[Meibomian glands : part IV. Functional interactions in the pathogenesis of meibomian gland dysfunction (MGD)]. / Meibom-Drüsen : Teil IV: Funktionelle Interaktionen in der Pathogenese der Dysfunktion (MGD).

Obstructive dysfunction of the meibomian glands (MGD) is surprisingly frequent in the general population and increases with age. Clinically, the focus is mainly on the consequences at the ocular surface in the sense of an evaporative dry eye syndrome. However, in addition, chronic obstruction of the meibomian glands also leads to degeneration of the secretory gland tissue which can result in a secondary hyposecretion even if the primary obstruction is later resolved by therapeutic approaches.Important influencing factors in the pathogenesis of obstructive MGDs and their interaction during the progression of the disease are systematically analyzed and displayed in a flow diagram. Age, hormonal disturbances and environmental influences, such as contact lenses, as well as qualitative alterations in the composition of the meibomian oil (meibum) lead to hyperkeratinization of the ductal epithelium and increased viscosity of the meibum which result, either alone or in combination, in obstruction of the duct and orifice. This leads to a lack of meibum on the lid margin and tear film with downstream hyperevaporative dry eye syndrome. At the same time, obstruction leads to a stasis of meibum inside the meibomian gland with increased pressure and resulting dilatation of the ducts and in atrophy of the acini with rarefaction of the secretory meibocytes and gland dropout. Stasis can also increase the growth of commensal bacteria, their production of oil degrading enzymes (lipases) and release of toxic mediators. These factors can, in return, act as self-enforcing feedback loops in the sense of vicious circles that aggravate the primary hyperkeratinization and compositional disturbance of meibum and can hence lead to a progressive MGD.

[Meibomian glands : part III. Dysfunction - argument for a discrete disease entity and as an important cause of dry eye]. / Meibom-Drüsen : Teil III: Dysfunktion (MGD) - Plädoyer für ein eigenständiges Krankheitsbild und wichtige Ursache für das trockene Auge.

Meibomian gland dysfunction (MGD), mainly synonymous with posterior blepharitis but typically without prominent inflammatory alterations of the lid margin, is a discrete disease entity and a frequent cause of wetting deficiencies of the ocular surface leading to dry eye disease that deserves increased recognition by clinicians. The history, classification, pathology, influencing factors, diagnostics and therapy are explained and discussed. MGD is mainly based on an obstructive mechanism caused by hyperkeratinization of the excretory duct and/or increased viscosity of the secretion (meibum) with subsequent deficiency of the tear film lipid layer. MGD is influenced by the hormonal status and by chemical and mechanical noxes as well as genetic defects and it occurs more frequently in women and generally increases with age. It results in stasis of meibum inside the glands, dilatation of the ductal system and eventually in atrophy and loss of glandular tissue (gland dropout). Careful investigation of the eyelids and lid margins with eversion, if necessary, should therefore be performed in every case of a wetting defect, notably before fitting contact lenses. Particularly important is the inspection of the meibomian orifices and diagnostic expression by mild mechanical compression of the lid.

[Sex hormones and dry eye]. / Sexualhormone und trockenes Auge.

Among ophthalmic diseases dry eye in its various forms, represents an entity with one of the highest prevalences and at the same time the lowest chance for causal therapy. Since some years there is growing evidence that sex hormones play a key role in the formation and course of the disease and thus provide potentially promising approaches for therapy. The objective of this article is to briefly outline current scientific knowledge on the relationship between androgens, estrogens,and progesterones on the one hand and the lacrimal gland and Meibomian glands respectively.

[Meibomian glands. Part I: anatomy, embryology and histology of the Meibomian glands]. / Meibom-Drüsen. Teil I: Anatomie, Embryologie und Histologie der Meibom-Drüsen.

The Meibomian glands are large sebaceous glands that are located as separate gland strands in parallel arrangement within the tarsal plates of the eyelids. Their oily product (meibum) is secreted by a holocrine mechanism during which the secretory cells (meibocytes) are completely transformed into the meibum after synthesis and accumulation of lipids. After production in the gland acini, meibum is transported through the ductal system via the connecting duct (ductule) and the central duct towards the orifice at the free lid margin close to the inner lid border. The embryological development of the Meibomian glands takes place during the differentiation of the eyelids in the sealing phase of the eyelids. They are not directly associated with hair follicles but share important similarities in embryology, structure and keratinization potency with the cilia. Similar to the sebaceous glands Meibomian glands are regulated via sex hormones and androgens have a supporting function whereas estrogens act antagonistically. However, in contrast to other sebaceous glands they also have a distinct innervation, apart from sympathetic and sensory primarily by parasympathetic fibers that share the innervation pattern of the lacrimal glands. The anatomy, embryology and histology of the Meibomian glands are explained here, mainly with respect to humans, in an extensive review.

