Changes In Collagen Composition Research Articles

Inflammatory Changes and Composition of Collagen during Cervical Ripening in Cows.

Simple SummaryOne cause of parturition abnormalities in cows may be the insufficient opening of the birth canal; however, the process by which the canal becomes flexible in cows is unknown. Herein, we observed changes in the cervix from late pregnancy to parturition to clarify the physiological changes related to cervical ripening during normal calving. Mucus and tissue samples from the cervix were collected from 41 cows at 30-day intervals from 200 to 260 days of gestation and at 7-day intervals from 260 days of gestation to parturition. The percentage of neutrophils in the mucus (PMN%) was calculated, and the concentration of interleukin (IL)-8, an inflammatory cytokine, was measured. The cervical tissues were observed under a microscope, and the percentage of type I collagen was calculated. The PMN% in the cervical mucus increased 5 weeks before delivery, peaking 1 week before calving; IL-8 was significantly increased at 295 days compared to that at 200 days of gestation. The percentage of type I collagen in the cervical tissue decreased significantly from 200 days to 274 days of pregnancy and continued to decrease thereafter until the week of calving. In conclusion, the cervix of cows begins to ripen at approximately 260 days of pregnancy.Dystocia and stillbirths in cows pose a high risk of loss of both dams and fetuses, thereby resulting in high economic losses. One of the causes of these problems is birth canal abnormalities. Thus, to prevent these occurrences, it is necessary to understand the mechanisms underlying cervical ripening. Although physiological inflammatory responses and changes in collagen composition have been reported in humans and mice, related information is scarce for cows. We observed inflammatory changes and changes in the collagen composition in the cervix from late pregnancy to parturition to clarify some of the physiological changes associated with cervical ripening during normal calving in cows. Cervical mucus and tissue samples were collected from 41 Japanese Black cows at 200, 230, and 260 days of gestation and at 7-day intervals thereafter until parturition. The percentage of polymorphonuclear neutrophils (PMN%) in the mucus was calculated, and interleukin (IL)-8 concentration was determined by enzyme-linked immunosorbent assay. Blood samples were collected from the jugular vein, and leukocyte counts were determined. Picrosirius red-stained cervical tissue specimens were observed under a polarizing microscope, and the percentage of type I and type III collagen areas in the cervical tissue were calculated. The PMN% in cervical mucus was lowest at 200 days gestation (12–13 weeks before delivery), significantly increased 5 weeks before (21.7 ± 0.04), and was highest 1 week before calving (50.9 ± 0.04). IL-8 levels were increased at 295 days compared with those at 200 days of pregnancy (p < 0.05). No significant changes were observed in the white blood cell counts. The percentage of type I collagen in the cervical tissue reached a maximum (91.4 ± 0.02%) on day 200, significantly decreased after 274 days (3 weeks before calving), and continued to decrease thereafter until the week of parturition. There was no significant change in type III collagen levels. The results suggest that cervical ripening progresses when PMNs begin to infiltrate the cervix at around 260 days of gestation (5–4 weeks before parturition), IL-8, which increases at the end of pregnancy, mobilizes PMNs, and enhances inflammation, and that type I collagen changes are useful as an indicator of cervical ripening.

Novel Biomarkers of Health and Degeneration in Human Intervertebral Discs: In-depth Proteomic Analysis of Collagen Framework of Fetal, Healthy, Scoliotic, Degenerate, and Herniated Discs.

