Hepatocyte growth factor and macrophage-stimulating protein are upregulated during excisional wound repair in rats

Hepatocyte growth factor (HGF) and macrophage-stimulating protein (MSP) are structurally related molecules that stimulate epithelial cell proliferation and migration. MSP also acts directly as a chemoattractant for resident macrophages. These activities are integral to the wound repair processes of inflammation, epithelialization and tissue remodelling. To begin to examine the involvement of HGF and MSP in healing of cutaneous wounds we have mapped the temporal expression of these two molecules and their receptors, MET and RON respectively, in adult rat excisional wounds. Four 2x2-cm full-thickness excisional wounds were created on the dorsum of 18 rats, and biopsies were taken through the wounds at 3, 5, 7, 14, 21, and 28 days postwounding. These biopsies were analyzed using immunofluorescent staining and in situ hybridization (ISH). The number of cells staining positively for HGF and MET significantly increased in response to wounding. HGF staining and mRNA peaked at 7 days postwounding whereas MET was upregulated earlier, peaking after 3 days. Both HGF and MET protein were observed in fibroblasts of the dermis and in the newly forming granulation tissue. ISH studies also revealed that fibroblasts at the wound edges and within the newly forming granulation tissue also expressed HGF and c-met mRNA. Immunofluorescent staining revealed both MSP and RON within the wound, with maximum staining occurring between 7 and 21 days for both the ligand and receptor. In addition, MSP co-localized with a small subset of ED1-positive cells (monocytes). In contrast, ED2-positive cells (macrophages) did not co-localize with MSP. Thus, increased expression of HGF, MSP and their receptors MET and RON respectively was observed in response to wounding. Furthermore, MSP co-localization with a subset of monocytes may confirm a role for MSP in the activation of mature macrophages, which may be important in tissue remodelling.     

Periostin localizes to cells in normal skin, but is associated with the extracellular matrix during wound repair

Epidermal tissue repair represents a complex series of temporal and dynamic events resulting in wound closure. Matricellular proteins, not normally expressed in quiescent adult tissues, play a pivotal role in wound repair and associated extracellular matrix remodeling by modulating the adhesion, migration, intracellular signaling, and gene expression of inflammatory cells, pericytes, fibroblasts and keratinocytes. Several matricellular proteins show temporal expression during dermal wound repair, but the expression pattern of the recently identified matricellular protein, periostin, has not yet been characterized. The primary aim of this study was to assess whether periostin protein is present in healthy human skin or in pathological remodeling (Nevus). The second aim was to determine if periostin is expressed during dermal wound repair. Using immunohistochemistry, periostin reactivity was detected in the keratinocytes, basal lamina, and dermal fibroblasts in healthy human skin. In pathological nevus samples, periostin was present in the extracellular matrix. In excisional wounds in mice, periostin protein was first detected in the granulation tissue at day 3, with levels peaking at day 7. Periostin protein co-localized with α-smooth muscle actin-positive cells and keratinocytes, but not CD68 positive inflammatory cells. We conclude that periostin is normally expressed at the cellular level in human and murine skin, but additionally becomes extracellular during tissue remodeling. Periostin may represent a new therapeutic target for modulating the wound repair process.     

Hormonal control of leydig cell differentiation

Summary The fine structure of the testicular interstitial cells of the 9-day-old mouse submitted to stimulation with human chorionic gonadotropin (HCG) is reported. As was previously described (Baillie 1964) the interstitial tissue of the prepubertal mouse testis is characterized by the presence of well differentiated epithelioid cells at a quiescent stage. They are characterized by large cytoplasmic depots of lipid droplets and glycogen particles in contrast to poorly developed membranous organelles. These cells are highly sensitive to the action of gonadotropins. Five daily injections of HCG cause their differentiation into cells with active secretory characteristics. The gonadotropin induces a marked depletion of the lipid droplets and glycogen content of the cytoplasm, concurrent with an unusual development of the membranes of the agranular endoplasmic reticulum. Golgi complexes and rough reticulum are prominent. Several changes also appear in the nucleus, especially in the nucleolus.The correlation of the present electron microscopic study of the interstitial cells under HCG stimulation with previous biochemical and physiological findings tentatively suggests that the immature Leydig cells exhibit the basic organization necessary for biosynthesis of steroid hormones.     

