1
|
Compositional and in Vitro Evaluation of Nonwoven Type I Collagen/Poly-dl-lactic Acid Scaffolds for Bone Regeneration. J Funct Biomater 2015; 6:667-86. [PMID: 26251924 PMCID: PMC4598677 DOI: 10.3390/jfb6030667] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2015] [Revised: 07/20/2015] [Accepted: 07/30/2015] [Indexed: 11/23/2022] Open
Abstract
Poly-dl-lactic acid (PDLLA) was blended with type I collagen to attempt to overcome the instantaneous gelation of electrospun collagen scaffolds in biological environments. Scaffolds based on blends of type I collagen and PDLLA were investigated for material stability in cell culture conditions (37 °C; 5% CO2) in which post-electrospinning glutaraldehyde crosslinking was also applied. The resulting wet-stable webs were cultured with bone marrow stromal cells (HBMSC) for five weeks. Scanning electron microscopy (SEM), confocal laser scanning microscopy (CLSM), Fourier transform infra-red spectroscopy (FTIR) and biochemical assays were used to characterise the scaffolds and the consequent cell-scaffold constructs. To investigate any electrospinning-induced denaturation of collagen, identical PDLLA/collagen and PDLLA/gelatine blends were electrospun and their potential to promote osteogenic differentiation investigated. PDLLA/collagen blends with w/w ratios of 40/60, 60/40 and 80/20 resulted in satisfactory wet stabilities in a humid environment, although chemical crosslinking was essential to ensure long term material cell culture. Scaffolds of PDLLA/collagen at a 60:40 weight ratio provided the greatest stability over a five-week culture period. The PDLLA/collagen scaffolds promoted greater cell proliferation and osteogenic differentiation compared to HMBSCs seeded on the corresponding PDLLA/gelatine scaffolds, suggesting that any electrospinning-induced collagen denaturation did not affect material biofunctionality within 5 weeks in vitro.
Collapse
|
2
|
Leme DM, Primo FL, Gobo GG, da Costa CRV, Tedesco AC, de Oliveira DP. Genotoxicity assessment of reactive and disperse textile dyes using human dermal equivalent (3D cell culture system). JOURNAL OF TOXICOLOGY AND ENVIRONMENTAL HEALTH. PART A 2015; 78:466-480. [PMID: 25785560 DOI: 10.1080/15287394.2014.999296] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Thousands of dyes are marketed daily for different purposes, including textile dyeing. However, there are several studies reporting attributing to dyes deleterious human effects such as DNA damage. Humans may be exposed to toxic dyes through either ingestion of contaminated waters or dermal contact with colored garments. With respect to dermal exposure, human skin equivalents are promising tools to assess in vitro genotoxicity of dermally applied chemicals using a three-dimensional (3D) model to mimic tissue behavior. This study investigated the sensitivity of an in-house human dermal equivalent (DE) for detecting genotoxicity of textile dyes. Two azo (reactive green 19 [RG19] and disperse red 1[DR1]) dyes and one anthraquinone (reactive blue 2 [RB2]) dye were analyzed. RG19 was genotoxic for DE in a dose-responsive manner, whereas RB2 and DR1 were nongenotoxic under the conditions tested. These findings are not in agreement with previous genotoxicological assessment of these dyes carried out using two-dimensional (2D) cell cultures, which showed that DR1 was genotoxic in human hepatoma cells (HepG2) and RG19 was nongenotoxic for normal human dermal fibroblasts (NHDF). These discrepant results probably may be due to differences between metabolic activities of each cell type (organ-specific genotoxicity, HepG2 and fibroblasts) and the test setup systems used in each study (fibroblasts cultured at 2D and three-dimensional [3D] culture systems). Genotoxicological assessment of textile dyes in context of organ-specific genotoxicity and using in vitro models that more closely resemble in vivo tissue architecture and physiology may provide more reliable estimates of genotoxic potential of these chemicals.
Collapse
Affiliation(s)
- Daniela Morais Leme
- a Departamento de Biologia Celular , Universidade Federal do Paraná (UFPR) , Curitiba , Paraná , Brazil
| | | | | | | | | | | |
Collapse
|
3
|
Abstract
Major skin loss from trauma or burns cannot always be replaced with the patient's own skin. An engineered skin replacement would restore the barrier function of the skin, remain permanently on the wound, and minimize late functional complications of wound contraction. Cultured epithelial autograft (CEA) sheets reproduce the epidermis' function and have been used in burn patients to close large wounds. There are several promising avenues for dermal replacement, but none has yet had wide clinical application.
Collapse
Affiliation(s)
- G G Gallico
- Department of Plastic Surgery, Massachusetts General Hospital, Boston, Massachusetts 02114
| | | |
Collapse
|
4
|
Li X, Shu R, Liu D, Jiang S. Different effects of 25-kDa amelogenin on the proliferation, attachment and migration of various periodontal cells. Biochem Biophys Res Commun 2010; 394:581-6. [PMID: 20214886 DOI: 10.1016/j.bbrc.2010.03.023] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2010] [Accepted: 03/04/2010] [Indexed: 10/19/2022]
Abstract
Previous studies have assumed that amelogenin is responsible for the therapeutic effect of the enamel matrix derivative (EMD) in periodontal tissue healing and regeneration. However, it is difficult to confirm this hypothesis because both the EMD and the amelogenins are complex mixtures of multiple proteins. Further adding to the difficulties is the fact that periodontal tissue regeneration involves various types of cells and a sequence of associated cellular events including the attachment, migration and proliferation of various cells. In this study, we investigated the potential effect of a 25-kDa recombinant porcine amelogenin (rPAm) on primarily cultured periodontal ligament fibroblasts (PDLF), gingival fibroblasts (GF) and gingival epithelial cells (GEC). The cells were treated with 25-kDa recombinant porcine amelogenin at a concentration of 10 microg/mL. We found that rPAm significantly promoted the proliferation and migration of PDLF, but not their adhesion. Similarly, the proliferation and adhesion of GF were significantly enhanced by treatment with rPAm, while migration was greatly inhibited. Interestingly, this recombinant protein inhibited the growth rate, cell adhesion and migration of GEC. These data suggest that rPAm may play an essential role in periodontal regeneration through the activation of periodontal fibroblasts and inhibition of the cellular behaviors of gingival epithelial cells.