Profiling proteins expressed in the nucleus pulposus (NP) of intervertebral discs (IVDs) in five different biological states. To evaluate the molecular complexity of the collagen (COL) framework and its role in the health and disease of human IVDs. Changes in COL composition have been linked to degenerative disk disease (DDD). Despite the fact that humans have 28 different types of COLs, most of the literature focuses solely on COL-1 and COL-2. This study used high-end proteomic technology to examine the entire COL composition of the human IVD across fetal (developmental-FD), normal (healthy-ND), scoliotic (early degeneration-SD), herniated (degenerate-DH), and degenerated (DD) disk phenotypes. Forty NP tissues were snap-frozen in liquid nitrogen (-196°C) immediately before being subjected to proteomic and bioinformatic analyses from five different disk phenotypes (eight each). Tandem mass spectrometric analysis revealed a total of 1,050 proteins in FDs, 1,809 in ND, 1,487 in SD, 1,859 in DH, and 1,538 in the DD group. Of 28 major collagens reported in the human body, this study identified 24 different collagens with 34 subtypes in NP. Fibril-forming collagens (COL-1, 2, and 11A1) and fibril-associated collagens with interrupted triple helices (COL-9A1, 12A1, and 14A1) were abundantly expressed in FDs, representing their role in the development of NP. Multiplexin (COL-15), a hybrid proteoglycan-collagen molecule, was discovered only in FDs. Degeneration was associated with COL2A1 downregulation and COL-10A1 upregulation. COL10 was discovered to be a new biomarker for disk degeneration. Besides COL-1 and 2, other important COLs (6, 9, 11, 12, 14, 15) with anabolic potential and abundant expression in the fetal phenotype could be investigated for tissue engineering and novel DDD therapy.

Collagen Biosynthesis, Processing, and Maturation in Lung Ageing.

In addition to providing a macromolecular scaffold, the extracellular matrix (ECM) is a critical regulator of cell function by virtue of specific physical, biochemical, and mechanical properties. Collagen is the main ECM component and hence plays an essential role in the pathogenesis and progression of chronic lung disease. It is well-established that many chronic lung diseases, e.g., chronic obstructive pulmonary disease (COPD) and idiopathic pulmonary fibrosis (IPF) primarily manifest in the elderly, suggesting increased susceptibility of the aged lung or accumulated alterations in lung structure over time that favour disease. Here, we review the main steps of collagen biosynthesis, processing, and turnover and summarise what is currently known about alterations upon lung ageing, including changes in collagen composition, modification, and crosslinking. Recent proteomic data on mouse lung ageing indicates that, while the ER-resident machinery of collagen biosynthesis, modification and triple helix formation appears largely unchanged, there are specific changes in levels of type IV and type VI as well as the two fibril-associated collagens with interrupted triple helices (FACIT), namely type XIV and type XVI collagens. In addition, levels of the extracellular collagen crosslinking enzyme lysyl oxidase are decreased, indicating less enzymatically mediated collagen crosslinking upon ageing. The latter contrasts with the ageing-associated increase in collagen crosslinking by advanced glycation endproducts (AGEs), a result of spontaneous reactions of protein amino groups with reactive carbonyls, e.g., from monosaccharides or reactive dicarbonyls like methylglyoxal. Given the slow turnover of extracellular collagen such modifications accumulate even more in ageing tissues. In summary, the collective evidence points mainly toward age-induced alterations in collagen composition and drastic changes in the molecular nature of collagen crosslinks. Future work addressing the consequences of these changes may provide important clues for prevention of lung disease and for lung bioengineering and ultimately pave the way to novel targeted approaches in lung regenerative medicine.

Порушення метаболізму протеогліканів і колагену у нирках за цукрового діабету: клініко-патогенетичні механізми та лабораторні маркери

