The structure of fibril-forming collagens

Effects of dietary hydroxyproline on collagen metabolism, proline 4-hydroxylase activity, and expression of related gene in swim bladder of juvenile Nibea diacanthus

This study was conducted to investigate the effects of dietary hydroxyproline (Hyp) on tissue collagen level, proline 4-hydroxylase (P4H) activity as well as transcript levels of COL1As (COL1A1 and COL1A2) and P4Hαs (P4Hα(I), P4Hα(II), and P4Hα(III)) in juvenile Nibea diacanthus. A total of 450 fishes were randomized to six equal groups and fed the diet with graded supplementary Hyp-0, 5, 10, 15, 20, and 25 g kg^-1 of dry matter for 8 weeks. Results showed that fish fed diets with 10 g kg^-1 Hyp had significantly higher acid-soluble collagen (ASC) and total collagen (TC) concentrations in swim bladder than fish fed with the other diets (P < 0.05). The activity of P4H in liver and swim bladder showed a similar trend, showing first increase and then decrease with increasing dietary Hyp (P < 0.05). The mRNA expression of COL1As in swim bladder and muscle were significantly higher than those in the liver and intestines. Meanwhile, with increasing dietary Hyp, the relative expression of COL1As genes in swim bladder showed a similar pattern with the TC concentrations of swim bladder, increased significantly initially followed by a decrease. Increased dietary Hyp content corresponded with significant decrease in the mRNA level of P4Hαs in swim bladder. These results indicated that the dietary Hyp promotes the collagen accumulation of swim bladder to some extent, and the promoting action may be related to the expression of COL1As. The optimum supplement of dietary Hyp was estimated from TC of swim bladder with piecewise regression analysis to be 9.66 g kg^-1.

A Modified Hydroxyproline Assay Based on Hydrochloric Acid in Ehrlich's Solution Accurately Measures Tissue Collagen Content

Collagen quantification has long been relevant to biomedical research and clinical practice to characterize tissues and determine disease states. The hydroxyproline assay, while a broadly employed method of quantifying collagen, uses perchloric acid to dissolve Ehrlich's reagent. Since perchloric acid poses occupational safety hazards and high costs, in this study, a new hydroxyproline assay was developed that replaces perchloric acid with a relatively safer and cheaper alternative, hydrochloric acid (HCl). To validate this biochemical technique, first, using either acid to dissolve Ehrlich's reagent, the assays were completed for native and engineered collagenous tissues. No statistical differences were identified between the assays (p = 0.32). Subsequently, both biochemical techniques were compared to amino acid analysis, considered a proteomics gold standard. Interestingly, utilizing HCl in lieu of perchloric acid yielded greater concordance with amino acid analysis (ρ_c = 0.980) than did the traditional assay (ρ_c = 0.947); that is, the HCl-based assay more closely estimates hydroxyproline content, and, consequently, true collagen content. Thus, using Ehrlich's reagent containing HCl in the hydroxyproline assay represents an advance in both mitigating laboratory safety hazards and improving biochemical collagen quantification.

Collagen remodeling and cardiac dysfunction in patients with hypertrophic cardiomyopathy: the significance of type III and VI collagens

BACKGROUND

The relationship between the extent of myocardial interstitial fibrosis, the percentage of each type of collagen, and cardiac function in patients with hypertrophic cardiomyopathy (HC) has not been established.

HYPOTHESIS

The study aimed to establish that increases in some types of collagen may correlate with cardiac dysfunction.

METHODS

Mallory-Azan staining and immunohistochemical staining by the avidin-biotin-complex (ABC) method using anticollagen antibodies were performed on the myocardial biopsy specimens in 35 patients with HC, and the percentage and type of collagen present was determined. Left ventricular (LV) function was evaluated by cardiac catheterization and ventriculography.

RESULTS

The percentage of myocardial interstitial fibrosis correlated highly with indices of LV diastolic and systolic function. The amount of type III collagen correlated significantly with the peak negative dp/dt, the rapid filling volume/stroke volume, and the ejection fraction (EF). Significant correlations also were noted between the amount of type VI collagen and peak negative dp/dt, peak positive dp/dt, and EF. Type I collagen did not correlate with any of the LV function indices, and type IV collagen correlated only with peak ejection rate. Type V collagen did not accumulate substantially in the myocardial interstitium.

CONCLUSIONS

The progression of myocardial interstitial fibrosis in the HC heart adversely impacts both the diastolic and systolic function of the LV. Increases in the percentage of type III and VI collagen correlate with cardiac dysfunction.

