Collagen polymorphism in experimental granulation tissue

Changes in collagen metabolites in serum after cemented hip and knee arthroplasty

Markers of types I and III collagen turnover were measured in serial blood samples collected preoperatively and 60 days after surgery in 13 patients undergoing cemented total hip arthroplasty and 11 patients undergoing cemented total knee arthroplasty. The markers were the carboxyterminal extension peptide of type I procollagen (PICP) and the aminoterminal extension peptide of type III procollagen (PIIINP). The course of serum PICP and serum PIIINP in the two treatment groups were uniform. Serum PICP showed an initial fall on day 4, thereafter increasing up to days 14-28 and was still elevated on day 60. Serum PIIINP was increased on day 4, reaching its maximum on days 14-21, and thereafter declined but remained elevated above initial values. Serum osteocalcin, a serological marker of osteoblast activity, showed no significant changes in the two treatment groups during the observational period. We suggest that the changes in serum PICP and serum PIIINP reflect collagen formation in healing soft connective tissue 60 days after cemented hip or knee arthroplasty.

Histological and biochemical analysis of the fibrous tissue induced by implantation of synthetic ligament (Dacron): an experimental study in a rat model

We conducted a comparative study to evaluate the quality and true nature of the fibrous tissue formed around synthetic grafts when used in ligament replacement. In one group of Lewis rats, a patellar ligament was replaced with a Dacron prosthesis; the comparison group received a tail tendon isograft. Two-, 4-, 8-, 12-, and 24-week comparisons showed histological and biochemical changes in the Dacron group alone that were consistent with foreign-body reaction. Specifically, the Dacron group showed infiltration by large numbers of macrophages and foreign-body, multinucleated giant cells. In addition, the capsule of fibrous tissue that developed around the Dacron ligaments was characterized by lower collagen solubility, a higher content of noncollagenous protein, and a higher proportion of type III collagen than that comprising the isografted tendons. The results of this study call into question the suitability of synthetics for ligament replacement.

A laboratory model to quantitate the resistance of collagen vascular grafts to biodegradation

Recent reports have shown that despite extensive preclinical testing, vascular grafts of biological origin undergo severe biodegradation and aneurysm formation after two or more years of implantation in man. The purpose of this study was to develop a laboratory model to quantitate and correlate the stability of crosslinked collagen grafts in vitro and in vivo. This resistance to biodegradation was assessed by measuring changes in suture pullout force and sample weight in response to controlled digestion with bacterial collagenase, in 0.5-cm-long cylindrical graft segments (chemically processed bovine carotid artery and human umbilical cord vein) that were implanted in the rat subcutis for 2 to 12 weeks. Scar tissue was removed from the explants by brief enzymatic digestion, a process that was inhibited when graft segments had become infected. Changes in dry weight were more consistent than were changes in wet weight; drying the graft segments had no effect on their degradation in vivo or in vitro. Intact cylindrical rings suffered somewhat less damage than did opened, flattened cylinders. Graft degradation increased markedly with implantation time, and was detected after only 3 weeks. We conclude that the rat subcutis model, when combined with controlled enzymatic digestion, first to remove scar tissue and then to challenge structural integrity, provides an accelerated assay by which to predict the stability of collagen vascular grafts.

Synthesis of type I collagen in healing wounds in humans

To quantify wound healing in surgical patients, samples of wound fluid were collected through a silicone rubber tube for 7 postoperative days and their concentrations of the carboxyterminal propeptide of type I procollagen (PICP) and the aminoterminal propeptide of type III procollagen (PIIINP) were measured with specific radioimmunoassays. The mean concentration of PICP in would fluid on day 1 was 207 +/- 92 (SD) micrograms/L, and on day 2 908 +/- 469 micrograms/L (p less than 0.001, signed rank test). On day 7, the mean concentration reached was 380 times higher than that of day 1 (79,330 +/- 54,151 micrograms/L). Only one peak of PICP antigenicity, corresponding to the intact propeptide as set free during synthesis of type I procollagen, was detected on Sephacryl S-300 gel filtration analysis of wound fluid samples. The mean concentration of PIIINP was 70 +/- 61 micrograms/L on day 1, 86 +/- 88 micrograms/L on day 2, and 180 +/- 129 micrograms/L on day 3 (p less than 0.001 when compared with day 1). Finally on day 7, a 250-fold concentration (17,812 +/- 9839 micrograms/L), compared with day 1, was reached. Methods described in the present paper allow separate and repetitive quantification of the synthesis of both type I and type III procollagen during human wound healing.

