The effect of platelet-derived growth factor on cell division and glycosaminoglycan synthesis by human skin and scar fibroblasts

Quantification of the Proliferation Index of Human Dermal Fibroblast Cultures with the ArrayScan™ High-Content Screening Reader

High-throughput cell-based assays are becoming a powerful approach in the drug discovery process. The ArrayScan™ high-content screening (HCS) reader is a cytometer based on a fully automated fluorescence microscope that is able to obtain quantitative information on the intensity and localization of fluorescence signals within single cells over a wide cell population. The aim of this work was to set up an automated HCS multiparameter analysis for the quantification of the in vitro proliferation index of normal human dermal fibroblast (NHDF) cultures. The authors stimulated starved NHDF with insulin-like growth factor-1, platelet-derived growth factor, epidermal growth factor, fibroblast growth factor, or serum, and they quantified the proliferation index by measuring the expression of Ki-67 antigen, the incorporation of bromodeoxyuridine (BrdU), and the phosphorylation of the retinoblastoma protein (pRb). This approach also allowed quantification of the mitotic index by phospho-histone H3 staining and the percentage of cells in the S-phase by BrdU incorporation. The proliferation data from the ArrayScan™ assays were validated by comparison with a reference enzyme-linked immunosorbent assay (ELISA) and by flow cytometry. The measured proliferation indices were highly reproducible in repeated measures and independent experiments. The authors therefore propose that the ArrayScan™ HCS system could be used for high-throughput multiparameter analysis and quantification of the proliferation of cellular cultures.

Rapid creation of skin substitutes from human skin cells and biomimetic nanofibers for acute full-thickness wound repair

Creation of functional skin substitutes within a clinically acceptable time window is essential for timely repair and management of large wounds such as extensive burns. The aim of this study was to investigate the possibility of fabricating skin substitutes via a bottom-up nanofiber-enabled cell assembly approach and using such substitutes for full-thickness wound repair in nude mice. Following a layer-by-layer (L-b-L) manner, human primary skin cells (fibroblasts and keratinocytes) were rapidly assembled together with electrospun polycaprolactone (PCL)/collagen (3:1, w/w; 8%, w/v) nanofibers into 3D constructs, in which fibroblasts and keratinocytes were located in the bottom and upper portion respectively. Following culture, the constructs developed into a skin-like structure with expression of basal keratinocyte markers and deposition of new matrix while exhibiting good mechanical strength (as high as 4.0 MPa by 14 days). Treatment of the full-thickness wounds created on the back of nude mice with various grafts (acellular nanofiber meshes, dermal substitutes, skin substitutes and autografts) revealed that 14-day-cultured skin substitutes facilitated a rapid wound closure with complete epithelialization comparable to autografts. Taken together, skin-like substitutes can be formed by L-b-L assembling human skin cells and biomimetic nanofibers and they are effective to heal acute full-thickness wounds in nude mice.

Unusual Morphologic Presentations of Blastic Plasmacytoid Dendritic Cell Neoplasm

We present 2 cases of blastic plasmacytoid dendritic cell neoplasm (BPDCN) showing unusual histological features. One patient, a 73-year-old male, presented with a nonpruritic macular erythema of the skin on the anterior and posterior chest wall, the biopsy of which was originally diagnosed as malignant melanoma. The neoplastic cells were negative for S100 and HMB45 and strongly positive for CD45, CD4, CD56, and CD123. The final diagnosis was a BPDCN associated with abundant melanin pigment and numerous melanophages. The second patient was a 73-year-old male with a 5-month history of small, slowly enlarging, bruise-like plaques on his limbs and chest. Histologic examination of the skin biopsy revealed an atypical cellular/myxoid infiltrate with numerous macrophages, which was originally diagnosed as consistent with lepromatous leprosy. The atypical cells were immersed in an alcian blue–positive myxoid matrix at pH 2.5. The Fite-Faraco stain was negative. Positive immunoreactivity was demonstrated for CD4, CD56, and CD123. Based on the histopathology and immunohistochemistry findings, a diagnosis of BPDCN with prominent myxoid matrix was rendered.