Collapse
Affiliation(s)
- Xiting Li
- Department of Periodontology, Ninth People's Hospital, Shanghai Jiao Tong University, School of Medicine, Shanghai Key Laboratory of Stomatology, No. 639 Zhi Zao Ju Road, Shanghai 200011, China
| | | | | | | |
Collapse
|
5
|
HAYNES S, SHUTTLEWORTH C, KIELTY C. Keratinocytes express fibrillin and assemble microfibrils: implications for dermal matrix organization. Br J Dermatol 2008. [DOI: 10.1046/j.1365-2133.1997.1762185.x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
|
6
|
Kearney JN. Yorkshire Regional Tissue Bank—Circa 50 Years of Tissue Banking. Cell Tissue Bank 2006; 7:259-64. [PMID: 16823504 DOI: 10.1007/s10561-006-9006-z] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2005] [Accepted: 01/10/2006] [Indexed: 11/30/2022]
Affiliation(s)
- John N Kearney
- National Blood Service Tissue Services, Deansbrook Road, Middlesex, Edgware, UK.
| |
Collapse
|
7
|
Grayson RE, Yamakoshi Y, Wood EJ, Agren MS. The effect of the amelogenin fraction of enamel matrix proteins on fibroblast-mediated collagen matrix reorganization. Biomaterials 2006; 27:2926-33. [PMID: 16443269 DOI: 10.1016/j.biomaterials.2005.12.026] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2005] [Accepted: 12/07/2005] [Indexed: 02/04/2023]
Abstract
Enamel matrix proteins (EMP), extracted from developing porcine teeth, promote not only periodontal regeneration but also cutaneous wound healing presumably via the amelogenin fraction. Because it is unclear whether the effect of EMP can be ascribed to amelogenins, we compared EMP with recombinant amelogenin in the relaxed dermal equivalent (DE) in vitro model for early wound contraction. EMP and recombinant porcine amelogenin (rP172) at 1 mg/ml were incorporated into DEs composed of human dermal fibroblasts and a type I collagen matrix. The area reduction, as a measure of contraction, as well as fibroblast numbers and TGF-beta1 levels, were quantified over 7 days in culture in the presence of 10% foetal bovine serum. Both EMP and recombinant amelogenin increased contraction (p < 0.005) and fibroblast numbers (p < 0.005) compared with controls (acetic acid vehicle and 1mg/ml porcine serum albumin) and the positive control TGF-beta1 added at 10 ng/ml. Increased contraction with EMP and recombinant amelogenin was most pronounced after the first day of incubation and was associated with elevated (p < 0.005) TGF-beta1 levels in conditioned medium. In conclusion, the amelogenin component of EMP augmented fibroblast-driven collagen matrix remodelling, at least partially, by increasing the endogenous production of TGF-beta1. These effects of EMP/amelogenin may be beneficial for cutaneous wound healing.
Collapse
Affiliation(s)
- Rachel E Grayson
- Department of Biochemistry and Molecular Biology, University of Leeds, Leeds LS2 9JT, UK
| | | | | | | |
Collapse
|
8
|
O'Leary R, Wood EJ. A novel in vitro dermal wound-healing model incorporating a response to mechanical wounding and repopulation of a fibrin provisional matrix. In Vitro Cell Dev Biol Anim 2004; 39:204-7. [PMID: 14613333 DOI: 10.1290/1543-706x(2003)039<0204:anivdw>2.0.co;2] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Previously our laboratory, and others, described an in vitro model for the study of fibroblast wound repopulation. The so-called punch-wounded, fibroblast-populated collagen lattice has been used extensively in tissue repair research. We now identify certain shortcomings with this model, which have led to its enhancement by the introduction of a provisional matrix fabricated in situ from fibrinogen and alpha-thrombin. In the previous model, fibroblasts repopulate the wound defect (WD) as a monolayer of cells and on reaching confluence, a process reminiscent of fibroplasia fills the wound space. The enhanced model, with fibrin acting as a provisional matrix, allowed fibroblasts to repopulate the WD as a three-dimensional network of cells that were morphologically different from cells migrating over the collagen substratum of the previous model. Fibroblast repopulation of the fibrin matrix was typically around double the rate of repopulation of the empty wound space. We propose this model as an enhanced, yet sufficiently reproducible, model for the study of fibroblast responses to tissue damage. It can be further enhanced by the addition of other cell types and matrix components.
