Browsing by Subject "Collagen"
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Item Adipose stromal cells enhance keratinocyte survival and migration in vitro, and graft revascularization in mouse wound healing model(2013-12-11) Knowles, Kellen Alexander; Berbari, Edward J.; March, Keith Leonard, 1963-; Ji, JulieIn the US, more than 1 million burn injuries are reported annually. About 45,000 injuries due to fires and burns result in hospitalization and ten percent of these result in death every year. Advances in burn treatment have led to a reduction in mortality rate over the last decades. Since more patients are surviving the initial resuscitation phase even with very large areas of skin being burned away, wound care has become increasingly important to ensure continued patient survival and improvement. While currently a common treatment for third degree burn wounds, skin grafts have several drawbacks. The availability of donor sites for autografts may be limited, especially in incidences of extensive skin loss. The rejection associated with the use of allografts and xenografts may render them inadequate or undesirable. Even if a suitable graft is found, poor retention due to infection, hematoma, and low vascularity at the recipient site are other drawbacks associated with the use of skin grafts as a primary treatment for severe burn wounds. As such, research has been done into alternative treatments, which include but are not limited to artificial skin, cell therapy, and growth factor application. We propose the delivery of adipose derived stem cells (ASC) in combination with endothelial progenitor cells (EC) via Integra Dermal Regenerative Template (DRT) to promote faster graft vascularization and thus faster healing of wounds. Integra DRT is an acellular skin substitute that consists of a dermal layer composed of bovine collagen and chondroitin-6-sulfate glycosaminoglycan, and an "epidermal" layer, which consists of silicone polymer. This silicone layer is removed after the collagen matrix is adequately vascularized (usually takes 2-3 weeks), and then a thin layer autograft is applied to the top of the neo-dermis. ASC are derived from the stromal-vascular fraction (SVF) of adipose tissue and are a readily available, pluripotent, mesenchymal cell known to promote angiogenesis. They are being explored as a treatment for a myriad of diseases and conditions, including wound healing. In combination with ECs, they form stable microvessel networks in vitro and in vivo. In our work, we found that ASC+EC form stable microvessel networks when cultured on Integra DRT. Also, ASC and ASC+EC conditioned media promoted both survival and migration of human epidermal keratinocytes compared to control medium. In a full thickness wound healing model, using healthy NSG mice, the ASC+EC case showed a significantly higher rate of wound closure compared to control. Based on best linear unbiased estimates (BLUE), the difference between the healing rates of ASC alone treatment and the Control treatment group is -0.45 +/- 0.22 mm²/day (p=0.041), which is not less than 0.025 and thus not statistically significant (Bonferroni Adjusted). However, the BLUE for the difference between the ASC+EC group and the Control group healing rates is -0.55 +/- 0.28 mm²/day (p = 0.017<0.025, Bonferroni Adjusted), which is statistically significant. Histology revealed a significantly higher number of vessels compared to control in both ASC alone and ASC+EC case. CD31 staining revealed the presence of human vessels in ASC+EC treatment scaffolds. We conclude that the combination of ASC and EC can be used to accelerate healing of full-thickness wounds when delivered to site of the wound via Integra. This result is especially compelling due to the fact that the mice used were all healthy. Thus our treatment shows an improvement in healing rate even compared to normal wound healing.Item Anisotropic Properties of Articular Cartilage in an Accelerated In Vitro Wear Test(Elsevier, 2020-09) Hossain, M. Jayed; Noori-Dokht, Hessam; Karnik, Sonali; Alyafei, Naomi; Joukar, Amin; Trippel, Stephen B.; Wagner, Diane R.; Mechanical and Energy Engineering, School of Engineering and TechnologyMany material properties of articular cartilage are anisotropic, particularly in the superficial zone where collagen fibers have a preferential direction. However, the anisotropy of cartilage wear had not been previously investigated. The objective of this study was to evaluate the anisotropy of cartilage material behavior in an in vitro wear test. The wear and coefficient of friction of bovine condylar cartilage were measured with loading in directions parallel (longitudinal) and orthogonal (transverse) to the collagen fiber orientation at the articular surface. An accelerated cartilage wear test was performed against a T316 stainless-steel plate in a solution of phosphate buffered saline with protease inhibitors. A constant load of 160 N was maintained for 14000 cycles of reciprocal sliding motion at 4 mm/s velocity and a travel distance of 18 mm in each direction. The contact pressure during the wear test was approximately 