Differences in vitro between fibroblast-like cells from cornea, heart, and skin of embryonic chicks

A bioinspired multifunctional hydrogel patch targeting inflammation and regeneration in chronic intestinal wounds

Healing of intestinal chronic wounds remains a major challenge as current therapies are ineffective in promoting proper regeneration of the damaged intestinal wall. An innovative concept, based on a bioinspired multifunctional alginate-melanin hybrid 3D scaffold, to target both inflammatory and regenerative processes, is proposed herein. Hydrogel-entrapped melanin nanoparticles demonstrated free-radical scavenging activity, supported by the neutralization of free-radicals in solution (90%), and the in vitro capture of reactive oxygen species (ROS) produced by stimulated macrophages in an inflammatory-mimicking environment. Notably, scaffolds could be reused (at least 3 times), while maintaining these properties. The extracellular matrix (ECM)-inspired biomaterial, containing protease-sensitive and integrin-binding domains, exhibited remarkable ability for cell colonisation. Human intestinal fibroblasts and epithelial cells (Caco-2) co-seeded on lyophilized scaffolds were able to invade/colonize the construct and produce endogenous ECM, key for neo-tissue formation and re-epithelialization. Scaffolds presented tuneable mechanical properties and could be used both in hydrated and freeze-dried states, maintaining their performance upon rehydration, which are attractive features for clinical application. Collectively, our results highlight the potential of biofunctionalized alginate-melanin hybrid 3D scaffolds as multi-therapeutic patches for modulating inflammation and tissue regeneration in chronic intestinal wounds, which address a major but still unmet clinical need. The proposed multi-therapeutic strategy may potentially be extended to the treatment of other chronic wounds.

Fibroblasts-a diverse population at the center of it all

The capacity of fibroblasts to produce and organize the extracellular matrix and to communicate with other cells makes them a central component of tissue biology. Even so, fibroblasts remain a somewhat enigmatic population. Our inability to fully comprehend these cells is in large part due to the paucity of unique cellular markers and to their pervasive diversity. Much of our understanding of fibroblast diversity has evolved from studies where subpopulations of these cells have been produced without resorting to cell surface markers. In this regard, cloning and mechanical separation of tissues prior to establishing cultures has provided multiple subpopulations. Nonetheless, in isolated situations, the expression or lack of expression of Thy-1/CD90 has been used to separate fibroblast subsets. The role of fibroblasts in intercellular communication is emerging through the implementation of organotypic studies in which three-dimensional fibroblast culture are combined with other populations of cells. Such studies have revealed critical paracrine loops that are essential for organ development and for wound repair. These studies also provide a backdrop for the emerging field of tissue engineering. The participation of fibroblasts in the regulation of tissue homeostasis and their contribution to the aging process are emerging issues that require better understanding. In short, fibroblasts represent a multifaceted, complex group of cells.

The fibroblast in morphogenesis and fibrosis: cell topography and surface-related functions

'Fibroblast' is a generic term for a population of cells responsible for the establishment, maintenance and repair of three-dimensional form in multicellular organisms. These cells are a major, semi-permanent resident of the 'extracellular space' and the fibroblast compartmentalizes this space to various purposes during the formation of collagen fibrils and fibril bundles. The boundaries of these extracellular compartments blend and overlap, but discrete regions can be identified which are involved in collagen fibril assembly and fibril bundle assembly. The formation of these extracellular compartments in both the tendon and cornea results from a series of fusions of membrane-limited structures, beginning with collagen secretory vacuoles fusing with the cell surface to form deep surface recesses within which fibrils assemble; and progressing through the lateral fusion of these recesses with the consequent formation of fibril bundles. The topography of the fibroblast is also specialized for matrix anchorage, for matrix and cell repositioning, and for matrix degradation.

Phenotypic responses to mechanical stress in fibroblasts from tendon, cornea and skin

Primary fibroblasts isolated from foetal mouse cornea, skin and tendon were subjected to linear shear stress and analysed for morphological parameters and by microarray, as compared with unstimulated controls. Approx. 350 genes were either up- or down-regulated by a significant amount, with 51 of these being common to all three cell types. Approx. 50% of altered genes in tendon and cornea fibroblasts were changed in common with one of the other cell types, with the remaining approx. 50% being specific to tendon or cornea. In skin fibroblasts, however, less than 25% of genes whose transcription was altered were specific only to skin. The functional spectrum of genes that were up- or down-regulated was diverse, with apparent house-keeping genes forming the major category of up-regulated genes. However, a significant number of genes associated with cell adhesion, extracellular matrix and matrix remodelling, as well as cytokines and other signalling factors, were also affected. Somewhat surprisingly, in these latter categories the trend was towards a reduction in mRNA levels. Verification of the mRNA quantity of a subset of these genes was performed by reverse transcriptase PCR and was found to be in agreement with the microarray analysis. These findings provide the first in-depth analysis of phenotypic differences between fibroblast cells from different tissue sources and reveal the responses of these cells to mechanical stress.