Collapse
Affiliation(s)
- R O'Leary
- School of Medicine, University of Leeds, Leeds, United Kingdom LS2 9JT
| | | |
Collapse
|
9
|
O'Leary R, Rerek M, Wood EJ. Fucoidan Modulates the Effect of Transforming Growth Factor (TGF)-.BETA.1 on Fibroblast Proliferation and Wound Repopulation in in Vitro Models of Dermal Wound Repair. Biol Pharm Bull 2004; 27:266-70. [PMID: 14758050 DOI: 10.1248/bpb.27.266] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Aberrant wound healing, either causing scarring or chronic wounds, is a significant cause of morbidity. There is therefore, considerable interest in agents which can modulate certain aspects of the wound healing process. Fucoidans, sulphated polyfucose polysaccharides which may be extracted from Fucus spp., have been shown to modulate the effects of a variety of growth factors through mechanisms thought to be similar to the action of heparin. We investigated the interaction between two commercial preparations of fucoidan and transforming growth factor (TGF)-beta(1). These preparations of fucoidan, as well as heparin, inhibited fibroblast proliferation at concentrations from 0.01 to 100 mg/ml. The anti-proliferative effects of 1 ng/ml TGF-beta(1) on dermal fibroblasts were abrogated by fucoidan preparation F7 when used at concentrations over 1 mg/ml. In a three dimensional in vitro model of wound repair, the fibroblast populated collagen lattice or "dermal equivalent", TGF-beta(1) reduced the rate of fibroblast repopulation of a wound defect created by punch biopsy. Addition of fucoidan to the model in the presence of TGF-beta(1) increased the rate of fibroblast repopulation of the wound and at 10 mg/ml of fucoidan the number of cells which had migrated into the wounded defect was similar to that of control cultures. These data suggest that fucoidan has properties which may be beneficial in the treatment of wound healing.
Collapse
Affiliation(s)
- Ronan O'Leary
- School of Medicine, University of Leeds, Leeds LS2 9JT, UK
| | | | | |
Collapse
|
10
|
Stephens P, Wall IB, Wilson MJ, Hill KE, Davies CE, Hill CM, Harding KG, Thomas DW. Anaerobic cocci populating the deep tissues of chronic wounds impair cellular wound healing responses in vitro. Br J Dermatol 2003; 148:456-66. [PMID: 12653737 DOI: 10.1046/j.1365-2133.2003.05232.x] [Citation(s) in RCA: 68] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
BACKGROUND Anaerobic cocci are estimated to be present in the deep tissues of over 50% of chronic skin wounds. While the part they play in the chronicity of these wounds is uninvestigated, anaerobic cocci have previously been shown to be involved in other chronic inflammatory human conditions. METHODS In this study the anaerobic microflora of the deep tissues of 18 patients with refractory chronic venous leg ulcers (mean age 80.3 years; mean duration > 24 months) was characterized using strict anaerobic culture conditions. The effect of the anaerobic organisms isolated from these tissues on extracellular matrix (ECM) proteolysis and cellular wound healing responses was studied using in vitro models. RESULTS Anaerobic organisms were present in the deep tissues of 14 of 18 wounds and were principally Peptostreptococcus spp. The effects of three Peptostreptococcus spp. isolated from these wounds (P. magnus, P. vaginalis and P. asaccharolyticus) on cellular wound healing responses were compared with those of two pathogenic organisms also isolated from these wounds (Pseudomonas aeruginosa and Citrobacter diversus). While the direct ECM proteolytic activity exhibited by the Peptostreptococcus spp. was limited, they did significantly inhibit both fibroblast and keratinocyte proliferation, but only at high concentrations. However, at lower concentrations peptostreptococcal supernatants profoundly inhibited keratinocyte wound repopulation and endothelial tubule formation. The magnitude of these effects varied between strains and they were distinct from those demonstrated by Pseudomonas aeruginosa and Citrobacter diversus. CONCLUSIONS These studies confirm the importance of anaerobic organisms in chronic wounds and demonstrate an indirect, strain-specific mechanism by which these microorganisms may play a part in mediating the chronicity of these wounds.
Collapse
Affiliation(s)
- P Stephens
- Department of Oral Surgery, Dental School, University of Wales College of Medicine, Cardiff, CF14 4XY, UK
| | | | | | | | | | | | | | | |
Collapse
|
11
|
Stephens P, Cook H, Hilton J, Jones CJ, Haughton MF, Wyllie FS, Skinner JW, Harding KG, Kipling D, Thomas DW. An analysis of replicative senescence in dermal fibroblasts derived from chronic leg wounds predicts that telomerase therapy would fail to reverse their disease-specific cellular and proteolytic phenotype. Exp Cell Res 2003; 283:22-35. [PMID: 12565817 DOI: 10.1016/s0014-4827(02)00021-6] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
The accumulation of senescent fibroblasts within tissues has been suggested to play an important role in mediating impaired dermal wound healing, which is a major clinical problem in the aged population. The concept that replicative senescence in wound fibroblasts results in reduced proliferation and the failure of refractory wounds to respond to treatment has therefore been proposed. However, in the chronic wounds of aged patients the precise relationship between the observed alteration in cellular responses with aging and replicative senescence remains to be determined. Using assays to assess cellular proliferation, senescence-associated staining beta-galactosidase, telomere length, and extracellular matrix reorganizational ability, chronic wound fibroblasts demonstrated no evidence of senescence. Furthermore, analysis of in vitro senesced fibroblasts demonstrated cellular responses that were distinct and, in many cases, diametrically opposed from those exhibited by chronic wound fibroblasts. Forced expression of telomerase within senescent fibroblasts reversed the senescent cellular phenotype, inhibiting extracellular matrix reorganizational ability, attachment, and matrix metalloproteinase production and thus produced cells with impaired key wound healing properties. It would appear therefore that the distinct phenotype of chronic wound fibroblasts is not simply due to the aging process, mediated through replicative senescence, but instead reflects disease-specific cellular alterations of the fibroblasts themselves.
