Increased Collagen Density Research Articles

Abstract 1116: Response to cyclooxygenase-2 inhibition is regulated by collagen dense stroma

Abstract Increased mammographic density correlates with over four-fold increase risk for breast cancer, making it one of the greatest risk factors known for this disease. High breast density is correlated to increased collagen in the breast tissue, and we have found that increased collagen in the Col1a1tm1jae mouse model promotes mammary tumor formation and progression. Increased collagen density in vitro elevates expression of PTGS2 (prostaglandin-endoperoxide synthase 2), the gene for cyclooxygenase-2 (COX-2), by over four fold. Because COX-2 over-expression is observed in 40% of invasive breast carcinoma cases and correlates with poor prognosis, we hypothesized that inhibition of COX-2 may be an effective therapeutic in the context of mammary tumors arising in dense tissue. Celecoxib is a selective non-steroidal anti-inflammatory drug (NSAID) that specifically inhibits COX-2. To understand how COX-2 affects response to collagen matrix density, we made use of our previously characterized mouse model of MMTV-PyVT tumors in a wild type (wt) or Col1a1tm1jae background (HD). Col1a1tm1jae /+ or wild-type (+/+) littermates were randomly assigned at 11 weeks of age to treatment with vehicle or celecoxib at 0.2mg per mouse per day. Oral treatment was given daily for 21 days. We found a link between matrix density and the role of COX-2. Tumors that arose on the dense Col1a1tm1jae background (HD) were larger and more invasive (p < .0001) and expressed higher levels of COX-2 and PGE2. COX-2 (wt = p = 0.0025, HD = p < 0.0001) and PGE2 (wt = p < 0.0196, HD = p = 0.0002) levels were both decreased in animals treated with celecoxib. Notably, cell proliferation as determined by Ki-67 staining decreased only in HD mice, and not in wt littermates, that received treatment with celecoxib (p = 0.0003, p = 0.0007, respectively). Additionally, the cancer associated fibroblast (CAF) population was diminished by celecoxib only in HD mice and not wt littermates (p = 0.0002). Celecoxib treatment altered collagen structure and the expression of the stromal protein, syndecan, only in Col1a1tm1jae/+ animals. Other features were affected by celecoxib in a non-density manner, as the total number of macrophages (wt = p = 0.0052, HD = p < 0.0001) and normal fibroblasts (wt = p = 0.0133, HD = p = 0.0003) were diminished in animals treated with celecoxib in both Col1a1tm1jae /+ and +/+ animals. Ongoing studies are aimed at identifying different macrophage populations, and which stromal cell populations are expressing COX-2 and PGE2. These findings suggest that COX-2 has a direct role in modulating tumor progression in dense matrices, which in turn promote more aggressive tumors. As dense breast tissue is a common occurrence, these findings suggest that COX-2 may be an effective therapeutic target for women with dense breast tissue. Citation Format: Karla Esbona, David Inman, Sandeep Saha, Kevin Eliceiri, Lee G. Wilke, Patricia J. Keely. Response to cyclooxygenase-2 inhibition is regulated by collagen dense stroma. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 1116. doi:10.1158/1538-7445.AM2014-1116

Cell jamming: Collective invasion of mesenchymal tumor cells imposed by tissue confinement

BackgroundCancer invasion is a multi-step process which coordinates interactions between tumor cells with mechanotransduction towards the surrounding matrix, resulting in distinct cancer invasion strategies. Defined by context, mesenchymal tumors, including melanoma and fibrosarcoma, develop either single-cell or collective invasion modes, however, the mechanical and molecular programs underlying such plasticity of mesenchymal invasion programs remain unclear. MethodsTo test how tissue anatomy determines invasion mode, spheroids of MV3 melanoma and HT1080 fibrosarcoma cells were embedded into 3D collagen matrices of varying density and stiffness and analyzed for migration type and efficacy with matrix metalloproteinase (MMP)-dependent collagen degradation enabled or pharmacologically inhibited. ResultsWith increasing collagen density and dependent on proteolytic collagen breakdown and track clearance, but independent of matrix stiffness, cells switched from single-cell to collective invasion modes. Conversion to collective invasion included gain of cell-to-cell junctions, supracellular polarization and joint guidance along migration tracks. ConclusionsThe density of the extracellulair matrix (ECM) determines the invasion mode of mesenchymal tumor cells. Whereas fibrillar, high porosity ECM enables single-cell dissemination, dense matrix induces cell–cell interaction, leader–follower cell behavior and collective migration as an obligate protease-dependent process. General significanceThese findings establish plasticity of cancer invasion programs in response to ECM porosity and confinement, thereby recapitulating invasion patterns of mesenchymal tumors in vivo. The conversion to collective invasion with increasing ECM confinement supports the concept of cell jamming as a guiding principle for melanoma and fibrosarcoma cells into dense tissue.This article is part of a Special Issue entitled Matrix-mediated cell behaviour and properties.