Immunolocalization of tenascin-C, alpha9 integrin subunit, and alphavbeta6 integrin during wound healing in human oral mucosa.

Tenascin-C (TN-C) and its isoforms are multidomain extracellular matrix (ECM) proteins that are believed to be involved in the regulation of stromal-epithelial interactions. Some of the interactions between TN-C and cells are mediated by integrins. In this study we analyzed the expression of TN-C and its large molecular weight splice isoform (TN-C(L)) and the putative TN-C-binding alpha9 and alphavbeta6 integrins during human wound repair. In 3-day-old oral mucosal wounds, immunoreactivity for alpha9 integrin localized abundantly at the migrating basal wound epithelial cells. TN-C and TN-C(L) were localized in the matrix between and underneath alpha9-expressing epithelial cells. In parallel with gradual downregulation of alpha9 integrin immunoreactivity in 7-day and older wounds, the expression of alphavbeta6 integrin was temporarily induced. Integrin alphavbeta6 co-localized in the same area as TN-C and TN-C(L) immunoreactivity at the cell-cell contacts of the basal and suprabasal cell layers of the wound epithelium. During granulation tissue formation and reorganization from 7 to 28 days after wounding, TN-C and TN-C(L) were abundantly localized in the granulation tissue. The findings show that TN-C(L) is expressed under the migrating epithelial front and in the granulation tissue during matrix deposition in wound repair. Preferential localization of alpha9 integrin in migrating epithelial cells and of alphavbeta6 integrin in epithelium after wound closure suggests different functions for these integrins in wound repair.     

The role of nuclear hormone receptors in cutaneous wound repair

The cutaneous wound repair process involves balancing a dynamic series of events ranging from inflammation, oxidative stress, cell migration, proliferation, survival and differentiation. A complex series of secreted trophic factors, cytokines, surface and intracellular proteins are expressed in a temporospatial manner to restore skin integrity after wounding. Impaired initiation, maintenance or termination of the tissue repair processes can lead to perturbed healing, necrosis, fibrosis or even cancer. Nuclear hormone receptors (NHRs) in the cutaneous environment regulate tissue repair processes such as fibroplasia and angiogenesis. Defects in functional NHRs and their ligands are associated with the clinical phenotypes of chronic non‐healing wounds and skin endocrine disorders. The functional relationship between NHRs and skin niche cells such as epidermal keratinocytes and dermal fibroblasts is pivotal for successful wound closure and permanent repair. The aim of this review is to delineate the cutaneous effects and cross‐talk of various nuclear receptors upon injury towards functional tissue restoration. Copyright © 2014 John Wiley & Sons, Ltd.     

The CXC chemokine cCAF stimulates precocious deposition of ECM molecules by wound fibroblasts, accelerating development of granulation tissue

Background  

During wound repair, fibroblasts orchestrate replacement of the provisional matrix formed during clotting with tenascin, cellular fibronectin and collagen III. These, in turn, are critical for migration of endothelial cells, keratinocytes and additional fibroblasts into the wound site. Fibroblasts are also important in the deposition of collagen I during scar formation. The CXC chemokine chicken Chemotactic and Angiogenic Factor (cCAF), is highly expressed by fibroblasts after wounding and during development of the granulation tissue, especially in areas where extracellular matrix (ECM) is abundant. We hypothesized that cCAF stimulates fibroblasts to produce these matrix molecules.     