Alteration of collagen composition and cross-linking in keloid tissues

Collagen composition and cross-linking in human keloid and normal skin tissues were analyzed biochemically. CNBr peptides were separated by 2-dimensional (2-D) mapping and high performance liquid chromatography (HPLC). The amounts of type I and type III collagen was quantified by 2-D scanning densitometry of fluorographs of 2-D maps derived from samples radioactively labelled in vitro by [3H]-NaBH4 in dimethylformamide. Keloid tissues contained 31.6 +/- 2.2 percent type III collagen as compared to 21.4 +/- 2.7 percent type III present in normal human skin dermis. HPLC profiles of CNBr peptides showed that approximately 5 percent of the high molecular weight material in keloids is mercaptoethanol reducible, compared to insignificant amounts in normal skin. 2-D maps derived from CNBr peptides of keloid collagen demonstrated thiol reduction sensitive alpha 1(III)-CB9 dimer as well as 24,000- and 32,000-dalton CNBr peptides, which were not mercaptoethanol reduction sensitive in normal skin due to cross-linking via the lysyl oxidase pathway. Also, a group of 20,000- to 25,000-dalton CNBr peptides, in the alpha 1(I)-CB6 cross-linking region were prominent in keloid tissues.

Type 3 procollagen peptide in bronchoalveolar lavage fluid. Poor indicator of course and prognosis in sarcoidosis

To investigate the role of bronchoalveolar lavage type 3 procollagen peptide as a prognostic indicator in sarcoidosis, we measured type 3 procollagen N-terminal peptide levels in lavage fluids from 84 sarcoidosis patients and monitored disease progress in these patients for a period of 12 months. Lavage procollagen peptide levels were significantly elevated in sarcoidosis patients compared to control subjects (p less than 0.001). No association was observed between lavage type 3 procollagen peptide and disease severity, as assessed by lung function tests. Follow-up monitoring of patients failed to demonstrate any relationship between subsequent functional deterioration and initial lavage type 3 procollagen peptide. These results suggest that elevated lavage type 3 procollagen peptide concentrations in sarcoidosis may reflect increased type 3 collagen synthesis associated with the inflammatory process rather than signal an early event in the development of chronic disease.

Isolation and characterization of collagen in Peyronie's disease

Peyronie's disease is characterized histologically by excessive collagen deposition in the lesion. We examined the collagen types in Peyronie's disease plaque tissues compared to unaffected tissues from the same patient, other control tissues, and Dupuytren's contracture. Gel electrophoresis of pepsin-solubilized collagen demonstrated the presence of type I collagen and an increased content of type III collagen in plaque tissue. Increased type III collagen was detected in apparently normal tissue adjacent to the plaque and in Dupuytren's lesion, confirming previous findings. Although the cause of excessive collagen accumulation of Peyronie's disease is unknown, the results suggest an imbalance in the regulation of extracellular matrix production leading to pathologic fibrosis.

Construction of a human pro alpha 1(III) collagen cDNA clone and localization of type III collagen expression in human fetal tissues

A cDNA clone for human pro alpha 1(III) collagen mRNA was isolated from a cDNA library constructed for human fetal skin RNA. The clone, pHFS3, was identified by restriction mapping and sequencing. Comparison with previously published human type III collagen sequences revealed some differences which may reflect individual variation. The clone was used to study the expression of type III collagen mRNA in various fetal tissues in comparison to the expression of type I collagen mRNAs. In 15-18-week fetal skin the ratio of alpha 1(I) to alpha 1(III) collagen mRNAs was 0.8. Diaphyseal and calvarial bone contained high amounts of type I collagen mRNA and low levels of type III collagen mRNA, resulting in high type I/type III ratios. In situ hybridization of sections of skeletal tissues was employed to identify the cells containing the mRNAs for types I, II and III procollagens. The results revealed differential expression patterns for these three collagen types in various human fetal tissues. Lack of coordinate expression suggests that production of type I and type III collagens is under different regulatory mechanisms in developing skeletal tissues.

Characterization of one phenotype of human periodontal granulation-tissue fibroblasts

Human granulation-tissue fibroblasts were cultured from oral chronic inflammatory lesions and compared with fibroblasts of healthy gingival connective tissue with respect to cell-surface sialoglycoproteins, and the synthesis of extracellular matrix components. Granulation-tissue fibroblasts exhibited a slower growth rate and larger size than their controls. Their cell-surface sialoglycoproteins resembled those of the control cells, except that the relative amount of glycoproteins in the 140-kd region was lower. The ratio of mRNAs for pro alpha l (I) and pro alpha l (III) collagen chains was decreased in granulation-tissue fibroblasts, although electrophoretic fractionation of the proteins did not reveal consistent differences in type I/type III collagen ratio. Granulation-tissue fibroblasts secreted into the culture medium a dermatan sulfate proteoglycan with a lower molecular weight. After digestion with chondroitinase ABC, the molecular weight of the core protein appeared to be identical with that of the control fibroblasts, suggesting a difference in the glycosylation of the core protein. These results support the theory that granulation-tissue fibroblasts represent a distinct phenotype of fibroblastic cells.