Alloxan diabetes alters the tensile strength, morphological and morphometric parameters of abdominal wall healing in rats

To investigate the effects of alloxan diabetes on the abdominal wall healing of rats undergoing laparotomy. Ninety-six male Wistar rats weighing between 200 and 300 grams, divided into two groups: non-diabetic group (G1) and another with untreated diabetes (G2). Three months after diabetes induction, the animals underwent a 5cm-long- laparotomy and 5.0 nylon monofilament suture. After the surgery, 12 animals from each group were euthanized on days 4, 14, 21 and 30 corresponding to the moments M1, M2, M3 and M4. In each moment a fragment of the abdominal wall containing the scar was removed for tensile strength measurement, histological and morphometric study. Clinical and biochemical parameters were also analyzed. G2 animals showed parameters compatible with severe diabetes and decreased plasma levels of insulin. The tensile strength in G2 was significantly smaller in M2 and M4, with a tendency to fall in the other two. Through light microscope, diabetic animals showed more difficulty to increase collagen density and contraction. G2 animals showed high cellularity of fibroblasts in later healing moments, with collagen thinning in M2 and M4. The abdominal wound healing in untreated diabetic animals was altered and led to a higher incidence of dehiscence and infections.

A model to determine the effect of collagen fiber alignment on heart function post myocardial infarction.

BackgroundAdverse remodeling of the left ventricle (LV) following myocardial infarction (MI) leads to heart failure. Recent studies have shown that scar anisotropy is a determinant of cardiac function post-MI, however it remains unclear how changes in extracellular matrix (ECM) organization and structure contribute to changes in LV function. The objective of this study is to develop a model to identify potential mechanisms by which collagen structure and organization affect LV function post-MI.MethodsA four-region, multi-scale, cylindrical model of the post-MI LV was developed. The mechanical properties of the infarct region are governed by a constitutive equation based on the uncrimping of collagen fibers. The parameters of this constitutive equation include collagen orientation, angular dispersion, fiber stiffness, crimp angle, and density. Parametric variation of these parameters was used to elucidate the relationship between collagen properties and LV function.ResultsThe mathematical model of the LV revealed several factors that influenced cardiac function post-MI. LV function was maximized when collagen fibers were aligned longitudinally. Increased collagen density was also found to improve stroke volume for longitudinal alignments while increased fiber stiffness decreased stroke volume for circumferential alignments.ConclusionsThe results suggest that cardiac function post-MI is best preserved through increased circumferential compliance. Further, this study identifies several collagen fiber-level mechanisms that could potentially regulate both infarct level and organ level mechanics. Improved understanding of the multi-scale relationships between the ECM and LV function will be beneficial in the design of new diagnostic and therapeutic technologies.

Abstract P1-06-02: Inflammatory stromal cell response induced by collagen dense stroma is regulated by cyclooxygenase-2 in a mouse breast cancer model