Cicatrization of the skin of the 7-day-old chick embryo cultured in vitro

A morphological study of in vitro wound healing has been performed by light, transmission and scanning electron microscopy in dorsal thoraco-lumbar skin of 7-day chick embryos. A circular wound, 750 microns in diameter, was punched out of dorsal skin, removing epidermis and the underlying dense dermis. Wound closure was completed within 96 to 120 hours. Feather bud development was not observed at the wound site. The epidermis began to migrate some 24 h after the wounding; the migration of peridermal cells preceded that of basal epidermal cells by some 12 hours. Mechanisms of the epidermal migration were similar to those observed in situ during wound healing of the integument in 5-day chick embryos (THEVENET, 1981), Superficial epithelization of bare dermis occurred as soon as 12 h after the injury. Cytoplasm of dermal cells exhibited many microtubules and a dilated rough endoplasmic reticulum. During the first 48 h, the epidermal cells established direct contacts and zones of close parallel apposition with epithelized dermal cell processes. The basement membrane lamina densa was maintained at the edges of the wound without retraction or ruffling. It was reconstituted concomitantly with the epidermal migration within 72 h. Cytoplasm of migratory epidermal and epithelized dermal cells exhibited many cytoskeleton structures.     

Ultrastructural immunolocalization of basic fibroblast growth factor in fibroblasts and extracellular matrix

Basic fibroblast growth factor (bFGF) is thought to play an important role in normal tissue repair and wound healing. It is a potent mitogenic and chemotactic factor for fibroblasts, regulating proliferation and extracellular matrix (ECM) production by these cells. In this study, we present morphologic evidence of the ultrastructural location of bFGF in fibroblasts and ECM using several antibodies, tissues, and species. Distinct labeling is seen in the nuclei of fibroblasts and some labeling in the cytosol. Immunolabeling of the cytosol excludes organelles involved in the usual secretory pathway, such as rough endoplasmic reticulum, Golgi apparatus, and secretory vacuoles. The same labeling is observed with either polyclonal or monoclonal antibodies. We suggest that bFGF functions as a nuclear protein in fibroblasts and is not secreted by a normal secretory pathway. Fibroblasts may export bFGF via unique cellular pathways that are clearly distinct from classic signal peptide mediated secretion. This may provide a source for ECM-resident bFGF. The same antibodies show different labeling intensity in the ECM. This protein, through integration into the ECM, may act as a local regulator and promote regeneration of these tissues after wounding. Direct evidence is the dramatic reduction of bFGF labeling in axotomized rat ECM collagen fibers versus control animals. Accepted: 20 December 1999     

Thymosin beta4 promotes matrix metalloproteinase expression during wound repair

Immobilized patients, diabetics, and the elderly suffer from impaired wound healing. The 43-amino acid angiogenic peptide thymosin beta4 (Tbeta4) has previously been found to accelerate dermal wound repair in rats, aged mice, and db/db diabetic mice. It also promotes corneal repair in both normal rats and mice. Because proteinases are important in wound repair, we hypothesized that Tbeta4 may regulate matrix metalloproteinase (MMP) expression in cells that are involved in wound repair. Analysis by RT-PCR of whole excised mouse dermal wounds on days 1, 2, and 3 after wounding showed that Tbeta4 increased several metalloproteinases, including MMP-2 and -9 expression by several-fold over control on day 2 after wounding. We further analyzed the metalloproteinases secreted in response to exogenous Tbeta4 by cells normally present in the wound. Western blot analysis of cultured keratinocytes, endothelial cells, and fibroblasts that were treated with increasing concentrations of Tbeta4 showed increases in the levels of MMP-1, -2, and -9 in a cell-specific manner. Tbeta4 also enhanced the secretion of MMP-1 and MMP-9 by activated monocytes. The central actin-binding domain, amino acids 17-23, had all of the activity for metalloproteinase induction. We conclude that part of the wound healing activity of Tbeta4 resides in its ability to increase proteinase activity via its central actin-binding domain. Thus, Tbeta4 may play a pivotal role in extracellular matrix remodeling during wound repair.     