2 MPa, which is in the range of that reported in the human knee and hip joint. Wear was measured by biochemically quantifying the glycosaminoglycans (GAGs) and collagen that was released from the tissue during the wear test. Collagen damage was evaluated with collagen hybridizing peptide (CHP), while visualization of the tissue composition after the wear test was provided with histologic analysis. Results demonstrated that wear in the transverse direction released about twice as many GAGs than in the longitudinal direction, but that no significant differences were seen in the amount of collagen released from the specimens. Specimens worn in the transverse direction had a higher intensity of CHP stain than those worn in the longitudinal direction, suggesting more collagen damage from wear in the transverse direction. No anisotropy in friction was detected at any point in the wear test. Histologic and CHP images demonstrate that the GAG loss and collagen damage extended through much of the depth of the cartilage tissue, particularly for wear in the transverse direction. These results highlight distinct differences between cartilage wear and the wear of traditional engineering materials, and suggest that further study on cartilage wear is warranted. A potential clinical implication of these results is that orienting osteochondral grafts such that the direction of wear is aligned with the primary fiber direction at the articular surface may optimize the life of the graft.Item Cirrhosis regression is associated with improved clinical outcomes in patients with nonalcoholic steatohepatitis(Wiley, 2022) Sanyal, Arun J.; Anstee, Quentin M.; Trauner, Michael; Lawitz, Eric J.; Abdelmalek, Manal F.; Ding, Dora; Han, Ling; Jia, Catherine; Huss, Ryan S.; Chung, Chuhan; Wong, Vincent Wai-Sun; Okanoue, Takeshi; Romero-Gomez, Manuel; Muir, Andrew J.; Afdhal, Nezam H.; Bosch, Jaime; Goodman, Zachary; Harrison, Stephen A.; Younossi, Zobair M.; Myers, Robert P.; Medicine, School of MedicineBackground and aims: Surrogate endpoints that predict complications are necessary for assessment and approval of NASH therapies. We assessed associations between histologic and noninvasive tests (NITs) of fibrosis with liver-related complications in patients with NASH cirrhosis. Approach and results: Patients with compensated cirrhosis due to NASH were enrolled in two placebo-controlled trials of simtuzumab and selonsertib. Liver fibrosis at baseline and week 48 (W48) was staged by NASH Clinical Research Network (CRN) and Ishak classifications and a machine learning (ML) approach, hepatic collagen and alpha-smooth muscle actin (α-SMA) expression were quantified by morphometry, liver stiffness (LS) was measured by transient elastography, and serum NITs (enhanced liver fibrosis [ELF], NAFLD fibrosis score [NFS], and Fibrosis-4 index [FIB-4]) were calculated. Cox regression determined associations between these parameters at baseline and their changes over time with adjudicated liver-related clinical events. Among 1,135 patients, 709 (62%) had Ishak stage 6 fibrosis, and median ELF and LS were 10.66 and 21.1 kPa, respectively. During a median follow-up of 16.6 months, 71 (6.3%) had a liver-related event; associated baseline factors included Ishak stage 6 fibrosis, and higher hepatic collagen, α-SMA expression, ML-based fibrosis parameters, LS, ELF, NFS, and FIB-4. Cirrhosis regression observed in 16% (176/1,135) between BL and W48 was associated with a lower risk of events versus nonregression (1.1% [2/176] vs. 7.2% [69/957]; HR, 0.16; 95% CI, 0.04, 0.65 [p = 0.0104]). Conversely, after adjustment for baseline values, increases in hepatic collagen, α-SMA, ML-based fibrosis parameters, NFS, and LS were associated with an increased risk of events. Conclusions: In patients with compensated cirrhosis due to NASH, regression of fibrosis is associated with a reduction in liver-related complications. These data support the utility of histologic fibrosis regression and NITs as clinical trial endpoints for NASH cirrhosis.Item Collagen COL22A1 maintains vascular stability and mutations in COL22A1 are potentially associated with intracranial aneurysms(The Company of Biologists, 2018-12-12) Ton, Quynh V.; Leino, Daniel; Mowery, Sarah A.; Bredemeier, Nina O.; Lafontant, Pascal J.; Lubert, Allison; Gurung, Suman; Farlow, Janice L.; Foroud, Tatiana M.; Broderick, Joseph; Sumanas, Saulius; Medical and Molecular Genetics, School of MedicineCollagen XXII (COL22A1) is a quantitatively minor collagen, which belongs to the family of fibril-associated collagens with interrupted triple helices. Its biological function has been poorly understood. Here, we used a genome-editing approach to generate a loss-of-function mutant in zebrafish col22a1 Homozygous mutant adults exhibit increased incidence of intracranial hemorrhages, which become more prominent with age and after cardiovascular stress. Homozygous col22a1 mutant embryos show higher sensitivity to cardiovascular stress and increased vascular permeability, resulting in a greater percentage of embryos with intracranial hemorrhages. Mutant embryos also exhibit