Isolation and clonal analysis of human epidermal keratinocyte stem cells in long-term culture

We developed a procedure for growing normal epidermal keratinocyte stem cells isolated from a single punch biopsy of adult human skin in long-term culture. Primary skin epithelial cells were maintained in collagen-coated plates with irradiated human neonatal foreskin fibroblasts (line HPI.1) as a feeder for more than 120 days, approximately 115 population doublings, without signs of replicative senescence. Clonal analysis revealed the presence of holoclones, meroclones, and paraclones. Only emerging colonies with high proliferative potentials and extensive capacities for division (holoclones and meroclones) were subcultured, favoring the expansion of stem cells and progenitors capable of prolonged self-maintenance when subcloned, thus accounting for the prevailing long-term proliferation of the original culture. We found that meroclones included bipotent progenitors capable of generating both keratinocytes and mucin-producing cells. The numbers of these cells were greater after confluence, suggesting that commitment for their differentiation occurred late in the life of a single clone. On a three-dimensional gelatin matrix and on a collagen layer containing the fibroblast feeder, cells isolated from the expansion of holoclones and meroclones formed stratified cohesive layers of keratinocytes that were able to further differentiate, as in normal skin. These results indicate that our procedure will serve as a valuable tool to study expansion of epidermal stem cells as well as the growth mechanisms and cell products associated with their growth and differentiation.

Multilineage differentiation of rhesus monkey embryonic stem cells in three-dimensional culture systems

In the course of normal embryogenesis, embryonic stem (ES) cells differentiate along different lineages in the context of complex three-dimensional (3D) tissue structures. In order to study this phenomenon in vitro under controlled conditions, 3D culture systems are necessary. Here, we studied in vitro differentiation of rhesus monkey ES cells in 3D collagen matrixes (collagen gels and porous collagen sponges). Differentiation of ES cells in these 3D systems was different from that in monolayers. ES cells differentiated in collagen matrixes into neural, epithelial, and endothelial lineages. The abilities of ES cells to form various structures in two chemically similar but topologically different matrixes were different. In particular, in collagen gels ES cells formed gland-like circular structures, whereas in collagen sponges ES cells were scattered through the matrix or formed aggregates. Soluble factors produced by feeder cells or added to the culture medium facilitated ES cell differentiation into particular lineages. Coculture with fibroblasts in collagen gel facilitated ES cell differentiation into cells of a neural lineage expressing nestin, neural cell adhesion molecule, and class III beta-tubulin. In collagen sponges, keratinocytes facilitated ES cell differentiation into cells of an endothelial lineage expressing factor VIII. Exogenous granulocyte-macrophage colony-stimulating factor further enhanced endothelial differentiation. Thus, both soluble factors and the type of extracellular matrix seem to be critical in directing differentiation of ES cells and the formation of tissue-like structures. Three-dimensional culture systems are a valuable tool for studying the mechanisms of these phenomena.

Cochlear Repair by Transplantation of Human Cord Blood CD133+ Cells to Nod-Scid Mice Made Deaf with Kanamycin and Noise

We investigated the fate of human cord blood CD133+ hematopoietic stem cells (HSC) transplanted intravenously (IV) into irradiated nodscid mice previously made deaf by ototoxic treatment with kanamycin and/or intense noise, to verify whether HSC engraft the cochlea and contribute to inner ear restoration, in vivo. We tested the presence of HLA.DQα1 by PCR, used for traceability of engrafted cells, finding evidence that HSC migrated to various host tissues, including the organ of Corti (OC). By histology, antibody and lectin-staining analysis, we confirmed that HSC IV transplantation in mice previously damaged by ototoxic agents correlated with the repair process and stimulation ex novo of morphological recovery in the inner ear, while the cochlea of control oto-injured, nontransplanted mice remained seriously damaged. Dual color FISH analysis also provided evidence of positive engraftment in the inner ear and in various mouse tissues, also revealing small numbers of heterokaryons, probably derived from fusion of donor with endogenous cells, for up to 2 months following transplantation. These observations offer the first evidence that transplanted human HSC migrating to the inner ear of oto-injured mice may provide conditions for the resumption of deafened cochlea, emerging as a potential strategy for inner ear rehabilitation.

