Collagen Resorption Research Articles

Influence of rapid- and slow-rate resorption collagen membrane in maxillary sinus augmentation.

To evaluate the effects of low- and rapid-resorption-rate bioabsorbable collagen membranes in maxillary sinus augmentation procedure in rabbits considering Schneiderian membrane (SM) reaction and bone tissue formation. Eighteen male adult rabbits underwent bilateral maxillary sinus augmentation with particulate bovine hydroxyapatite to be divided into three groups, as follows: Group C - control, no membrane; Group RR - rapid resorbable collagen membrane; and Group SR - slow-resorbable collagen membrane. The animals were euthanized after 30 and 120days for specimen's removal to be prepared and analyzed under light microscopy, histomorphometry, and immunohistochemistry for Runx2 and VEGF labeling. Histopathology evaluation presented similar healing pattern among the groups with a satisfactory response of SM, both at day 30 and day 120. Bone histomorphometry did not reveal significant differences among the groups, as well as immunohistochemistry analysis, which presented intense immunolabeling for both proteins in all groups. The presence of both membranes did not negatively interfere in bone formation and remodeling, and the focal mild inflammatory reaction caused by their degrading process did not impair the reconstructive procedure.

Slight Changes in the Mechanical Stimulation Affects Osteoblast- and Osteoclast-Like Cells in Co-Culture

SummaryBackground: Osteoblast- and osteoclast-like cells are responsible for coordinated bone maintenance, illustrated by a balanced formation and resorption. Both parameters appear to be influenced by mechanical constrains acting on each of these cell types individually. We hypothesized that the interactions between both cell types are also influenced by mechanical stimulation. Methods: Co-cultures of osteoblast- and osteoclast-like cells were stimulated with 1,100 µstrain, 0.1 or 0.3 Hz for 1-5 min/day over 5 days. Two different setups depending on the differentiation of the osteoclast-like cells were used: i) differentiation assay for the fusion of pre-osteoclasts to osteoclasts, ii) resorption assay to determine the activity level of osteoclast-like cells. Results: In the differentiation assay (co-culture of osteoblasts with unfused osteoclast precursor cells) the mechanical stimulation resulted in a significant decrease of collagen-1 and osteocalcin produced by osteoblast-like cells. Significantly more TRAP-iso5b was measured after stimulation for 3 min with 0.1 Hz, indicating enhanced osteoclastogenesis. In the resorption assay (co-culture of osteoblasts with fused osteoclasts) the stimulation for 3 min with 0.3 Hz significantly increased the resorption activity of osteoclasts measured by the pit formation and the collagen resorption. The same mechanical stimulation resulted in an increased collagen-1 production by the osteoblast-like cells. The ratio of RANKL/OPG was not different between the groups. Conclusion: These findings demonstrate that already small changes in duration or frequency of mechanical stimulation had significant consequences for the behavior of osteoblast- and osteoclast-like cells in co-culture, which partially depend on the differentiation status of the osteoclast-like cells.

Abstract 422: Relationship Between N-Telopeptide-Mediated Bone Mineral Resorption and Peripheral Arterial Disease

Background: Patients with peripheral arterial disease (PAD) have a higher incidence of hip bone loss and non-spinal fractures independent of their cardiovascular risk or degree of claudication. The mechanisms explaining this excess risk of osteoporosis are poorly understood. N-telopeptide (NTX) is an amino-terminal cross-linked type I collagen peptide that is released during fibrillogenesis, reflecting both the derivative products of bone collagen and bone resorption. When elevated, it serves as an early marker for osteoporosis and predictor of therapeutic response. We hypothesized that patients with PAD have reduced bone mineral content and that PAD is associated with biomarkers of accelerated bone mineral resorption. Methods: We analyzed data from 4354 participants ages 40 years or older with measured ankle-brachial indexes (ABI) from the National Health and Nutrition Examination Survey from 1999 to 2002, defining PAD as an ABI < 0.9 in either leg. N-telopeptides were measured in the urine. Total bone mineral content and bone mineral density were measured using dual energy X-ray absorptiometry. Results: The overall prevalence of PAD was 4.4 % (S.E, 0.3). The geometric mean of NTX was 248.3 nmol (S.E, 7.0). NTX decreased with age. Women, non-Hispanic blacks and obese individuals had significantly higher NTX levels, whereas diabetics had reduced NTX levels. Current smokers, chronic kidney disease and PAD patients tended to have higher levels as well. In an age, gender, and race adjusted multivariate analysis, one standard deviation increase in NTX level was associated with a three-fold increase in the odds of having reduced total bone mineral density (OR 3.22, p <0.0001). Additionally, patients with PAD had significantly increased odds of having NTX levels in the higher tertile (O.R 1.57, p=0.035). This association persisted even after further adjustment for obesity, smoking, and C-reactive protein. Conclusion: Peripheral arterial disease is associated with reduced levels of bone mineral content and density. PAD is independently associated with N-telopeptides, suggesting abnormal type I collagen metabolism abnormalities. Further prospective studies will determine the role of NTX as a marker of osteoporosis found in PAD and their relationship with walking activity.