dilations and irregular structure of cranial vessels. To test whether COL22A1 is associated with vascular disease in humans, we analyzed data from a previous study that performed whole-exome sequencing of 45 individuals from seven families with intracranial aneurysms. The rs142175725 single-nucleotide polymorphism was identified, which segregated with the phenotype in all four affected individuals in one of the families, and affects a highly conserved E736 residue in COL22A1 protein, resulting in E736D substitution. Overexpression of human wild-type COL22A1, but not the E736D variant, partially rescued the col22a1 loss-of-function mutant phenotype in zebrafish embryos. Our data further suggest that the E736D mutation interferes with COL22A1 protein secretion, potentially leading to endoplasmic reticulum stress. Altogether, these results argue that COL22A1 is required to maintain vascular integrity. These data further suggest that mutations in COL22A1 could be one of the risk factors for intracranial aneurysms in humans.Item Collagen in Wound Healing(MDPI, 2021-05-11) Mathew-Steiner, Shomita S.; Roy, Sashwati; Sen, Chandan K.; Medicine, School of MedicineNormal wound healing progresses through inflammatory, proliferative and remodeling phases in response to tissue injury. Collagen, a key component of the extracellular matrix, plays critical roles in the regulation of the phases of wound healing either in its native, fibrillar conformation or as soluble components in the wound milieu. Impairments in any of these phases stall the wound in a chronic, non-healing state that typically requires some form of intervention to guide the process back to completion. Key factors in the hostile environment of a chronic wound are persistent inflammation, increased destruction of ECM components caused by elevated metalloproteinases and other enzymes and improper activation of soluble mediators of the wound healing process. Collagen, being central in the regulation of several of these processes, has been utilized as an adjunct wound therapy to promote healing. In this work the significance of collagen in different biological processes relevant to wound healing are reviewed and a summary of the current literature on the use of collagen-based products in wound care is provided.Item Compression-induced structural and mechanical changes of fibrin-collagen composites(Elsevier, 2017-07) Kim, O. V.; Litvinov, R. I.; Chen, J.; Chen, D. Z.; Weisel, J.W.; Alber, M. S.; Medicine, School of MedicineFibrin and collagen as well as their combinations play an important biological role in tissue regeneration and are widely employed in surgery as fleeces or sealants and in bioengineering as tissue scaffolds. Earlier studies demonstrated that fibrin-collagen composite networks displayed improved tensile mechanical properties compared to the isolated protein matrices. Unlike previous studies, here unconfined compression was applied to a fibrin-collagen filamentous polymer composite matrix to study its structural and mechanical responses to compressive deformation. Combining collagen with fibrin resulted in formation of a composite hydrogel exhibiting synergistic mechanical properties compared to the isolated fibrin and collagen matrices. Specifically, the composite matrix revealed a one order of magnitude increase in the shear storage modulus at compressive strains>0.8 in response to compression compared to the mechanical features of individual components. These material enhancements were attributed to the observed structural alterations, such as network density changes, an increase in connectivity along with criss-crossing, and bundling of fibers. In addition, the compressed composite collagen/fibrin networks revealed a non-linear transformation of their viscoelastic properties with softening and stiffening regimes. These transitions were shown to depend on protein concentrations. Namely, a decrease in protein content drastically affected the mechanical response of the networks to compression by shifting the onset of stiffening to higher degrees of compression. Since both natural and artificially composed extracellular matrices experience compression in various (patho)physiological conditions, our results provide new insights into the structural biomechanics of the polymeric composite matrix that can help to create fibrin-collagen sealants, sponges, and tissue scaffolds with tunable and predictable mechanical properties.Item Control of Bone Matrix Properties by Osteocytes(Frontiers Media, 2021-01-18) Creecy, Amy; Damrath, John G.; Wallace, Joseph M.; Biomedical Engineering, School of Engineering and TechnologyOsteocytes make up 90–95% of the cellular content of bone and form a rich dendritic network with a vastly greater surface area than either osteoblasts or osteoclasts. Osteocytes are well positioned to play a role in bone homeostasis by interacting directly with the matrix; however, the ability for these cells to modify bone matrix remains incompletely understood. With techniques for examining the nano- and microstructure of bone matrix components including hydroxyapatite and type I collagen