Distribution of Different Collagen Types in the Rat's Tympanic Membrane and Its Suspending Structures

BACKGROUND

The objective of the study was to investigate the histological distribution of collagens in the healthy rat's tympanic membrane.

METHODS

Immunohistochemical analysis of collagen type I, II, III, and IV in the tympanic membranes in healthy adult female Sprague-Dawley rats. The staining was semiquantified using light microscopy in a blinded fashion, not knowing what type of collagen the slide had been stained for.

RESULTS

The pars tensa of the tympanic membrane was mainly stained for collagen type II and IV. The fibrous annulus could on immunohistochemistry be subdivided into an inner and an outer portion. The inner portion of the fibrous annulus was mainly stained for collagen type II, whereas the outer portion was most strongly stained for collagen type III and collagen type IV. The test-retest reliability of the semiquantative method was 81%.

CONCLUSION

Collagen type II and IV are the major collagen constituents of the pars tensa of the tympanic membrane. The outer portion of the fibrous annulus has collagen type III and IV as its major constituents, whereas the inner portion is made up of collagen type II.

cDNA cloning and characterization of Type I procollagen α1 chain in the skate Raja kenojei

A full-length cDNA of the Type I procollagen alpha1 [pro-alpha1(I)] chain (4388 bp), coding for 1463 amino acid residues in the total length, was determined by RACE PCR using a cDNA library constructed from 4-week embryo of the skate Raja kenojei. The helical region of the skate pro-alpha1(I) chain consisted of 1014 amino acid residues - the same as other fibrillar collagen alpha chains from higher vertebrates. Comparison on denaturation temperatures of Type I collagens from the skate, rainbow trout (Oncorhynchus mykiss) and rat (Rattus norvegicus) revealed that the number of Gly-Pro-Pro and Gly-Gly in the alpha1(I) chains could be directly related to the thermal stability of the helix. The expression property of the skate pro-alpha1(I) chain mRNA and phylogenetic analysis with other vertebrate pro-alpha1(I) chains suggested that skate pro-alpha1(I) chain could be a precursor form of the skate Type I collagen alpha1 chain. The present study is the first evidence for the primary structure of full-length pro-alpha1(I) chain in an elasmobranch.

Comparison of different electrokinetic separation modes applicable to a model peptide mixture (collagen type I and III CNBr fragments)

A number of electromigration separation modes were applied to the separation of CNBr-released peptides from rat tail tendon collagen (microemulsion electrokinetic chromatography, methanol- or ethanol-modified background electrolytes and the separation in the presence of molecular sieving effect exerting polymer, both in the presence and absence of SDS). Electrodriven separations with a Hypersil C8 packed capillary were investigated as well. The best separations were obtained with either the molecular sieving effect exerting polymer (polyethylene oxide) in the background electrolyte (whether SDS was present or absent) or with the electrodriven chromatography using the C8 reversed-phase packed capillary. In the latter separation system, it was possible to separate 25-27 peaks of the theoretically expected 24 peptides in the analyzed mixture of which 17 were at least tentatively identified. The additional peaks apparently stem from the incomplete cleavage of the parent collagen alpha chains. Successful separations can be done either with predominating molecular sieving or hydrophobic partitioning mechanism.

Abalone collagens: immunological properties and seasonal changes of their mRNA levels

The antisera were raised against pepsin-solubilized abalone collagen and its corresponding gelatin. The reactivity against abalone collagen was higher with the anti-collagen than anti-gelatin antiserum. The two antisera recognized all type I collagens from various vertebrates, whereas these had no reactivity against vertebrate type III and type V collagens. Furthermore, both antisera reacted with only alpha 2(I) chains from chicken, rat, and calf. The strong reactivity was observed against the two antisera in the case of invertebrate and protochordate collagens, especially for turban shell collagen. The seasonal changes of collagen mRNA levels were examined in relation to those of collagen content. Haliotis discus collagens (Hdcols) 1 alpha and 2 alpha coding for abalone collagen pro alpha-chains showed quite similar patterns. The highest mRNA levels in adductor and foot muscles for the two collagens were observed in December and January, in good agreement with the increase of collagen content. The mRNA levels decreased in July and August when collagen content decreased. These results indicate that collagen transcription levels are closely related to collagen contents.