Differential stimulation of collagenase and chemotactic activity in fibroblasts derived from rat wound repair tissue and human skin by growth factors

Epidermal growth factor and cartilage-derived basic fibroblast growth factor (EGF and CD-bFGF) are mitogens shown to increase the rate of wound repair in animal models. In addition to being a mitogen for granulation tissue, CD-bFGF stimulates the recruitment of cells to the wound site. CD-bFGF and a closely-related chondrosarcoma-derived fibroblast growth factor stimulated chemotaxis of granulation tissue cells in vitro, each factor having a maximum activity at a concentration of 55 pM. Epidermal growth factor was also a potent chemoattractant for rat granulation tissue fibroblasts; however, maximum activity was obtained at 1.7 nM. Cells from all stages of wound repair were chemotactically responsive to these factors, but there was some attenuation of the response to bFGF in cells derived from fully-organized day 28 granulation tissue. Collagenase-catalyzed restructuring of collagen, an additional significant feature of wound repair, is probably critical to cell movement in an extracellular matrix. Cells derived from organizing (6-day old) sponge granulation tissue secreted latent collagenase constitutively in vitro. In the presence of serum, the production of collagenase was stimulated three-four fold by 1.8 nM bFGF derived either from cartilage or chondrosarcoma. When serum was present, as at a wound site, collagenase production was not enhanced by the addition of EGF. Cells from fully organized, day 21 sponge granulation tissue did not secrete latent collagenase constitutively and could not be stimulated to do so by the addition of EGF, bFGF, or phorbol ester. Human skin fibroblast collagenase production was also stimulated by bFGF and was refractory to EGF. While both classes of growth factor have the ability to promote wound healing, the varying responses they elicit in cell populations from the wound site emphasize the different pathways of cellular activation.

Early changes in dermal collagen of mice exposed to chronic UVB irradiation and the effects of a UVB sunscreen

Our previous studies have shown that hairless albino mice receiving chronic UVB irradiation show an increase in type III collagen, in the irradiated skin, after 12-36 weeks treatment. In this study we wished to find the earliest time at which such collagen changes were detectable and also to ascertain whether a topically applied UV-B sunscreen could prevent such changes. Groups of 10 hairless albino mice were irradiated, dorsally, with a daily dose of 62 mJcm-2 UVB for 3, 6, 9, and 12 weeks. Three parallel groups were used. They received a) no topical treatment, b) sunscreen vehicle alone, and c) sunscreen (containing 2-ethylhexyl 4'-methoxy-cinnamate) applied dorsally at 2 microliter cm-2. Dorsal and ventral (non-irradiated) skin samples were taken and the types I and III collagen quantified densitometrically after cyanogen bromide digestion and polyacrylamide gel electrophoresis. The ratio of dorsal/ventral type III collagen (D/V III) was determined for each mouse. The topical treatments caused no change in D/V III in the non-irradiated animals. In the non-topically treated group the irradiated animals showed a considerable increase in D/V III, compared with controls, at 12 weeks (P less than 0.001). The group treated with sunscreen vehicle alone also showed a significant increase in D/V III at week 12 (P less than 0.01). Both these groups showed a slight elevation in D/V III at week 6. The group treated with sunscreen showed no significant difference in D/V III between irradiated and control animals at any time.

Wound closure: evidence of cooperation between fibroblasts and collagen matrix

The closure of severe wounds where viable tissue has been destroyed by trauma involves the depositing of a new connective tissue matrix, the amount of which is dictated by the severity of trauma. That new connective tissue matrix is immature, and in some cases, can reduce itself. When this occurs in a healing wound it is called wound contraction. When it occurs in the scar of a healed wound, it is called scar contracture. Forces generated in fibroblasts organise the surrounding connective tissue matrix, and this is responsible for the contraction of wounds and the contracture of scars. The experimental work presented here supports the idea that these contractile forces residing in the fibroblast work as individual units to contract the wound. There is no evidence to support the idea of the myofibroblast, a specialised cell, being responsible for contractile forces, as reported. The morphological appearance of stress fibres, which denote the presence of myofibroblasts, may, in fact, signify the termination of the generation of contractile forces. Control of cellular contractile forces appears to be linked to the composition of the connective tissue matrix. A matrix rich in type III collagen contracts faster and to a greater degree than one made from type I collagen. It is suggested that granulation tissue and immature scar with a matrix rich in type III collagen will contract more readily than a more mature scar with less type III collagen. Evidence presented from in vitro models suggests that fibroblasts generate the forces of contraction, and collagen controls those forces in wound closure and scar contracture.