becoming more widespread, there is great potential to uncover novel roles for the osteocyte in maintaining bone quality. In this review, we begin with an overview of osteocyte biology and the lacunar–canalicular system. Next, we describe recent findings from in vitro models of osteocytes, focusing on the transitions in cellular phenotype as they mature. Finally, we describe historical and current research on matrix alteration by osteocytes in vivo, focusing on the exciting potential for osteocytes to directly form, degrade, and modify the mineral and collagen in their surrounding matrix.Item Correlation analysis of cartilage wear with biochemical composition, viscoelastic properties and friction(Elsevier, 2023) Joukar, Amin; Creecy, Amy; Karnik, Sonali; Noori-Dokht, Hessam; Trippel, Stephen B.; Wallace, Joseph M.; Wagner, Diane R.; Orthopaedic Surgery, School of MedicineHealthy articular cartilage exhibits remarkable resistance to wear, sustaining mechanical loads and relative motion for decades. However, tissues that replace or repair cartilage defects are much less long lasting. Better information on the compositional and material characteristics that contribute to the wear resistance of healthy cartilage could help guide strategies to replace and repair degenerated tissue. The main objective of this study was to assess the relationship between wear of healthy articular cartilage, its biochemical composition, and its viscoelastic material properties. The correlation of these factors with the coefficient of friction during the wear test was also evaluated. Viscoelastic properties of healthy bovine cartilage were determined via stress relaxation indentation. The same specimens underwent an accelerated, in vitro wear test, and the amount of glycosaminoglycans (GAGs) and collagen released during the wear test were considered measures of wear. The frictional response during the wear test was also recorded. The GAG, collagen and water content and the concentration of the enzymatic collagen crosslink pyridinoline were quantified in tissue that was adjacent to each wear test specimen. Finally, correlation analysis was performed to identify potential relationships between wear characteristics of healthy articular cartilage with its composition, viscoelastic material properties and friction. The findings suggest that stiffer cartilage with higher GAG, collagen and water content has a higher wear resistance. Enzymatic collagen crosslinks also enhance the wear resistance of the collagen network. The parameters of wear, composition, and mechanical stiffness of cartilage were all correlated with one another, suggesting that they are interrelated. However, friction was largely independent of these in this study. The results identify characteristics of healthy articular cartilage that contribute to its remarkable wear resistance. These data may be useful for guiding techniques to restore, regenerate, and stabilize cartilage tissue.Item Effects of Collagen Gel Stiffness on Cdc42 Activities of Endothelial Colony Forming Cells during Early Vacuole Formation(2013-08-14) Kim, Seung Joon; Na, Sungsoo; Xie, Dong; Li, JiliangRecent preclinical reports have provided evidence that endothelial colony forming cells (ECFCs), a subset of endothelial progenitor cells, significantly improve vessel formation, largely due to their robust vasculogenic potential. While it has been known that the Rho family GTPase Cdc42 is involved in this ECFC-driven vessel formation process, the effect of extracellular matrix (ECM) stiffness on its activity during vessel formation is largely unknown. Using a fluorescence resonance energy transfer (FRET)-based Cdc42 biosensor, we examined the spatio-temporal activity of Cdc42 of ECFCs in three-dimensional (3D) collagen matrices with varying stiffness. The result revealed that ECFCs exhibited an increase in Cdc42 activity in a soft (150 Pa) matrix, while they were much less responsive in a rigid (1 kPa) matrix. In both soft and rigid matrices, Cdc42 was highly activated near vacuoles. However, its activity is higher in a soft matrix than that in a rigid matrix. The observed Cdc42 activity was closely associated with vacuole formation. Soft matrices induced higher Cdc42 activity and faster vacuole formation than rigid matrices. However, vacuole area is not dependent on the stiffness of matrices. Time courses of Cdc42 activity and vacuole formation data revealed that Cdc42 activity proceeds vacuole formation. Collectively, these results suggest that matrix stiffness is critical in regulating Cdc42 activity in ECFCs and its activation is an important step in early vacuole formation.Item Effects of estrogen depletion and drug treatment on collagen microstructure: implications(SpringerNature, 2015-05-27) Wallace, Joseph M.; Bone, Henry G.; Department of Biomedical Engineering, School of Engineering and TechnologyCommentary on: Cauble MA, Rothman E, Welch K, Fang M, Duong LT, Pennypacker BL, Orr BG, Holl MMB. Alteration of Type I collagen microstructure induced by estrogen depletion can be prevented with drug treatment. BoneKEy 2015; 4: 697. doi:10.1038/ bonekey.2015.66.