Platelet-derived growth factor and transforming growth factor-beta enhance tissue repair activities by unique mechanisms

Platelet-derived growth factor (PDGF) and transforming growth factor-beta (TGF-beta) markedly potentiate tissue repair in vivo. In the present experiments, both in vitro and in vivo responses to PDGF and TGF-beta were tested to identify mechanisms whereby these growth factors might each enhance the wound-healing response. Recombinant human PDGF B-chain homodimers (PDGF-BB) and TGF-beta 1 had identical dose-response curves in chemotactic assays with monocytes and fibroblasts as the natural proteins from platelets. Single applications of PDGF-BB (2 micrograms, 80 pmol) and TGF-beta 1 (20 micrograms, 600 pmol) were next applied to linear incisions in rats and each enhanced the strength required to disrupt the wounds at 5 d up to 212% of paired control wounds. Histological analysis of treated wounds demonstrated an in vivo chemotactic response of macrophages and fibroblasts to both PDGF-BB and to TGF-beta 1 but the response to TGF-beta 1 was significantly less than that observed with PDGF-BB. Marked increases of procollagen type I were observed by immunohistochemical staining in fibroblasts in treated wounds during the first week. The augmented breaking strength of TGF-beta 1 was not observed 2 and 3 wk after wounding. However, the positive influence of PDGF-BB on wound breaking strength persisted through the 7 wk of testing. Furthermore, PDGF-BB-treated wounds had persistently increased numbers of fibroblasts and granulation tissue through day 21, whereas the enhanced cellular influx in TGF-beta 1-treated wounds was not detectable beyond day 7. Wound macrophages and fibroblasts from PDGF-BB-treated wounds contained sharply increased levels of immunohistochemically detectable intracellular TGF-beta. Furthermore, PDGF-BB in vitro induced a marked, time-dependent stimulation of TGF-beta mRNA levels in cultured normal rat kidney fibroblasts. The results suggest that TGF-beta transiently attracts fibroblasts into the wound and may stimulate collagen synthesis directly. In contrast, PDGF is a more potent chemoattractant for wound macrophages and fibroblasts and may stimulate these cells to express endogenous growth factors, including TGF-beta, which, in turn, directly stimulate new collagen synthesis and sustained enhancement of wound healing over a more prolonged period of time.     

Fine structural changes in uterine smooth muscle and fibroblasts in response to estrogen

The fine structure of the estrogen-primed uterus was examined in two series of rats, with emphasis upon the alterations in smooth muscle cells and fibroblasts. The first series of animals were mature animals that were sacrificed at diestrus or estrus. The second series consisted of prepubertal rats (57–70 g) that received subcutaneous injections of estradiol-17 β in 20% alcohol. Four groups of animals received the hormone twice daily for 3 days for a total dose of 0.06, 0.6, 6.0, or 60.0 µg, respectively. An estrogenic response was observed in all groups as indicated by an increase in uterine weight. Control groups consisted of either untreated animals or animals receiving 20% alcohol. All animals were sacrificed on the 4th day. The fibroblasts and smooth muscle cells in the controls were similar to their counterparts in the mature animal in diestrus. They were small, contained relatively little rough endoplasmic reticulum, and the connective tissue cells appeared like fibrocytes. All of the estrogen-treated animals were similar in appearance and were comparable to their counterparts in the mature animal in estrus. Both the smooth muscle cells and the fibroblasts were increased in size, demonstrated a marked enlargement and dilation of ergastoplasmic cisternae, and contained increased numbers of attached and free cytoplasmic ribosomes. The presence of an extensive rough endoplasmic reticulum in the smooth muscle cells of the stimulated uterus is in marked contrast to the appearance of these cells in other tissues. These observations correlate with previous biochemical studies by other workers, in which estrogens have been shown to promote the synthesis of uterine RNA, collagen, and noncollagenous protein, and suggest that smooth muscle cells may participate in the synthesis of connective tissue proteins.     