Adult stem cell plasticity: fact or artifact?

There has been unprecedented recent interest in stem cells, mainly because of the hope they offer for cell therapy. Adult stem cells are an attractive source of cells for therapy, especially in view of the recent claims that they are remarkably plastic in their developmental potential when exposed to new environments. Some of these claims have been either difficult to reproduce or shown to be misinterpretations, leaving the phenomenon of adult stem cell plasticity under a cloud. There are, however, other examples of plasticity where differentiated cells or their precursors can be reprogrammed by extracellular cues to alter their character in ways that could have important implications for cell therapy and other forms of regenerative treatment.

Identification of two types of smooth muscle cells from rabbit urinary bladder

Cells from the muscular layer of neonatal (3-day-old) rabbit urinary bladders were dissociated with collagenase, and cultured in M199 supplemented with 10% fetal bovine serum and antibiotic-antimycotic. Cells in culture were of two types: long and short. The short cells were thick and spindle-shaped, and the long cells were flat and elongated. The long cells can be about 15 times longer than the short cells. The short cells do not divide, but the long cells divide readily. Expressions of smooth muscle and non-muscle myosins, alpha-smooth muscle actin, vimentin, and h-caldesmon were determined by immuno-fluorescence microscopy using specific antibodies. Both types of cells react strongly with antibodies against smooth and non-muscle myosins. Unlike the short cells, the long cells also contain alpha-actin and vimentin. The expression of h-caldesmon was very weak in both cell types. Also, cells dissociated from the smooth muscle layers of adult (6-month-old) rabbit bladder were cultured under the same conditions as the cells from the neonatal bladders to see if the heterogeneity of smooth muscle cells, exhibited by cells from neonatal rabbits, is also shown by cells from adult bladder. Two types of cells were also identified. The cells were then fixed and examined with the same panel of antibodies that we used for the neonatal cells. The long cells from adult bladder muscle express similar proteins to those in the neonatal long cells, and the short cells were stained positively with smooth muscle myosin, non-muscle myosin, alpha-smooth muscle actin, and lightly with caldesmon. Although the absence of vimentin in the short cells from adults is similar to that from neonatal, the strong expression of alpha-actin in the adult short cells is unlike the short cells from neonatal rabbits, in which their expression is barely detectable.

In vitro radiation sensitivity of mouse lung fibroblasts isolated by flow cytometry

PURPOSE

Recently, we have isolated two major fibroblast cells (Thy-1+, Thy-1-) from mouse LAF1 lung tissue using the anti-Thy-1 antibody expression and fluorescence activated cell sorter. To examine the possibility that x- or gamma-ray-induced pulmonary fibrosis at the late stage of injury could arise from radioresistant cell subpopulations, the radiation sensitivities of Thy-1+ and Thy-1- cells were evaluated by the colony forming assay.

METHODS AND MATERIALS

Cell survival curves, repair of potentially lethal damage (PLD) and sublethal damage (SLD), and cell-age response curves were obtained after Cs-137 gamma-ray irradiation.

RESULTS

The cell survival curves measured after 0-10 Gy gamma-ray showed that Thy-1+ cells were slightly more radioresistant than Thy-1- cells. The D0, n, alpha, and beta values measured from the survival curves also confirmed this observation. After a single dose of 10 Gy, a small amount of PLD repair was observed in Thy-1- cells, while no PLD repair was found in Thy-1+ cells. Although the initial cell survival level of Thy-1- cells was lower, the final survival levels of Thy-1+ and Thy-1- cells became identical at 8 h after irradiation due to the PLD repair. After split-dose irradiation of 4 Gy followed by 4 Gy, a similar extent and rate of SLD repair was found in Thy-1+ and Thy-1- cells. Cell-age response curves were obtained from irradiated G0/G1, S, and G2M cells separated by centrifugal elutriation and irradiated with 8 Gy gamma-ray. The results indicated that Thy-1+ and Thy-1- cells had a similar S resistant, and G1, G2M-sensitive radiation cell-age response curve.

CONCLUSIONS

This study suggests that the selection of radioresistant lung fibroblast may not be responsible for the development of lung fibrosis in irradiated LAF1 mouse.