The modulation of contraction of fibroblast populated collagen lattices by types I, II, and III collagen

Human dermal fibroblasts incorporated in a polymerized collagen lattice reduce the size of that matrix. When cell number, collagen concentration, and medium are identical, lattices made with type III collagen contract faster and to a greater degree than those made with type I collagen. The latter contract faster and to a greater degree than those made with type II collagen.

UVB-induced collagen changes in the skin of the hairless albino mouse

Biochemical techniques have been used to measure ultraviolet-B (UVB)-induced changes in dermal collagen composition. Hairless albino mice were irradiated dorsally with a daily dose of 62 mJ/cm2 UVB for 12, 24, 30, and 36 weeks. Nonirradiated controls were housed under identical conditions. Additional groups were irradiated for similar periods and kept for a further 6-24 weeks without irradiation. Skin samples were taken from dorsal and ventral (nonirradiated) surfaces and types I and III collagen were quantified densitometrically after cyanogen bromide digestion and polyacrylamide gel electrophoresis. Type III collagen was expressed as a percentage of the total types I and III collagen and the ratio of dorsal/ventral type III (D/V III) was determined for each mouse. The ratio increased significantly in irradiated animals whereas it decreased in the corresponding period in control animals. In irradiated mice withdrawn from UV exposure the ratio D/V III tended to revert to control levels. These data are in agreement with those of our previous human studies, which showed an increase in type III collagen in sun-exposed skin when compared with covered sites.

Demonstration of elevated type I and type III procollagen mRNA levels in cutaneous wounds treated with helium-neon laser. Proposed mechanism for enhanced wound healing

To assess laser modulation of wound healing, full-thickness cutaneous wounds were produced in the backs of pigs, and subjected to treatment with helium-neon laser. For comparison, some wounds were treated with non-laser energy source (a tungsten light) or left untreated as controls. Type I and type III procollagen mRNA levels were determined in the wounds by molecular hybridization with cDNA probes. The results indicated that type I and type III mRNA levels were markedly increased at days 17 and 28 of the healing in wounds treated with He-Ne laser, when compared to control or tungsten light-treated wounds. The results suggest that helium-neon laser stimulates wound healing by enhancing procollagen gene expression. These observations may have relevance to previous clinical studies suggesting that helium-neon laser stimulates wound healing.

Immunofluorescent localization of structural collagen types in endochondral fracture repair

A nonimmobilized rat tibial fracture model of endochondral osseous repair was examined for the unique localizations of specific collagen genetic types. At various stages of the healing process, the demineralized callus was reacted with immunofluorescent antibodies directed against the type specific forms of matrix collagen. Type III collagen rapidly appeared (day 8-10) and remained in the primitive mesenchymal callus until remodeled. It was particularly prominent in the highly vasoformative regions and the pericallus encapsulation but not present in preexisting cortical and neoformed lamellar bone. The type II collagen, a marker of cartilage, was uniquely located only in areas of chondroid differentiation and calcification. Type II collagen was absent from all bone and was not identified beneath the repairing intact periosteum. The differentiating chondrocytes synthesized type II collagen on an underlayer of type III collagen already within the mesenchymal matrix. From these studies of genetically unique collagen markers, it appears that only in areas of motion or anoxia does an intermediate of chondroid tissue appear. The utilization of specific type II and type III collagen immunofluorescent antibodies has facilitated the understanding of the fracture repair process and has acted as an indicator for unique matrix components.

Collagen type distribution in healing of synthetic arterial prostheses

Layers of tissue encapsulating vascular prostheses recovered from humans were extracted and analyzed by SDS-polyacrylamide gel electrophoresis to determine the distribution of genetically distinct collagen types. Type V collagen was in maximal concentration in extracts of tissues nearest to the prosthesis lumen, type III in extracts of chronically inflamed tissue filling the interstices of the porous prosthesis, and type I in extracts of fibrous occlusive or outer capsule tissue. This pattern of distribution of collagen types across the prosthesis wall may have arisen due to the influence of modulating factors originating in the blood flowing through the prosthesis, and factors produced by inflammatory cells chronically present at the tissue-biomaterial interface. The increased proportion of type V collagen at or near the lumen may contribute to the recognized antithrombogenic properties of human pseudointima.