The testicular interstitial tissue of the amphibian Physalaemus fuscumaculatus

Summary The fine structure of the interstitial tissue of the testis of Physalaemus fuscumaculatus is described. Epithelioid cells identified as Leydig cells occur scattered in the interstitial tissue. Their cytoplasm contains a well developed smooth and rough surfaced endoplasmic reticulum arranged in whorls. The mitochondria present typical tubular cristae and unusual inclusions of a granular material. In spite of the distinctive characteristics reported here, it is assumed that the function of the Leydig cells is basically similar to that of the steroid synthetizing cells of the testicular interstitial tissue of higher vertebrates.An unusual feature is the presence of numerous melanophores randomly distributed in the capsule of the testis and in the interstitium. They are polyhedric cells with poorly developed organelles, numerous melanosomes, and long cytoplasmic processes.A large amount of collagen is present in the intercellular spaces closely related with undifferentiated cells, most of which are assumed to be fibroblasts.This work was supported by a Grant of the Consejo Nacional de Investigationes Científicas y Técnicas, and by Grant M-63-121 from the Population Council.Career investigators of the Consejo Nacional de Investigationes Científicas y Técnicas.Research Fellow of the same Institution.     

Fine structure and its functional properties of the endostyle of Ascidians,Ciona intestinalis

Summary For the purpose used in understanding thyroid phylogenesis, the fine structure and the iodine metabolism of the endostyle of Ascidians,Ciona intestinalis, was studied by electron microscopy and electron microscopic autoradiography. There are 8 kinds of zones in the endostyle.Zone 1, 3, and 5 cells, especially zone 1 cells, are characterized by numerous long cilia. These cells which show no indications of protein-secretion but numerous small vesicles and cytoplasmic filaments might play a role in catching and transporting food, absorption of liquid and supporting the endostylar construction.Zone 2, 4, and 6 cells are large and characterized by well developed rough endoplasmic reticulum and numerous electron-dense secretory granules which are considered to be synthesized in the rough endoplasmic reticulum and transported to the Golgi apparatus to mature. They, which are somewhat similar to the pancreatic exocrine cells in fine structure, are believed to secrete the proteinous or mucoproteinous substances which might be related to the digestion of food.Zone 7 and 8 cells which might be homologous to the thyroid cell of the higher vertebrate contains poorly developed rough endoplasmic reticulum, small Golgi apparatus, a few multivesicular bodies, a few lysosomes, and numerous small vesicles. In addition zone 8 cells bear cilia on their apical surface. The cytoplasmic characteristics of these cell types, especially of zone 8 cells, are fairly similar to those of type 2C and type 3 cells of the endostyle of a larval lamprey, though the rough endoplasmic reticulum is not so well developed. By electron microscopic autoradiography numerous silver grains were observed on the apical cell membrane region of zone 7 and 8 cells, especially of zone 8 cells, 1, 4, 6, 16 and 24 hours after immersion in sea water containing¹²⁵I. This fact suggests that the iodination takes place in the apical cell membrane region of these cells. The materials in the endostylar lumen is washed away during the fixation and dehydrating processes of the tissue. Therefore, the possibility of iodination of thyroglobulin-like substances taking place within the endostylar lumen cannot be ruled out. Grains were also found in the multivesicular bodies and lysosomes after 4, 6, 16 and 24 hours, especially 16 and 24 hours. It seems that the organic iodine might be reabsorbed into the cytoplasm of these cells.This investigation was supported by research grant from Dr. Henry C. Buswell Research Fellowship.On leave from Department of Anatomy, Hiroshima University, School of Medicine, as a Visiting Research Professor. The authors wish to express their hearty thanks to Dr. Oliver P. Jones for his valuable criticism.     