Identifying the key enzymes involved in matriptase-induced cartilage aggrecan and collagen resorption

Identifying the key enzymes involved in matriptase-induced cartilage aggrecan and collagen resorption

Neutrophil Depletion Blocks Early Collagen Degradation in Repairing Cholestatic Rat Livers

Biliary obstruction results in a well-characterized cholestatic inflammatory and fibrogenic process; however, the mechanisms and potential for liver repair remain unclear. We previously demonstrated that Kupffer cell depletion reduces polymorphonuclear cell (neutrophil) (PMN) and matrix metalloproteinase (MMP)8 levels in repairing liver. We therefore hypothesized that PMN-dependent MMP activity is essential for successful repair. Male Sprague-Dawley rats received reversible biliary obstruction for 7 days, and the rat PMN-specific antibody RP3 was administered 2 days before biliary decompression (repair) and continued daily until necropsy, when liver underwent morphometric analysis, immunohistochemistry, quantitative RT-PCR, and in situ zymography. We found that RP3 treatment did not reduce Kupffer cell or monocyte number but significantly reduced PMN number at the time of decompression and 2 days after repair. RP3 treatment also blocked resorption of type I collagen. In addition, biliary obstruction resulted in increased expression of MMP3, MMP8, and tissue inhibitor of metalloproteinase 1. Two days after biliary decompression, both MMP3 and tissue inhibitor of metalloproteinase 1 expression declined toward sham levels, whereas MMP8 expression remained elevated and was identified in bile duct epithelial cells by immunohistochemistry. PMN depletion did not alter the hepatic expression of these genes. Conversely, collagen-based in situ zymography demonstrated markedly diminished collagenase activity following PMN depletion. We conclude that PMNs are essential for collagenase activity and collagen resorption during liver repair, and speculate that PMN-derived MMP8 or PMN-mediated activation of intrinsic hepatic MMPs are responsible for successful liver repair.

Dietary genistein stimulates mammary hyperplasia in gilts

The possible role of the phytoestrogen genistein on prepubertal development of mammary glands, hormonal status and bone resorption was investigated in gilts. Forty-five gilts were fed a control diet containing soya (CTLS, n = 15), a control diet without soya (CTL0, n = 15) or the CTLS diet supplemented with 2.3 g of genistein daily (GEN, n = 15) from 90 days of age until slaughter (day 183 ± 1). Both basal diets were isonitrogenous and isocaloric. Jugular blood samples were obtained on days 89 and 176 to determine concentrations of isoflavone metabolites (on day 176 only), prolactin, estradiol, progesterone, insulin-like growth factor 1 (IGF1), and N-telopeptide of type I collagen (NTx; on day 176 only). At slaughter, mammary glands were excised, parenchymal and extraparenchymal tissues were dissected, and composition of parenchymal tissue (protein, fat, dry matter (DM), DNA) was determined. Histochemical analyses of mammary parenchyma were performed. Dietary genistein increased parenchymal protein (P < 0.05) while decreasing DM (P < 0.05) and tending to lower fat content compared with the CTLS, but not the CTL0, diet. There was more parenchymal DNA (1.26 v. 0.92 mg/g, P < 0.05) in GEN than CTLS gilts, likely reflecting an increase in the quantity of mammary epithelial cells. Circulating concentrations of genistein were increased in GEN gilts (P < 0.001) but concentrations of hormones or NTx (indicator of bone collagen resorption) were not affected by GEN (P > 0.1). Percentage of estradiol receptor alpha (ERα)-positive epithelial cells was lower (P < 0.05) in GEN than CTLS gilts, whereas 5-bromo-2′-deoxyuridine labeling index was unaltered (P > 0.1). Transcript levels for ERα, ERβ, IGF1, epidermal growth factor (EGF), epidermal growth factor receptor and transforming growth factor alpha were not altered by treatments. Supplementation of the diet with genistein during the growing phase in gilts, therefore, led to hyperplasia of mammary parenchymal tissue after puberty; yet, even though circulating genistein was increased, this was not accompanied by changes in mammary expression of selected genes or circulating hormone levels.