The article considers the issue of disorders of connective tissue metabolism in diabetes mellitus. Glycosylation of structural components of connective tissue and glucose toxicity have been found to determine the pathogenesis of late complications of diabetes mellitus. The most common concept of the pathogenesis of diabetes is metabolic, according to which all variants of diabetes mellitus, including blood vessels, their basement membrane, are associated with primary disorders of lipid, glycoprotein, protein and carbohydrate metabolism due to complete or partial insufficiency. It has been found that the formation of interstitial fibrosis in the kidneys of patients with diabetes begins in the preclinical stages of diabetic nephropathy. The leading cause of interstitial fibrogenesis is hyperglycemia; exacerbate proteinuria fibrosis, activation of the renin-angiotensin system, chronic inflammation and the formation of myofibroblasts in the interstitium. According to the results of the study of aspects of early diagnosis of kidney damage in type 1 diabetes mellitus, it was found that the development of diabetic nephrosclerosis is characterized by qualitative and quantitative changes in collagen composition in the glomeruli and interstitium, rebalance between collagen synthesis and breakdown, glycosaminoglycans, increased synthesis of fibrogenic growth factors and oxidative modification of proteins. The formation of diabetic nephropathy in patients with diabetes is also characterized by the accumulation of collagen types IV and VI, the appearance of interstitial collagen types III and I in the glomeruli, as well as the accumulation of collagen of all types in tubulointerstitium. Quantitative and qualitative characteristics of sulfated glycosaminoglycans of urine in human diabetes indicated different degrees of development of diabetic nephropathy. Glycosaminoglycans hyperexcretion was observed in patients with diabetes mellitus without proteinuria. In patients with microalbuminuria, glycosaminoglycans hyperexcretion was even more pronounced. It was also found that in diabetes, the total excretion of sulfated glycosaminoglycans in the urine doubles. Conclusion. Thus, in diabetes mellitus, an important pathogenetic link in the violation of the morpho-functional state of the kidneys is the degradation of collagen and proteoglycans of the basement membranes of the glomeruli, as well as interstitial fibrosis. This is reflected in changes in urinary glycosaminoglycans excretion, in particular heparansulfate and chondroitin sulfate, which may serve as a marker of proteoglycan metabolism disorders in the kidneys. Patients with diabetes also have an increase in the urine of hydroxyproline, which indicates an increase in the intensity of collagen metabolism in patients

New pathogenetic perspectives in Pelvic Organ Prolapse (POP): the possible role of the cross-talk between AGEs, MAPK and Smads

Collagen and MMPs play a pivotal role in the pathophysiology of the Pelvic Organ Prolapse (1). In POP samples a switch between type I and type III collagen together with a simultaneous activation of MMPs have been observed and the main consequence of these changes is the loss of mechanical support in the vaginal wall (2). Aim of this study was to prove that AGEs induces the activation of MMPs through ERK1/2 and synchronically stimulates changes in collagen composition directly through Smads. The case group consisted of 20 patients suffering from stage III genital prolapse undergoing colpohysterectomy and anterior and posterior plastic vaginal surgery and 10 control patients treated with laparohysterectomy for uterine fibromatosis. Histological and Immunohistochemical analysis using AGE, RAGE, ERK 1/2, Smads 2-3, Smad 7, MMP-3 and collagen I-III were performed. AGE and ERK 1/2 were also evaluated using Western-Blot analysis. POP samples from anterior vaginal wall showed disorganization and a distortion of the normal muscularis architecture. In POP samples AGE, ERK 1/2, Smad 2-3, MMP-3 and collagen III were upregulated in muscularis whereas in controls Smad 7 and collagen I were increased in the same layer. RAGE was mild or absent both in controls and prolapse. In summary we suggest the possible role of these new markers in the pathogenesis of POP but further studies are required to elucidate if the change of these molecules is the reason or the result of POP disease.

Cardiac-Restricted IGF-1Ea Overexpression Reduces the Early Accumulation of Inflammatory Myeloid Cells and Mediates Expression of Extracellular Matrix Remodelling Genes after Myocardial Infarction.

Strategies to limit damage and improve repair after myocardial infarct remain a major therapeutic goal in cardiology. Our previous studies have shown that constitutive expression of a locally acting insulin-like growth factor-1 Ea (IGF-1Ea) propeptide promotes functional restoration after cardiac injury associated with decreased scar formation. In the current study, we investigated the underlying molecular and cellular mechanisms behind the enhanced functional recovery. We observed improved cardiac function in mice overexpressing cardiac-specific IGF-1Ea as early as day 7 after myocardial infarction. Analysis of gene transcription revealed that supplemental IGF-1Ea regulated expression of key metalloproteinases (MMP-2 and MMP-9), their inhibitors (TIMP-1 and TIMP-2), and collagen types (Col 1α1 and Col 1α3) in the first week after injury. Infiltration of inflammatory cells, which direct the remodelling process, was also altered; in particular there was a notable reduction in inflammatory Ly6C+ monocytes at day 3 and an increase in anti-inflammatory CD206+ macrophages at day 7. Taken together, these results indicate that the IGF-1Ea transgene shifts the balance of innate immune cell populations early after infarction, favouring a reduction in inflammatory myeloid cells. This correlates with reduced extracellular matrix remodelling and changes in collagen composition that may confer enhanced scar elasticity and improved cardiac function.