Ultrastructure of the eyes of the grass shrimp,Palaemonetes pugio

Summary The cone cells and corneagenous cells possess extensive networks of smooth tubular endoplasmic reticulum that may be involved in optical reflectance and light-adaptational responses, respectively. The extracellular basal lamina of the basement membrane is confluent with glial cell capillary walls and may prove to be a viaduct for the transmission of hemolymph-borne substances to the retina or of retinal degradation products to the hemolymph. In addition to dense pigment granules, the distal pigment cells are shown for the first time to contain migratory reflecting platelets that are usually polymorphic in light-adapted eyes but are rectangular in dark-adapted eyes. In the latter these plates become aligned against the crystalline cones and presumably contribute to the reflection superposition optics of the grass shrimp. Dark-adapted retinular cells possess well-developed perirhabdomal cisternae, oblong or ovoid mitochondria, generally vesicular rough endoplasmic reticulum, and occasional, spherical, calcium-like intrarhabdomal inclusions. Light-adapted retinular cells possess poorly developed perirhabdomal cisternae, lamelliform rough endoplasmic reticulum, and condensed mitochondria frequently associated with lipid droplets and pigment granules. The cytoplasmic boundaries of the reflecting pigment cells expand into the extracellular spaces between individual ommatidial retinular cells during dark adaptation and recede to the interommatidial extracellular spaces during light adaptation. Cytoplasmic microfilament bundles found only at the bases of partially light-adapted rhabdomeric microvilli may be involved in microvillar shortening.     

The process of skin healing in experimentally wounded carp

The process of skin healing was studied in thin sections of adult mirror-carp, superficially wounded with a razor blade in a scaleless region. Shortly after wounding, epidermal cells from both sides of the wound moved towards the wound cavity. The cells moved as compact groups, without severing the normal intercellular desmosomes. The moving cells displayed phagocytotic activity of cellular debris during the migration. The phagosomes reacted with diaminobenzidine, revealing strong peroxidase content. The normally abundant pinocytotic vesicles from the basal layer of filament cells vanished during the first hour after wounding, and reappeared after 2 days; 24 h after wounding, desmosomes interconnected the filament cells from both sides of the wound. Due to profuse mucus secretion, the number of mucous cells from the epidermal stratum was markedly reduced. Rodlet cells appeared 1 h after wounding in the external region of the epidermis. There was pronounced increase in alkaline phosphatase content of the pavement cells 10 min after wounding; this enzyme appeared around the ridges of the pavement cells and inside the mucous cells 20 min later.
In the dermis, the region surrounding the wound was darkened, blood cells extravasated, and penetrated partially into the epidermis. After 2 days, dermal fibroblasts displayed intense phagocytosis; after 8 days they were particularly abundant in the region of regenerating tissue and were secreting large quantities of collagen. Marked changes in the relative frequency of the different types of leucocyte occurred during the post-wounding days.     

Fine structure,pattern of division,and course of wound phloem in Coleus blumei

The wound phloem bridges which have developed six days after interrupting an internodal vascular bundle contain wound sieve-elements, companion cells, and phloem parenchyma cells. An analysis of the meristematic activity responding to the wounding clearly demonstrates that three consecutive divisions are prerequisite to the formation of phloem mother-cells. Companion cells are obligatory sister cells of wound sieve-elements, connected to the latter by specific plasmatic strands and provided with a dense protoplast. Six days after wounding most of the wound sieve-elements are still at a nucleate state of development, but already have characteristic P-protein bodies and plastids containing sieve-element starch. Their cytoplasmic differentiation corresponds to the changes recorded during maturation of ordinary sieve elements. Sieve-plate pores penetrate through preexisting parenchyma cell walls, only, and develop from primary pitfield-plasmodesmata. Wound sieve-elements do not connect to preexisting bundle sieve-elements, they open a new tier of young sieve elements produced by cambial activity.     