Characterization of recombinant type II collagen: arthritogenicity and tolerogenicity in DBA/1 mice

Recombinant human type II collagen (rhCII) was produced using both the HT1080 mammalian cell expression system (rhCIIht) and a baculovirus expression system (rhCIIbac). The biosynthesis of CII requires extensive post-translational modifications, such as the hydroxylation of prolyl and lysyl residues and glycosylation of hydroxylysyl residues. Amino acid analyses indicated that the rhCIIbac was adequately hydroxylated at prolyl residues but underhydroxylated at lysyl residues and underglycosylated compared with tissue-derived hCII, while rhCIIht was hyperhydroxylated and hyperglycosylated at lysyl residues. When the murine collagen-induced arthritis (CIA) model was used to investigate the immunological properties of the two forms of recombinant CII, each induced a high incidence of arthritis following immunization of susceptible mice when emulsified with complete Freund's adjuvant (CFA). However, the severity of the arthritis, as assessed by the number of affected limbs, was significantly higher in mice immunized with rhCIIht than in mice immunized with rhCIIbac. These data indicate that the degree of hydroxylysine glycosylation may play a role in the induction of the arthritogenic response to CII. Each of the recombinant collagens was comparable to tissue-derived hCII in their ability to induce tolerance and suppress arthritis when given as intravenous or oral tolerogens. Taken together, our data suggest that recombinant CII can be prepared in adequate amounts for therapeutic uses and that the material is immunologically comparable to tissue-derived hCII when used to induce tolerance.

An alpha2(I) glycine to aspartate substitution is responsible for the presence of a kink in type I collagen in a lethal case of osteogenesis imperfecta

Type I collagen synthesized by cultured skin fibroblasts was analyzed biochemically and molecularly to characterize the defect in a patient affected by lethal Osteogenesis Imperfecta. The SDS-Urea-PAGE of procollagen and collagen revealed a broad alpha1(I) band, a normal alpha2(I) and another alpha2(I) band migrating equidistant between alpha1 and alpha2. When synthesized in the presence of alphaalpha'-dipyridyl, an inhibitor of prolyl and lysyl hydroxylation, procollagen and collagen of media and cell layers contained both normal and slower alpha2(I), but only normal alpha1(I). The persistence of the two forms of alpha2(I) chains suggested a mutation in a COL1A2 gene. CNBr cleavage of collagen yielded overmodified alpha1(I) CB3 and CB7 peptides and delayed migration of the alpha2(I) CB3-5 peptide. A delayed CB3-5 was also found after alpha,alpha'-dipyridyl treatment. These data localized the mutation between aa 353 and 551 in alpha2(I) (CB3-5). Sequencing the subcloned alleles in this region revealed a G-->A transition at nt 1671 in one allele, changing Gly 421 to Asp in an alpha2(I) chain. The mutation was demonstrated to occur on the paternally derived allele, using a common C-->A polymorphism at alpha2(I) nt 1585 and by the presence of a rare variant, Arg618-->Gln (Phillips et al., 1990), in the paternal genomic DNA and the proband's mutant allele. Procollagen processing was normal. The Tm of the slow alpha2(I) collagen was 2 degrees C lower than the control, indicating decreased triple helix stability. Mutant collagen was incorporated in the extracellular matrix deposited by cultured fibroblasts. The dramatic delay in alpha2(I) electrophoretic mobility must be induced by the Gly-->Asp substitution, since the Arg-->Gln variant causes only mild electrophoretic delay. Substantial delay in gel mobility even in the absence of overmodification suggested the presence of a kink in the mutated alpha2(I) chains. Rotary shadowing electron microscopy of secreted fibroblast procollagen confirmed the presence of a kink in the region of the helix containing the glycine substitution. The kinking of the collagen helix occurs in the absence of dimer formation. Kinking may interfere with normal helix folding, as well as with the interactions of collagen fibrils with the collagenous and non-collagenous extracellular matrix proteins.

Quantitation of collagen types I, III and V in tissue slices by capillary electrophoresis after cyanogen bromide solubilization

A method for the determination of the proportions of major fiber-forming collagens (types I, III and V) in soft connective tissue was elaborated. The method is based on the release of insoluble collagen by CNBr with subsequent separation of the arising peptides. For routine application the peptides are separated by capillary electrophoresis (50 mM phosphate pH 2.5, 15 kV, 50 degrees C, 70/60 cm x 70 microns I.D. capillary with UV detection at 200 nm). Quantitation of collagen type I can be done either on the basis of spiking the sample with a peptide mixture obtained from a known amount of collagen type I, or by spiking the sample with an equimolar mixture of the two peptides [alpha 1(I)CB2 and alpha 1(I)CB4] (constituting a fused peak) along with alpha 1(III)CB2 and alpha 1(V)CB1. Compared to the previously published methods the procedure is faster and does not require isolation of marker peptides by tedious chromatographic procedures in a preceding preparatory step. Good results are obtained within a wide range of run buffer concentrations and applied voltages; conversely, intensive cleaning of the capillary after every three runs is recommended with a new capillary after 20-30 runs.