Collapse
Affiliation(s)
- Phil Stephens
- Department of Oral Surgery, Medicine, and Pathology, University of Wales College of Medicine, Cardiff, UK
| | | | | | | | | | | | | | | | | | | |
Collapse
|
12
|
White P, Thomas DW, Fong S, Stelnicki E, Meijlink F, Largman C, Stephens P. Deletion of the homeobox gene PRX-2 affects fetal but not adult fibroblast wound healing responses. J Invest Dermatol 2003; 120:135-44. [PMID: 12535210 DOI: 10.1046/j.1523-1747.2003.12015.x] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The phenotype of fibroblasts repopulating experimental wounds in vivo has been shown to influence both wound healing responses and clinical outcome. Recent studies have demonstrated that the human homeobox gene PRX-2 is strongly upregulated in fibroblasts within fetal, but not adult, mesenchymal tissues during healing. Differential homeobox gene expression by fibroblasts may therefore be important in mediating the scarless healing exhibited in early fetal wounds. RNase protection analysis demonstrated that murine Prx-2 expression was involved in fetal but not adult wound healing responses in vitro. Using fibroblasts established from homozygous mutant (Prx-2-/-) and wild-type (Prx-2+/+) murine skin tissues it was demonstrated that Prx-2 affected a number of fetal fibroblastic responses believed to be important in mediating scarless healing in vivo; namely cellular proliferation, extracellular matrix reorganization, and matrix metalloproteinase 2 and hyaluronic acid production. These data demonstrate how Prx-2 may contribute to the regulation of fetal, but not adult, fibroblasts and ultimately the wound healing phenotype. This study provides further evidence for the importance of homeobox transcription factors in the regulation of scarless wound healing. A further understanding of these processes will, it is hoped, enable the targeting of specific therapies in wound healing, both to effect scarless healing and to stimulate healing in chronic, nonhealing wounds such as venous leg ulcers.
Collapse
Affiliation(s)
- Philip White
- Department of Oral Surgery, Medicine, and Pathology, University of Wales College of Medicine, Cardiff, UK
| | | | | | | | | | | | | |
Collapse
|
13
|
|
14
|
Stephens P, Davies KJ, Occleston N, Pleass RD, Kon C, Daniels J, Khaw PT, Thomas DW. Skin and oral fibroblasts exhibit phenotypic differences in extracellular matrix reorganization and matrix metalloproteinase activity. Br J Dermatol 2001; 144:229-37. [PMID: 11251552 DOI: 10.1046/j.1365-2133.2001.04006.x] [Citation(s) in RCA: 106] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
BACKGROUND Oral mucosal wounds are characterized by rapid re-epithelialization and remodelling. In vitro, oral mucosal fibroblasts exhibit a fetal phenotype with increased extracellular matrix reorganizational ability, migration and experimental wound repopulation when compared with skin fibroblasts. OBJECTIVES To investigate whether phenotypic differences in the expression and production of matrix metalloproteinase (MMP) -2 and tissue inhibitors of metalloproteinases (TIMPs) could play an important part in mediating these in vitro differences. METHODS Skin and oral mucosal fibroblast MMP-2, TIMP-1 and TIMP-2 mRNA expression and protein production were studied in three-dimensional collagen lattices using quantitative competitive reverse transcriptase-polymerase chain reaction (QCRT-PCR), enzyme-linked immunosorbent assay (ELISA), zymography and reverse zymography. RESULTS Oral mucosal fibroblasts exhibited increased levels of the 62-kDa active form of MMP-2 and lattice contraction when compared with skin fibroblasts. Oral mucosal and skin fibroblast MMP-2 gene expression and synthesis of the 72-kDa pro-MMP-2 was similar as assessed by QCRT-PCR, zymography and ELISA. Differential MMP-2 activation was, however, related to phenotypic differences in TIMP activity between the skin and oral mucosal fibroblasts, as assessed by reverse zymography. CONCLUSIONS These studies propose a mechanism by which fibroblast phenotype may contribute directly to the observed preferential remodelling of oral wounds.
Collapse
Affiliation(s)
- P Stephens
- Department of Oral Surgery, Medicine and Pathology, Dental School, University of Wales College of Medicine, Cardiff CF4 4XY, UK
| | | | | | | | | | | | | | | |
Collapse
|
15
|
Stephens P, Hiscox S, Cook H, Jiang WG, Zhiquiang W, Thomas DW. Phenotypic variation in the production of bioactive hepatocyte growth factor/scatter factor by oral mucosal and skin fibroblasts. Wound Repair Regen 2001; 9:34-43. [PMID: 11350638 DOI: 10.1046/j.1524-475x.2001.00034.x] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Hepatocyte growth factor/scatter factor (HGF/SF) is a pleiotropic growth factor produced principally by cells of mesenchymal origin. HGF/SF is an important mitogen, morphogen, and motogen and plays an important role in wound healing, tumorigenesis and particularly fetal development. Oral mucosal fibroblasts exhibit a fetal phenotype, including an increased extracellular matrix reorganizational ability, cellular migration and experimental wound repopulation in comparison to skin fibroblasts. In this study the expression, production, and bioactivity of HGF/SF by oral mucosal and skin fibroblasts was investigated. Although both oral mucosal and skin fibroblasts expressed HGF/SF, the oral mucosal fibroblasts produced significantly increased amounts of total HGF/SF (p < 0.01) as measured by enzyme-linked immunosorbent assay and bioactive HGF/SF as measured by cell scatter and cell-dissociation techniques (p < 0.01). The possible effect of increased HGF/SF in production mediating the previously described preferential responses of oral mucosal fibroblasts was studied in vitro. Reverse transcriptase-polymerase chain reaction-Western blotting and immunocytochemistry methods all showed that both oral mucosal and skin fibroblasts expressed and produced the c-Met receptor. Recombinant HGF (20-40 ng/mL) however, failed to affect fibroblast repopulation of monolayer wounds or cellular proliferation. In contrast, recombinant HGF significantly increased ECV304 wound repopulation. These studies provide direct evidence of another mechanism by which site-specific variations in fibroblast phenotype may contribute in a paracrine fashion to the rapid reepithelialization and revascularization of oral wounds.