GW24-e2948 Small interfering RNA transfection in cultured cardiac fibroblasts

ObjectivesSmall interfering RNA (siRNA) methodology suppresses specific gene expression, thus mimicking loss-of-function mutation and enabling in vitro and in vivo gene function analysis. siRNA technology is also a promising tool...

Tenascin-C and type I and III collagen expression in total Achilles tendon rupture. An immunohistochemical study.

Tendon tissue degeneration and changes in collagen composition play a role in spontaneous rupture of the human Achilles tendon. Tenascin-C has been shown to be present in the tissue pathology and changes in tissue loading. We made an immunohistological study of the expression of tenascin-C and type I and III collagens in ruptured human Achilles tendons. Three tissue samples in ten individuals, one from the Achilles tendon rupture and two control samples from four and sixteen centimeters proximal in same tendon were collected at surgery. The specimen were fixed and labelled with specific antibodies to type I and III procollagens (PICP, PINP and PIIINP), mature type III collagen (IIINTP) and tenascin-C. The amount of reacting tissue was evaluated visually and graded on a semiquantitative scale. No difference in the expression of tenascin-C was found between the sites. Instead, mature type III collagen content (p=0.008) and type III collagen synthesis (p=0.016) were significantly increased at the rupture site relative to the control site 2. The amount of newly synthesized type I collagen (PINP, PICP) was relatively high at all sites, as expected. The expression of type III collagen is increased at the rupture site in the human Achilles tendon, but that of tenascin-C remains unchanged. This finding supports a tissue composition alteration background for Achilles tendon rupture, while the role of mechanical loading at the rupture site remains controversial.

Analysis of gene expression in human tendon pathology

Chronic tendon pain is extremely common but little is known about the pathology of early stages of the disease, mainly due to the lack of human tendon biopsy material. Most chronic tendinopathy (tendinitis) involves changes in collagen composition, such as an increase in collagen type III compared to collagen type I, consistent with an attempt by the tenocytes to repair minor matrix damage (Riley et al. 1994). There is also evidence for increased collagen turnover associated with changes in the relative activities of interstitial collagenase (MMP-1) and its inhibitor (TIMP) (Riley et al. 1997). Growth factors and cytokines such as transforming growth factor beta (TGFb) and IL-1 are involved in matrix repair after injury and are likely to have a role in the regulation of tendon metabolism, although their activity in chronic tendinopathy is currently not known. Ultrasound-guided needle biopsies have recently been used to investigate tendon pathology (Movin et al. 1997) providing valuable material from relatively early stages of tendon disease, prior to rupture. However such tissue samples are very small — sometimes less than 5 mg wet weight — and present particular difficulties for molecular and biochemical analysis. The aims of this project are to: develop and optimize a method for the extraction of RNA and protein from very small tendon tissue samples; use this RNA in a quantitative RT-PCR-based method to measure levels of mRNA of proteins such as the collagens, MMP-1, TIMP, TGFβ, IL-1 and GAPDH; compare mRNA and protein levels in the same specimens, using semiquantitative immunoblotting. Materials and methods RNA was extracted using either Trizol reagent or a modification of ‘TriSpin’ method (Reno et al. 1997). A rotor-stator homogenizer was used to disrupt tendon tissue samples in Trizol or in a home-made monophasic reagent containing phenol, isoamyl alcohol, guanidinium isothiocyanate and beta-mercaptoethanol (PIG-B) (Weber et al. 1994). After addition of chloroform and phase separation, RNA was extracted from the aqueous phase of the Trizol reagent by alcohol precipitation or from the aqueous phase of PIG-B by using commercially available spin columns. Total RNA was used in a quantitative RT-PCR-based method which used an external standard curve generated by coamplification of increasing amounts of in vitro transcribed wild-type mRNA with constant amount of competitor mimic mRNA which had an internal deletion (Ravaggi et al. 1994). Primers for TGFb and IL-1 were purchased from Stratagene. Other primer sequences were taken from published data (Wagget et al. 1998) or designed using GCG software. Protein was extracted from the organic phase of the extraction reagents by alcohol precipitation, separated by SDS-PAGE, transferred to PVDF for immunoblotting with antibodies to MMP-1, TIMP-1, collagen I and collagen III and detected using a chemiluminescent detection system (ECL plus, Amersham).