Three-dimensional energy-minimized model of human type II "Smith" collagen microfibril

A procedure is described for constructing a three-dimensional model of fibril-forming human type II collagen based on the "Smith" microfibril model. This model is a complex of five individual collagen triple-helical molecules, and is based on known structural parameters for collagen. Both experimental and theoretical data were used as constraints to guide the modeling. The resulting fibril model for type II collagen is in agreement with both physical and chemical characteristics produced by experimental staining patterns of type II fibrils. Some advantages of the type II model are that the stereochemistry of all the sidechain groups is accounted for, and specific atomic interactions can now be studied. This model is useful for: development of therapeutics for collagen related diseases; development of synthetic collagen tissues; design of chemical reagents (i.e., tanning agents) to treat collagen-related products; and study of the structural and functional aspects of type II collagen. Described is the procedure by which the Smith microfibril of type II collagen was developed using molecular modeling tools, validation of the model by comparison to electron-microscopic images of fibril staining patterns, and some applications of this microfibril model.

Collagen remodelling in myocardia of patients with diabetes

AIMS

To investigate collagen remodelling in the interstitium of the heart in patients with diabetes.

METHODS

Immunohistochemical study of the biopsied myocardium using type specific anticollagen antibodies (I, III, IV, V, VI) was performed in 12 patients with non-insulin dependent diabetes mellitus and six non-diabetic patients. There was no history of hypertension or coronary artery stenosis in any of the patients.

RESULTS

Noticeable accumulations of collagen types I, III, and VI in the myocardial interstitium were recognised in both groups, but little accumulation of types IV or V was found. Types I and III mainly stained in the perimysium and perivascular region, while type VI predominantly stained in the endomysium. There was no disease specific accumulation of collagen in diabetes mellitus. The percentage of total interstitial fibrosis in the myocardium was significantly higher in the diabetic group than in the control group (p < 0.05). Although the percentages of collagen types I and VI did not differ between the two groups, the percentage type of III was significantly higher in the diabetic group than in the controls (p < 0.01).

CONCLUSIONS

Collagen remodelling mainly as a result of an increase in collagen type III in the perimysium and perivascular region, occurs in the hearts of patients with diabetes.

Partial protein sequence of the globular domain of alpha 4(IV) collagen chain: sites of sequence variability and homology with alpha 2(IV)

The globular domain (NC) of alpha 4(IV) collagen chain was partially sequenced and compared with the NC domain of other collagen IV chains. The alpha 4(IV) NC domain was found to be most closely related to alpha 2(IV) NC domain but distinct from the NC domain of alpha 1(IV), alpha 2(IV), alpha 3(IV) and alpha 5(IV) collagen chains. Partial sequence, representing nearly one half of alpha 4(IV) NC domain, shows 56%, 69%, 51% and 54% identity with the corresponding NC domains of alpha 1(IV), alpha 2(IV), alpha 3(IV) and alpha 5(IV) collagen chains, respectively. A short, highly polar, region of variable sequence is found near the carboxy terminus of alpha 4(IV) NC domain. This sequence corresponds to a non-conserved region among NC domains, suggesting functional specialization at this site. It exhibits high surface probability with predicted structural differences among NC domains. These results confirm uniqueness of alpha 4(IV) NC domain and indicate its structural relatedness to other NC domains of collagen IV.

Quantitation of type I, III, and V collagens in human tissue samples by high-performance liquid chromatography of selected cyanogen bromide peptides

A method to determine the proportions of the major fiber-forming collagens (types I, III, and V) in noncartilaginous human tissues is presented. The procedure relies on direct solubilization of tissue collagen as cyanogen bromide peptides. The peptides are subjected to cation exchange chromatography followed by gel permeation chromatography in a manner consistent with the rapid resolution and quantitation of relatively low-molecular-weight marker peptides for each collagen. The marker peptides utilized for type I, III, and V collagens are alpha 1 (I)-CB2, alpha 1 (III)-CB2, and alpha 1 (V)-CB1, respectively. Quantitation of the peptides is attained as a function of ultraviolet absorbance during gel permeation chromatography. The nature of the marker peptides, the use of high-performance liquid chromatography techniques, and quantitation of the peptides by ultraviolet absorbance renders the method suitably rapid, sensitive, and accurate for routine evaluations of collagen composition. The utility of the method is illustrated in the presentation of analyses on specimens of placental membranes and blood vessel walls.