Abstract Breast cancer is the most common invasive cancer in women, causing 40,000 deaths yearly in the United States. Increased mammographic density correlates with over four-fold increase risk for breast cancer, making it one of the greatest risk factors known for this disease. High breast density is mainly attributable to elevated collagen matrix deposition in the breast tissue, and we have found that increased collagen in the Col1a1tm1jae mouse model promotes mammary tumor formation and progression. Increased collagen density in vitro increases expression of PTGS2 (prostaglandin-endoperoxide synthase 2), the gene for cyclooxygenase-2 (COX-2), by over four fold. COX-2 over-expression is observed in 40% of invasive breast carcinoma cases and correlates with poor prognosis. Based on these findings, we hypothesized that inhibition of COX-2 may be an effective therapeutic in the context of mammary tumors arising in dense tissue. Celecoxib is a selective non-steroidal anti-inflammatory drug (NSAID) that specifically inhibits COX-2. To understand how COX-2 affects response to collagen matrix density, we utilized our previously characterized mouse model of MMTV-PyVT tumors in a wild type (wt) or Col1a1tm1jae background (HD, High Density). Col1a1tm1jae heterozygote or wt littermates were randomly assigned at 11 weeks of age to treatment with vehicle or celecoxib at 0.2mg per mouse per day. Oral treatment was given daily for 21 days. We found that MMTV-PyVT tumors responded to celecoxib in a manner that is regulated by matrix density. Tumors that arose on the dense Col1a1tm1jae background (HD) were larger and more invasive (p < .0001) and expressed higher levels of COX-2 and PGE2 than their wt littermates. Both COX-2 (wt: p = 0.0025, HD: p < 0.0001) and PGE2 (wt: p = 0.0196, HD: p = 0.0002) levels were decreased in animals treated with celecoxib. However, Ki-67 and syndecan 1 levels decreased only in HD mice that received treatment with celecoxib (p = 0.0003, p = 0.0007, respectively). In addition, total number of macrophages (wt: p = 0.0052, HD: p < 0.0001) and fibroblasts (wt: p = 0.0133, HD: p = 0.0003) were diminished in animals treated with celecoxib independently of collagen density. On the other hand, cancer associated fibroblast (CAF) population was diminished only in HD mice treated with celecoxib (p = 0.0002) which, along with the synedan-1 result suggests that celecoxib selectively abrogates the inflammatory response from reactive stroma only. Consequently, we find that celecoxib treatment remodels collagen fiber organization, such that it more closely resembles wt assembly. Ongoing studies will identify different macrophage populations, and which stromal cell populations express COX-2 and PGE2. These findings suggest that COX-2 has a direct role in modulating tumor progression in dense matrices which promote invasion. Moreover, these findings suggest that COX-2 may be an effective therapeutic target for women with dense breast tissue. Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P1-06-02.

Preliminary exploration of the development of a collagenous artificial dura mater for sustained antibiotic release

Background Intracranial infection is one of the most common complications of open craniocerebral injury and of conventional craniotomy in neurosurgery. The presence of blood-brain barrier leads to lower drug concentrations in the cerebrospinal fluid than in the venous blood. Increasing the intravenous dosage or frequency carries the risk of systemic adverse reactions or infections in other parts of the body. Developing an artificial dura mater (ADM) for sustained antibiotic release for use during neurosurgery can solve the problems perfectly. Methods Three types of drug-loaded ADMs made of collagen and containing cefuroxime sodium, ceftriaxone sodium, or norvancomycin were prepared. The antibacterial activity and sustained release characteristics of the ADMs were examined using bacteriostatic and release tests. Results Single-layered collagen based ADMs (40 mm×50 mm×5 mm) containing 18 mg cefuroxime sodium or ceftriaxone sodium were not suitable for continued development because of drug preservation and stability issues. Using smaller ADMs (20 mm×30 mm×7 mm), containing 4.86 mg of norvancomycin, with increased collagen density and a three-layered film with two outer drug-free films above and below the antibiotic layer resulted in sustained cumulative release of 2.91 mg (59.9%) of norvancomycin over 72 hours. The similar factor (f2) comparison method proved that products from a same batch were statistically significant similar (f2 >50). Conclusions Artificial ADMs made of collagen can be processed to provide a mature dural repair material for the sustained release of norvancomycin. This system may provide a basis for developing sustained release materials for other drugs.

11β-Hydroxysteroid dehydrogenase blockade prevents age-induced skin structure and function defects

Glucocorticoid (GC) excess adversely affects skin integrity, inducing thinning and impaired wound healing. Aged skin, particularly that which has been photo-exposed, shares a similar phenotype. Previously, we demonstrated age-induced expression of the GC-activating enzyme 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1) in cultured human dermal fibroblasts (HDFs). Here, we determined 11β-HSD1 levels in human skin biopsies from young and older volunteers and examined the aged 11β-HSD1 KO mouse skin phenotype. 11β-HSD1 activity was elevated in aged human and mouse skin and in PE compared with donor-matched photo-protected human biopsies. Age-induced dermal atrophy with deranged collagen structural organization was prevented in 11β-HSD1 KO mice, which also exhibited increased collagen density. We found that treatment of HDFs with physiological concentrations of cortisol inhibited rate-limiting steps in collagen biosynthesis and processing. Furthermore, topical 11β-HSD1 inhibitor treatment accelerated healing of full-thickness mouse dorsal wounds, with improved healing also observed in aged 11β-HSD1 KO mice. These findings suggest that elevated 11β-HSD1 activity in aging skin leads to increased local GC generation, which may account for adverse changes occurring in the elderly, and 11β-HSD1 inhibitors may be useful in the treatment of age-associated impairments in dermal integrity and wound healing.