Dexamethasone Alters the Hepatic Inflammatory Cellular Profile Without Changes in Matrix Degradation During Liver Repair Following Biliary Decompression

Biliary atresia is characterized by extrahepatic bile duct obliteration along with persistent intrahepatic portal inflammation. Steroids are standard in the treatment of cholangitis following the Kasai portoenterostomy, and were advocated for continued suppression of the ongoing immunologic attack against intrahepatic ducts. Recent reports, however, have failed to demonstrate an improved patient outcome or difference in the need for liver transplant in postoperative patients treated with a variety of steroid regimes compared with historic controls. In the wake of progressive liver disease despite biliary decompression, steroids are hypothesized to suppress inflammation and promote bile flow without any supporting data regarding their effect on the emerging cellular and molecular mechanisms of liver repair. We have previously shown in a reversible model of cholestatic injury that repair is mediated by macrophages, neutrophils, and specific matrix metalloproteinase activity (MMP8); we questioned whether steroids would alter these intrinsic mechanisms. Rats underwent biliary ductal suspension for 7 d, followed by decompression. Rats were treated with IV dexamethasone or saline at the time of decompression. Liver tissue obtained at the time of decompression or after 2 d of repair was processed for morphometric analysis, immunohistochemistry, and quantitative RT-PCR. There was a dramatic effect of dexamethasone on the inflammatory component with the initiation of repair. Immunohistochemistry revealed a reduction of both ED1+ hepatic macrophages and ED2+Kupffer cells in repair compared with saline controls. Dexamethasone treatment also reduced infiltrating neutrophils by day 2. TNF-alpha expression, increased during injury in both saline and dexamethasone groups, was markedly reduced by dexamethasone during repair (day 2) whereas IL-6, IL-10, and CINC-1 remained unchanged compared with saline controls. Dexamethasone reduced both MMP8 and TIMP1 expression by day 2, whereas MMP9, 13, and 14 were unchanged compared with sham controls. Despite substantial cellular and molecular changes during repair, collagen resorption was the same in both groups Dexamethasone has clear effects on both the hepatic macrophage populations and infiltrating neutrophils following biliary decompression. Altered MMP and TIMP gene expression might suggest that steroids have the potential to modify matrix metabolism during repair. Nevertheless, successful resorption of collagen fibrosis proceeded presumably through other MMP activating mechanisms. We conclude that steroids do not impede the rapid intrinsic repair mechanisms of matrix degradation required for successful repair.

Differential Toll-like receptor-dependent collagenase expression in chondrocytes

Objectives:To characterise the catabolic response of osteoarthritic chondrocytes to Toll-like receptor (TLR) ligands.Methods:Induction of the collagenases, matrix metalloproteinase (MMP)1 and MMP13, by TLR ligands was assessed in chondrocytes by real-time...

The role of hyperhomocysteinemia as well as folate, vitamin B6 and B12 deficiencies in osteoporosis – a systematic review

Hyperhomocysteinemia (HHCY) has been suggested as a new risk factor for osteoporosis. Recent epidemiological, clinical and experimental studies provide a growing body of data, which is reviewed in this article. Epidemiological and (randomized) clinical trials suggest that HHCY increases fracture risk, but has minor effects on bone mineral density. Measurement of biochemical bone turnover markers indicates a shift of bone metabolism towards bone resorption. Animal studies confirm these observations showing a reduced bone quality and stimulation of bone resorption in hyperhomocysteinemic animals. Homocysteine (HCY) has been found to accumulate in bone by collagen binding. Cell culture studies demonstrate that high HCY levels stimulate osteoclasts but not osteoblasts, indicating again a shift of bone metabolism towards bone resorption. Regarding B-vitamins, only a few in vivo studies with equivocal results have been published. However, two large cell culture studies confirm the results obtained with exogenous HCY administration. In addition, HHCY seems to have adverse affects on extracellular bone matrix by disturbing collagen crosslinking. In conclusion, existing data suggest that HHCY (and possibly B-vitamin deficiencies) adversely affects bone quality by a stimulation of bone resorption and disturbance of collagen crosslinking.

