Type V collagen in experimental granulation tissue

Building the case for the calcitonin receptor as a viable target for the treatment of glioblastoma

Researchers are actively seeking novel targeted therapies for the brain tumour glioblastoma (GBM) as the mean survival is less than 15 months. Here we discuss the proposal that the calcitonin receptor (CT Receptor), expressed in 76-86% of patient biopsies, is expressed by both malignant glioma cells and putative glioma stem cells (GSCs), and therefore represents a potential therapeutic target. Forty-two per cent (42%) of high-grade glioma (HGG; representative of GSCs) cell lines express CT Receptor protein. CT Receptors are widely expressed throughout the life cycle of organisms and in some instances promote apoptosis. Which of the common isoforms of the CT Receptor are predominantly expressed is currently unknown, but a functional response to cell stress of the insert-positive isoform is hypothesised. A model for resistant malignancies is one in which chemotherapy plays a direct role in activating quiescent stem cells for replacement of the tumour tissue hierarchy. The putative role that the CT Receptor plays in maintenance of quiescent cancer stem cells is discussed in view of the activation of the Notch-CT Receptor-collagen V axis in quiescent muscle (satellite) stem cells. The pharmacological CT response profiles of four of the HGG cell lines were reported. Both CT responders and non-responders were sensitive to an immunotoxin based on an anti-CT Receptor antibody. The CALCR mRNA exhibits alternative splicing commonly associated with cancer cells, which could result in the atypical pharmacology exhibited by CT non-responders and an explanation of tumour suppression. Due to the inherent instability of CALCR mRNA, analysis of CT Receptor protein in patient samples will lead to improved data for the expression of CT Receptor in GBM and other cancers, and an understanding of the role and activity of the splice variants. This knowledge will aid the effective targeting of this receptor for treatment of GBM.

Matrix composition in 3-D collagenous bioscaffolds modulates the survival and angiogenic phenotype of human chronic wound dermal fibroblasts

There is a substantial need for new strategies to stimulate cutaneous tissue repair in the treatment of chronic wounds. To address this challenge, our team is developing modular biomaterials termed "bead foams", comprised of porous beads synthesized exclusively of extracellular matrix (ECM) and assembled into a cohesive three-dimensional (3-D) network. In the current study, bead foams were fabricated from human decellularized adipose tissue (DAT) or commercially-sourced bovine tendon collagen (COL) to explore the effects of ECM composition on human wound edge dermal fibroblasts (weDF) sourced from chronic wound tissues. The DAT and COL bead foams were shown to be structurally similar, but compositionally distinct, containing different levels of glycosaminoglycan content and collagen types IV, V, and VI. In vitro testing under conditions simulating stresses within the chronic wound microenvironment indicated that weDF survival and angiogenic marker expression were significantly enhanced in the DAT bead foams as compared to the COL bead foams. These findings were corroborated through in vivo assessment in a subcutaneous athymic mouse model. Taken together, the results demonstrate that weDF survival and paracrine function can be modulated by the matrix source applied in the design of ECM-derived scaffolds and that the DAT bead foams hold promise as cell-instructive biological wound dressings. STATEMENT OF SIGNIFICANCE: Biological wound dressings derived from the extracellular matrix (ECM) can be designed to promote the establishment of a more permissive microenvironment for healing in the treatment of chronic wounds. In the current work, we developed modular biomaterials comprised of fused networks of porous ECM-derived beads fabricated from human decellularized adipose tissue (DAT) or commercially-available bovine collagen. The bioscaffolds were designed to be structurally similar to provide a platform for investigating the effects of ECM composition on human dermal fibroblasts isolated from chronic wounds. Testing in in vitro and in vivo models demonstrated that cell survival and pro-angiogenic function were enhanced in the adipose-derived bioscaffolds, which contained higher levels of glycosaminoglycans and collagen types IV, V, and VI. Our findings support that the complex matrix composition within DAT can induce a more pro-regenerative cellular response for applications in wound healing.

Topical Collagen-Based Biomaterials for Chronic Wounds: Rationale and Clinical Application

Significance: The extracellular matrix (ECM) is known to be deficient in chronic wounds. Collagen is the major protein in the ECM. Many claims are made while extolling the virtues of collagen-based biomaterials in promoting cell growth and modulating matrix metalloproteinases. This review will explore the rationale for using topical collagen or ECM as an interface for healing. Recent Advances: Rapid improvements in electrospinning and nanotechnology have resulted in the creation of third-generation biomaterials that mimic the native ECM, stimulate cellular and genetic responses in the target tissue, and provide a platform for controlled release of bioactive molecules and live cells. Although the major focus is currently on development of artificial tissues and organ regeneration, better understanding of the mechanisms that stimulate wound healing can be applied to specific deficits in the chronic wound. Critical Issues: When choosing between the various advanced wound-care products and dressings, the clinician is challenged to select the most appropriate material at the right time. Understanding how the ECM components promote tissue regeneration and modulate the wound microenvironment will facilitate those choices. Laboratory discoveries of biomolecular and cellular strategies that promote skin regeneration rather than repair should be demonstrated to translate to deficits in the chronic wound. Future Directions: Cost-effective production of materials that utilize non-mammalian sources of collagen or ECM components combined with synthetic scaffolding will provide an optimal structure for cellular ingrowth and modulation of the chronic wound microenvironment to facilitate healing. These bioengineered materials will be customizable to provide time-released delivery of bioactive molecules or drugs based on the degradation rate of the scaffold or specific signals from the wound.