Wound-Healing Potential of the Root Extract of Albizzia lebbeck

The present investigation is an attempt to scientifically validate the traditional use of the roots of the plant Albizzia lebbeck in Ayurvedic system of medicine for curing wounds. The study included phytochemical standardization of the ethanol root extract of A.lebbeck, which was further subjected to oral acute toxicity study. Wound-healing activity of the ethanol root extract was evaluated using incision and excision wound models. Biochemical parameters such as hydroxyproline, hexuronic acid, hexosamine, and antioxidant enzymes like superoxide dismutase, reduced glutathione and free radical parameters including lipid peroxidation and nitric oxide were evaluated on the 10th post-wounding day following dead space method. For confirmation of activity, histopathology of the wounds and granulation tissues from excision and dead space wound model were performed. The study also included assessment of antibacterial activity of ethanol root extract against strains implicated in wound infection. The ethanol root extract was found to be highly rich in flavonoids, saponins, phenols, and tannins, while the amount of rutin was found to be 4.66 % w/w. It significantly increased the wound breaking strength showing a ceiling effect at 500 mg/kg p. o. The ethanol root extract at 500 mg/kg p. o. depicted an optimum wound contraction on the 18th day, while complete wound contraction was observed at the 22nd post wound day. It also demonstrated a significant increase in dry tissue weight, total protein, hydroxyproline, hexosamine, hexuronic acid, superoxide dismutase, and reduced glutathione levels, whereas a decrease in the levels of lipid peroxidation and nitric oxide was also observed with a potential antibacterial activity. Histopathological studies revealed a normal epithelization and fibrosis which was evidenced through an increase in collagen density. Thus, the study scientifically validated the wound-healing activity of the ethanol root extract along with a potential antibacterial property which may be attributed to the enhanced collagen synthesis and a potential antioxidant activity.

Stiff Collagen Matrices Increase Tumorigenic Prolactin Signaling in Breast Cancer Cells

Clinically, circulating prolactin levels and density of the extracellular matrix (ECM) are individual risk factors for breast cancer. As tumors develop, the surrounding stroma responds with increased deposition and cross-linking of the collagen matrix (desmoplasia). In mouse models, prolactin promotes mammary carcinomas that resemble luminal breast cancers in women, and increased collagen density promotes tumor metastasis and progression. Although the contributions of the ECM to the physiologic actions of prolactin are increasingly understood, little is known about the functional relationship between the ECM and prolactin signaling in breast cancer. Here, we examined consequences of increased ECM stiffness on prolactin signals to luminal breast cancer cells in three-dimensional collagen I matrices in vitro. We showed that matrix stiffness potently regulates a switch in prolactin signals from physiologic to protumorigenic outcomes. Compliant matrices promoted physiological prolactin actions and activation of STAT5, whereas stiff matrices promoted protumorigenic outcomes, including increased matrix metalloproteinase-dependent invasion and collagen scaffold realignment. In stiff matrices, prolactin increased SRC family kinase-dependent phosphorylation of focal adhesion kinase (FAK) at tyrosine 925, FAK association with the mitogen-activated protein kinase mediator GRB2, and pERK1/2. Stiff matrices also increased co-localization of prolactin receptors and integrin-activated FAK, implicating altered spatial relationships. Together, these results demonstrate that ECM stiffness is a powerful regulator of the spectrum of prolactin signals and that stiff matrices and prolactin interact in a feed-forward loop in breast cancer progression. Our study is the first reported evidence of altered ECM-prolactin interactions in breast cancer, suggesting the potential for new therapeutic approaches.