Effects of platelet derived growth factor (PDGF) on fibronectin (FN) production by human skin and scar fibroblasts

The fibroblast-type cell found in hypertrophic scars and keloids demonstrates an elevated fibronectin (FN) production, compared to the same type of cell in normal dermis. We wished to determine if the effects of platelet derived growth factor (PDGF) on FN production in these cell types would be equivalent or different. Cell lines were established from the dermis (reticularis) of hypertrophic scars, keloids, uninvolved normal skin adjacent to the lesions, including an assumed normal skin adjacent to a keloid (AS), and normal skin from a different uninjured patient (DS). Each parent tissue from which the cell lines originated was diagnosed histologically. Each hypertrophic scar, keloid and normal adjacent skin, with one exception, showed typical histologic findings confirming the clinical diagnosis. DS was also normal. AS, although assumed to be normal, in fact, demonstrated portions of nodules from the adjacent keloid. All cell lines were grown under standard conditions with subconfluent cells metabolically labeled for radioimmunoassays measuring FN at passage 3 (8 to 9 weeks in culture) in the absence and presence of PDGF. Significant differences in production of FN/cell and FN/PR/cell between two hypertrophic scars and their matched normal skins and for one keloid and its matched normal skin were observed. However, no significant difference was observed between the other keloid and AS, nor between the other hypertrophic scar and DS. PDGF significantly stimulated FN production in 2 of 4 NS cell lines, and in the AS cell line. By FN/cell values, 2 of 5 cell lines from the lesions were inhibited and one was increased. In terms of FN/PR/cell, 1 of 5 cell lines from the lesions was stimulated and the others showed no differences. The mixed results may be attributable to the likelihood that the cell lines represent mixed populations. This study demonstrates the importance of: 1) histological characterization of all parent tissues from which cell lines are derived, and 2) matching cell lines from lesions with cell lines from uninvolved normal dermis, in the same individual.

Acceleration of cutaneous wound healing by transient p53 inhibition

The increase of cell proliferation during early wound healing is thought to be regulated by a decrease of apoptosis. In contrast, the reduction of cellularity during final wound maturation may be controlled by an increase of apoptotic cell death. Herein we studied whether p53 is involved in wound healing-associated apoptosis and whether transient inhibition of p53 is effective to improve the early healing process of cutaneous wounds. Using intravital microscopic and immunohistochemical techniques in hairless mice, we demonstrated that in vivo inhibition of p53 by pifithrin-alpha (PFT-alpha; 2.2 mg/kg ip) accelerates early epithelialization and neovascularization of cutaneous wounds by (i) promoting leukocyte recruitment, (ii) increasing cell proliferation, and (iii) reducing apoptotic cell death. We further show that final wound closure with down-regulation of cell proliferation is not inhibited by PFT-alpha treatment, indicating that transient blockade of p53 function does not affect the process of wound maturation. Western blot analysis revealed that PFT-alpha lowered nuclear but not cytoplasmic p53, implying that cytoplasmic retention of p53 mediates the antiapoptotic effects of PFT-alpha. Furthermore, PFT-alpha significantly increased expression of proliferating cell nuclear antigen protein in whole extracts of cutaneous tissue and caused a rise in proliferation of wild-type, but not mutant, p53-expressing keratinocytes. From our study we conclude that transient inhibition of p53 supports the early cell proliferation required for rapid tissue repair and that this may represent an attractive approach in the treatment of delayed wound healing.

Dermatomyositis and mucinosis

BACKGROUND

Mucin deposition is a common feature in autoimmune collagen diseases including dermatomyositis. Nevertheless, clinical manifestations of mucinosis are uncommon in patients with dermatomyositis. Two cases of mucinosis associated with dermatomyositis are reported.

PATIENTS

A 53-year-old woman presented with symmetrical plaques on the upper limbs formed by the coalescence of small, violaceous papules. In addition, she showed the typical cutaneous and muscle features of dermatomyositis. A 44-year-old woman with dermatomyositis of 5 years' evolution developed linear, flesh-colored papules across the flexural creases of her palms and fingers.

RESULTS

Skin biopsy of the upper limb lesions in the first patient showed epidermal changes compatible with dermatomyositis and dermal mucin deposition. Histopathologic examination of the palmar lesions of the second patient showed less intense epidermal changes of dermatomyositis and dermal mucin deposition.

CONCLUSIONS

Mucin deposition in patients with dermatomyositis may have an unusual clinical presentation, and it should be considered in the differential diagnosis of atypical cutaneous lesions in these patients.