Transforming Growth Factor-β2 Suppresses Collagen Cleavage in Cultured Human Osteoarthritic Cartilage, Reduces Expression of Genes Associated with Chondrocyte Hypertrophy and Degradation, and Increases Prostaglandin E 2 Production

Articular cartilage degeneration in osteoarthritis (OA) involves type II collagen degradation and chondrocyte differentiation (hypertrophy). Because these changes resemble growth plate remodeling, we hypothesized that collagen degradation may be inhibitable by growth factors known to suppress growth plate hypertrophy, namely transforming growth factor (TGF)-beta2, fibroblast growth factor (FGF)-2, and insulin. Full-depth explants of human OA knee articular cartilage from arthroplasty were cultured with TGF-beta2, FGF-2, and insulin in combination (growth factors) or individually. In cultured explants from five OA patients, collagenase-mediated type II collagen cleavage was significantly down-regulated by combined growth factors as measured by enzyme-linked immunosorbent assay. Individually, FGF-2 and insulin failed to inhibit collagen cleavage in some OA explants whereas TGF-beta2 reduced collagen cleavage in these 5 explants and in 19 additional explants. Moreover, TGF-beta2 effectively suppressed cleavage at low concentrations. Together or individually these growth factors did not inhibit glycosaminoglycan (primarily aggrecan) degradation while TGF-beta2 occasionally did. Semiquantitative reverse transcriptase-polymerase chain reaction of articular cartilage from six OA patients revealed that TGF-beta2 suppressed expression of matrix metalloproteinase-13 and matrix metalloproteinase-9, early (PTHrP) and late (COL10A1) differentiation-related genes, and proinflammatory cytokines (interleukin-1beta, tumor necrosis factor-alpha). In contrast, TGF-beta2 up-regulated PGES-1 expression and prostaglandin E(2) release. These observations show that TGF-beta2 can suppress collagen resorption and chondrocyte differentiation in OA cartilage and that this may be mediated by prostaglandin E(2). Therefore TGF-beta2 could provide therapeutic control of type II collagen degeneration in OA.

Cytokine synergy, collagenases and cartilage collagen breakdown.

We have investigated proteinases that degrade cartilage collagen. We show that pro-inflammatory cytokines act synergistically with oncastatin M to promote cartilage collagen resorption by the up-regulation and activation of matrix metalloproteinases (MMPs). The precise mechanisms are not known, but involve the up-regulation of c-fos, which binds to MMP promoters at a proximal activator protein-1 (AP-1) site. This markedly up-regulates transcription and leads to higher levels of active MMP proteins.

Elevated levels of collagen cross-link residues in gingival tissues and crevicular fluid of teeth with periodontal disease.

Lysylpyridinoline (LP) and hydroxylysylpyridinoline (HP) are collagen cross-link residues. Lysylpyridinoline is present in most tissues, whereas LP is present mainly in mineralized tissue. Both are elevated in tissue with increased collagen resorption. The purpose of this investigation was to assess if the concentrations of LP and HP are elevated in gingiva and gingival crevicular fluid (GCF) of teeth with advanced periodontitis (AP). We investigated human gingival biopsies of healthy teeth (n = 19) and teeth with AP (n = 43) in 49 individuals. Samples of GCF from 54 teeth with AP were collected in seven patients and compared with samples from 11 patients with experimentally induced gingivitis. Levels of LP and HP were measured by HPLC and fluorescence detection. Gingival concentrations of HP but not LP around teeth with advanced periodontitis were significantly elevated compared with teeth with healthy periodontium. While significant amounts of HP and LP were measurable in the GCF of teeth with AP, no HP and LP was identified 3 months following non-surgical periodontal therapy of the teeth or in fluid from teeth subjected to experimentally induced gingivitis. Elevated concentrations of HP and LP in GCF may serve as indicators of ongoing destruction of periodontal tissues and alveolar bone in advanced periodontitis.

Low serum levels of intact osteocalcin in patients with congestive heart failure.