Scanning electron microscopy of stromal cells of human placental villi throughout pregnancy

Summary Morphological changes in fixed stromal cells and Hofbauer cells were studied throughout pregnancy in different types of placental chorionic villi by scanning electron microscopy. In the mesenchymal villus the fixed stromal cells were characterized by thin cytoplasmic processes. Hofbauer cells exhibited blebs on their surface. Large sail-like processes with a crescent profile which surrounded well developed stromal channels and a small cell body typified the small reticulum cells of the immature intermediate villus. The Hofbauer cells here displayed blebs, microplicae and large lamellipodia. Short cytoplasmic expansions and a large cell body characterized the fibroblasts present inside the stem villus. Hofbauer cells were rare, having blebs or a few short lamellipodia. The mature intermediate villus contained small and large reticulum cells. The latter had a much larger cell body than the small ones and displayed a few short cytoplasmic processes partly delimiting narrow incomplete stromal channels. Occasional Hofbauer cells with small microplicae and/or blebs were present. The small reticulum cells and fibroblasts present in the terminal villus showed similar morphological features as above. However, the former exhibited less developed cytoplasmic extensions and therefore no stromal channels were observed. In the terminal villus, the morphology of the rare Hofbauer cells was similar to that found in the mature intermediate villus.     

WOUND HEALING AND COLLAGEN FORMATION : VI. The Origin of the Wound Fibroblast Studied in Parabiosis

Healing skin wounds were studied in a series of parabiotic rats. The femurs of one parabiont of each pair were shielded whilst both animals were given 800 r from a Co⁶⁰ source. The animals were wounded 3 days after irradiation. Each animal with partially shielded marrow was then given tritiated thymidine intraperitoneally daily while the cross-circulation was arrested by clamping. After the thymidine-³H had cleared the blood, the clamp was released. Animals were sacrificed, and wounds were prepared for radioautography 1, 2, and 6 days after wounding. In the wounds of the shielded animals thymidine-³H was observed in epidermis, endothelium, leukocytes, fibroblasts, and mast cells. Only neutrophilic leukocytes, monocytes, and lymphocytes were labeled, as determined by light and electron microscope radioautography, in the wounds of each nonshielded parabiont. None of the many fibroblasts present were found to contain label in the wounds of the nonshielded parabionts through the 6 day period. These observations provide further evidence that wound fibroblasts do not arise from hematogenous precursors and, therefore, must arise from adjacent connective tissue cells.     

Dynamics of cell movement during the wound repair of human surface respiratory epithelium.

Epithelial wound repair represents an important process by which the epithelial barrier integrity recovers after wounding. To evaluate and quantify the dynamics of surface airway cell movement during the wound repair process, we developed an in vitro wounding model of human respiratory cells in culture and we analyzed the wound repair by using videomicroscopic and image analysis techniques. We observed that wound closure occurred within 6 hours, due to the spreading and migration of the cells surrounding the wounded surface. The migration rate of the cells at the leading edge of the wound surface increased progressively up to 26 microns/h during the repair process which was characterized by a uniform centripetal direction of cell movement. The distance travelled by these cells was 2.5 fold longer than the distance travelled by ciliated cells which were located far from the wound area. These results suggest that cell migration after wounding is an important process by which the respiratory epithelial barrier integrity is maintained.     

The development of a collagenous connective tissue in the locust, Locusta migratoria

The ejaculatory duct of adult male locusts is surrounded by a thick layer of collagenous tissue. It starts to develop during the second instar when a group of cells come to lie adjacent to the basal regions of the epidermal cells which form the duct. From the fourth instar onwards, connective tissue is present between these cells. The matrix contains many collagen fibrils, some of which are very large and of irregular cross section. The banding periodicity is about 625 A. The cells differentiate into typical fibroblasts with highly dilated rough endoplasmic reticulum and small Golgi complexes. In the sexually mature adult, the cells are smaller and appear less active.