Effects of photostimulation on wound healing in diabetic mice

BACKGROUND AND OBJECTIVE

Low-level laser irradiation at certain fluences and wavelengths can enhance the release of growth factors from fibroblasts and stimulate cell proliferation in vitro. We evaluated whether low-level laser irradiation can improve wound healing in diabetes mellitus.

STUDY DESIGN/MATERIALS AND METHODS

Genetically diabetic mice (C57BL/Ksj/db/db) were used as the animal model for this wound healing study. The experimental animals were divided among four groups: negative control, positive control (topical basic fibroblast growth factor [bFGF] on wound), laser therapy group; and a combination group of laser therapy and topical bFGF. An argon dye laser (Lexel Auora Model 600) at a wavelength of 630 nm and an output of 20 m W/cm2 was used as the light source. The speed of wound closure and histological evaluation were used to analyze the experimental results.

RESULTS

Laser irradiation enhanced the percentage of wound closure over time as compared to the negative control group (58.4 +/- 2.6 vs. 40.8 +/- 3.4 at day 10 and 95.7 +/- 2 vs. 82.3 +/- 3.6 at day 20, P < .01). Histological evaluation showed that laser irradiation improved wound epithelialization, cellular content, granulation tissue formation, and collagen deposition in laser-treated wounds as compared to the negative control group (6.4 +/- 0.16 vs. 3.8 +/- 0.13 at day 10 and 12 +/- 0.21 vs. 8.2 +/- 0.31, P < .01).

CONCLUSION

This study of laser biostimulation on wound healing in diabetic mice suggests that such therapy may be of great benefit in the treatment of chronic wounds that occur as a complication of diabetes mellitus.

Treatment of peri-implant defects with combination growth factor cement

BACKGROUND

The use of growth factor agents in the regeneration of oral tissues is an area of current investigation. Combinations of growth factors have been used synergistically to improve tissue regeneration. The aim of this study was to determine the effects of a combination growth factor cement (GFC) on guided bone regeneration around dental implants.

METHODS

A combination of bone morphogenetic protein-2 (BMP-2), transforming growth factor-beta (TGF-beta), platelet-derived growth factor (PDGF), and basic fibroblast growth factor (bFGF) was used in a bioabsorbable, non-hydroxyapatite, calcium phosphate cement. Five adult hound dogs were used to compare the effects of GFC, plain cement, and control (no cement). The right and left second, third, and fourth mandibular premolar teeth were extracted; the implant osteotomies were prepared; and a uniform circumferential gap was prepared 1.5 mm beyond the width of the implant in the coronal half of the osteotomy for cement placement. Titanium machine-polished dental implants were placed in the prepared sites, and coronal defects were treated according to previously randomized, assigned modality. A bioabsorbable collagen membrane was secured over the control site, and the flaps were closed primarily. The dogs were maintained on a soft diet to avoid soft tissue trauma. The dogs were sacrificed at 3 months. The specimens were sectioned, mounted, and stained with Stevenel's blue and van Gieson's picric fuchsin. The bone-to-implant contact and bone 1 mm peripheral to the implant surface were recorded with a computerized microscopic digitizer.

RESULTS

The findings of this study indicate a significant effect of GFC on increased bone-to-implant contact and amount of bone per surface area compared with the other treatment modalities (P <0.0009). Plain cement demonstrated slight but nonsignificant increases compared with the control (P>0.05).

CONCLUSIONS

GFC increases bone-to-implant contact and bone surface area within peri-implant defects. Further studies may be beneficial to determine the feasibility of its use for other regenerative applications.

The effects of growth factors on Tenon's capsule fibroblasts in serum-free culture