Transient expression of mouse pro-α3(V) collagen gene (Col5a3) in wound healing

The α3(V) chain is poorly characterized among type V collagen chains. Pro-α3(V) collagen is expressed in newly synthesized bone as well as in the superficial fascia of developing muscle. Present study examined the expression in a mouse model of wound healing. Real-time reverse transcriptase polymerase chain reaction and in situ hybridization revealed transient expression of pro-α3(V) chain at a lower level than other fibrillar collagen genes after injury. Immunohistochemistry showed a similar expression pattern in the injured skin. In addition, electron microscopy showed that pro-α3(V) chain was localized in the amorphous nonfibrillar region, but not in fine or dense fibrils. The pro-α3(V) chain co-localized with heparan sulfate, which appeared in the skin after injury and might bind via an acidic segment of the pro-α3(V) chain. The matrix containing the pro-α3(V) chain may therefore be needed for the initiation of wound healing.

Fibrosis and matrix metalloproteinases in rat renal allografts

The temporal activity and gene expression of matrix metalloproteinases (MMPs) and tissue inhibitors of matrix metalloproteinase (TIMP) were investigated in a rat model of chronic allograft nephropathy. Gelatinolytic activity of MMP-2 and -9 were demonstrated by zymography, and MMP-2,-9 and TIMP-3 mRNA by in situ hybridization. The generation of fibrosis was determined as total collagen content/DNA. Significantly more latent and active MMP-2, as well as latent MMP-9, were seen in allografts than in autografts. Intense MMP-2 mRNA expression was demonstrated in the allografts during the first 20 days after transplantation, located mainly in the interstitium of the kidney. In addition, some tubular cells expressed MMP-2 mRNA. After day 20, MMP-2 gene expression was faint. MMP-9 mRNA expression in allografts was located mainly in the glomerulus. TIMP-3 mRNA expression was downregulated in allografts. MMP-2, MMP-9 and TIMP-3 seem to play a critical role in the development of fibrosis in the renal allograft.

Effects of jump training on procollagen alpha(1)(i) mRNA expression and its relationship with muscle collagen concentration

The aim of this study was to examine the effects of a prolonged high-intensity exercise, jumping, on procollagen alpha(1)(I) mRNA level and collagen concentration in different muscles of trained (T) and control (C) rabbits. Procollagen alpha(1)(I) mRNA expression was much higher (2.8 to 23.5 times) in semimembranosus proprius (SMP), a slow-twitch oxidative muscle, than in extensor digitorum longus (EDL), rectus femoris (RF), and psoas major (Psoas) muscles, both fast-twitch mixed and glycolytic, whatever group was considered (p < 0.001). Procollagen alpha(1)(I) mRNA level also decreased significantly between 50 and 140 days in all muscles (0.001< p < 0.01). However, mRNA levels were 16 to 97% greater at 140 days in all muscles of T animals compared to C ones (0.01< p <0.05). Collagen concentrations of EDL and RF muscles were also higher (14 to 19%) in T than in C rabbits at 90 and 140 days (0.001 < p < 0.05). In the whole sample, collagen concentration was negatively associated with the procollagen alpha(1)(I) mRNA level in EDL and RF muscles (- 0.49 < r < (- 0.44, p < 0.05), while being positively related to mRNA expression in SMP and Psoas muscles (0.65 < r < 0.85, p < 0.01). It is concluded that jump training clearly restricts the decrease of procollagen (I) mRNA level and probably affects collagen synthesis level. In trained rabbit muscles, the maintenance of a better synthesis level could partly explain the higher collagen concentrations found in EDL and RF at 140 days. Nevertheless, the collagen degradation process seems to play the main role in the increase of total collagen concentration with age in EDL and RF muscles.

The fibroblast-populated collagen matrix as a model of wound healing: a review of the evidence

The fibroblast-populated collagen matrix (FPCM) has been utilized as an in vitro model of wound healing for more than 2 decades. It offers a reasonable approximation of the healing wound during the phases of established granulation tissue and early scar. The gross and microscopic morphology of the FPCM and the healing wound are similar at analogous phases. The processes of proliferation, survival/apoptosis, protein synthesis, and contraction act in similar directions in these two models, and the response to exogenous agents also is consistent between them. If its limitations are respected, then the FPCM can be used as a model of the healing wound.