Impaired bone metabolism is a frequent complication following heart transplantation. Little is known, however, about possible alterations in bone turnover of pretransplant patients with congestive heart failure (CHF). We therefore studied biomarkers of bone turnover in 21 male patients with CHF (New York Heart Association [NYHA] classification > II) compared with 21 controls (NYHA classification < II). Biomarkers of bone formation (intact osteocalcin and carboxy-terminal propeptide of type I collagen), markers of bone resorption (N-telopeptide and C-telopeptide of type I collagen), undercarboxylated osteocalcin (an indicator of fracture risk), and concentrations of calcium, parathyroid hormone, and vitamin D metabolites (25-hydroxyvitamin D and calcitriol) were measured in fasting blood samples. Serum levels of intact osteocalcin were 44.5% lower (P < 0.01), and the ratio of undercarboxylated-to-intact osteocalcin was 113% higher (P < 0.01) in the patients in comparison with the controls. Moreover, patients had 34% lower 25-hydroxyvitamin D levels (P < 0.01) and 22% lower calcitriol levels (P < 0.05) than the controls. The bone resorption markers, N-telopeptide and C-telopeptide; the bone formation marker, carboxy-terminal propeptide of type I collagen; parathyroid hormone levels; and albumin-adjusted serum calcium concentrations did not differ between patients and controls (all P values > 0.05). In summary, there were no biochemical signs of enhanced bone collagen resorption in pretransplant CHF patients. However, the low serum levels of intact osteocalcin and the high ratio of undercarboxylated-to-intact osteocalcin deserve further consideration.

Fibrogenesis and collagen resorption in the heart and skeletal muscle of Calomys callosus experimentally infected with Trypanosoma cruzi: immunohistochemical identification of extracellular matrix components.

Intense inflammatory lesions and early development of interstitial fibrosis of the myocardium and skeletal muscle with spontaneous regression, have been described in Calomys callosus infected with Trypanosoma cruzi. The genetic types of collagen present in this model were investigated through immunohistochemistry using specific antibodies, combined with histopathology and Picro-Sirius staining of collagen. Thirty-five calomys were infected with the Colombian strain of T. cruzi and sacrificed at 24, 30, 40, 60 and 90 days post-infection. Inflammatory lesions and fibrogenesis were prominent at the early phase of infection and significantly decreased during late infection. Immunoisotyping of the matrix components was performed by indirect immunofluorescence on 5 micro m thick cryostat sections using specific antibodies against laminin, fibronectin and isotypes I, III and IV of collagen. In the early phase, positive deposits of all the matrix components were present, with predominance of fibronectin, laminin and collagens types I and III in the myocardium and of types III and IV in the skeletal muscles. From the 40th day, type IV collagen predominates in the heart. At the late phase of infection (60th to 90th day), a clear fragmentation and decrease of all the matrix components were detected. Findings of the present study indicate that a modulation of the inflammatory process occurs in the model of C. callosus, leading to spontaneous regression of fibrosis independent of the genetic types of collagen involved in this process.

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Time pattern of exercise-induced changes in type I collagen turnover after prolonged endurance exercise in humans.

Type I collagen is known to adapt to physical activity, and biomarkers of collagen turnover indicate that synthesis can be influenced by a single intense exercise bout, but the exact time pattern of these latter changes are largely undescribed. In the present study, 17 healthy young males had their plasma concentrations of the carboxyterminal propeptide of type I procollagen (PICP), a marker of collagen formation, and the immunoactive carboxyterminal cross-linked telopeptide (ICTP), a marker of collagen resorption, measured before and immediately postexercise, as well as 1, 2, 3, 4, 5, and 6 days after completion of a marathon run (42 km). Serum concentrations of creatine kinase (S-CK) were measured as an indicator of muscular breakdown in response to the exercise bout. After a transient decrease in collagen formation immediately after exercise (plasma PICP concentration: 176 +/- 17 microg/liter to 156 +/- 9 microg/liter)(P < 0.05), concentrations rose in the days following the marathon, peaked 72 hours after exercise (197 +/- 8 microg/liter)(P < 0.05 versus basal), and returned to basal values similar to those 5 days postexercise (170 +/- 10 microg/liter). Apart from a short increase immediately after exercise, collagen resorption did not change from basal levels throughout the remaining period (P > 0.05). Muscle breakdown was elevated during the days following the exercise and peaked 24 hours after the exercise (S-CK concentration: 3,133 +/- 579 U/liter). The findings in the present study indicate that type I collagen synthesis is accelerated in response to prolonged strenuous exercise, reaching a peak after 3 days and returning to preexercising levels 5 days after the completion of a marathon run.