This study was performed to develop and improve a completely defined in vitro ocular wound-healing model of fibroblast proliferation for glaucoma filtration surgery. This model is essential for the investigation of protein-sensitive drugs and cytokines. Tenon's capsule fibroblasts in their third passage were incubated overnight, washed free of serum, and fed defined media, Aim V or Clonetics FBM serum-free medium containing platelet-derived growth factor, basic fibroblast growth factor, epidermal growth factor, or fibronectin at various dilutions and in combinations at optimum concentrations. Proliferation was measured by 3H-thymidine incorporation at 1, 3, and 7 days. Morphology was compared to controls fed Minimum Essential Medium + 10% serum. Single factors stimulated the greatest amount of thymidine uptake on day 3. Optimum concentrations were epidermal growth factor at 5 ng/ml, basic fibroblast growth factor at 10 ng/ml and platelet-derived growth factor at 20 ng/ml. Identical combinations of factors stimulated nearly twice the thymidine uptake in Clonetics medium as in Aim V. Epidermal growth factor activity was inhibited by either basic fibroblast growth factor or platelet-derived growth factor. Basic fibroblast growth factor and platelet-derived growth factor together produced a less than additive effect. The performance of either serum-free medium may be improved by the addition of basic fibroblast growth factor or platelet-derived growth factor. The optimum serum-free medium (Clonetics FBM) with growth factors was unable to stimulate proliferation as much as Minimum Essential Medium + 10% NBS, but was successful in maintaining viability during the 7 day test period.

Papulonodular mucinosis associated with systemic lupus erythematosus: possible mechanisms of increased glycosaminoglycan accumulation

BACKGROUND

The mechanism for the production of papulonodular mucinosis in patients with lupus erythematosus (LE) is not known.

OBJECTIVE

Our purpose was to determine whether fibroblasts in a patient with LE and papulonodular mucinosis produced more mucin than normal fibroblasts and whether this mucin production could be stimulated by the patient's serum.

METHODS

Skin fibroblasts from a patient with systemic LE and massive papulonodular mucin deposition, as well as normal fibroblasts, were incubated in the presence of serum from the patient or from a healthy volunteer. The production of glycosaminoglycan by fibroblasts was analyzed.

RESULTS

Fibroblasts from the patient produced more glycosaminoglycan than did normal fibroblasts. Glycosaminoglycan production was increased in all cells when incubated in the presence of the patient's serum.

CONCLUSION

Cutaneous mucin deposition in patients with papulonodular LE skin lesions is associated with increased glycosaminoglycan production by dermal fibroblasts. Our preliminary observations suggest glycosaminoglycan production by these fibroblasts appears to be stimulated by a factor, (or factors) in the patient's serum that is yet to be identified.

Extracellular matrix accumulation in immune-mediated tubulointerstitial injury

The accumulation of excessive extracellular matrix (ECM) following tubular injury likely represents an imbalance between ECM production and degradation. We assessed the temporal relationship between the accumulation of ECM, cell adhesion molecules, matrix degrading proteinases, and their inhibitors in a rat model of anti-tubular basement membrane (TBM) antibody-associated tubulointerstitial nephritis (TIN) by the RNase protection assay and immunohistochemistry. There was an increase in the steady state expression of fibronectin (FN) and alpha 2(IV) collagen mRNAs beginning on day 7 with the onset of neutrophil infiltration. An increase in alpha 1(III) collagen and alpha 1-integrin did not occur until days 9 and 10, respectively, at which time mononuclear leukocytes were the predominant infiltrating cell. Increased levels of FN, alpha 1(III), alpha 2(IV) and alpha 1-integrin mRNAs occurred through day 14. By immunohistochemistry, increased accumulation of collagen IV, heparan sulfate proteoglycan, and laminin were detected along the thicken TBM; collagens I and III were immunolocalized within the tubulo-interstitium, while FN was present in both the TBM and interstitium in rats with TIN on day 14. The increase in matrix accumulation was associated with little or no increase in proteinases. u-PA transcripts fell beginning on day 8, with recovery to control values by day 12. Transin mRNA was found at low levels only on days 8 and 9, and the protein could not be detected by Western blotting. In contrast, these changes were associated with an increase in proteinase inhibitors, so that TIMP and PAI-1 mRNAs increased beginning on day 7 and persisted through day 14.(ABSTRACT TRUNCATED AT 250 WORDS)

Platelet-derived growth factor stimulates hyaluronate but not proteoglycan synthesis by human gingival fibroblasts in vitro