Extracellular binding sites of IgA anti-jejunal antibodies on normal small bowel detected by indirect immunoelectronmicroscopy

Patients with dermatitis herpetiformis (DH) have IgA deposition in the papillary dermis and in the lamina propria of the small bowel. In addition, most of DH patients' sera contain IgA class anti-reticulin antibodies, anti-endomysium antibodies (EMA), and anti-jejunal antibodies (JAB) during times of gluten intake. In previous studies, JAB and EMA seemed to be identical and related to the group of anti-reticulin antibodies. In the present study, pre-embedding en bloc immunoelectronmicroscopic methods were applied for analysis of the ultrastructural binding sites of JAB on monkey and rabbit small bowels. These substrates were incubated with sera from DH patients strongly positive for JAB. Simultaneous investigations with the PAP technique and with 5 nm gold-labeled protein A or second antibodies visualized the bound IgA identically: it was associated with collagen fibrils underlying the epithelial and cryptal basement membranes and with collagen fibrils around capillaries. Staining was also detected along the endomysial collagen fibrils of smooth muscle layers, around elastica and smooth muscle cells of blood vessel walls, and along collagen fibrils near smooth muscle cells in the lamina propria. Neither the peroxidase product nor gold deposition was detected directly on the fibers, but was associated with amorphous material surrounding collagen fibers of different diameters. The distribution of JAB-stained structures corresponded to the localization of reticulin network of the small bowel. Our data indicate that JAB recognize an antigen or antigens associated with an amorphous component of the reticulin-collagen structure of jejunum and may have identical binding sites, as anti-reticulin antibodies and EMA.

Collagenolytic enzymes assayed by spectrophotometry with suspensions of reconstituted collagen fibrils

Collagenolytic enzymes were quantitated by a method based on spectrophotometry of suspended reconstituted collagen fibrils. To obtain optically stable suspensions it was necessary to perform a short sonication of the aggregated fibrils at 10 degrees C. When fibrils were cleaved with mammalian fibroblast collagenase at 35 degrees C the triple helical collagen fragments (TCA and TCB) would uncoil spontaneously and the decreasing turbidity was used as an estimate of enzyme activity. The method is a specific collagenase assay since a possible cleavage in the non-helical parts of the collagen molecule with contaminating proteinases is without effect on the turbidity of the suspension and the collagen substrate is not converted to gelatin at 35 degrees C. After 1 h of incubation 0.2 U (equivalent to 0.2 micrograms) of fibroblast collagenase could be detected. In purification procedures with microbial collagenases many fractions were tested by overnight incubations in disposable cuvettes. Sealing of cuvettes with square silicone stoppers allowed rotation of enzyme-substrate mixtures directly in the cuvettes. Only standard laboratory equipment is required for this assay, which is not dependent on radiolabeling or preparation of specific immunologic reagents.

Detection of procollagen biosynthesis using peptide-specific antibodies

Peptides corresponding to selected sequences of the alpha 1 chain of the COOH propeptide of type I and type III human procollagen were synthesized and used as antigens to develop polyclonal and monoclonal antibodies. The antibodies were shown to be epitope specific using a peptide-based solid phase enzyme-linked immunoadsorbent assay. The antibodies were specific for the appropriate procollagens and the COOH propeptides isolated from serum-free culture supernatants of human skin fibroblasts. The rabbit antisera directed to the type I synthetic peptide bound the intact procollagen molecule and both the procollagen alpha 1(I) and alpha 2(I) chains after the reduction of the disulfide bonds. In addition, the antisera bound intact type I COOH propeptide, generated by bacterial collagenase treatment of procollagen, and the individual chains of the propeptide after reduction. In contrast, a monoclonal antibody to the type I peptide was able to bind only to the reduced form of the COOH propeptide. Both rabbit polyclonal and murine monoclonal antibodies directed to the type III synthetic peptide bound the intact and the individual chains of type III procollagen as well as the intact and reduced forms of the type III COOH propeptide. The antibodies have been used to detect procollagen synthesis in two human osteosarcoma cell lines and the differential expression of procollagen in the culture medium of rat lung fibroblasts grown in the presence or absence of glucocorticoids.

Immunoelectron microscopic localization of human type III collagen in human gastrointestinal carcinomas

Ultrastructural immunolocalization of human type III collagen/procollagen was investigated in 28 cases of human gastrointestinal carcinoma by the pre-embedding method using a monoclonal antibody. In addition to immunoreactivity on collagen fibers, amorphous or finely fibrillar immunoreactive substances were observed in the extracellular matrix adjacent to the plasma membrane and in the cisternae of rough endoplasmic reticulum (rER). These substances were considered to represent type III procollagen and/or collagen before fiber formation. Cytoplasmic recesses containing immunoreactive fibers were also observed. These findings related to collagen production were detected in stromal fibroblasts in 16 of 28 cases and in carcinoma cells in six of 28 cases. The positivity rate of these findings was lower in diffuse-type gastric carcinoma. The present study thus clarified further details of collagen production and secretion, and revealed that carcinoma cells may also be involved in the production of stromal collagen in some cases as well as stromal fibroblasts.