[Meibomian glands. Part II: physiology, characteristics, distribution and function of meibomian oil]. / Meibom-Drüsen. Teil II: Physiologie, Eigenschaften, Verteilung und Funktion des Meibom-Ols.

The oily secretion (meibum) of the Meibomian glands forms the superficial layer of the pre-ocular tear film and reduces evaporation of the aqueous phase. Meibum is a complex mixture of various lipids and minor protein components as well as other components of the secretory meibocytes, which form a clear liquid at body temperature. The exact composition and functions of meibum are still partly unknown, in particular the interaction of the water insoluble non-polar lipids with the polar, partly water soluble, lipids and potentially with proteins, which altogether interact to maintain the connection with the underlying aqueous tear phase. Meibum is transported within the gland by the force of secretory pressure from continuous secretion and by muscular action of the orbicularis muscle and Riolans muscles during blinking. After delivery of meibum onto the posterior lid margin the oil moves from the posterior lid margin reservoir onto the tear meniscus and is pulled as a thin layer onto the pre-ocular tear film every time the lid opens. During lid closure it is compressed and a small part is continuously renewed. Meibum also has a barrier function against the spillage of tears over the inner border of the lid and against the entry of skin lipids (sebum) from the free lid margin.

On the relationship between farmland biodiversity and land-use intensity in Europe.

Worldwide agriculture is one of the main drivers of biodiversity decline. Effective conservation strategies depend on the type of relationship between biodiversity and land-use intensity, but to date the shape of this relationship is unknown. We linked plant species richness with nitrogen (N) input as an indicator of land-use intensity on 130 grasslands and 141 arable fields in six European countries. Using Poisson regression, we found that plant species richness was significantly negatively related to N input on both field types after the effects of confounding environmental factors had been accounted for. Subsequent analyses showed that exponentially declining relationships provided a better fit than linear or unimodal relationships and that this was largely the result of the response of rare species (relative cover less than 1%). Our results indicate that conservation benefits are disproportionally more costly on high-intensity than on low-intensity farmland. For example, reducing N inputs from 75 to 0 and 400 to 60kgha-1yr-1 resulted in about the same estimated species gain for arable plants. Conservation initiatives are most (cost-)effective if they are preferentially implemented in extensively farmed areas that still support high levels of biodiversity.

Mixed biodiversity benefits of agri-environment schemes in five European countries.

Agri-environment schemes are an increasingly important tool for the maintenance and restoration of farmland biodiversity in Europe but their ecological effects are poorly known. Scheme design is partly based on non-ecological considerations and poses important restrictions on evaluation studies. We describe a robust approach to evaluate agri-environment schemes and use it to evaluate the biodiversity effects of agri-environment schemes in five European countries. We compared species density of vascular plants, birds, bees, grasshoppers and crickets, and spiders on 202 paired fields, one with an agri-environment scheme, the other conventionally managed. In all countries, agri-environment schemes had marginal to moderately positive effects on biodiversity. However, uncommon species benefited in only two of five countries and species listed in Red Data Books rarely benefited from agri-environment schemes. Scheme objectives may need to differentiate between biodiversity of common species that can be enhanced with relatively simple modifications in farming practices and diversity or abundance of endangered species which require more elaborate conservation measures.

[Eye-associated lymphoid tissue (EALT) is continuously spread throughout the ocular surface from the lacrimal gland to the lacrimal drainage system]. / Augen-assoziiertes lymphatisches Gewebe (EALT) durchzieht die Augenoberfläche kontinuierlich von der Tränendrüse bis in die ableitenden Tränenwege.