A quantitative study of the differential expression of alpha-smooth muscle actin in cell populations of follicular and non-follicular origin

Alpha-smooth muscle actin (ASMA) is an actin isoform present in the filaments of smooth muscle cells, myofibroblasts, and a specific region of hair follicle dermal sheath in vivo. We employed double immunofluorescence, two-dimensional electrophoresis, Western blots and DNA, protein, and actin isoform determinations to quantify the relative levels of ASMA in four populations of cultured hair follicle dermal cells, and fibroblasts derived from three regions of adult and comparable areas of 4-d rat skin. Although follicle sheath populations were morphologically similar, they contained variable proportions of cells that expressed ASMA. Tissue from the most positive region in situ, the lower/mid sheath, also gave rise to the most positive cells in culture (98%), followed by the end bulb (85%) and then upper sheath (50%). The follicle dermal cells (including papilla 81%) displayed and maintained levels of expression well above those obtained for adult (below 10%) or 4-d (9-40%) fibroblasts, and even cultured smooth muscle cells. It was also confirmed that levels of expression in adult fibroblasts could be positively correlated with hair follicle density in the biopsies from which they were initiated. Differential expression of ASMA in follicle subpopulations provides an insight into how their behavior may be linked to their specialized functions, for example, their likely involvement in the mechanics of the hair cycle. Moreover, the proposition that hair follicle dermal cells represent unappreciated constituents of general skin fibroblast cultures has substantial implications.

Behavior of embryonic chick heart cells in culture. 1. Cellular responses to insulin-transferrin-selenium

Muscle cell-enriched primary cell cultures were prepared from 8-day embryonic chick heart ventricles (74% of these cells showed positive staining with anti-cardiac myosin antibody). To determine if ITS (a commercial mixture of insulin, transferrin, and selenium) affects these cardiac muscle cells, immunostaining and autoradiography were performed to determine the Muscle Cell Labeling Index (MLI). MLI represents the proportion of cardiac myosin-positive cells that specifically incorporated [3H]thymidine. The MLI for ITS-treated cells was 52%. Controls in Serum-free Nutrient Medium (SFNM) had a MLI of 27%. Combinations of growth signals also were tested. Whereas 5% Fetal Bovine Serum (FBS) was optimal for stimulation of [3H]thymidine incorporation, 10 and 20% FBS elicited an inhibitory effect. Addition of ITS enhanced the stimulatory effect of FBS and relieved some of the inhibitory effect. TGF-beta also was shown to have inhibitory effect on [3H]thymidine incorporation in these heart cells, but the inhibitory effect was not seen when it was added with ITS. Staining with anti-cardiac myosin antibody revealed that when the cells were cultured with ITS for 6 or 10 days, the percentages of muscle cells were 65 and 59%, whereas the percentages of muscle cells of controls in SFNM dropped to 44 and 31% respectively. Additional experiments showed that cell number increased in the presence of 5% FBS. In contrast, although ITS stimulated DNA synthesis, it did not immediately stimulate complete cell division. The percentage of muscle cells remained around 74% in the presence of 5% FBS, whereas it fell slightly (to 65%) in SFNM. This study showed that cardiac muscle cells from 8-day embryos in culture were responsive to ITS, FBS and TGF-beta and that ITS may be permissive for continued expression of differentiation of embryonic cardiac muscle cells.

Morphologic and functional characteristics of subpopulations of murine lung fibroblasts grown in vitro

Fibrotic development is a common response of the lung to toxic or deleterious insult. For example, the lung is the dose-limiting organ for irradiation of the thorax for primary or metastatic lesions, due in large part to latent fibrosis. The development of the fibrotic response reflects a cascade of cell-cell and cell-extracellular matrix interactions, the ultimate target of which is the fibroblast. There is increasing evidence of subpopulations of pulmonary fibroblasts, which may have differing roles in either the initiation or progression of fibrosis. Recently we described two fibroblast subpopulations from the murine lung, which differ in the presence or absence of the membrane antigen Thy-1 (Phipps et al., 1989). These Thy-1+ and Thy-1- subpopulations are stable and differ in certain functions, such as the production of cytokines and the display of Class II MHC antigens. To determine the morphologic development of the two subpopulations and their growth characteristics in vitro, cultures of the two cell subtypes were prepared for transmission and scanning electron microscopy at varying stages of growth. Thy-1+ fibroblasts are more spindle-shaped, contain intracellular lipid, exhibit abundant cell-cell contacts, and are capable of secreting large amounts of collagen and modest amounts of fibronectin. Thy-1- fibroblasts are more rounded and spread, contain no intracellular lipid droplets, possess more intracellular microfilaments and microtubules, and synthesize less collagen and more fibronectin than do Thy-1+ cells. There are no significant differences between the two subpopulations insofar as growth rates are concerned, but Thy-1+ fibroblasts possess an additional DNA peak during periods of early growth.