Angiotensin II induces connective tissue growth factor gene expression via calcineurin-dependent pathways

Connective tissue growth factor (CTGF) is a polypeptide implicated in the extracellular matrix synthesis. Previous studies have provided evidence that angiotensin II (Ang II) promotes collagen synthesis and regulates collagen degradation. We investigated whether or not CTGF mediates the profibrotic effects of Ang II in the heart and kidneys and the role of calcineurin-dependent pathways in CTGF gene regulation. In transgenic rats harboring human renin and angiotensinogen genes, Ang II induced an age-dependent increase in myocardial CTGF expression, which was 3.5-fold greater compared to normotensive Sprague Dawley (SD) rats. CTGF overexpression correlated closely with the Ang II-induced rise in blood pressure. CTGF mRNA and protein were located predominantly in areas with leukocyte infiltration, myocardial, and vascular lesions and co-localized with TGFbeta(1), collagen I, and collagen III mRNA expressions. Ang II induced CTGF mRNA and protein to a lesser extent in the kidneys, predominantly in glomeruli, arterioles, and in the interstitium with ample inflammation. However, no expression was found in the right ventricle or pulmonary arteries. Blockade of calcineurin activity by cyclosporine A completely normalized Ang II-induced CTGF overexpression in heart and kidney, suppressed the inflammatory response, and mitigated Ang II-induced cell proliferation and apoptosis. In contrast, blockade of mTOR (target of rapamycin) pathway by everolimus, further increased the expression of CTGF even though everolimus ameliorated cell proliferation and T-cell-mediated inflammation. Our findings provide evidence that CTGF mediates Ang II-induced fibrosis in the heart and kidneys via blood pressure and calcineurin-dependent pathways.

Cyclosporine induces myocardial connective tissue growth factor in spontaneously hypertensive rats on high-sodium diet

BACKGROUND

The introduction of cyclosporine (CsA) has led to an improvement in the prognosis of solid organ transplantation. However, drug-induced hypertension and nephrotoxicity, associated with the development of atherosclerosis and coronary heart disease, still worsen the long-term outcome of CsA-treated patients. Whether the CsA-induced myocardial changes are associated with the induction of connective tissue growth factor (CTGF), a recently found polypeptide implicated in extracellular matrix synthesis, is not known.

METHODS

Spontaneously hypertensive rats (8-9 weeks old) were treated with CsA (5 mg x kg(-1) x d(-1) subcutaneously) for 6 weeks. The influence of angiotensin-converting enzyme inhibition (enalapril 30 mg x kg(-1) x d(-1) orally) and angiotensin-1 receptor blockade (valsartan 3 and 30 mg x kg(-1) x d(-1) orally) on CsA toxicity was also investigated. Myocardial morphology was examined, and vascular lesions were scored. Localization and the quantitative expression of CTGF, as well as collagen I and collagen III, mRNA were evaluated by in situ hybridization and Northern blot.

RESULTS

CsA-induced hypertension and nephrotoxicity were associated with myocardial infarcts and vasculopathy of the coronary arteries. CsA increased myocardial CTGF, collagen I, and collagen III mRNA expressions by 91%, 198%, and 151%, respectively. CTGF mRNA expression colocalized with the myocardial lesions. Blockade of the renin-angiotensin system prevented vascular damage and the CsA-induced CTGF, collagen I, and collagen III mRNA overexpressions in the heart.

CONCLUSIONS

CsA increases CTGF, collagen I, and collagen III mRNA expressions in the heart. The induction of CTGF gene is mediated, at least in part, by angiotensin II.

Cloning of cDNA for rat pro alpha1(V) collagen mRNA. Expression patterns of type I, type III and type V collagen genes in experimental granulation tissue

A cDNA clone for rat pro alpha1(V) collagen mRNA was constructed using PCR amplification, with primers based on human and hamster COL5A1 gene sequences. The clone pRCVA1 is 560 nucleotides long and it encodes for the carboxy propeptide of type V procollagen. Homology shared with type I collagen sequence was 64%, with type II collagen 65% and with type III collagen 61%. To evaluate the spatial and temporal expression of type V collagen mRNA in wound healing model, subcutaneously implanted viscose cellulose sponges in rats were used to induce granulation tissue formation. Analyses on granulation tissue were carried out on days 5, 8, 14, 21, 30, 59 and 84. Specific cDNA probes to pro alpha1(I), pro alpha1(III) and pro alpha1(V) collagen mRNA were used in slot blot, Northern and in situ hybridization. Type I collagen gene expression was upregulated at the initial stage of wound healing, type III collagen gene expression was constant and from the day 14 onwards type I and III collagen gene expressions were at the same level. Type V collagen gene expression was seen at every time point studied but at a considerably lower level than type I and III collagens. In situ hybridization showed that type V collagen was expressed in two different cell types. In conclusion, type V collagen was expressed in the wound healing model from at least day 5 onwards and it was synthesized by fibroblast-like and rounded cells.