D-periodic assemblies of type I procollagen

The solubility limit of purified chick type I procollagen, incubated at 37 degrees C in phosphate-buffered saline, was found to be in the range 1 to 1.5 mg/ml. At higher concentrations large aggregates formed. These comprised: (1) D-periodic assemblies; (2) narrow filaments with no apparent periodicity; and (3) segment-long-spacing-like aggregates. The D-periodic assemblies, which predominated at high concentrations, were separated from the other types of aggregate and found to be ribbon-like. Ribbons were uniform in thickness (approximately 8 nm) and up to 1 micron wide. Staining patterns showed features similar to those in native-type collagen fibrils. Immunolabelling indicated that the carboxyl-terminal propeptide domains were close to the carboxyl-terminal gap-overlap junction, and that the amino-terminal propeptide domains were folded over into the amino-terminal side of the overlap zone. Both propeptide domains appeared to be located on the surface of the assemblies. These observations show that intact propeptide domains hinder, but do not prevent, the formation of D-periodic assemblies. The presence of the propeptide domains on the surface of a growing assembly could restrict its lateral growth and limit its final thickness.

Type I and type III collagen interactions during fibrillogenesis

There is some evidence that type I and type III collagens may be present in the same fibril. In order to demonstrate this, double labeling immunofluorescence microscopy and immunoelectron microscopy were performed with antibodies directed against the collagen molecule and the aminopropeptide domains of type I and type III procollagens using embryonic (postabortion) and adult human skin. Double indirect and protein A immunoelectron microscopy were carried out with 5- and 15-nm gold particles. Skin extracts were also studied by immunoblotting. Double immunofluorescence microscopy with antibodies against type I and type III collagen molecules revealed patterns of fluorescence that were identical in both fetal and adult skins. Immunofluorescence microscopy using an antibody directed against the aminopropeptide of type III procollagen labeled the entire dermis in both embryonic and adult skins. In contrast, although the aminopropeptide of type I procollagen was present throughout embryonic dermis, it was markedly reduced in adult dermis, except for the epidermo-dermal junction. Double immunoelectron microscopy of fetal skin revealed labeling of the aminopropeptide of type I and type III procollagens on the same thin (20-30 nm) fibrils. Large type I fibrils (90-100 nm) were coated with type III collagen molecules and their corresponding aminopropeptide but not with the aminopropeptide of type I procollagen. The aminopropeptide of type I procollagen was present on thin fibrils only at the epidermo-dermal junction in adult skin. Immunoblotting of skin extracts revealed the presence of both pN-type III procollagen (collagen plus the aminopropeptide) and pN-type I procollagen in fetal skin, but only pN-type III in adult skin. This study demonstrates that type I and type III collagens coexist within the same fibril and that the aminopropeptide of type III procollagen is present at the surface of type I collagen fibrils that apparently have reached full growth.

Type II collagen distribution in the ear of the guinea pig fetus

By using monoclonal antibodies to type II collagen and immunohistochemical techniques, we studied the distribution of type II collagen in the developing guinea pig ear. Type II collagen appearance and disappearance corresponded to cartilage development and resorption. Type II collagen was identified in Meckel's and Reichert's cartilages, the cartilage plate of the auricle and external acoustic meatus, the ossicles, eustachian tube cartilage, and the otic capsule. Type II collagen also appeared with the development of structures in noncartilaginous parts including the tympanic membrane, tympanic annulus, basilar membrane, spiral limbus, spiral ligament, and osseous spiral lamina, Rosenthal's canal, the maculae of the utricle and saccule, and the semicircular canal membrane, crista ampullaris, and endolymphatic duct. Type II collagen is distributed widely in the ear after the early stages of development. Thus, type II collagen should be considered an important structural component of the ear.

Immunoelectron microscopical evidence that type V collagen is a fibrillar collagen: importance for an aggregating capability of the preparation for reconstituting banding fibrils

Type V collagen has already been shown, in many immunohistochemical studies, to be widely distributed in connective tissues. Its supramolecular structure, however, has been unclear. We demonstrate that the major aggregates formed from type V collagen solution in vitro are fine fibrils with a D-periodic banding pattern. Further, by using the immunogold labeling method, we find that these fibrils react strongly with anti-type V collagen antibody. Electronmicroscopic examination showed three kinds of aggregate: fine fibrils with periodic banding pattern, fine fibrils without banding pattern, and non-fibrillar materials. Both striated and nonstriated fibrils, when incubated with rat polyclonal anti-human type V collagen IgG followed by incubation with 15 nm-gold conjugated goat anti-rat IgG, were labeled with colloidal gold. We conclude that type V can be classified as a fibrillar collagen. Also, from the present findings together with previous studies, we believe type V collagen may exist in vivo in various connective tissues as fine fibrils with a 67 nm-periodic banding pattern, by itself, or with type I or type III fibrillar collagen, being located between, and connecting the basal lamina and interstitial collagen fibers.