Skeletal muscle injury--molecular changes in the collagen during healing

Changes in the collagen types and cross-linking of granulation and scar tissue in the injured site of partially ruptured gastrocnemius muscle were studied after a reproducible contusion injury to the left calf of a rat. In normal i.m. collagen the proportion of Type I collagen was considerably higher than Type III. Following injury there was a rapid increase in the proportion of Type III collagen reaching a maximum at 5 days after injury. After a further 2 days the proportion of Type I had increased significantly resulting in a decrease of the Type III/I ratio to below that of the control. However, as healing progressed there was a gradual shift back to the Type III/I ratio for normal i.m. collagen. The collagen produced in response to an injury was initially stabilized by the stable keto-imine cross-link hydroxylysino-5-keto-norleucine, characteristic of embryonic collagenous tissues. The proportion of the stable keto-imine cross-link gradually decreased, and a reversion to the cross-link pattern of normal uninjured i.m. collagenous connective tissue occurred towards the end of the 42-day follow-up period. The present biochemical study demonstrates that during the early phases of the repair process there is a reversion to the collagens typically present in high proportions in embryonic dermal connective tissue. This suggests that the fibroblasts have the ability to modify their product expression under varying circumstances. The study also demonstrates the importance of collagen cross-linking in determining the tensile strength of collagen fibre during the repair process.

Changes in collagen types during the healing of rabbit tooth extraction wounds

Three alpha chains of type V collagen--alpha 1 (V), alpha 2 (V), and alpha 3 (V)--were initially demonstrated together with the expected collagen types I and III in the pepsin-soluble fraction of both normal mandibular bone and tooth extraction wound tissues of rabbits, as analyzed by sodium dodecyl sulfate-gel electrophoresis. The total collagen content of each extraction wound, as determined by the hydroxyproline assay, was observed to increase continuously from day 5 through day 17 and then leveled off or decreased. The ratio of type V to type I collagen was significantly higher in the initial stage of wound healing and decreased sharply down to the level of mandibular bone by day 5. The ratio of type III to type I collagen in the pepsin-soluble fraction increased and reached a maximum on day 5, whereas it was maximal on day 7 in the cyanogen bromide-soluble fraction, and thereafter decreased gradually in both fractions. The ratio for the pepsin-soluble fraction was, however, significantly higher than that for the cyanogen bromide-soluble fraction in the early stage of wound healing.

Tendons and ligaments: a morphological and biochemical comparison

The purpose of this study was to compare selected rabbit tendons and ligaments morphologically and biochemically. Five representative structures from each of six age- and sex-matched rabbits were compared. Biochemical analyses included total collagen, reducible collagen cross-links, quantitative collagen typing, DNA, and glycosaminoglycans. Histological and chemical differences were demonstrated between the tendons and the ligaments. Smaller differences were also found between the individual ligaments (collateral and cruciate) and between the two tendons (patellar and Achilles) that were examined. These findings suggest that ligaments are more metabolically active than tendons, having more plump cellular nuclei, higher DNA content, larger amounts of reducible cross-links, and the presence of more type III collagen, as compared with tendons. They also contain slightly less total collagen than tendons and more glycosaminoglycans. We conclude that the tendons and ligaments studied have unique histological and biochemical characteristics, despite their gross similarities. Relatively increased metabolic activity in ligaments, implied by our findings, may be species specific, age related (transient), or may truly represent a structural expression of functional need for more rapid adaptation. Further investigation of other similarities or differences between particular ligaments (or tendons) is indicated, and attention is directed toward the importance of such variables in development of models for tendon and ligament studies.

Myofibroblast-like cells in human anterior capsular cataract

In six cases of anterior capsular cataract, cells present in the subcapsular zone were investigated. In addition to organelles previously described, the cells were found to contain 7 nm and 15 nm filaments, suggestive of actin and myosin. The cells varied in shape from elongated or flat to rounded. Maculae adhaerentes, gap junctions and basement membranes were present. It is concluded that these cells closely resemble myofibroblasts, by virtue of their cytology and behaviour. The significance of this observation, concerning hypotheses on the genesis of anterior capsular cataract is discussed.

The distribution of types I and III collagen and fibronectin in the healing equine tendon

During tissue response to injury the glycoproteins fibronectin and Type III collagen are synthesized in increased amounts. We have studied the distribution of these molecules in the healing tendon at various times after injury by comparison with that of the major constituent of normal tendon, Type I collagen. Immunofluorescent localization demonstrated the presence of fibronectin throughout the tendon within one week after injury. Staining was found in the matrix, both around capillaries and around fibroblast-like cells. Fibronectin was still apparent in the healing tendon at one month after injury, but after a further two months was no longer detectable. Type III collagen was present both in pericellular and matrix locations until three months after injury, and matrix staining was apparent during the entire fourteen-month period under study. Type III collagen was also found throughout the matrix of the contralateral superficial flexor tendon during this period.