Short-Term Response of Mitomycin C on the Human Rectus Muscle Following Strabismus Surgery: Histological, Ultrastructural, and Biomechanical Evaluation

This study investigated the inflammatory effect of intraoperative mitomycin C (MMC) on adhesion reformation in human rectus muscles. Ten consecutive patients who underwent medial rectus resection had their postoperative rectus muscles divided into two groups: control group (n = 10) and MMC group (n = 10). In the MMC group, the muscle was soaked for 2 min with MMC, prepared as a 0.2 mg/mL (0.02%) solution. The 0.02% MMC reactions were examined using histological analysis with hematoxylin-eosin (inflammatory response) and Masson's trichrome (collagen fibrils), immunoreactivities of cyclooxygenase-II (inflammatory response), and collagen type I and III, scanning electron microscopy analysis to quantify the diameter and D-periodicity of collagen fibrils, and atomic force microscopy analysis to quantify the diameter, D-periodicity, and adhesion force of collagen fibrils. The rectus muscles treated with 0.02% MMC showed a significantly increased inflammatory response (p < 0.05), increased collagen density (p < 0.0001), increased fibril diameter (p < 0.001 or p < 0.05), and decreased fibril adhesion force (p < 0.005) compared to the rectus muscles in the control group. MMC simultaneously caused an inflammatory response as well as nanostructural and biomechanical property changes in the collagen fibril network.

Las sendas del Qi

Acupuncture channels are entities which have been reported since antiquity. Nevertheless, the demonstration of their existence has become one of the most controversial research topics in Traditional Chinese Medicine. Although the data are not conclusive, there is strong evidence which indicates that cutaneous regions in which the acupuncture channels are located are different from the rest. In these regions, electrical resistance is lower thus permitting the faster propagation of electromagnetic waves. This hypothesis is also supported by different histological (increased collagen density) and biochemical (high concentration of neurotransmitters and vasoactive substances) findings. Overall, the hypothesis of the existence of acupuncture channels has gained weight, but further research is required to characterize in more depth their properties.

An airway smooth muscle cell niche under physiological pulsatile flow culture using a tubular dense collagen construct

Bioengineered tissue equivalents should provide physiologically relevant biochemical and mechanical cues to support the growth and differentiation of seeded cells. Herein, tubular dense collagen constructs (TDCCs) with collagen content comparable to native extracellular matrix were used to investigate the effect of shear stress alone (i.e. under laminar fluid flow), and shear stress in combination with circumferential strain (i.e. under pulsatile fluid flow) on the proliferation, alignment, and phenotype of three-dimensionally (3D) seeded airway smooth muscle cells (ASMCs). In addition, the effect of ASMC-mediated remodelling on TDCC matrix morphological and mechanical properties was investigated. Compared to static culture, pulsatile flow increased seeded ASMC growth by 70%, improved the homogeneity of cell distribution within the TDCCs and induced differential cellular alignment depending on the primary stimuli. Specifically, within the inner wall, where shear stress is predominant, ASMCs were aligned parallel to fluid flow direction, while within the outer wall ASMCs were aligned parallel to the circumferential strain (perpendicular to fluid flow). In contrast, under laminar flow, ASMCs were aligned parallel to fluid flow direction within both walls. Compared to laminar flow, pulsatile flow resulted in increased positive staining for α-smooth muscle actin, and in up-regulated typical ASMC contractile markers suggesting that circumferential strain modulates ASMC differentiation. Pulsatile flow also caused a 60 and 30% increase in collagen density within both acellular and cellular TDCCs, respectively, which was reflected in an increased apparent modulus. Compared to static culture, pulsatile stimulation of cellular constructs resulted in 70% higher circumferential strength. The TDCCs provide ASMC niche for greater insight into the responses of 3D seeded SMCs to physiologically equivalent in vitro dynamic conditioning.

Short-term effect of cryotherapy on human scleral tissue by atomic force microscopy

This study investigated the inflammatory effect of cryotherapy application on collagen matrix network in human infant sclera. Donor scleral tissues taken from three infant patients divided into five groups: control group, sham-treated group, and three cryotreated groups. In the cryotherapy groups, the sclera was treated for 5 s, 10 s, and 20 s with -80°C freezing by a cryosurgical system. The cryotreated reactions were examined using double histological analysis with hematoxylin-eosin and Masson's trichrome, and atomic force microscopy analysis to quantify the diameter and D-banding of collagen fibrils. The infant scleral tissues treated with cryotherapy showed a significantly increased collagen density associated with inflammatory response (p < 0.05), increased fibril diameter (p < 0.005) compared to the scleral tissues in the control group. The results directly suggest that the cryotherapy affects the morphology of scleral collagen.