The glycosaminoglycan chain of decorin plays an important role in collagen fibril formation at the early stages of fibrillogenesis

Decorin is a multifunctional small leucine-rich proteoglycan involved in the regulation of collagen fibrillogenesis. In patients with a variant of Ehlers-Danlos syndrome, about half of the secreted decorin lacks the single glycosaminoglycan side chain. Notably, these patients have a skin-fragility phenotype that resembles that of decorin null mice. In this study, we investigated the role of glycanated and unglycanated decorin on collagen fibrillogenesis. Glycosaminoglycan-free decorin, generated by mutating Ser4 of the mature protein core into Ala (DCN-S4A), showed reduced inhibition of fibrillogenesis compared with the decorin proteoglycan. Interestingly, using a 3D matrix generated by decorin-null fibroblasts, an increase in fibril diameter was found after the addition of decorin, and even greater effects were observed with DCN-S4A. To avoid potential side effects of artificial tags, adenoviruses containing decorin and DCN-S4A were used to transduce decorin-null fibroblasts prior to matrix formation. Both molecules were efficiently incorporated into the matrix, with no changes in collagen composition and network formation, or altered expression of the related proteoglycan biglycan. Both decorin and DCN-S4A mutants increased the collagen fibril diameter, with the latter showing the most prominent effects. These data show that at early stages of fibrillogenesis, the glycosaminoglycan chain of decorin has a reducing effect on collagen fibril diameter.

Molecular characterization of post-thrombotic syndrome

The post-thrombotic syndrome represents a poorly understood and significant vascular health problem. This review focuses on our current understanding of the pathogenesis of post-thrombotic syndrome. We emphasize the cellular and molecular mechanisms that are responsible for the critical components of post-thrombotic syndrome. These include the initiation of deep venous thrombosis, the pathogenesis of elevated venous pressure, and the factors responsible for nonhealing of venous stasis ulcers.

A physiologic three-dimensional cell culture system to investigate the role of decorin in matrix organisation and cell survival

In vivo cells exist in a three-dimensional environment generated and maintained by multiple cell–cell and cell–matrix interactions. Proteoglycans, like decorin, affect these complex interactions. Thus, we sought to investigate the role of decorin in a three-dimensional environment where the matrix was generated over time by decorin-deficient fibroblasts in the presence of l-ascorbic acid 2-phosphate. The cells were viable and proliferated in response to FGF2. Decorin was incorporated in the matrix and caused a ∼2 nm shift in the average diameter of the collagen fibrils, and the range and distribution of the fibrils became narrower and more uniform. Although there were no appreciable changes in collagen composition, we found that exogenous decorin induced the de novo synthesis of collagen I and V and cross-linked β (I). In the early phases of the three-dimensional culture, decorin reduced apoptosis. However, following the establishment of a three-dimensional matrix, the cells did not require decorin for their survival.

Temporal changes in collagen composition and metabolism during rodent palatogenesis

Cleft lip and palate is a common craniofacial malformation in man. The aetiology is multifactorial and not known. Since collagen is a major structural component of the developing palate, we studied its composition and metabolism during palate shelf formation and elevation in the rat. Palatal shelves were harvested at embryonic days (E) 15, 16 and 17 as well as post-partum. Palatal collagen increased threefold from E15 to E17 and tenfold from E17 to 5-day-old pups. Palatal calcification was seen in the main, post-partum. Collagen cross-linking, which may be important in shelf elevation and union, varied. The concentration of hydroxylysyl-pyridinolone cross-links was greatest prior to shelf elevation, declining thereafter. Similarly, the highest concentration of dihydroxylysinononorleucine was seen at E16 and this supports the concept of a compliant mesenchymal shelf responding to an intrinsic elevating force. We then determined if enzymes responsible for matrix degradation, matrix metalloproteinases (MMP) and the tissue inhibitors of metalloproteinases (TIMPs) altered over the same time periods. MMP-2, and TIMP-1 and TIMP-2 were identified by gelatin zymography and reverse zymography, respectively. MMP-3 activity was determined with a fluorogenic substrate assay. TIMP-1, TIMP-2 and MMP-3 levels remained constant from E15 to E17. The MMP-2 levels showed a significant elevation from E15 to E16 and E16 to E17. This suggests the regulation of extracellular matrix is likely to be of importance in palate morphogenesis.