INTRODUCTION: Components of the mucosal immune system (MALT) have been identified in the conjunctiva (as CALT) and the lacrimal drainage system (as LDALT). Their structural and functional relation with the established immune protection by the lacrimal gland is unclear. MATERIAL AND METHODS: Macroscopically normal and complete tissues of the conjunctiva, lacrimal drainage system and lacrimal gland from human body donors were investigated by analysis of translucent whole mounts, and using histology, immunohistology as well as scanning and transmission electron microscopy. RESULTS: A typical diffuse lymphoid tissue, composed of effector cells of the immune system (T-lymphocytes and IgA producing plasma cells) under an epithelium that contains the IgA transporter SC, is not isolated in the conjunctiva and lacrimal drainage system. It is anatomically continuous from the lacrimal gland along its excretory ducts into the conjunctiva and from there via the lacrimal canaliculi into the lacrimal drainage system. Lymphoid follicles occur in a majority (about 60%) and with bilateral symmetry. The topography of CALT corresponds to the position of the cornea in the closed eye. CONCLUSION: These results show that the MALT of the lacrimal gland, conjunctiva and lacrimal drainage system constitute an anatomical and functional unit for immune protection of the ocular surface. Therefore it should be integrated as an "eye-associated lymphoid tissue" (EALT) into the MALT system of the body. EALT can detect ocular surface antigens by the lymphoid follicles and can supply other organs and the ocular surface including the lacrimal gland with specific effector cells via the regulated recirculation of lymphoid cells.

[Dry eye disease as a complex dysregulation of the functional anatomy of the ocular surface. New concepts for understanding dry eye disease]. / Das trockene Auge als komplexe Fehlregulation der funktionellen Anatomie der Augenoberfläche. Neue Impulse zum Verständnis des trockenen Auges.

INTRODUCTION: Dry eye disease is a disorder of the tear film that results in epithelial damage and in a disruption of the normal homeostasis at the ocular surface. It is widespread and causes symptoms ranging from discomfort to blindness. METHODS: A review of the existing literature was used to compare different past and recent concepts for the understanding of dry eye disease with a focus on aspects of the integrating functional anatomy of the ocular surface. RESULTS: The understanding of the pathogenesis of dry eye disease has proceeded from the mere recognition of a lack of tears to a consideration of their quality and to the concept of wetting of the ocular surface. However, several other aspects as epithelial differentiation, innervation, hormonal status or immune protection contribute to the intact functional anatomy of the ocular surface. Recently it has been recognized that immunologically regulated mechanisms of inflammation represent a primary or secondary pathogenetic factor for dry eye disease. This is conceivably regulated by the cells of the physiological mucosal immune defence system, the eye-associated lymphoid tissue (EALT). Androgens represent an important trophic factor for the ocular surface and their deficiency predisposes to inflammation. CONCLUSION: Dry eye disease represents a complex dysregulation of the functional anatomy of the ocular surface that can start from different alterations (e.g. insufficient secretion, defects in wetting or innervation). Immune-based inflammation is able to interconnect and negatively reinforce these different pathomechanisms, resulting in a vicious circle.

Lacrimal drainage-associated lymphoid tissue (LDALT): a part of the human mucosal immune system.

PURPOSE: Mucosa-associated lymphoid tissue (MALT) specifically protects mucosal surfaces. In a previous study of the human conjunctiva, evidence was also found for the presence of MALT in the lacrimal sac. The present study, therefore, aims to investigate its morphology and topographical distribution in the human lacrimal drainage system. METHODS: Lacrimal drainage systems (n = 51) obtained from human cadavers were investigated by clearing flat wholemounts or by serial sections of tissue embedded in paraffin, OCT compound, or epoxy resin. These were further analyzed by histology, immunohistochemistry, and electron microscopy. RESULTS: All specimens showed the presence of lymphocytes and plasma cells as a diffuse lymphoid tissue in the lamina propria, together with intraepithelial lymphocytes and occasional high endothelial venules (HEV). It formed a narrow layer along the canaliculi that became thicker in the cavernous parts. The majority of lymphocytes were T cells, whereas B cells were interspersed individually or formed follicular centers. T cells were positive for CD8 and the human mucosa lymphocyte antigen (HML-1). Most plasma cells were positive for IgA and the overlying epithelium expressed its transporter molecule secretory component (SC). Basal mucous glands were present in the lacrimal canaliculi and in the other parts accompanied by alveolar and acinar glands, all producing IgA-rich secretions. Primary and secondary lymphoid follicles possessing HEV were present in about half of the specimens. CONCLUSIONS: The term lacrimal drainage-associated lymphoid tissue (LDALT) is proposed here to describe the lymphoid tissue that is regularly present and belongs to the common mucosal immune system and to the secretory immune system. It is suggested that it may form a functional unit together with the lacrimal gland and conjunctiva, connected by tear flow, lymphocyte recirculation, and probably the neural reflex arc, and play a major role in preserving ocular surface integrity.