Collapse
Affiliation(s)
- P Stephens
- Department of Oral Surgery, Medicine and Pathology, University of Wales College of Medicine, Cardiff, United Kingdom
| | | | | | | | | | | |
Collapse
|
16
|
Cook H, Davies KJ, Harding KG, Thomas DW. Defective extracellular matrix reorganization by chronic wound fibroblasts is associated with alterations in TIMP-1, TIMP-2, and MMP-2 activity. J Invest Dermatol 2000; 115:225-33. [PMID: 10951240 DOI: 10.1046/j.1523-1747.2000.00044.x] [Citation(s) in RCA: 141] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Chronic leg wounds are characterized by defective remodeling of the extracellular matrix, failure of reepithelialization, and prolonged inflammation. The hypothesis that this defective extracellular matrix remodeling is associated with phenotypic differences in the activity of the matrix metalloproteinases and tissue inhibitors of metalloproteinases was studied in chronic wound and patient-matched normal fibroblasts in three-dimensional collagen lattice systems. Chronic wound fibroblasts exhibited no differences in morphology or proliferation (p > 0.1) compared with patient-matched uninvolved dermal fibroblasts. The ability of chronic wound fibroblasts to reorganize extracellular matrix was significantly impaired, however, in comparison to the uninvolved dermal fibroblasts (p < 0.01). This difference in extracellular matrix reorganization was not related to differences in proliferation within the collagen lattices (p > 0.05) or attachment to type I collagen (p > 0.1). Marked differences were evident in matrix metalloproteinase-2 activity between chronic wound and patient-matched normal fibroblasts. Whereas levels of pro-matrix metalloproteinase-2 were similar between the two fibroblast populations (p > 0.1), the chronic wound fibroblasts exhibited significantly decreased levels of the 62 kDa active form of matrix metalloproteinase-2 (p < 0.01). Reverse zymography and enzyme-linked immunosorbent assay demonstrated that the decreased matrix metalloproteinase-2 activity was associated with increased production of tissue inhibitors of metalloproteinase-1 and -2 by the chronic wound fibroblasts (p < 0.05). Increased production of tissue inhibitors of metalloproteinases in chronic wound fibroblasts was also reflected in decreased levels of matrix metalloproteinase-1 (p < 0.005). These data suggest that the impaired ability of chronic wound fibroblasts to reorganize extracellular matrix in vitro is related to decreased levels of active matrix metalloproteinase-2 and matrix metalloproteinase-1 resulting from increased production of tissue inhibitors of metalloproteinase-1 and -2 by chronic wound fibroblasts. These findings provide a mechanism to explain the impaired cellular responses and extracellular matrix reorganization observed in chronic leg wounds in vivo.
Collapse
Affiliation(s)
- H Cook
- Department of Oral Surgery, Medicine and Pathology, University of Wales College of Medicine, Cardiff, U.K
| | | | | | | |
Collapse
|
17
|
Jayne DG, O'Leary R, Gill A, Hick A, Guillou PJ. A three-dimensional in-vitro model for the study of peritoneal tumour metastasis. Clin Exp Metastasis 2000; 17:515-23. [PMID: 10763918 DOI: 10.1023/a:1006606006878] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Peritoneal metastasis is a frequent complication of gastrointestinal malignancy. We have developed a three-dimensional model of the human peritoneum that simulates the metastatic process in vitro. Peritoneal fibroblasts were incorporated into collagen lattices, allowed to contract, then overlaid with mesothelial cells. Scanning and transmission electron microscopy showed the model to have similar physical properties to human peritoneum. Mesothelial expression of the beta1 integrin family, the basement membrane proteins fibronectin, laminin, collagen types III and IV, and the cell adhesion molecules ICAM-1, VCAM-1 and PECAM were assessed and showed similar results to in vivo tissue. Gastrointestinal tumour cells seeded onto the model exhibited mesothelial adhesion, cell spreading and vesicle formation, and invasion of the mesothelial monolayer on scanning electron microscopy. Two distinct patterns of tumour cell growth were observed using light microscopy: a superficial spreading layer, and discrete invasive deposits. Invasion was accompanied by disruption of the mesothelial monolayer, degradation and re-orientation of the matrix, and rudimentary tumour cell differentiation. We believe the use of this in vitro peritoneal model will facilitate the study of the molecular mechanisms involved in the metastatic process.
Collapse
Affiliation(s)
- D G Jayne
- Professorial Surgical Unit, St. James's University Hospital, Leeds, UK.
| | | | | | | | | |
Collapse
|
18
|
Scott KA, Wood EJ, Karran EH. A matrix metalloproteinase inhibitor which prevents fibroblast-mediated collagen lattice contraction. FEBS Lett 1998; 441:137-40. [PMID: 9877181 DOI: 10.1016/s0014-5793(98)01542-7] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
Matrix metalloproteinases (MMPs) and the specific tissue inhibitors of metalloproteinases (TIMPs) are involved in tissue turnover in normal and pathological processes including wound healing. Marimastat, a potent inhibitor of MMPs, was used to investigate the role of MMPs in an in vitro wound contraction model, the dermal equivalent, in which fibroblasts are grown in a collagen matrix. Marimastat inhibited fibroblast-mediated lattice contraction and this inhibition was reversible upon removal of the inhibitor, indicating that MMPs play an important role in fibroblast-mediated collagen lattice contraction, modelling what may happen when granulation tissue contracts in a healing wound.