The effect of PDGF-BB on human gingival fibroblasts was monitored in an in vitro system. PDGF was found to be mitogenic for these cells, although it required the presence of low concentrations of fetal calf serum to be active. Proteoglycan and hyaluronate synthesis was analyzed by labeling newly synthesized macromolecules with [35S]-sulfate or [3H]-glucosamine, respectively. Identification of specific glycosaminoglycans was achieved by selective enzymatic or chemical degradations. It was found that cells cultured in the presence of PDGF showed no discernible differences in proteoglycan synthesis relative to the control cultures. There were no alterations in amounts of proteoglycans synthesized, types of sulfated glycosaminoglycans synthesized, or relative hydrodynamic sizes of the proteoglycans. In contrast to the proteoglycans, hyaluronate synthesis was significantly increased in the presence of PDGF. The increase in [3H]-glucosamine incorporation into newly synthesized hyaluronate correlated with an increase in the activity of the enzyme hyaluronate synthetase but could not be accounted for entirely by changes in the specific activity of sugar nucleotide precursors, which did alter slightly under differing culture conditions. It is concluded from these results that PDGF stimulates gingival fibroblasts to proliferate and is associated with a differential effect of proteoglycan and hyaluronate synthesis. These observations may correlate with the observed early events associated with wound healing and repair.

Effect of exogenous heparin on anchorage-independent growth of fibroblasts induced by transforming cytokines

Heparin at concentrations below 100 micrograms/ml stimulated anchorage-independent growth of NRK 49F (normal rat kidney fibroblasts, American type culture collection) rat fibroblasts at suboptimal cytokine concentrations but inhibited it at higher heparin concentrations regardless of the cytokine concentration. Heparin did not stimulate growth above that seen at optimal cytokine concentrations, suggesting that it alters the cellular response to the cytokines. These data suggest natural protein-glycosaminoglycan interactions play a role in modulating or mediating the actions of transforming cytokines and suggest they may play a role in acquisition of the transformed phenotype.

PDGF-receptor localizes to mesangial, parietal epithelial, and interstitial cells in human and primate kidneys

There is evidence that platelet derived growth factor (PDGF) is a mediator of proliferative changes in renal arteries and mesangium in human disease, in the mesangium in experimental mesangial proliferative glomerulonephritis, and in the interstitium in a rodent model of angiotensin II mediated hypertension. We utilized a monoclonal antibody to the beta-subunit of the PDGF-receptor to localize constitutive expression of this receptor in human and nonhuman primate tissues. Tissues were fixed in cold 2 or 4% paraformaldehyde, and immunohistochemical techniques both at the light microscopic level and immunoelectron microscopy were employed. In the glomerulus, there is widespread expression of this molecule by mesangial cells, and there is frequent expression on the apical and lateral surface of parietal epithelial cells. There is also widespread expression of this molecule by cortical and medullary peritubular interstitial cells, but not by glomerular or peritubular capillary endothelium or other renal parenchymal structures. The identification of receptors capable of binding PDGF B-chain at each of these sites: (1) provides a basis for PDGF mediated mesangial proliferation in human disease; (2) provides a basis for PDGF mediated interstitial cell migration and/or proliferation and/or activation at sites of tubulointerstitial injury; and (3) suggests that glomerular parietal epithelial cells may be responsive to stimulation by PDGF.

PDGF: a multifunctional growth factor

hPDGF is the major growth factor of human blood serum. In vivo, it is apparently synthesized by megakaryocytes and is transported in blood stored in the alpha granules of platelets. hPDGF is a heterodimer of two homologous polypeptide chains (PDGF-1(A) and PDGF-2(B] linked together by disulphide bonds. The PDGF-1(A) chain is encoded by a gene localized in chromosome 7 and the PDGF-2(B) chain is encoded by the c-sis proto-oncogene localized in chromosome 22. The hPDGF heterodimer and its two isoforms, the PDGF-1(A) and PDGF-2(B) homodimers, are potent mitogens and chemoattractants for target cells such as diploid fibroblasts, osteoblasts, arterial smooth muscle cells and brain glial cells. The PDGF-1(A) homodimer binds only to its specific receptor alpha, and the hPDGF heterodimer and PDGF-2(B) homodimer bind to both receptors a and b. In addition to their mitogenic action, PDGF stimulates important cellular metabolic activities, including protein, lipid and prostaglandin synthesis. It appears to be an important factor in early development and in vivo appears to modulate tissue regeneration and remodelling during wound healing and osteogenesis. The inappropriate expression of PDGF genes and their mitogenic products has been linked to several proliferative disorders such as fibrosis, atherosclerosis and neoplasia.