Collagen-type synthesis in human-hair papilla cells in culture

Hair-papilla derived cells were grown in monolayer culture and revealed the typical morphology and growth pattern which was similar but not identical to control fibroblasts. Hair-papilla cells were found to produce considerable amounts of collagen type I and type III and fibronectin. Type IV collagen production could not be detected. The ratio of collagen type III and type I clearly differed from the pattern observed in normal fibroblasts, being much higher in hair-papilla cells, where type III accounted for more than 20% of total collagen synthesis. These data show that hair-papilla derived cells have biosynthetic capacities similar to those of human skin fibroblasts as well as characteristic differences, indicating that they represent a specialized fibroblast subpopulation.

Isolation and growth characteristics of adult human tendon fibroblasts

An explant method for the isolation of fibroblasts from adult human tendon is described. Cells were successfully isolated from 22 out of 27 common biceps tendons obtained from cadaveric donors (age range 11-83 years). The fibroblasts could be maintained in culture using standard methods and morphologically resembled those of synovial rather than dermal origin. Growth characteristics of 12 cell lines were assessed by deoxyribose nucleic acid (DNA) synthesis using [3H]thymidine incorporation in response to stimulation by fetal calf serum. Cells obtained separately from superficial and deep parts of the tendons produced almost identical responses. No significant reduction in growth response with increasing age was found when related to the age of the donor. Therefore this study did not show any age related defect in the short term tendon fibroblast replicative responses to serum.

The in vitro properties of dermal papilla cell lines established from human hair follicles

The in vitro properties of cells cultured from the dermal papilla of human hair follicles were studied and compared with those of lines of dermal fibroblasts derived from the same material. In serial subcultures, the dermal papilla cells displayed a spread out, polygonal cellular morphology at stationary growth phases and a tendency to form multi-layered aggregates before reaching confluence. Aggregation was particularly marked when papilla cells were grown on collagen gels. In contrast, dermal fibroblasts grew as branching, parallel arrays of spindle-shaped cells which remained as monolayers until confluence. Compared with dermal fibroblasts, papilla cells also exhibited a shorter in vitro survival time. The properties of cultured human papilla cells are similar to those of rat vibrissa papilla cells.

Attachment and extracellular matrix differences between tendon and synovial fibroblastic cells

Fibroblasts of the synovium of sheathed tendons were isolated, and their biochemical properties were compared with those of the fibroblasts of the remaining tendon. The synovial cells had a lower attachment efficiency than did the tendon cells. On the day of cell isolation the synovial cells synthesized collagen as 10% of their total protein, whereas the tendon cells synthesized 30% collagen. After growth in fetal bovine serum (FBS), the percentage of collagen synthesized by both populations decreased; however, the synovial cells still made less collagen than did the tendon cells (5 versus 11%). On the basis of cyanogen bromide peptide analysis, the synovial cells were found to synthesize Types I and III collagen in primary culture, whereas the tendon cells synthesized only Type I. The synovial cells also synthesized two to three times less sulfated glycosaminoglycans in culture than did the tendon cells. Thus, the two cell populations differed in attachment efficiency and in their biosynthesis of collagen and sulfated glycosaminoglycans. These differences reflect extracellular matrix differences that have been observed in the tendon in vivo. In addition, the results augment existing data showing that not all fibroblasts have identical phenotypes.

Cell-surface associated proteins of corneal fibroblasts: dissection with monoclonal antibodies

It is now generally accepted that the cell surface is involved in the interaction of the cells with the extracellular matrix. To identify and characterize cell-surface-associated components of corneal fibroblasts, several monoclonal antibodies were developed. Hybridomas were developed by fusing mouse myeloma cells SP2/OAg14 with spleen cells from mice immunized with membrane fractions of corneal fibroblasts grown in culture. Twenty-five hybridomas secreting monoclonal antibodies to cell-surface components were selected by an enzyme-linked immunosorbent assay using corneal fibroblasts grown in microtiter plates as the substrate. Immunohistochemical staining demonstrated that the antigenic determinants recognized by these antibodies were not present on corneal epithelial cells, but were present on skin fibroblasts. The antigenic determinants recognized by two of these antibodies, designated 10D2 and 716, were matrix components of the corneal stroma. Immunochemical characterization of the antigens was carried out by indirect precipitation of the radioactively labeled cellular proteins with the monoclonal antibodies and sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) analysis of the precipitates. Four antibodies were able to precipitate antigens from cell extract in detectable amounts. Antibodies designated 5E2, 9G2, and 10D2 recognized antigens consisting of polypeptides of approximate molecular weights 105K and 110K, while antibody 716 recognized an antigen of 100K molecular weight. However, based on the tissue distribution and cell-surface distribution, these antibodies reacted with different antigenic determinants. The antigen recognized by 716 was also secreted by cells in culture but consisted of 220K and 200K polypeptide chains. It was tentatively identified as cellular fibronectin, based on the reaction of this antigen with polyclonal antibodies to plasma fibronectin.