Splice of life: toward understanding genetic determinants of oral diseases

The introduction of recombinant DNA technology has led to a rapid advancement of our knowledge of genes and genomic structure. Such technology, applied to the human genome, has provided valuable information concerning the nature and possible treatment of inherited disorders throughout the human life span. A number of oral diseases can be attacked by use of molecular biological techniques in conjunction with genetic linkage analysis. It will be possible to identify carriers of inherited diseases, to utilize prenatal and antenatal diagnosis when appropriate, and to pursue studies on the mode of inheritance of specific oral diseases. Present and projected advances in this dimension of dental research provide the knowledge and strategies for approaching and solving a number of major problems as we continue to pave the way for improvements in the diagnosis, treatment, and prevention of many oral and craniofacial diseases. This position paper examines a few of the promising areas and suggests future goals toward establishing a knowledge of the genetic determinants for oral diseases.

Covalent structure of collagen. Amino acid sequence of an arthritogenic cyanogen bromide peptide from type II collagen of bovine cartilage

Bovine articular type II collagen was prepared by limited pepsin digestion, differential salt fractionation and carboxymethylcellulose chromatography. Cyanogen bromide digestion of purified type II collagen alpha chains yielded twelve distinct peptides designated CB1-12. The peptide alpha 1(II)-CB11 was isolated by carboxymethylcellulose chromatography and Sephadex G-75S gel filtration. Automated Edman degradation together with chymotrypsin, thermolysin and trypsin digestion enabled identification of its complete amino acid sequence. Compared with type I and type III collagen, the data show similarity with alpha 1(I)-CB8 and alpha 1(III)-CB6-1-8-10-2 peptides, respectively. The peptide is located within residues 124-402 of the alpha 1(II) collagen chain and with its identification, now extends the known amino acid sequence of bovine type II cartilage collagen to 660 amino acid residues including alpha 1(II)-CB1-2-6-12-11-8-10 (partial). This corresponds to alpha 1(I)-CB0-1-2-4-5-8-3-7 (partial; 1-660) and alpha 1(III)-CB3A-3B-3C-7-6-1-8-10-2-4-5 (partial; 1-660) of bovine alpha 1(I) and alpha 1(III) collagen chains.

Increased expression of the gene for the pro alpha 1(IV) chain of basement-membrane procollagen in cultured skin fibroblasts from two variants of osteogenesis imperfecta

Fibroblasts from two lethal variants of osteogenesis imperfecta were shown to synthesize increased amounts of type IV procollagen. Previous studies established that one of these variants had a non-functional allele for the pro alpha 2 chain of type I procollagen, whereas the other pro alpha 2(I) allele contained a mutation leading to synthesis of shortened pro alpha 2(I) chains. In the two variants, the relative level of mRNA for pro alpha 1(IV) was 31 and 42% of the level of mRNA for pro alpha 1(I) chains. A value of less than 2% was found for a third lethal and four non-lethal variants of osteogenesis imperfecta. Immunofluorescent staining of fibroblasts from the two variants synthesizing increased amounts of type IV procollagen indicated that a homogeneous population of cells synthesized both type IV and type I procollagen. The results suggest that mutations in the type I procollagen genes that result in osteogenesis imperfecta can be associated with increased expression of the genes for type IV procollagen.