Effects of growth factors on mucosal scar fibroblasts in culture--a possible role of growth factors in scar formation

Various growth factors are known to play important roles in wound healing, especially in an early inflammatory phase. However, their roles in subsequent scar formation phase are relatively unexplored. The aim of this study is to investigate the mechanisms of regulation in scar formation by these factors. Scar fibroblasts (SF) were obtained from immature scar tissue made at rat hard palate 1 month after excision and normal fibroblasts (NF) were obtained from the palatal mucosa of untreated control animals. SF showed a longer doubling time, and increased level of protein synthesis when compared to NF. Platelet-derived growth factor (PDGF) and epidermal growth factor (EGF) stimulated [3H]-thymidine uptake less effectively in SF than in NF. In both cells, transforming growth factor-beta 1 (TGF-beta 1) inhibited EGF-induced stimulation of [3H]-thymidine uptake, but had no effects when it was added alone. TGF-beta 1 increased collagen synthesis more effectively in SF than in NF. These data indicate that the growth factors may play key roles in regulating proliferation and metabolic activity of fibroblasts during scar formation.

Effect of retinoic acid on platelet-derived growth factor (PDGF) bioactivity and type-B PDGF receptors in normal and psoriatic human fibroblasts

Psoriasis is a common skin disease in which retinoids have beneficial effects. It offers a model for the study of benign hyperproliferation with abnormal differentiation. The dermis has a prominent role in the appearance of epidermal lesions. It is therefore of interest to study the factors that modulate dermal cell proliferation. In this study, the role of retinoids in modulating platelet-derived growth factor (PDGF) bioactivity was studied in normal (six subjects) and psoriatic fibroblasts from involved and uninvolved tissues (six patients). Retinoic acid treatment (for 4 d at 10(-6) M) of psoriatic fibroblasts significantly increased the chemotactic effect of PDGF in these cells (p less than 0.01 and p less than 0.05, respectively, in involved and uninvolved skin at 20 ng/ml of platelet-derived growth factor as measured in a modified Boyden Chamber Assay). In the same way, retinoic acid treatment of psoriatic fibroblasts increased the mitogenicity of platelet-derived growth factor in these cells. Retinoic acid treatment has no significant effect on the mitogenic and chemotactic activity of PDGF in normal fibroblasts. The binding of the homodimer BB PDGF to its type-B receptor, which mediates the mitogenic and chemotactic effect of PDGF, was not modified by retinoic acid treatment either in psoriatic and/or normal fibroblasts. These results suggest that retinoic acid may modulate the PDGF bioactivity in psoriatic fibroblasts not by affecting the binding of this ligand to these cells but by influencing a post-receptor event.

Differences in the biological activities of transforming growth factor-beta and platelet-derived growth factor in vivo

Transforming growth factor-beta 1 (TGF-beta 1 and recombinant platelet-derived growth factor-BB (rPDGF-BB) promoted an extensive, dose-dependent development of fibrous connective tissue when continuously delivered for 8 days by mini-osmotic pumps implanted subcutaneously in adult guinea pigs. Biochemical analyses demonstrated that TGF-beta 1 and rPDGF-BB stimulated dose-dependent increases in the dry weight, and protein, DNA, collagen, and glycosaminoglycan (GAG) contents of the fibrous connective tissue capsule that enveloped the pumps. The GAG/DNA mass ratio was markedly elevated by TGF-beta 1, but the collagen/DNA, protein/DNA, and collagen/protein ratios were not significantly increased. In contrast, rPDGF-BB generally decreased these mass ratios. Histological analyses suggested that this was due to the fact that rPDGF-BB induced a very cellular response with a marked influx of neutrophils and fibroblasts. TGF-beta 1 induced significantly less cellular response, which consisted primarily fibroblasts and macrophages. These results indicated that rPDGF-BB and TGF-beta 1 induced connective tissue deposition in vivo in a dose-dependent fashion, although the cellular nature of the responses as well as the structural composition of the extracellular matrices were clearly distinguishable between the two growth factors.