Conjunctiva-associated lymphoid tissue in the human eye.

PURPOSE: Mucosa-associated lymphoid tissue (MALT) represents a part of the immune system located at mucosal surfaces. Its presence in the human eye is the point in question in the current study. Its occurrence, components, topography, and probable functional significance in the human conjunctiva and lacrimal drainage system were investigated. METHODS: Fifty-three complete conjunctival sacs were obtained from cadaveric eyes, prepared as flat wholemounts, stained, optically cleared, observed in total thickness, and sectioned for light microscopic histology, immunohistochemistry, and electron microscopy. Eight lacrimal sacs and adhering canaliculi were prepared accordingly. RESULTS: Lymphoid tissue was mainly observed in the palpebral conjunctiva, more pronounced in the upper than in the lower lid. It occurred in different forms: 1) In all specimens, diffuse lymphoid tissue of lymphocytes and plasma cells, most of which were IgA positive, formed a thin layer in the lamina propria. The overlying epithelium produced secretory component. 2) In approximately three fifths of the conjunctival sacs, organized follicular accumulations were embedded in this layer. They had a lenticular shape, were composed of B lymphocytes, and were apically covered by lymphoepithelium. 3) Both types could be associated with the conjunctival crypts. Lymphoid tissue with similar characteristics, including secondary follicles, was also observed inside the lacrimal drainage system. High endothelial venules were present in all types of lymphoid tissue. CONCLUSIONS: Human conjunctiva and lacrimal drainage system show an associated lymphoid tissue (suggesting the term conjunctiva-associated lymphoid tissue [CALT]) that contains all components necessary for a complete immune response. Expression of immunoglobulins and secretory component indicates that the conjunctiva belongs to the secretory immune system.

Paclitaxel: an effective antineoplastic agent in the treatment of xenotransplanted hepatoblastoma.

BACKGROUND: Hepatoblastoma is an uncommon liver tumor of infancy and early childhood. Though most patients with nonmetastatic hepatoblastomas can be cured by defining surgical strategies and chemotherapy regimes, new drugs are needed for children with advanced hepatoblastomas. The activity of paclitaxel as a new antineoplastic agent with limited experience in pediatric oncology was studied in a xenograft model. PROCEDURE: Hepatoblastoma cell suspensions from three children were transplanted subcutaneously into nude mice NMRI (nu/nu). One of the primary tumors was an embryonal multifocal hepatoblastoma, whereas the other tumors were embryonal/fetal hepatoblastomas localized on a liver lobe. After 4 weeks, xenografted tumor sizes reached 50-100 mm3. The xenografted tumors resembled their originals histologically and produced high levels of alpha-fetoprotein. The efficiency of paclitaxel at equitoxic doses was analyzed. RESULTS: Paclitaxel produced an effect in all three hepatoblastomas. There was a significant reduction of tumor volume (P < 0.001) and alpha-fetoprotein levels after chemotherapy (P < 0.0001). The proliferation activity of the tumor cells corresponded with these results. Histologically, after treatment with paclitaxel the tumor regression was 35%-49%. The mechanism of paclitaxel action could be demonstrated by light microscopy immunohistochemistry and electron microscopy. CONCLUSIONS: The preliminary results in phase I trials of solid tumors in children and the results of this study suggest that paclitaxel in phase II studies can now be entertained for patients with hepatoblastoma.

3-D coculture of hepatic sinusoidal cells with primary hepatocytes-design of an organotypical model.