Epithelial stem cells of the eye surface

OBJECTIVES

Epithelial stem cells of the eye surface, of the cornea and of the conjunctiva, have the ability to give rise to self renewal and progeny production of differentiated cells with no apparent limit. The two epithelia are separated from each other by the transition zone of the limbus. The mechanisms adopted by stem cells of the two epithelia to accomplish their different characteristics, and how their survival, replacement and unequal division that generates differentiated progeny formation are controlled, are complex and still poorly understood. They can be learned only by understanding how stem cells/progenitors are regulated by their neighbouring cells, that may themselves be differently unspecialised, forming particular microenvironments, known as 'niches'. Stem cells operate by signals and a variety of intercellular interactions and extracellular substrates with adjacent cells in the niche. Technical advances are now making it possible to identify zones in the corneal limbus and conjunctiva that can house stem cells, to isolate and expand them ex vivo and to control their behaviour creating optimal niche conditions. With improvements in biotechnology, regenerative cornea and conjunctiva transplantation using adult epithelial stem cells becomes now a reality.

RESULTS AND CONCLUSIONS

Here we review our current understanding of stem cell niches and illustrate recent significant progress for identification and characterization of adult epithelial stem cells/progenitors at cellular, molecular and mechanistic levels, improvement in cell culture techniques for their selective expansion ex vivo and prospects for a variety of therapeutic applications.

Selective growth and expansion of human corneal epithelial basal stem cells in a three-dimensional-organ culture

We report on a three dimensional (3D)-organotypic culture in vitro for selective growth and expansion of human corneal epithelial stem cells. Limbal corneal explants were cultured on porous collagen sponges submerged in Epilife medium containing 10% fetal bovine serum. The fragments were analyzed by immunohistochemistry for the expression and distribution of a spectrum of corneal epithelium markers: p63, CK-19, CK-3, Ki-67, pan-cytokeratins and vimentin. Early in culture the epithelium began to exfoliate losing its differentiated high-zone layers into the medium, maintaining only basal and few parabasal cells (mostly both p63 and CK-19 positive), which had remained attached to the specimen. After 14 days a new epithelium was formed displaying an increasing prominence of basal and suprabasal cells that, sliding onto the whole explant, showed the tendency to underlay stromal tissue and infiltrate into the underlaying sponge. After 21 days, sponge and fragments were incubated with trypsin-EDTA and dispersed epithelial cells were pipetted on a feeder monolayer of mitomycin-c-treated murine NIH.3T3 fibroblasts. Colonies of undifferentiated epithelial cells (p63, CK-19 and Ki-67 positive, CK-3 negative) were obtained: their cells, if seeded onto a collagen matrix containing embedded primary human corneal fibroblasts as feeder, provided the basic building blocks for reconstructing in vitro a 3D-multilayered corneal epithelium.

Primate embryonic stem cells create their own niche while differentiating in three-dimensional culture systems

Rhesus monkey embryonic stem cells (ESCs) (R366.4), cultured on a three-dimensional (3D) collagen matrix with or without human neonatal foreskin fibroblasts (HPI.1) as feeder cells, or embedded in the collagen matrix, formed complex tubular or spherical gland-like structures and differentiated into phenotypes characteristic of neural, epithelial and endothelial lineages. Here, we analysed the production of endogenous extracellular matrix (ECM) proteins, cell-cell adhesion molecules, cell-surface receptors, lectins and their glycoligands, by differentiating ESCs, forming a micro-environment, a niche, able to positively influence cell behaviour. The expression of some of these molecules was modulated by HPI.1 cells while others were unaffected. We hypothesized that both soluble factors and the niche itself were critical in directing growth and/or differentiation of ESCs in this 3D environment. Creating such an appropriate experimental 3D micro-environment, further modified by ESCs and modulated by exogenous soluble factors, may constitute a template for adequate culture systems in developmental biology studies concerning differentiation of stem cells.

