transplantation of cultured autologous cardiomyocytes into an infarct region using a biodegradable scaffold instead of syringe injection provides another promising option for cardiomyocyte transplantation, which warrants further study.

New cell-based technologies in bone and cartilage tissue engineering. II. Cartilage regeneration

A tissue engineering, cell-based therapeutic approach could be essential for extensive bone or cartilage reconstruction. This article is divided in two chapters and describes new cell-based surgical techniques for cartilage and bone reconstruction. The second part of the article, regarding cartilage repair, describes a new arthroscopic surgical technique for tissue engineered cartilage grafting. A 3-dimensional hyaluronic acid support is used for autologous chondrocyte culturing. The technique reduces morbidity of classic autologous implant avoiding open surgery and periosteal flap use. With this technique is possible to reduce the patient morbidity, time and cost of surgery.

Use of an oil-hydraulic microinjection pump for subretinal infusions

The injection of cell suspensions or drugs into the subretinal space is a new promising option of vitreoretinal surgery for the treatment of degenerative retinal disorders. We used a manual oil-hydraulic microinjection pump to subretinally inject suspensions of retinal pigment epithelial cells in Royal College of Surgeons rats and in patients suffering from age-related macular degeneration with geographic atrophy. The histological examination of the treated rat eyes showed that cell suspensions could be placed precisely in the subretinal space. Intra- and postoperative outcome of the patients in the clinical trial revealed no retinal complications during 6 months of follow up. We suggest the oil-hydraulic microinjection pump to be a valuable instrument for controlled and precisely dosed atraumatic infusion or aspiration of small volumes of cell suspensions, fluids or drugs in vitreoretinal surgery.