Models for cocultures of parenchymal (PC) and nonparenchymal cells (NPC) of the liver relied on mixing the cells in a two-dimensional configuration or on establishing spheroidal aggregates. In vivo hepatic nonparenchymal cells, such as endothelial cells and Kupffer cells, are separated from parenchymal cells by extracellular matrix (ECM). Due to their location outside of the space of Disse they can form a barrier toward the sinusoid. Hepatocytes are attached to ECM of the space of Disse via two opposing sinusoidal surfaces. No three-dimensional coculture model reflecting this specific microenvironment of the liver cell plates in vivo has been available to date. We designed a three-dimensional model by positioning NPC on top of PC enclosed as a monolayer within a collagen sandwich. A gas-permeable membrane support can be used to allow the supply of oxygen to the resulting cell plate also from underneath the cell layers. Morphological analysis was performed by inverse and cross-sectional studies by light microscopy, scanning, and transmission electron microscopy of the coculture model. Cuboidal hepatocytes formed confluent layers below the NPC layer. They regularly expressed bile canaliculi at intercellular contact zones. Both sinusoidal surfaces expressed microprojections. Characteristic NPC including endothelial cells, Kupffer cells, and Ito cells completely covered the second matrix layer within a week. Kupffer cells were located on top of endothelial cells. Ito cells were intermingled and could be identified by their intracytoplasmic lipid droplets. LPS stimulation of cocultures resulted in a depression of albumin secretion. Phase I and phase II metabolites of the cytochrome P-450 1A1 substrate ethoxyresorufin were generated independently from the presence of cocultured NPC. This study describes the development of a novel three-dimensional coculture model, which intends to mimic more closely the microenvironment of the hepatic sinusoid by respecting the specific plate structure of the liver parenchyma. The model could serve as a complex tool to study potential collaborations between PC and NPC of the liver.

Tacrolimus (FK 506) biotransformation in primary rat hepatocytes depends on extracellular matrix geometry.

Established in vitro models for studies of hepatic drug biotransformation include the use of primary hepatocytes. In normal liver the space of Disse provides the possibility of bilateral attachment to extracellular matrix for each hepatocyte. This configuration is disrupted by the cell isolation procedure of normal liver tissue, which delivers suspensions of round shaped cells. In standard culture configurations this unphysiologic cell shape terminates in a morphological dedifferentiation and inability to biotransform drugs. This study analyses the relevance of extracellular matrix geometry in hepatocyte monolayer configurations for expression and activity of cytochrome P450 3A. This enzyme is involved in the biotransformation of a large number of pharmaceuticals including the immunosuppressants tacrolimus and sirolimus. Morphological analysis of primary rat hepatocytes cultured with and without overlay of collagen type I was performed by transmission and scanning electron microscopy. Expression and activity of cytochrome P450 3A was studied by Western blot and the use of two model drugs specific for this enzyme. To this purpose the immunosuppressive drugs tacrolimus and sirolimus were used. Metabolites were analyzed by HPLC and HPLC/MS. Two sided attachment to extracellular matrix induces profound changes of the hepatocellular morphology in vitro resulting in the reconstitution of a polyhedric cell shape. This phenomenon is paralleled by an enhanced expression of cytochrome P450 3A and corresponding metabolic activity. As shown for tacrolimus biotransformation, the model may be useful to study complex metabolic patterns. In addition this model may facilitate studies of the kinetics of hepatocellular drug biotransformation in a setting with prolonged stability.

Reconstruction of liver tissue in vitro: geometry of characteristic flat bed, hollow fiber, and spouted bed bioreactors with reference to the in vivo liver.

Bioreactors currently being developed for hybrid artificial livers vary greatly with respect to their microenvironment. The specific architecture modifies the relationship parenchymal and nonparenchymal cells have with the exchange surfaces of the bioreactor. Most designs are either based on hollow fiber, spouted bed, or flat bed devices. This diversity is contrasted by the uniform and unique organization of the in vivo liver. The liver cells are arranged as plates and both sinusoidal surfaces of the hepatocytes are enclosed within the matrix of the space of Disse. In this study we intended to define the in vivo liver tissue characteristics in a manner useful for an organotypical approach to hepatic tissue engineering. Transmission electron microscopy of an in vivo liver was utilized to describe these ratios. The ratios defined in this study are based on the constant hepatocellular expression of two sinusoidal surfaces. A relationship is established between the expression of the sinusoidal surfaces and their use as attachment and exchange surfaces inside a bioreactor. The presence of biliary surfaces and nonparenchymal cell surfaces is compared. The functional relevance of an in vivo like extracellular matrix geometry for oxidative biotransformation of primary hepatocytes in vitro was studied using the two model drugs cyclosporin and rapamycin. The generation of the hydroxylated cyclosporin metabolites AM 9 and AM 1 and four rapamycin metabolites was analyzed by high performance liquid chromatography (HPLC). It is shown that the cell-specific biotransformation rates at 1 week in culture in matrix overlayed hepatocytes was 5-10 times that of hepatocytes without matrix overlay. Bilaminar membrane (BLM) bioreactors were used to reconstruct extracellular matrix geometry, three-dimensional cell plates, and sinusoidal analogs in between cell plates.