Laryngeal aging and acoustic changes in male rat ultrasonic vocalizations

This study examined changes in the acoustic and temporal structure of ultrasonic vocalizations as a function of age and correlated acoustic changes with vocal fold microstructure. Ultrasonic vocalizations were recorded in three age groups of male rats: aged (24-26 months), middle-aged (17-18 months), and young (4-5 months). Acoustic and structural changes in vocal fold tissue were evident by 18 months of age. Histological analyses revealed decreased density of elastin and hyaluronic acid and increased collagen density in the middle-aged and aged groups compared to the young rats. Laryngeal microstructure correlated with some of the ultrasonic acoustic features. These results show that male Long Evans rats experience changes in ultrasonic acoustic structure by middle age, and these changes correlate with deterioration in laryngeal microstructure. Ultrasonic vocalizations can be used as a model system for age-related degeneration in vocal fold structure and function.

Hypoxic Culture and Insulin Yield Improvements to Fibrin-Based Engineered Tissue

We examined the effect of insulin supplementation and hypoxic culture (2% vs. 20% oxygen tension) on collagen deposition and mechanical properties of fibrin-based tubular tissue constructs seeded with neonatal human dermal fibroblasts. The results presented here demonstrate that constructs cultured under hypoxic conditions with insulin supplementation increased in collagen density by approximately five-fold and both the ultimate tensile strength (UTS) and modulus by more than three-fold compared with normoxic (20% oxygen tension), noninsulin supplemented controls. In addition, collagen deposited on a per-cell basis increased by approximately four-fold. Interaction was demonstrated for hypoxia and insulin in combination in terms of UTS and collagen production on a per-cell basis. This interaction resulted from two distinct processes involved in collagen fibril formation. Western blot analysis showed that insulin supplementation alone increased Akt phosphorylation and the combined treatment increased collagen prolyl-4-hydroxylase. These molecules are distinct regulators of collagen deposition, having an impact at both the transcriptional and posttranslational modification stages of collagen fibril formation that, in turn, increase collagen density in the tissue constructs. These findings highlight the potential of utilizing insulin supplementation and hypoxic culture in combination to increase the mechanical strength and stiffness of fibrin-based engineered tissues.

Effect of Fibrin Glue on Collagen Deposition after Autologous Fascia Grafting in Rabbit Vocal Folds

Fibrin glue (FG) is a reaction product of fibrinogen and thrombin that forms a fibrin clot responsible for tissue adhesion. However, FG and its components may interfere with wound healing by interacting with cytokines such as transforming growth factor-beta (TGF-beta). The objective of this study was to investigate the effect of FG on collagen deposition after fascia grafting in the vocal folds of rabbits. Eighteen rabbits underwent autologous fascia grafting in both vocal folds, and the left side was fixed with FG. Each animal was painlessly sacrificed after 7, 30, or 90 days. The larynx was removed, and the vocal folds were prepared for histomorphometric analysis by picrosirius red staining to evaluate collagen deposition around the graft. There was a significant increase in collagen density around the grafts at 90 days in the vocal folds that were fixed with FG (p=0.0102) compared with the control vocal folds. Application of FG altered collagen deposition around the fascia grafts, leading to significantly increased collagen density after 90 days. Differences found in the composition of the extracellular matrix in later stages of the healing process are a result of changes that occur in the beginning of this process. Therapeutic interventions, such as the use of FG and/or its components, performed in the early stages of wound healing may interfere with the complex interactions of fibroblasts, inflammatory cells, and cytokines (especially TGF-beta), thereby modulating the healing process.

Aerobic interval training attenuates pathological cardiovascular remodeling in aortic‐banded miniature swine

Cardiac hypertrophy (CH) in response to hypertension or myocardial infarction is a pathological indicator associated with heart failure. Recent evidence indicates exercise training can attenuate or reverse this response creating a physiological phenotype. The purpose of this study was to examine cardiovascular remodeling in aortic‐banded (AB) sedentary (HFSED, n=6), AB exercise trained (HFTR, n=5; 3 days/wk, 15 wks, started 2 mo. post‐AB) and control sedentary (n=5) male Yucatan miniature swine. At the start of training, end diastolic and systolic volume and dimension were increased in both AB groups. Left ventricular (LV) hypertrophy, indicated by increased heart weight:body weight (BW), LV+septum (LV+S):BW, LV+S:RV, and cardiomyocyte cross‐sectional area, was similar in both AB groups postmortem. Increased LV fibrosis (23%) and collagen (36%) observed in HFSED animals was attenuated by exercise. LV mitochondrial dysfunction, measured by Ca2+ induced mitochondrial swelling, was greater in HFSED vs. HFTR animals. Exercise attenuated increased medial collagen deposition in the right coronary artery seen in HFSED, while increasing collagen density in the left circumflex artery. In conclusion, CH appears more physiological in exercise trained AB swine when compared to their sedentary counterparts as evident by decreased LV fibrosis, collagen, and mitochondrial dysfunction. NIH HL093982 &amp; HL52490