Collapse
Affiliation(s)
- K A Scott
- School of Biochemistry and Molecular Biology, University of Leeds, UK
| | | | | |
Collapse
|
19
|
Myers SA, Wolowacz RG. Tetracycline-based MMP inhibitors can prevent fibroblast-mediated collagen gel contraction in vitro. Adv Dent Res 1998; 12:86-93. [PMID: 9972128 DOI: 10.1177/08959374980120012701] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Collagen gels in vitro can be contracted by fibroblasts. The role of matrix metalloproteinases (MMPs) in the contraction of collagen lattices by human neonatal foreskin fibroblasts (HuFFs) was investigated in tissue culture media supplemented by various doses of known gelatinase inhibitors. Fluorescent assays with model gelatinase substrates and media conditioned by fibroblasts apparently confirmed the ability of chemically modified tetracyclines (CMTs) to act as inhibitors of MMP2, and zymography demonstrated that this was the major cell-derived MMP activity. There were no observable effects on the rate of contraction of attached FPCLs containing 6 x 10(4) HuFFs (passages 18-25) with either CMT-5 or CMT-2 at all concentrations tested (0-100 micrograms/mL). However, at greater than 20 micrograms/mL doxycycline and greater than 5 micrograms/mL CMT-3, FPCL contraction was completely abolished. Quantitative assessment of cell viability by means of the MTT assay in monolayer and qualitatively within the FPCLs with CalceinAM suggested that differences were not due to cytotoxic effects. Seeding FPCLs with lower-passage fibroblasts produced identical trends. These results may implicate the involvement of MMPs in the process of gel contraction, although tetracyclines have effects additional to their ability to inhibit MMPs directly.
Collapse
Affiliation(s)
- S A Myers
- Smith & Nephew Group Research Centre, York, United Kingdom
| | | |
Collapse
|
20
|
al-Khateeb T, Stephens P, Shepherd JP, Thomas DW. An investigation of preferential fibroblast wound repopulation using a novel in vitro wound model. J Periodontol 1997; 68:1063-9. [PMID: 9407398 DOI: 10.1902/jop.1997.68.11.1063] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
To overcome the difficulties of studying wounding and wound repopulation in monolayer systems, a 3-dimensional model of wound repopulation has been developed which allows the in vitro investigation of fibroblast migration in response to experimental wounding. This model was utilized to determine whether fibroblasts derived from sites which demonstrate preferential healing (child and oral mucosal fibroblasts) possessed an increased ability to repopulate experimental wounds when compared to adult dermal fibroblasts. Fibroblasts were established from specimens derived from healthy donors undergoing minor elective surgery. Standard wounds were created in fibroblast populated collagen lattices (FPCLs) which were then overlaid upon an extracellular wound matrix. Fibroblast repopulation of the wounds was studied over 12 days using light- and scanning electron microscopy and quantified using computerized image analysis. Wound repopulation by fibroblasts derived from child donors (n = 3) was significantly (P < 0.001) more rapid than their adult tissue-matched counterparts (n = 3). Wound repopulation by oral mucosal fibroblasts (n = 3) was significantly greater than that exhibited by age-matched dermal fibroblasts (n = 3; P < 0.05). These differences were not reflected in differences in DNA synthesis (P > 0.5) or cell number (P > 0.5) within similar attached FPCL systems. These findings further support the concept of a gradual transition from the fetal to adult phenotype in wound healing. The potential applications of the model are discussed.
Collapse
Affiliation(s)
- T al-Khateeb
- Department of Oral and Maxillofacial Surgery, Faculty of Dentistry, Jordan University of Science and Technology, Irbid, Jordan
| | | | | | | |
Collapse
|
21
|
HAYNES S, SHUTTLEWORTH C, KIELTY C. Keratinocytes express fibrillin and assemble microfibrils: implications for dermal matrix organization. Br J Dermatol 1997. [DOI: 10.1111/j.1365-2133.1997.tb03695.x] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
|
22
|
Daniels JT, Kearney JN, Ingham E. An investigation into the potential of extracellular matrix factors for attachment and proliferation of human keratinocytes on skin substitutes. Burns 1997; 23:26-31. [PMID: 9115606 DOI: 10.1016/s0305-4179(96)00061-7] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
The purpose of this investigation was to assess the potential of commercially available extracellular matrix proteins, as enhancers of human keratinocyte attachment and proliferation, with a view to their incorporation into a skin equivalent. The following substrates were studied: type I and type IV collagen, fibronectin, gelatin and laminin. Human keratinocytes were cultured in low-calcium, serum-free medium. The number of cells attached to each substrate, observed under phase-contrast inverted microscopy in randomly selected fields of view, were counted 2 h afterseeding. Measurements of growth rate and colony-forming efficiency were made at 24-h intervals. None of the substrates tested were found to have an effect significant enough to warrant further investigation or inclusion into skin equivalent.