Ultrastructural and functional differentiation of hepatocytes under long-term culture conditions.

BACKGROUND: Studies on hepatocytes grown in different culture systems have shown that these cells rapidly dedifferentiate on a single support with liquid medium on top (single gel technique). However, in systems sandwiching them between two layers of extracellular matrix (double gel technique), the cells are able to regain and maintain typical light microscopical appearance and function. Their ultrastructural morphology is as yet unknown. METHODS: Isolated, adult rat hepatocytes were grown in both systems, and their fine structure (thin section electron microscopy) and the functional ability of albumin production (immunoassay) were studied and compared in both culture systems after 2, 7, and 14 days. RESULTS: The hepatocytes in conventional single gel culture did not completely regain their normal morphology and rapidly underwent progressive dedifferentiation. This was characterized by loss of cell polarization in terms of obliteration of the bile canaliculi-like intercellular expansions, loss of cell membrane differentiations, and reduction of organelles. Cytoskeletal components gradually increased, building up large filamentous zones underneath the plasma membrane. In double gel culture, the hepatocytes reachieved and maintained intact morphology and polarity over at least 14 days. The bile canaliculi were formed, preserved, or even enlarged and were associated with dense peribiliary bodies and Golgi fields. The plasma membrane facing both collagen layers bore numerous cytoplasmic microprojections like the sinusoidal surfaces of the hepatocytes in situ. Cell organelles, glycogen particles, and lipid droplets were always present. CONCLUSIONS: The hepatocyte is a cell type in which ultrastructural and functional differentiation are strongly interdependent. For these cells, the morphological microenvironment (i.e. the bipolar position of the extracellular matrix) may be as important or even more decisive for maintenance of normal cell differentiation than modifications of the composition of the matrix itself or addition of other cell types, as focused in other studies.

A novel bioreactor design for in vitro reconstruction of in vivo liver characteristics.

We have constructed a bioreactor aimed at imitating the three-dimensional micro- and macroenvironment of the liver. In vivo hepatocytes are arranged in plates of cell monolayers and are specifically attached with both sinusoidal surfaces to the space of Disse which contains extracellular matrix. Nonparenchymal cells are located on the other side of the space of Disse toward the sinusoid. For supporting monolayer hepatocytes with bipolar attachment to the extracellular matrix, we used a double gel culture technique that sandwiches hepatocytes between two layers of collagen. In double gel cultures, albumin production increases during an adaptive period to the in vitro environment. In contrast to conventional single gel hepatocytes, double gel hepatocytes maintain expression of sinusoidal microvilli and a polyhedric cell shape in culture as seen by transmission electron microscopy. Albumin production in the bioreactor was stable. The organotypical bioreactor concept is an example of organ mimicry and may provide the basis for the organ-otypical development of a full-sized hybrid artificial liver.

An organotypical in vitro model of the liver parenchyma for uptake studies of diagnostic MR receptor agents.

Testing of receptor-specific MR contrast agents targeted to the liver is hampered by a shortage of viable in vitro models with in vivo-like hepatocellular morphology. Coated pits are ultrastructural signs of an active receptor mediated endocytosis in hepatocytes. Expression of coated pits by matrix overlaid hepatocytes was studied by transmission electron microscopy. Binding of a rhodaminated asialoglycoprotein receptor agent (MION-ASF-rh) was assessed by fluorescence microscopy. Fluorescence of cells exposed to MION-ASF-rh with D(+)-galactose reduced fluorescent light emission to a level of 58% of MION-ASF-rh-induced fluorescence. After preincubation with the hepatotoxin CCl4 a dose-dependent decrease in fluorescent light emission resulted. Hepatocytes maintained a homogeneous cell surface expression, with microprojections, coated pits, and vesicles on both sinusoidal surfaces. Matrix overlaid primary hepatocytes constitute a viable, morphologically and functionally differentiated model. This model can be used to study receptor binding, uptake, and blockage of diagnostic magnetopharmaceuticals under controlled conditions.