Changes in the collagenous matrix of the aging human lamina cribrosa.

The age-related changes in the biochemical composition of the collagenous matrix of the human lamina cribrosa were investigated. An age range (3 weeks to 92 years old) of human laminae cribrosae, dissected free of any surrounding structures which contained collagen, were analysed for collagen solubility (n = 58) total collagen content (n = 46), proportion of collagen types (n = 38), and collagen cross linking (n = 30), using hydroxyproline analysis, scanning densitometry of peptides after cyanogen bromide digestion, and high performance liquid chromatography, respectively. Age-related changes included an increase in total collagen and a decrease in the proportion of type III collagen within the lamina cribrosa. The collagen cross link pyridinoline was present at low levels, but demonstrated no trend with age. An age-related increase was found in pentosidine, an advanced glycation product. These changes in collagen composition imply that the mechanical properties of the lamina cribrosa are altered, resulting in a stiffer, less resilient structure with age. Such alterations in structure may contribute to the increased susceptibility of the elderly to axonal damage in chronic open angle glaucoma.

Changes in collagen composition and cross-links in bone and skin of osteoporotic postmenopausal women treated with percutaneous estradiol implants

To determine the effects of percutaneous estradiol (E2) implants on the collagen composition and maturity in the bone and skin of osteoporotic postmenopausal women.Sixteen postmenopausal women with low bone mineral density were treated for 1 year with 75-mg E2 implants. Iliac crest bone and skin biopsies were analyzed for collagen content and collagen cross-links before treatment and at 1 year. Dual energy x-ray absorptiometry of the lumbar spine and proximal femur was also performed before and after 1 year of therapy.The cortical bone showed a significant increase in the mature cross-links of both hydroxylysylpyridinoline (P < .01) and lysylpyridinoline (P < .01), with a significant reduction in the percentage of collagen (P < .001). The pattern was similar in trabecular bone, with lysylpyridinoline increasing significantly (P < .05). The skin exhibited a significant reduction in the immature cross-link hydroxylysinonorleucine (P < .01), but no significant change in the percentage of collagen content or the mature cross-link histidinohydroxylysinonorleucine. The median increases in bone density were 11.5% at the spine and 4.34% at the total hip. The median post-treatment serum E2 level was 639 pmol/L.Bone mineral density increased at all the sites measured in the spine and proximal hip. The quality of the collagen within the transiliac biopsies had matured in that the concentration of the mature collagen cross-links had increased. These findings support a reduction in the turnover of bone collagen following estrogen replacement therapy. More important, the formation of a more mature collagen fiber should help to reduce the risk of future bone fracture.

Tendon degeneration and chronic shoulder pain: changes in the collagen composition of the human rotator cuff tendons in rotator cuff tendinitis.