Human conjunctival epithelial precursor cells and their progeny in 3D organotypic culture

We report on an in vitro organ culture method to investigate human conjunctival epithelial basal precursor cells and their progeny within a more natural three-dimensional microenvironment. Conjunctival fragments were cultured on gelatin sponges in medium with 10% FBS. The conjunctival phenotype of the epithelium was confirmed by the expression and distribution of a panel of markers (p63, CK-13/CK-10, CK-19, Ki-67, PAS for goblet cells, CD45 for infiltrating interlamellar leukocytes and nestin for mesenchymal and ocular epithelial precursor cells). After 7 days, the epithelium had exfoliated its superficial layers (mostly CK-19( )positive cells and all goblets), maintaining only 1-2 layers of basal/parabasal cells, p63, CK-13/CK-10 and nestin positive cells, firmly attached to the specimen. After 14 days, a new multilayered epithelium was formed, consisting of p63, CK-13/CK-10, nestin positive cells and in the high-zone CK-19 positive cells with new goblets. Additionally, we found interlamellar leukocytes which had probably migrated from capillaries that continued to be well maintained in the subepithelial stroma. Cells dispersed from conjunctival epithelium and co-cultured with feeder post-mitotic NIH3T3 fibroblasts formed mosaics displaying a basal epithelial phenotype. These cells expressed CD133 as revealed by RT-PCR. These organ cultures provide new opportunities to investigate epithelial reconstitution of the conjunctival surface and changes that may have occurred to their stem/precursor cells during adaptation to varying conditions in vitro.

Selective growth of epithelial basal cells from human prostate in a three-dimensional organ culture

BACKGROUND

A three-dimensional organotypic culture method has been developed for selectively growing epithelial basal cells from human benign prostate.

METHODS

Tissue fragments were cultured on sponges for several weeks and the viability of luminal and basal epithelium and cellular responses to 4,5alpha-dihydrotesterone (DHT) stimulation were studied.

RESULTS

The gland tissue could be successfully maintained showing preservation of ducts and lobules as in vivo. Without DHT, a progressive hyperplasia of basal cells was observed: these cells proliferated with retention of the lumen or forming nests with squamous differentiation, lining the surface of the fragment and migrating to the underlying sponge. In contrast, secretory cells disappeared. Epithelial cells isolated from long-term cultures showed a typical basal cell-immunophenotype. DHT-treated tissues maintained a much higher percentage of luminal cells than untreated tissues.

CONCLUSIONS

These systems allow the study of proliferation and differentiation of basal cells within their natural microenvironment as well as prostate pathobiology.

Establishment of an organotypic in vitro culture system and its relevance to the characterization of human prostate epithelial cancer cells and their stromal interactions

Human prostatic adenocarcinoma fragments (1-6mm) were cultured on collagen sponges in medium supplemented or not supplemented with 4,5alpha-dihydrotesterone (DHT) until 3 weeks, maintaining the three-dimensional (3D) epithelial and stromal organization present in the tumor in vivo. With time, in the presence of DHT, locally progressive cribriform nests of neoplastic cells with proliferative rates higher than those inside the fragment developed on the surface, while the stroma became more dissociated, and fibrosis replaced the muscular component. The 3D-culture provides a promising approach for studying the development and phenotype of prostate epithelial tumor progenitor cells and their stromal interactions.

A three-dimensional organotypic culture of the human uterine exocervix for studying mucosal epithelial differentiation and migrating leukocytes

We report on a three-dimensional organotypic culture in vitro of explants from the human uterine exocervix. Exocervical fragments (2-3 mm3) from pre-menopausal women were cultured on sponges submerged in Dulbecco's Modified Eagle's Medium containing p-nonylphenol and 10% fetal bovine serum for up to 3 weeks and the viability and cellular responses were assayed. The fragments were analyzed by immunohistochemistry for the expression and distribution of a broad spectrum of cellular markers: p63, Ki-67, involucrin, high molecular weight cytokeratins, estrogen receptor-alpha, vimentin, CD45, and CD31. The fragments preserved their tissue architecture and cellular heterogeneity comparable to that observed in exocervical tissue in vivo. Prior to culture, the original epithelium was composed of stratified multilayered keratinocytes with integrated monocyte/dendritic-like cells in the basal and suprabasal layers. The epithelium began to exfoliate in culture and within 4 days appeared to have lost its differentiated high-zone layers of keratinocytes. After 10 days a new epithelium, slightly different from the original one, was formed; it displayed an increasing prominence of basal and suprabasal keratinocyte layers, containing infiltrating leukocytes that had probably migrated from the submucosa. The epithelium subsequently lost its organization, concomitant with a progressive involution of the stroma. Subepithelial capillaries appeared to be well maintained throughout the culture period. Aside from the maintenance of cellular heterogeneity within the fragments of exocervix, these culture systems are a valuable tool for studying the mechanisms of epithelial regeneration, and may prove to be a useful model for studying mucosal immunity.