Ultrastructural characteristic of collagen resorption in cirrhotic liver

Partial hepatectomy of mouse cirrhotic liver leads to rapid degeneration of hypertrophied connective tissue. Enlarged cisterns of the smooth endoplasmic reticulum lie close to the plasma membrane on the sinusoidal surface of hepatocyte. Golgi apparatus of Kupffer cells is hypertrophied, swollen collagen fibrils lose their specific striation. Microvilli of hepatocyte plasmalemma separate swollen collagen fibrils and draw them into the cytoplasm. Lysosomes, peroxisomes, and hypertrophied Golgi apparatus are spread from the sinusoidal surface to bile capillaries, which indicates that these structures are involved in collagen lysis and release of metabolites into the bile capillary. After partial hepatectomy of cirrhotic liver, hepatocytes, Kupffer cells, and neutrophils play the major role in collagen lysis. Kupffer cells and neutrophils are involved in the lysis of collagen fibrils during CCl4-induced liver cirrhosis.

Increased TIMP-1 activity results in increased expression of gelatinases and altered cell motility

Matrix metalloproteinases are proteolytic enzymes which play a major role in resorption of collagen and other components of the extracellular matrix. They are controlled by specific inhibitors, so-called tissue inhibitors of metalloproteinases (TIMPs). The balance between matrix metalloproteinases and TIMPs seems to play a major role in controlling extracellular matrix homeostasis and cell migration. The influence of TIMP-1 on migration behaviour was explored in human hepatoma cells transiently and stably transfected with mouse TIMP-1, and incubated with biologically active TIMP-1. Transfection and biosynthesis were verified by Northern blotting, Western blotting, metabolic labeling, and reverse zymography. Overexpression of and incubation with TIMP-1 resulted in suppressed migration and seemed to enhance cell-cell contact. Using gelatin zymography and Western blotting we measured a significant increase of matrix metalloproteinases-2 and matrix metalloproteinases-9 in cells transfected with TIMP-1. This new phenomenon may be of important physiological significance in modulating TIMP and MMP expression. Our results indicate a functional involvement of TIMP-1 in matrix homeostasis and some automatic control in matrix turnover.

Matrix remodeling in healing rabbit Achilles tendon.

Biochemical, biomechanical and ultrastructural properties of the connective tissue matrix were investigated during the early remodeling phase of tissue repair in experimentally tenotomized and repaired rabbit Achilles tendons. Sterile surgical tenotomy was performed on the right Achilles tendons of 14 rabbits and allowed to heal for 15 days. The animals were euthanized and the Achilles tendons excised from both limbs. The left contralateral Achilles tendon of each rabbit was used as a control in the experiments. Prior to biochemical analysis, both intact and healing tendons were tested for their biomechanical integrity. The results revealed that the healing tendons had regained some of their physicochemical characteristics, but differed significantly from the intact left tendons. The healing tendons regained 48% tensile strength, 30% energy absorption, 20% tensile stress, and 14% Young's modulus of elasticity of intact tendons. In contrast, biochemical analysis showed that the healing tendons had 80% of the collagen and 60% of the collagen crosslinks (hydroxypyridinium) of normal tendons. Sequential extraction of collagen from the tissues yielded more soluble collagen in the healing tendons than intact tendons, suggesting either an increase in collagen synthesis and/or enhanced resorption of mature collagen in healing tendons compared to intact tendons. Electron microscopic studies revealed remarkable differences in the ultrastructure between intact and healing tendons. These observations could explain, in part, the connective tissue response to healing during the early phases of tissue remodeling.

Extra- and intracellular collagen resorption by macrophages and fibroblasts in postpartum uterine involution

Localization of catepsin B in rat uterus during postpartum involution was studied by electron microscopy using histochemical methods. The product of histochemical reaction was found in collagen-containing vacuoles in macrophages and fibroblasts, on their cytolemma and adjacent collagen fibrils, which indicated the involvement of these cells into intra- and extracellular collagen resorption in the uterus.