Type V collagen during granulation tissue development

The collagen content, as determined by hydroxyproline assay, of experimental granulation tissue in rats was observed to increase rapidly 21 days, and less rapidly to 90 days of tissue development. Resistance of the collagen to pepsin digestion reached a maximum at 21 days, suggesting more extensive or more stable crosslinking at that time. Type V collagen and the expected collagen types I and III were present in pepsin extracts of the granulation tissue as determined by SDS-polyacrylamide gel electrophoresis. Over 3 months of tissue development the relative quantity of type V collagen, as evidenced by changes in the alpha B chain, varied in parallel with the changing vascularity of the tissue, suggesting an association with capillary endothelial cells and angiogenesis.

Biochemical features of pseudomembrane at the bone-cement interface of loosened total hip prostheses

Biochemical features of pseudomembrane formed at the bone-cement interface of 13 failed total hip replacements were studied and histological examination of the pseudomembrane was conducted. The results of biochemical analyses revealed on average hydroxyproline, 86 micrograms/mg; water content, 57%; hexosamine, 12 micrograms/mg; glucosamine/galactosamine, 1.4%; and calcium, 2.1%. Approximately 78% of collagen was extracted with pepsin, whereas only 8 and 0.3% collagen were extracted with acetic acid and neutral salt, respectively. On further differential salting out of the extracted collagen, about 77% was type I collagen, 19% type III, and 2.6% type V. Unlike pseudoarthrosis of fracture, no type II collagen was identified. Overall biochemical features in the light of the histological appearance suggested that pseudomembrane resembles granulation tissue. Bone healing mechanisms at the bone-cement interface appear to differ from that of fracture healing.

Reversibility of D-penicillamine induced collagen alterations in rat skin and granulation tissue

Granulation tissue was produced in rats by subcutaneous implantation of Visella sponges. D-penicillamine (D-pen) 100 or 500 mg/kg was administered daily for 42 days by gastric tubing. Pairfed, placebo treated animals were included as controls. Half of the groups were kept for additionally 28 days without medication. The inhibitory effect of D-pen on cross-link formation in newly synthesized collagen was readily reversible. By contrast, cross-link deficiency lasting beyond the observation period was observed in the higher polymeric collagen variants released by dilute acid, heat exposure or limited pepsin proteolysis as estimated by solubility, alpha/beta chain ratio and/or aldehyde content. By SDS-polyacrylamide gel electrophoresis on gels containing 3.6 M urea it was shown that purified dermal acid soluble collagen from treated animals consisted of a mixture of type I and III collagen, whereas only type I collagen was detected in controls. The band pattern was identical in reduced and unreduced collagen samples. Four weeks after D-pen discontinuance type III collagen had disappeared from the acid extract. Moreover, the ratio of type III to type I collagen in the pepsin digest from both granulation tissue and skin showed a persistent rise with D-pen. These observations indicate that D-pen destabilized type III collagen in particular by interference with its disulfide linkages. The amount of granulation tissue remained unaffected throughout the experiment, whereas the skin collagen content decreased at the higher dose level. The regeneration was not completed by the end of the observation period. Modulation of the molecular stability of granuloma collagens may be of relevance for the antirheumatoid effect of D-pen, but the sustained effect on normal tissues may imply a long standing impairment of their supportive capacity.

Alterations in collagen production in mixed mononuclear leukocyte-fibroblast cultures

The cell-cell interactions between fibroblasts and mononuclear leukocytes (MNL) which promote alterations in collagen accumulation were examined using a system of co-culture of human fibroblasts and peripheral blood MNL. The stimulation of collagen production was optimal after 48 h of co-culture and the increase in collagen correlated directly with the number of MNL added. The enhancement of collagen production was seen in both autologous and allogeneic co- cultures. Stimulation of non-collagenous protein was also noted. Co- culture supernatants contained soluble substances that were capable of stimulating collagen production, although they stimulated collagen production to a lesser degree than direct co-culture. Fractionation of these supernatants on Sephadex G-200 revealed a predominant area of stimulatory activity at 160,000 mol wt. Lesser areas of activity were noted at molecular weights of 80,000 and 25,000. Determination of the types of collagen produced by fibroblasts during co-culture with MNL showed that the ratio of type I:III collagen was decreased. These alterations in both the quantitative and qualitative accumulation of collagen mimic the changes often seen in wound healing and early inflammation suggesting that cellular interactions between fibroblasts and MNL may be important in the modulation of collagen production in normal and pathologic states.