To analyse the collagen composition of normal adult human supraspinatus tendon and to compare with: (1) a flexor tendon (the common biceps tendon) which is rarely involved in any degenerative pathology; (2) degenerate tendons from patients with chronic rotator cuff tendinitis. Total collagen content, collagen solubility and collagen type were investigated by hydroxyproline analysis, acetic acid and pepsin digestion, cyanogen bromide peptide analysis, SDS-PAGE and Western blotting. The collagen content of the normal cadaver supraspinatus tendons (n = 60) was 96.3 micrograms HYPRO/mg dry weight (range 79.3-113.3) and there was no significant change across the age range 11 to 95 years. There was no significant difference from the common biceps tendon [93.3 (13.5) micrograms HYPRO/mg dry weight, n = 24]. Although extremely insoluble in both acetic acid and pepsin, much of the collagen was soluble after cyanogen bromide digestion [mean 47.9% (29.8)]. Seventeen per cent (10/60) of the 'normal' cadaver supraspinatus tendon sample contained more than 5% type III collagen, although none of the common biceps tendons had significant amounts. Degenerate supraspinatus and subscapularis tendons had a reduced collagen content [83.8 (13.9) micrograms/mg dry weight and 76.9 (16.8) micrograms/mg dry wt respectively) and were more soluble in acetic acid, pepsin and cyanogen bromide (p < 0.001). Eighty two per cent (14/17) of supraspinatus tendons and 100% (8/8) of subscapularis tendons from patients with tendinitis contained more than 5% type III collagen. The changes in collagen composition in rotator cuff tendinitis are consistent with new matrix synthesis, tissue remodelling and wound healing, in an attempt to repair the tendon defect, even in old and degenerate tendons. An increase in type III collagen in some 'normal' cadaver supraspinatus tendons is evidence that changes in collagen synthesis and turnover may precede tendon rupture. These changes may be the result of repeated minor injury and microscopic fibre damage or a consequence of local factors such as reduced vascular perfusion, tissue hypoxia, altered mechanical forces and the influence of cytokines. These collagenous changes may accumulate with age and substantially weaken the tendon structure, predisposing the tendon to rotator cuff tendinitis and eventual tendon rupture.

Enhanced deposition of predominantly type I collagen in myocardial disease

The myocardium consists of a muscle fibre array surrounded and interspersed by a network of connective tissue, principally collagen, which maintains the functional integrity of the heart. Changes in collagen composition may therefore contribute to altered ventricular function. Collagen composition was examined in cardiac tissue from 15 patients undergoing orthotopic cardiac transplantation. Of these, 10 had severely impaired left ventricular function due to coronary artery disease. The remaining five had dilated cardiomyopathy. Normal heart tissue was taken at autopsy from 25 patients who died of causes unrelated to cardiovascular disease. Left ventricular collagen concentration, estimated from hydroxyproline levels, increased from 48.6 ± 4.1 mg/g dry weight of tissue in the control group to 95.3 ± 9.7 mg/g ( P < 0.01) in patients with dilated cardiomyopathy and to 63.5 ± 9.8 mg/g in the coronary artery disease group. This increase was attributable to an increase in absolute concentrations of both type I and III collagen, determined by separation of cyanogen bromide peptides by sodium dodecyl sulphate polyacrylamide gel electrophoresis. However, there was a significant decrease in the proportion of type III collagen (compared with type I plus III) from 41.8 ± 1.1% in controls, to 34.6 ± 1.5% ( P < 0.01) in the coronary artery disease group and 35.8 ± 2.8% ( P < 0.05) in the dilated cardiomyopathy group. These results suggest that excessive collagen production, with a preponderance of type I, occurs in these forms of myocardial disease, indicative of a remodelling of the collagen matrix, which, by increasing passive myocardial stiffness may contribute to impaired heart function seen in these groups of patients.

The redistribution of collagen in expanded pig skin

Silicone tissue expanders were inserted subcutaneously in the buttocks of nine young pigs and gradually inflated to maximum capacity over 5 weeks. On the control side the expanders were left uninflated. Island buttock flaps were then raised, the expanders removed and the flaps spread into the same sites for 10 days. The tissue was harvested. Area measurements and full thickness skin biopsies were taken 10 days after flap inset in order to study the changes in collagen composition and isotypes in the skin layers. Ten days after inset of the flap the expanded skin had a mean 47% increase in surface area, was 9% thinner (from surface to implant), mostly due to thinning of the subcutaneous zone, but was not significantly different in water content, relative to the control skin. The expanded skin had a significant 9.3% increase (P<0.01, t test) in collagen content of the dermis. The relative proportions of Types I and III were not significantly changed by skin expansion in either the dermal/epidermal or subcutaneous/capsular zones. It is speculated that tensile factors during expansion stimulate the biosynthetic activity and/or mitotic activity of fibroblasts in the dermis to produce this gain in collagen in the expanded compared with unexpanded tissue.