Collagens of normal and cirrhotic human liver

The collagens of normal and end-stage alcoholic cirrhotic human liver were investigated. Mild conditions of pepsin digestion were employed to preserved the more pepsin sensitive type IV collagen molecules while increasingly more harsh conditions were used which solubilized the type I and type III hepatic collagens. The total hepatic collagen content was elevated from 1.8-2.1 in normal liver to 7.3-8.2 percent in the end-stage alcoholic liver. The graded pepsin digestion resulted in solubilization of 76-90 percent of the total hepatic collagen. The genetically distinct types of collagen were fractionated into types I, III, IV and V preparations using judicious salt precipitation from dilute acid and neutral pH solutions. The average distribution of collagen was 42.5, 39.5, 6.9 and 10.6 percent types I, III, IV and V collagen respectively in normal liver compared to 56.6, 28.0, 5.5 and 9.6 percent respectively in the end-stage alcoholic livers. An additional 0.6 and 0.5 percent in normal and end-stage cirrhotic liver respectively were located in a fraction separating out of the salt concentration required for type VI collagen. The type IV collagen of basement membrane was separated into the constituent 95Kda alpha 1(IV) and alpha 2(IV) polypeptide chains by Agarose A 5m gel filtration with subsequent (carboxymethyl) CM-cellulose chromatography. These chains were indistinguishable from similar chains of type IV collagen isolated previously from human placenta. The type V collagen alpha chains, alpha 1(V) and alpha 2(V) were purified by a combination of Diethylaminoethyl (DEAE) and CM-cellulose chromatography. The individual chains were fragmented with cyanogen bromide to yield 9 peptides from the alpha 1(V) chain and 10 peptides from the alpha 2(V) collagen chain. These were purified and analyzed for amino acid content and molecular weight. The study suggests that all collagen types were elevated in the end-stage alcoholic liver, but type I collagen was disproportionately increased over all other collagens. These results are consistent with previous studies which demonstrated an elevated type I collagen in other fibrotic conditions such as lung fibrosis and hypertrophic scar. They do not, however, agree with the suggested disproportionate elevation of type V collagen in human alcoholic liver. The reasons for this discrepancy are discussed.

Increased concentrations of proteoglycan components in the synovial fluids of patients with acute but not chronic joint disease

Synovial fluid samples (139) from 121 patients with rheumatoid arthritis, osteoarthritis, pseudogout, chronic pyrophosphate arthritis, gout, and reactive arthritis were analysed for cartilage proteoglycan components. Keratan sulphate (KS) epitope was determined by a competitive radioimmunoassay, and total sulphated glycosaminoglycans (S-GAG) were determined after papain digestion by a specific dye binding assay. Increased concentration of both KS epitope and S-GAG were found in synovial fluid from joints with acute inflammatory arthropathy (gout, pseudogout, and reactive arthritis). Analysis of consecutive samples from the same joint at different stages showed that the concentration of KS epitope or total S-GAG varied with acute inflammatory activity. In samples from patients with chronic conditions during active and inactive inflammatory phases concentrations were much lower and not distinguishable among these disease groups. The detection of raised concentration of proteoglycan components may reflect the rapid depletion or greatly increased turnover of proteoglycan in the articular cartilage during acute inflammation in the joint. This did not appear to be sustained in most patients with chronic joint diseases.

Further evidence for the correlation between the primary structure and the stain exclusion banding pattern of the segment-long-spacing crystallites of collagen

Recently, we have noted the direct correlation between the primary structure of type I collagen and the electron microscopical banding pattern of the negatively stained segment-long-spacing (SLS) crystallites (K. Kobayashi, T. Ito, and T. Hoshino (1986), J. Electr. Microsc. 35, 272-275). In this paper, we examined the correlation in the other types of collagen. Unstained light bands (stain excluding bands) of the negatively stained SLSs of type II and type III collagens were located at the clusters of large hydrophobic amino acid residues along the respective molecules. Photographic averaging of the pattern improved the visual comparison of the correlation. We also noted a few occasions of discrepancy from the above-mentioned correlation. Preliminary computer simulation experiments revealed that, among amino acid parameters so far reported, only the hydrophobicity values of G. D. Rose and S. Roy (1980, Proc. Natl. Acad. Sci. USA 77, 4643-4647) explained the ability of amino acids for the negative staining (stain exclusion) of the collagen SLSs.

Complete nucleotide sequence of the region encompassing the first twenty-five exons of the human pro alpha 1(I) collagen gene (COL1A1)

Dysfunctions of the genes coding for the two chains of the human type-I procollagen result in genetic disorders that affect the integrity of bone, ligaments, tendons, and other connective tissues. While the primary amino acid (aa) sequence of one of the two type-I subunits, pro alpha 2(I), has been derived in its entirety from the analysis of overlapping cDNAs, the sequence of the first 247 aa residues of the helical domain of the other polypeptide, pro alpha 1(I), had yet to be determined. To this end, we have sequenced nearly 4 kb of the human pro alpha 1(I) collagen gene and identified twelve open reading frames whose conceptual amino acid translation exhibits 95% homology to the first 247 aa of rat alpha 1(I) chain. Furthermore, with these and other data, some of which previously unpublished, we have derived the complete sequence of the first 7618 bp of the gene. This region comprises the 25 exons encoding the N-terminal pre-propeptide and five of the eight cyanogen-bromide-derived peptides. This information therefore represents a most useful reference for the characterization of molecular defects in individuals affected by various connective tissue disorders.