Types I and III collagens and the activities of prolyl hydroxylase and galactosylhydroxylysyl glucosyltransferase in skin lesions of tuberous sclerosis

Collagen synthesis and the ratios of collagen types I and III were assayed from the skin lesions of five subjects with tuberous sclerosis. Collagen synthesis, measured by the activities of prolyl hydroxylase and galactosylhydroxylysyl glucosyltransferase, was clearly increased in three angiofibromas of these patients and in one soft tumour of the face, but it was unchanged in shagreen patches. The total collagen content was decreased in angiofibromas, indicating either increased turnover of collagen or an increased amount of cellular or other macromolecular elements in these lesions. The proportions of types I and III collagens, estimated by cyanogenbromide digestion and SDS-gel electrophoresis, were 80-90% and 10-20%, respectively, in all samples except two angiofibromas, in which the relative amount of type III collagen was increased. This may indicate that angiofibromas of tuberous sclerosis are heterogenous with respect to the collagen types they contain, and that there may be disturbed cell growth or collagen synthesis, with individual variation from case to case.

Metabolism of rat skin collagen: the effect of arrested development and subsequent catch-up growth on the stability of the connective tissue fibers

The growth of 33 day-old rats was temporarily arrested by feeding a low-protein diet for 6 weeks. The skin collagen hydroxyproline was labelled previously at 31 days by giving a single intraperitoneally injection of L-[5-3H] proline. This label was rapidly incorporated during the subsequent 2 days of normal growth and then remained at a steady level in the skin collagen when growth was halted. Control animals continued to incorporate label for 2 weeks and then the level of [3H] hydroxyproline declined as this label was subsequently lost from the skin collagen. During arrested development, the skin collagen became increasingly insoluble and the analysis of reducible crosslinks revealed a pattern similar to the collagen of an older animal. In addition the isometric tension developed per unit mass of collagen during thermal denaturation was three-fold greater than that from the age-matched control animals. Refeeding the normal diet gave an immediate burst of rapid growth. The pre-labelled collagen did not turnover during this period since there was no significant change in the level of labelled hydroxyproline in the skin. The newly synthesized collagen, which diluted out these older fibers, appeared to be immature, since it was initially rich in type III, it was very poorly crosslinked, and it caused a fall in the isometric tension value. It was concluded that there need not be limited degradation of the older collagen fibers in skin as an a priori requirement for growth.

D-penicillamine-induced angiopathy in rats. Changes in aortic collagen, glycosaminoglycans, DNA and RNA in rats treated with D-penicillamine

Male Sprague-Dawley rats were treated with D-penicillamine (D-pen) in doses of 100, 250 or 500 mg/kg per day for 10, 32, 42 or 70 days. In addition animals were examined 28 days after withdrawal from 42 day's treatment with D-pen at 100 or 500 mg/kg per day. Pair-fed rats served as controls. The changes in aortic collagen, glycosaminoglycans (GAGs), DNA and RNA were studied. D-Pen had a dose- and time-related solubilizing effect on aortic collagen, which regained normal resistance to extraction within 28 days after cessation of the treatment. In contrast, D-pen caused a progressive accumulation of hydroxyproline (Hyp) in the aortic wall during and after treatment, probably mediated by an increased number of matrix synthesizing cells, as judged by augmentation of the DNA content in the presence of unaltered Hyp/DNA and RNA/DNA ratios. The relative amount of type III collagen was increased after 500 mg/kg per day D-pen for 10 and 42 days. High doses of D-pen increased the percentage of water in the aortic wall and reduced the ratio of Hyp to total tissue protein, suggesting an increased content of water-binding substances. This was confirmed by GAG accumulation. Hyaluronic acid (HA) and chondroitin 4,6-sulphate (CHS) were predominant after 32 and 42 days, whereas CHS, heparan sulphate (HS) and dermatan sulphate (DS) prevailed after 70 days of treatment. These observations suggest that processes of repair and regeneration are elicited secondary to the inhibitory effect of D-pen on aortic collagen and elastin crosslinking. Hypertrophy of the vessel wall may imply an increased rigidity, resulting in further increase of the susceptibility to haemodynamic injury.

Fibronectin in experimental granulation tissue

The temporal appearance of fibronectin in experimental granulation tissue has been studied using the immunoperoxidase technique on material fixed in formaldehyde, embedded in paraffin and pretreated with pepsin. Furthermore, the relationship between the distribution of fibronectin and connective tissue fibres, demonstrated as either argyrophilic or red by the van Gieson method, has been investigated. Fibronectin was demonstrated as part of the fibrinous network in the sponge before the formation of granulation tissue. In the development of granulation tissue fibronectin was seen in the initial cellular stage codistributed with the newly formed fibres, first the argyrophilic fibres and later with those stained red by the van Gieson method, too. With maturation of the granulation tissue, predominated by these fibres, the amount of fibronectin was gradually reduced. The presence of fibronectin in the sponge already before the formation of granulation tissue suggests that fibronectin in the initial stage of inflammation derives from plasma. The increase in amount of fibronectin corresponding to the cellular (fibroblastic) proliferation and the formation of fibres, both argyrophilic and van Gieson positive, indicates that fibronectin in young granulation tissue is synthesized by fibroblastic cells. The relationship between the morphologically demonstrated argyrophilic fibres and van Gieson positive fibres and the biochemical type III and type I collagens is discussed.