Expression of different glycosaminoglycan synthetic phenotypes by lapine dermal and dermal wound fibroblasts

Synthesis of extracellular matrix by dermal fibroblasts is an important component of cutaneous wound repair. Scar remodeling and maturation is generally seen as the result of a fibroblast-regulated equilibrium between production and degradation of specific matrix constituents. Fibroblasts from normal dermis, reparative granulation tissue and mature scars were compared in vitro in terms of their ability to produce extracellular glycosaminoglycans (GAGs). All cell lines secreted dermatan sulfate (DS) and chondroitin sulfate (CS) into the culture medium. Hyaluronate (HA) was detected in medium from mature granulation tissue and scar cells, but little or none was found in medium from early granulation tissue or skin cells. In medium from normal skin fibroblasts, an unusual GAG was identified as a potential variant of DS on the basis of co-migration with HA but susceptibility to digestion with chondroitinase ABC. Heparan sulfate (HS) was the major pericellular GAG of all cultures except the mature scar cells, which contained a predominance of DS. A second pericellular GAG was identified as CS in mature granulation tissue cells, scar cells and skin cells; while HA was identified in the pericellular matrix of early granulation tissue cells. In addition, fibroblasts from both skin and early granulation tissue contained a GAG believed to be a variant of CS. These differences in GAG synthesis/secretion between cells maintained under identical culturing conditions could indicate either that distinct fibroblastic substrains exist during different stages of healing or that influences present during the healing process induce stable phenotypic alterations that are maintained through explant culturing and subsequent subcultivation.

Fibronectin and glycosaminoglycan synthesis by fibrotic pig fibroblasts in primary culture

Synthesis of fibronectin and glycosamingoglycans (GAGs) was studied in fibroblasts from pigs with post-irradiation subcutaneous fibrosis. Fibrosis was developed in the femoral muscle by local gamma irradiation with a dose of 60 Gy. Normal fibroblasts were obtained from the healthy skin of the same animal. To measure GAG and fibronectin synthesis fibrotic and normal fibroblasts were labeled with 3H-glucosamine, 35S-sulfate and 35S-methionine. Fibrotic fibroblasts synthesized 2.5 times as much fibronectin as normal skin fibroblasts but total protein synthesis did not change. Parallel enhanced secretion of hyaluronic acid and dermatan sulfate into the cell culture medium were also observed. GAGs from the pericellular layer of trypsin-digested fibrotic fibroblasts exhibited increased 3H incorporation, but reduced 35S-sulfate incorporation. The largest reduction in the latter was observed for heparan sulfate. These results indicate that the fibroblasts from the well developed fibrotic tissue maintain enhanced synthesis of matrix macromolecules in primary cultures. Structural and/or metabolic changes in secreted GAGs, combined with the stimulation of tissue repair by growth factors may be responsible for the excessive deposition of collagen in post-irradiation fibrosis.

Increased fibronectin production by cell lines from hypertrophic scar and keloid

Primary cell lines of fibroblasts from 8 tissues were established--three from hypertrophic scars (HS), one keloid (K) and four from the normal uninvolved dermis adjacent to each lesion. The objective was to quantify and compare all eight cell lines on the basis of fibronectin (FN) produced per cell and per total protein (PR). Two hypertrophic scars and their adjacent skin cell lines were evaluated by the ELISA method for FN and a micro Lowry assay for PR. The scar lines showed statistically significant increases in the amount of FN/cell compared to the cell lines from their adjacent normal dermis. The third hypertrophic scar and the keloid with their adjacent skin cell lines were assayed for FN and PR by radioimmunoprecipitation. Subconfluent cells were metabolically labeled with 35S-methionine for 20 hours. Harvested media and cell monolayers were assayed for radioactivity incorporated into FN and PR. The percentage of FN/PR was significantly higher in media for HS and K compared to the adjacent normal skin lines in the three passages tested. These results support our previous immunofluorescence studies and demonstrate that a fibroblast-type cell line from a hypertrophic scar or keloid produces more FN/PR over time than the normal fibroblast-type cell line from adjacent uninvolved dermis.

Increased chemotactic and mitogenic response of psoriatic fibroblasts to platelet-derived growth factor

The effect of increasing doses from 1.25 to 10 ng/ml of PDGF was tested for chemotactic and mitogenic activity on psoriatic fibroblasts cultured from involved and uninvolved skin of five patients compared to normal fibroblasts from five matched control subjects. The chemotactic response of psoriatic fibroblasts from involved skin (p less than 0.05) and uninvolved skin (p less than 0.005) is significantly enhanced compared to normal fibroblasts. Similarly, PDGF in the presence of platelet poor human plasma is a more potent mitogenic agent in psoriatic fibroblasts than in normal fibroblasts. This increased sensitivity of psoriatic fibroblasts to PDGF may be related to the inflammatory and vascularization processes involved in psoriatic dermis.