Collapse
Affiliation(s)
- J T Daniels
- Yorkshire Regional Tissue Bank, Pinderfields General Hospital, Wakefield, UK
| | | | | |
Collapse
|
23
|
Stephens P, Genever PG, Wood EJ, Raxworthy MJ. Integrin receptor involvement in actin cable formation in an in vitro model of events associated with wound contraction. Int J Biochem Cell Biol 1997; 29:121-8. [PMID: 9076946 DOI: 10.1016/s1357-2725(96)00123-9] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Actin cables have been reported to act in vivo as contractile 'purse strings' capable of closing embryonic wounds through generation of circumferential tension. Furthermore, their involvement in wounds within in vitro model systems suggests that actin cable contraction may be an important mechanism involved in the process of wound closure. The aim of this study therefore, was to investigate the appearance of actin cables in a contracting fibroblast populated collagen lattice, an in vitro model of events associated with wound contraction. Utilising this in vitro model, the time-course of actin cable production was investigated and the involvement of integrin receptors analysed using immunofluorescent labelling techniques. Over a period of hours distinct cellular cable-like structures developed at the edges of collagen lattices coinciding with the onset of contraction. Cellular organisation within the cable was evident as was polymerisation of actin microfilaments into elongated stress fibres forming a continuous cell-cell 'actin cable' around the circumference of the lattice. Immunolocalisation demonstrated that integrin receptor subunits beta 1 and alpha 2 but not alpha 5 were involved in apparent intimate cell-cell contact between juxtaposed fibroblasts within this actin cable. This study demonstrates the involvement of integrin receptors in actin cable formation within collagen lattice systems undergoing reorganisation. Such integrin involvement may enable participating cells to respond to the tensional status of their surrounding environment and via cell-cell communication, to permit a co-ordinated contraction of the cable. It is concluded that integrin receptor involvement in active actin cable contraction may be involved in the process of wound contraction.
Collapse
Affiliation(s)
- P Stephens
- Department of Oral Surgery, Medicine and Pathology, Dental School, University of Wales College of Medicine, Cardiff, U.K
| | | | | | | |
Collapse
|
24
|
Stephens P, Davies KJ, al-Khateeb T, Shepherd JP, Thomas DW. A comparison of the ability of intra-oral and extra-oral fibroblasts to stimulate extracellular matrix reorganization in a model of wound contraction. J Dent Res 1996; 75:1358-64. [PMID: 8831630 DOI: 10.1177/00220345960750060601] [Citation(s) in RCA: 81] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
Intra-oral wounds, like wounds in children, demonstrate privileged healing when compared with adult wounds at extra-oral sites. This study investigated whether this preferential healing is related to an increased ability of oral mucosal fibroblasts to reorganize extracellular matrix (ECM) when compared with their dermal counterparts. ECM reorganization was investigated by means of a fibroblast-populated collagen lattice (FPCL) system. The effect of donor age was also investigated in this system. Differences in ECM reorganization and FPCL contraction were evident: FPCL contraction was more rapid by oral mucosal fibroblasts than dermal fibroblasts (p < 0.01). FPCL contraction was also greater in child (donor < 10 years) than adult (donor > 18 years) oral mucosal fibroblasts (p < 0.01). These differences were not related to phenotypic differences in cell viability (p > 0.5), DNA synthesis (p > 0.05), and cell number (p > 0.5) within the FPCLs, or cellular attachment to collagen (p > 0.07). FPCL contraction was not stimulated by the addition of conditioned medium from oral mucosal or dermal fibroblasts (p > 0.05). These data show that the significantly increased ability of oral mucosal fibroblasts to reorganize ECM in vitro, when compared with dermal fibroblasts, represents a distinct phenotypic contractile difference, rather than differences in their production of soluble mediators or cell attachment to ECM.
Collapse
Affiliation(s)
- P Stephens
- Department of Oral Surgery, Medicine and Pathology, Dental School, University of Wales College of Medicine, Cardiff, United Kingdom
| | | | | | | | | |
Collapse
|
25
|
Jung CM, Matsushita O, Katayama S, Minami J, Ohhira I, Okabe A. Expression of the colH gene encoding Clostridium histolyticum collagenase in Bacillus subtilis and its application to enzyme purification. Microbiol Immunol 1996; 40:923-9. [PMID: 9013490 DOI: 10.1111/j.1348-0421.1996.tb01161.x] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
The colH gene encoding 116-kDa collagenase of Clostridium histolyticum (cColH) was cloned into an Escherichia coli-Bacillus subtilis shuttle vector to develop a method for purification of recombinant collagenase (rColH). When plasmid pJCM310 containing the colH gene was introduced into B. subtilis DB104 and the transformant was grown in LB broth at 37 C, stability of the plasmid was not maintained. However, stability was partly improved by growing the transformant in a modified LB broth containing 0.5 M sodium succinate with gentle shaking at 35 C. When the transformant was grown to an optical density of 0.4 at 600 nm in this medium, pJCM310 was stable and rColH was produced in sufficient amounts. rColH was purified to homogeneity by ammonium sulfate precipitation, gel filtration and ion-exchange chromatography. The yield of rColH from an 800-ml culture was 0.53 mg and its specific activity was estimated to be 1,210 U per mg of protein. The purified rColH was capable of degrading native type-I collagen fibril from bovine achilles tendon, as was demonstrated by zymography. A comparison of the N-terminal amino acid sequence between cColH and rColH revealed that rColH has 10 extra N-terminal amino acid residues. However, the peptide mapping of rColH with V8 protease was virtually identical to that of cColH. Furthermore, the molecular mass of rColH was estimated to be 112,999 Da by mass spectrometry, coinciding with the value of 112,977 Da, which was predicted from the nucleotide sequence of the colH gene. Therefore, the recombinant B. subtilis culture is capable of serving as a useful source for enzyme purification.