Collagen types in keratoconus

Collagen types in normal human and keratoconus corneas were separated by salt fractionation and thermal gelation in the pepsin-soluble fraction of the lyophilized tissues. Peptic digestion indicated no significant differences between normal and keratoconus corneas. Further collagen characterization was performed using SDS-PAGE. Collagen concentration were determined via hydroxyproline. Soluble collagens from normal human cornea represent 85% collagen type I, maximally 10% collagen type III and 5% collagen type V. Soluble collagens of keratoconus corneas consist of 90% type I collagen and maximally 5% type II and type V collagen.

Biochemical and histological changes in pulmonary fibrosis induced in rabbits with intratracheal bleomycin

Pulmonary fibrosis was induced in rabbits by an intratracheal instillation of bleomycin. Histologically, at 2 weeks there was inflammation but only limited evidence of increased collagen deposition; at 8 weeks the inflammatory response had subsided and increased collagen deposition, characteristic of early interstitial fibrosis, was observed. Biochemical analyses showed bleomycin treatment caused marked increases in the total amounts of RNA, DNA, mixed protein, collagen and elastin when compared to controls (P less than 0.001 in all cases). Furthermore the increases were essentially complete by 2 weeks where the contents had increased by 110 +/- 13%, 60 +/- 11%, 148 +/- 12%, 94 +/- 15% and 89 +/- 11% respectively (P less than 0.001 in all cases). When collagen and elastin were expressed as concentrations with respect to wet weight, total protein or DNA content, the changes were not statistically significant. No changes were observed in the relative amounts of type I and type III collagen. It is concluded that: (1) compared to biochemical analysis, histology is relatively insensitive in detecting the early increases in connective tissue proteins; (2) measurements of lung collagen and elastin should be expressed as total lung contents wherever possible; the concentration of these proteins may remain unchanged, especially in the early stages of fibrosis, due to concomitant increases in other lung constituents; (3) changes in the relative amounts to types I and III collagens do not play a major role in the pathology of this form of pulmonary fibrosis.

Immunohistochemical study of collagen types in human foetal lung and fibrotic lung disease

Highly purified type-specific anti-collagen antibodies (prepared in animals to types I, II, III, and IV bovine collagen) were used in an indirect immunofluorescence method for the study of human lung collagen. The tissue localisation of each collagen type, and the apparent type I:III collagen ratio was assessed in normal foetal and adult lung and in fibrotic lung lesions. In the latter, the relationship of the findings to the natural history of the lesion was considered. This method was compared with routine connective tissue stains. The following observations were made. (1) Foetal lung in the canalicular phase of development proved a useful substrate for validating and standardizing the procedure. (2) Collagen fluorescence was more sensitive than connective tissue stains in detecting collagen in foetal tissues and sites of early fibrosis. (3) On the basis of collagen-type fluorescence, two distinctive patterns of fibrosis were recognised. Areas of mature collagen surrounding vessels and bronchi and in established scar tissue, for example in asbestotic pleural plaques, were virtually exclusively type I collagen. By contrast, areas of early active fibrosis like sarcoid nodules and organising pneumonia, which usually contained variable numbers of fibroblasts and chronic inflammatory cells, were characterised by an increased proportion of type III collagen and a greater intensity of both types I and III collagen fluorescence. The possible significance of this change in type III:I collagen ratio is discussed. Determination of the stage of fibrotic lesions by this method might have applications in the prediction of disease progression, and influence management of some conditions.

Keloids: a review

Keloids are predominantly fibrous tumors which appear as firm, variably pruritic or tender growths near a site of injury. Usually appearing between the ages of 10 and 30, most keloids are located on the upper back, shoulders, earlobes, and anterior portion of the chest. The etiology remains unknown, but the accumulated fibrous tissue is associated with increased cellularity and increased metabolic activity of keloid fibroblasts. Isolated keloid fibroblasts demonstrate normal growth characteristics along with increased collagen and proteoglycan synthesis. Numerous keloid treatments have been attempted, but variable success has followed either single use or combinations of intralesional corticosteroid injection, surgery, pressure devices, radiation, cryosurgery, and systemic chemotherapy.