Lentivirus Immobilization to Nanoparticles for Enhanced and Localized Delivery From Hydrogels

Hydrogels can provide a controllable cell microenvironment for numerous applications in regenerative medicine, and delivery of gene therapy vectors can be employed to enhance their bioactivity. We investigated the delivery of lentiviral vectors from hydrogels, and employed the immobilization of lentivirus to hydroxylapatite (HA) nanoparticles as a means to retain and stabilize vectors within hydrogels, and thereby increase delivery efficiency. Entrapment of the vector alone within the hydrogel maintained the activity of the virus more effectively compared to the absence of a hydrogel, and release was slowed with an increasing solid content of the hydrogel. Association of the lentivirus with HA increased the activity of the complexes, with HA increasing the virus activity for 72 hours. Cells seeded onto lentivirus-HA-loaded hydrogels had a decreased number of infected cells outside of the hydrogel relative to the absence of HA. In vivo studies with collagen hydrogels loaded with lentivirus and HA-lentivirus demonstrated sustained and localized transgene expression for at least 4 weeks, with increased expression using the lentivirus-HA complex. This strategy of nanoparticle immobilization to stabilize and retain vectors is broadly applicable to hydrogels, and may provide a versatile tool to combine gene therapy and biomaterials for applications in regenerative medicine.

Ultrasound accelerates healing of normal wounds but not of ischemic ones

To examine the influence of therapeutic ultrasound (US) on repair of standard and ischemic cutaneous lesions, full-thickness excisional wounds were made in rats and treated with a US 3 MHz, 0.5 W/cm(2) pulsed duty cycle. We used five experimental groups: control (received US powered off on the day of surgery, and on the second and fourth day), control US (received US on the day of surgery, and on the second and fourth day), ischemic (received US powered off on the day of surgery, and on the second and fourth day), ischemic US 3X (received US on the day of surgery, and on the second and fourth day) and ischemic US 5X (received US in the day of surgery, first, second, third and fourth day). The control US group showed acceleration in wound contraction 7 days after wounding, an increase in collagen density, and only focal inflammatory areas. Neo-epidermis formation was more advanced in the control US group than in the control one. Wound contraction was delayed in the ischemic group when compared with the control group as well as the ischemic US 3X group, was but slightly accelerated in the ischemic US 5X group when compared with the ischemic group 7 days after wounding. Reepithelialization was delayed in both ischemic US groups when compared with the ischemic group. The number of inflammatory cells was higher in both US ischemic groups. We conclude that US therapy accelerates wound healing in normal wounds and delays wound healing in ischemic wounds.

Liver‐derived extracellular matrix as a biologic scaffold for acute vocal fold repair in a canine model

The objective of the study was to evaluate a naturally derived liver extracellular matrix (L-ECM) scaffold for repair of an acute injury to the vocal fold lamina propria in a canine model. The vocal fold lamina propria was removed bilaterally in four dogs. One vocal fold in each dog was repaired with a porcine L-ECM scaffold, which was chosen because it contains hepatocyte growth factor, an antifibrotic growth factor that aids the healing of vocal folds. The other vocal fold was left untreated. At 3 months after surgery, morphologic and histologic analysis was performed to assess the vocal fold shape, collagen density, collagen composition, elastic fiber content, and glycosaminoglycan content. The L-ECM-treated vocal fold showed increased collagen density in the superficial aspect of the vocal fold (P < .05). The L-ECM-treated vocal fold also showed an increased collagen III/I ratio as compared to the nontreated group (P < .05). However, the elastic fiber content was found to be increased in both groups, and the glycosaminoglycan content was decreased in both groups as compared to the normal vocal fold (P < .05) with no differences detected between groups. The L-ECM scaffold did not restore the biochemical composition or histologic appearance of the injured vocal fold as compared to normal. However, the increased ratio of collagen III/I and elastic fiber content suggests that L-ECM leads to formation of connective tissue that may be more pliable as compared to no treatment. Additional investigation, including functional assessment, is warranted.