Collapse
Affiliation(s)
- C M Jung
- Department of Microbiology, Faculty of Medicine, Kagawa Medical University, Japan
| | | | | | | | | | | |
Collapse
|
26
|
Middelkoop E, de Vries HJ, Ruuls L, Everts V, Wildevuur CH, Westerhof W. Adherence, proliferation and collagen turnover by human fibroblasts seeded into different types of collagen sponges. Cell Tissue Res 1995; 280:447-53. [PMID: 7781041 DOI: 10.1007/bf00307818] [Citation(s) in RCA: 45] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
We describe an in vitro model that we have used to evaluate dermal substitutes and to obtain data on cell proliferation, the rate of degradation of the dermal equivalent, contractibility and de novo synthesis of collagen. We tested three classes of collagenous materials: (1) reconstituted non-crosslinked collagen, (2) reconstituted collagen that was chemically crosslinked with either glutaraldehyde, aluminium alginate or acetate, and (3) native collagen fibres, with or without other extracellular matrix molecules (elastin hydrolysate, hyaluronic acid or fibronectin). The non-crosslinked reconstituted collagen was degraded rapidly by human fibroblasts. The chemically crosslinked materials proved to be cytotoxic. Native collagen fibres were stable. In the absence of ascorbic acid, the addition of elastin hydrolysate to this type of matrix reduced the rate of collagen degradation. Both elastin hydrolysate and fibronectin partially prevented fibroblast-mediated contraction. Hyaluronic acid was only slightly effective in reducing the collagen degradation rate and more fibroblast-mediated contraction of the material was found than for the native collagen fibres with elastin hydrolysate and fibronectin. In the presence of ascorbate, collagen synthesis was enhanced in the native collagen matrix without additions and in the material containing elastin hydrolysate, but not in the material with hyaluronic acid. These results are indicative of the suitability of tissue substitutes for in vivo application.
Collapse
Affiliation(s)
- E Middelkoop
- Department of Cell Biology and Histology, Academic Medical Center, Amsterdam, The Netherlands
| | | | | | | | | | | |
Collapse
|
27
|
Teasdale B, Sieber VK, Riches DJ, Nanchahal J. Cryopreservation of cultured dermal fibroblast impregnated collagen gels. Burns 1993; 19:406-10. [PMID: 8216768 DOI: 10.1016/0305-4179(93)90062-d] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
The survival of cultured dermal fibroblasts was evaluated following manufacture, freezing and disaggregation of fibroblast-impregnated collagen gels. The concentration which gave optimal cell survival was determined for three cryoprotectants (glycerol, dimethyl, sulphoxide (DMSO) and ethanediol) and their efficacy compared. DMSO led to the highest cell viability after freezing and thawing. The effect of rate of freezing was also compared and 0.5 degree C/min (within the range 20 degrees C to -70 degrees C) was found to result in a significant enhancement of cell viability in comparison with freezing at 1.0 degree C/min or rapid freezing.
Collapse
Affiliation(s)
- B Teasdale
- Department of Anatomy, Queen Mary and Westfield College, University of London, UK
| | | | | | | |
Collapse
|
28
|
Glutaraldehyde crosslinking of human dermis: a factorial assessment of the crosslinking protocol. ACTA ACUST UNITED AC 1993. [DOI: 10.1016/0267-6605(93)90044-8] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
|
29
|
|
30
|
Nanchahal J, Ward CM. New grafts for old? A review of alternatives to autologous skin. BRITISH JOURNAL OF PLASTIC SURGERY 1992; 45:354-63. [PMID: 1638287 DOI: 10.1016/0007-1226(92)90004-h] [Citation(s) in RCA: 72] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Immediate resurfacing of skin defects is a challenging prospect, especially in patients with extensive full-thickness burns. Currently, split-thickness autografts offer the best form of wound coverage, but limited donor sites and their associated morbidity have prompted the search for alternatives. The application of allogeneic skin is restricted by availability and the risk of transmission of infection, whilst synthetic skin substitutes are simply expensive dressings. The problems of limited expansion may be overcome by culturing keratinocytes in vitro. Unlike autologous cells, allogeneic keratinocytes are available immediately, although they survive for less than a week when applied to full-thickness skin defects. Moreover, the absence of a dermal component in these grafts predisposes to instability and contracture. A cross-linked collagen and glycosaminoglycan dermal substitute, covered with thin split-skin grafts or cultured autologous keratinocytes, shows promise in burns patients. An alternative is a collagen matrix populated by allogeneic fibroblasts and overlaid with cultured autologous or allogeneic keratinocytes. The clinical application of cultured grafts remains imperfect but offers the prospect of immediate coverage and massive expansion.
Collapse
Affiliation(s)
- J Nanchahal
- Department of Plastic and Reconstructive Surgery, Charing Cross Hospital, London
| | | |
Collapse
|
31
|
Abstract
Cryopreservation of human skin keratinocytes and fibroblast cells has been evaluated using three cryoprotectants at various concentrations, three cooling rates and two warming rates. Optimal combinations of factors were determined. Selection for tolerance to cryopreservation was not detected after repeated freeze/thaw cycles. A beneficial effect of serum was shown to be cooling rate dependent.
Collapse
Affiliation(s)
- J N Kearney
- Yorkshire Regional Tissue Bank, Pinderfields General Hospital, Wakefield, UK
| |
Collapse
|
32
|
|
33
|
Otto WR, Dover R, Nanchahal J, Dhital SK. Dermal equivalents. Biomaterials 1990; 11:447. [PMID: 2207237 DOI: 10.1016/0142-9612(90)90103-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
|