Sedat Dogru, Gabriela M. Alba, Kirk C. Pierce, Tianbai Wang, Danial Sharifi Kia, Michael B. Albro
{"title":"Cell mediated reactions create TGF-β delivery limitations in engineered cartilage","authors":"Sedat Dogru, Gabriela M. Alba, Kirk C. Pierce, Tianbai Wang, Danial Sharifi Kia, Michael B. Albro","doi":"10.1016/j.actbio.2024.10.032","DOIUrl":null,"url":null,"abstract":"<div><div>During native cartilage development, endogenous TGF-β activity is tightly regulated by cell-mediated chemical reactions in the extracellular milieu (e.g., matrix and receptor binding), providing spatiotemporal control in a manner that is localized and short acting. These regulatory paradigms appear to be at odds with TGF-β delivery needs in tissue engineering (TE) where administered TGF-β is required to transport long distances or reside in tissues for extended durations. In this study, we perform a novel examination of the influence of cell-mediated reactions on the spatiotemporal distribution of administered TGF-β in cartilage TE applications. Reaction rates of TGF-β binding to cell-deposited ECM and TGF-β internalization by cell receptors are experimentally characterized in bovine chondrocyte-seeded tissue constructs. TGF-β binding to the construct ECM exhibits non-linear Brunauer–Emmett–Teller (BET) adsorption behavior, indicating that as many as seven TGF-β molecules can aggregate at a binding site. Cell-mediated TGF-β internalization rates exhibit a biphasic trend, following a Michaelis–Menten relation (<span><math><msub><mi>V</mi><mrow><mi>m</mi><mi>a</mi><mi>x</mi></mrow></msub></math></span> = 2.4 molecules cell<sup>-1</sup> s<sup>-1</sup>, <span><math><msub><mi>K</mi><mi>m</mi></msub></math></span> = 1.7 ng mL<sup>-1</sup>) at low ligand doses (≤130 ng/mL), but exhibit an unanticipated non-saturating power trend at higher doses (≥130 ng/mL). Computational models are developed to illustrate the influence of these reactions on TGF-β spatiotemporal delivery profiles for conventional TGF-β administration platforms. For TGF-β delivery via supplementation in culture medium, these reactions give rise to pronounced steady state TGF-β spatial gradients; TGF-β concentration decays by ∼90 % at a depth of only 500 μm from the media-exposed surface. For TGF-β delivery via heparin-conjugated affinity scaffolds, cell mediated internalization reactions significantly reduce the TGF-β scaffold retention time (160–360-fold reduction) relative to acellular heparin scaffolds. This work establishes the significant limitations that cell-mediated chemical reactions engender for TGF-β delivery and highlights the need for novel delivery platforms that account for these reactions to achieve optimal TGF-β exposure profiles.</div></div><div><h3>Statement of significance</h3><div>During native cartilage development, endogenous TGF-β activity is tightly regulated by cell-mediated chemical reactions in the extracellular milieu (e.g., matrix and receptor binding), providing spatiotemporal control in a manner that is localized and short acting. However, the effect of these reactions on the delivery of exogenous TGF-β to engineered cartilage tissues remains not well understood. In this study, we demonstrate that cell-mediated reactions significantly restrict the delivery of TGF-β to cells in engineered cartilage tissue constructs. For delivery via media supplementation, reactions significantly limit TGF-β penetration into constructs. For delivery via scaffold loading, reactions significantly limit TGF-β residence time in constructs. Overall, these results illustrate the impact of cell-mediated chemical reactions on TGF-β delivery profiles and support the importance of accounting for these reactions when designing TGF-β delivery platforms for promoting cartilage regeneration.</div></div>","PeriodicalId":237,"journal":{"name":"Acta Biomaterialia","volume":"190 ","pages":"Pages 178-190"},"PeriodicalIF":9.4000,"publicationDate":"2024-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Acta Biomaterialia","FirstCategoryId":"5","ListUrlMain":"https://www.sciencedirect.com/science/article/pii/S174270612400624X","RegionNum":1,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q1","JCRName":"ENGINEERING, BIOMEDICAL","Score":null,"Total":0}
引用次数: 0
Abstract
During native cartilage development, endogenous TGF-β activity is tightly regulated by cell-mediated chemical reactions in the extracellular milieu (e.g., matrix and receptor binding), providing spatiotemporal control in a manner that is localized and short acting. These regulatory paradigms appear to be at odds with TGF-β delivery needs in tissue engineering (TE) where administered TGF-β is required to transport long distances or reside in tissues for extended durations. In this study, we perform a novel examination of the influence of cell-mediated reactions on the spatiotemporal distribution of administered TGF-β in cartilage TE applications. Reaction rates of TGF-β binding to cell-deposited ECM and TGF-β internalization by cell receptors are experimentally characterized in bovine chondrocyte-seeded tissue constructs. TGF-β binding to the construct ECM exhibits non-linear Brunauer–Emmett–Teller (BET) adsorption behavior, indicating that as many as seven TGF-β molecules can aggregate at a binding site. Cell-mediated TGF-β internalization rates exhibit a biphasic trend, following a Michaelis–Menten relation ( = 2.4 molecules cell-1 s-1, = 1.7 ng mL-1) at low ligand doses (≤130 ng/mL), but exhibit an unanticipated non-saturating power trend at higher doses (≥130 ng/mL). Computational models are developed to illustrate the influence of these reactions on TGF-β spatiotemporal delivery profiles for conventional TGF-β administration platforms. For TGF-β delivery via supplementation in culture medium, these reactions give rise to pronounced steady state TGF-β spatial gradients; TGF-β concentration decays by ∼90 % at a depth of only 500 μm from the media-exposed surface. For TGF-β delivery via heparin-conjugated affinity scaffolds, cell mediated internalization reactions significantly reduce the TGF-β scaffold retention time (160–360-fold reduction) relative to acellular heparin scaffolds. This work establishes the significant limitations that cell-mediated chemical reactions engender for TGF-β delivery and highlights the need for novel delivery platforms that account for these reactions to achieve optimal TGF-β exposure profiles.
Statement of significance
During native cartilage development, endogenous TGF-β activity is tightly regulated by cell-mediated chemical reactions in the extracellular milieu (e.g., matrix and receptor binding), providing spatiotemporal control in a manner that is localized and short acting. However, the effect of these reactions on the delivery of exogenous TGF-β to engineered cartilage tissues remains not well understood. In this study, we demonstrate that cell-mediated reactions significantly restrict the delivery of TGF-β to cells in engineered cartilage tissue constructs. For delivery via media supplementation, reactions significantly limit TGF-β penetration into constructs. For delivery via scaffold loading, reactions significantly limit TGF-β residence time in constructs. Overall, these results illustrate the impact of cell-mediated chemical reactions on TGF-β delivery profiles and support the importance of accounting for these reactions when designing TGF-β delivery platforms for promoting cartilage regeneration.
期刊介绍:
Acta Biomaterialia is a monthly peer-reviewed scientific journal published by Elsevier. The journal was established in January 2005. The editor-in-chief is W.R. Wagner (University of Pittsburgh). The journal covers research in biomaterials science, including the interrelationship of biomaterial structure and function from macroscale to nanoscale. Topical coverage includes biomedical and biocompatible materials.