The wound fibroblast and macrophage. I: Wound cell population changes observed in tissue culture

The number and type of cells which migrated from sequential explants of wounded fascia in rats reflected the dense and changing cell populations observed in healing wounds. Macrophages appeared in large numbers from explants taken in the 5 days following injury, thereafter fibroblast-like cells predominated. The results support the hypothesis that the fibroblast-like cell of tissue culture is the same as the wound fibroblast. The technique can be used to obtain wound cells and provides a useful bridge between in vivo and in vitro means of investigating wound repair.

Some metabolic differences between human skin and aponeurosis fibroblasts in culture

Two types of human fibroblast strains were studied in culture. One was derived from abdomen skin and the other from abdominal muscle aponeurosis. Tissue-specific differences were found between these two cell strains. Skin fibroblasts had faster doubling time, smaller cell volume, and lower glucose consumption when compared to aponeurosis fibroblasts. Furthermore, extracellular amino acid variations showed some specific differences, in particular a lack of serine consumption in skin fibroblasts.

Cell-surface changes accompanying aging in human diploid fibroblasts: effects of tissue, donor age and genotype

The generality of age-related changes in concanavalin A (Con A)-mediated red blood cell (RBC) adsorption to human diploid fibroblasts was investigated on fibroblast-like cells from fetal lung, heart, liver, skin and muscle tissues. All the cells examined showed the continuous increase from early passages in RBC adsorption with the RBC coating method (in which Con A-coated RBCs are adsorbed to fibroblasts) and the incraease only at phase III with the fibroblast coating method (in which RBCs are adsorbed to Con A-coated fibroblasts). All of the four strains of lung fibroblasts gave nearly the same extent of the age-related change in RBC adsorption, when expressed as a function of percentage life span consumed, indicating that the change in RBC adsorption is independent of genetic heterogeneity and conditions of primary culture. Liver and heart fibroblasts also gave results similar to those of lung fibroblasts. However, skin and muscle fibroblasts were lower in their RBC adsorption capacity throughout the life span. The continuous age-related increase in RBC adsorption to these cells could be sensitized by using glutaraldehyde-prefixed RBCs, trypsinized RBCs or phytohemagglutinin P in place of Con A. The relevance of the phenotype of in vitro aging revealed by RBC adsorption to in vivo aging was also demonstrated on skin fibroblasts from different ages of donors using glutaraldehyde-prefixed RBCs. In addition, fibroblasts from patients with Werner's syndrome, an hereditary disease manifested by early and widespread degenerative changes, showed senescent phenotype in RBC adsorption even at early passages.

Synthesis of types I, III and AB2 collagen by chick tendon fibroblasts in vitro

Tendons from 14--17-day-old chick embryos contain predominantly type I collagen and about 5% AB2 collagen; type III collagen is not detectable by biochemical methods, such as sodium dodecyl sulfate/polyacrylamide gel electrophoresis or cyanogen bromide pattern, but can be visualized by immunofluorescence staining with collagen-type-specific antibodies. Similarly, freshly dissociated tendon cells secrete only type I collagen into the culture medium but no significant amounts of type III collagen [Uitto, J., Lichtenstein, J. R., and Bauer, E. A. (1976) Biochemistry, 15, 4935--4942]. Transfer of tendon cells from chick embryos to monolayer conditions, however, initiated synthesis of type III collagen in about 10% of the cells within three days, as visualized by immunofluorescence staining. Secretion of type III collagen into the culture medium can also be detected by sodium dodecyl sulfate/polyacrylamide gel electrophoresis. With increasing number of passages the number of cells producing type III collagen reached levels of about 80% after the third passage, while 90% of all cells stained positively for type I collagen. This is reflected by an increase of production of type III collagen as determined by CM-cellulose chromatography. Using velocity sedimentation, the secretion of type III procollagen and of pN-collagen (carrying the amino-terminal extension only), into the culture medium of a second-passage tendon cell culture was detected. This study provides new evidence that the phenotype of cells may alter during transfer from the environment in vivo to conditions in vitro and that additional changes may occur with time in culture.