Morpho-functional modifications of human neutrophils induced by aqueous cigarette smoke extract: comparison with chemiluminescence activity

Cigarette smoking plays an important role as a cause of morbidity and mortality in humans, involving respiratory, cardiovascular, digestive and reproductive systems. Tobacco smoke contains a large number of molecules, some of which are proven carcinogens. Although not fully understood, polymorphonuclear leukocytes seem to play a crucial role in the mechanisms by which tobacco smoke compounds are implicated in smoke-related diseases. In this paper the effects of an aqueous cigarette smoke extract on the expression of adhesion molecules of polymorphonuclear leukocytes together with the changes in the cell morphology have been related to the chemiluminescence activity. The results obtained show that polymorphonuclear leukocytes treated with aqueous cigarette smoke extract are significantly impaired, as suggested by the changes of chemiluminescence activity, of membrane receptors (CD18, CD62), myeloperoxidase expression and of cell morphology. Altogether the present data indicate that treated polymorphonuclear leukocytes are ineffectively activated and therefore unable to phagocytize zymosan particles.

Optimizing microwave-assisted solvent extraction (MASE) of pesticides from soil

Microwave-assisted solvent extraction (MASE) was investigated as an alternative for extraction of parathion (O,O-diethyl O-4-nitrophenyl phosphorothioate), methyl parathion (O,O-dimethyl O-4-nitrophenyl phosphorothioate), p,p'-DDE [1,1'-dichloro-2,2-bis(4-chlorophenyl)ethane], hexachlorobenzene (HCB), simazine (6-chloro-N2,N4-diethyl- 1 ,3,5-triazine-2,4-diamine) and paraquat dichoride (1,1'-dimethyl-4,4'-bipyridinium) from two different soils and from an earthworm-growing substrate. The matrices were fortified with 14C-radiolabeled pesticides and extracted with various solvent systems under different microwave conditions. Recoveries of more than 80% could be obtained depending on the used microwave conditions and solvent, except for paraquat whose recovery was generally less efficient. Thus, MASE can be successfully used to extract pesticides from environmental and biological samples and could be a viable alternative to conventional extraction methods. The technique uses smaller amounts of organic solvents, thereby minimizing the costs of the analysis and the disposal of waste solvent.

Prolonged human/sheep cellular chimerism following transplantation of human hemopoietic stem cells into the ewe celomic cavity

We evaluated the possibility of prolonged chimerism formation in fetus and lamb, following human cord blood-selected CD133+ hemopoietic stem cell (HSC) transplantation into the celomic cavity of ewes at a pre-immune fetal age (44-45 days of pregnancy). Nineteen ewes were injected with HSC and 5 controls with a saline solution. By PCR, HLA-DQ alpha 1 and 6 human microsatellites (CODIS) were used for HSC traceability. FISH analysis was performed with 8 human DNA probes from different chromosomes, to confirm chromosomal integrity, nuclear DNA localization and donor DNA identification. Immunological staining for revealing HLA-DQ alpha 1 expression demonstrated multilineage engraftment. Both HLA-DQ alpha 1 and microsatellites were detected in different tissues of 3 available aborted fetuses, to a lesser extent in 11 lambs tested at 2-months, but not 12-months after birth. Although only 1 fetus of siblings of each sheep was injected, all siblings revealed positive engraftments. Microsatellite analysis showed evidence of human allele segregation in different tissues of individual fetuses and lambs. FISH analysis confirmed chimerism and the presence of human chromosomes. Non-detection of some human gene sequences in different chromosomes and random finding of allele segregation for some human heterozygous microsatellites were found in different tissues of individual animals. Controls born from un-transplanted ewes never revealed any human DNA sequences nor HLADQ alpha 1 expression.