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Moreno-Flores O, Rausch MK, Tepole AB. The role of interface geometry and appendages on the mesoscale mechanics of the skin. Biomech Model Mechanobiol 2024; 23:553-568. [PMID: 38129671 DOI: 10.1007/s10237-023-01791-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2023] [Accepted: 10/29/2023] [Indexed: 12/23/2023]
Abstract
The skin is the largest organ in the human body and serves various functions, including mechanical protection and mechanosensation. Yet, even though skin's biomechanics are attributed to two main layers-epidermis and dermis-computational models have often treated this tissue as a thin homogeneous material or, when considering multiple layers, have ignored the most prominent heterogeneities of skin seen at the mesoscale. Here, we create finite element models of representative volume elements (RVEs) of skin, including the three-dimensional variation of the interface between the epidermis and dermis as well as considering the presence of hair follicles. The sinusoidal interface, which approximates the anatomical features known as Rete ridges, does not affect the homogenized mechanical response of the RVE but contributes to stress concentration, particularly at the valleys of the Rete ridges. The stress profile is three-dimensional due to the skin's anisotropy, leading to high-stress bands connecting the valleys of the Rete ridges through one type of saddle point. The peaks of the Rete ridges and the other class of saddle points of the sinusoidal surface form a second set of low-stress bands under equi-biaxial loading. Another prominent feature of the heterogeneous stress pattern is a switch in the stress jump across the interface, which becomes lower with respect to the flat interface at increasing deformations. These features are seen in both tension and shear loading. The RVE with the hair follicle showed strains concentrating at the epidermis adjacent to the hair follicle, the epithelial tissue surrounding the hair right below the epidermis, and the bulb or base region of the hair follicle. The regions of strain concentration near the hair follicle in equi-biaxial and shear loading align with the presence of distinct mechanoreceptors in the skin, except for the bulb or base region. This study highlights the importance of skin heterogeneities, particularly its potential mechanophysiological role in the sense of touch and the prevention of skin delamination.
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Affiliation(s)
- Omar Moreno-Flores
- School of Mechanical Engineering, Purdue University, AB Tepole, 585 Purdue Mall, West Lafayette, USA
| | - Manuel K Rausch
- Department of Aerospace Engineering and Engineering Mechanics, The University of Texas at Austin, Austin, USA
| | - Adrian B Tepole
- School of Mechanical Engineering, Purdue University, AB Tepole, 585 Purdue Mall, West Lafayette, USA.
- Weldon School of Biomedical Eng, Purdue University, West Lafayette, USA.
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2
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Ledwon JK, Applebaum SA, Progri B, Han T, Vignesh O, Gutowski KS, Chang AB, Reddy NK, Tepole AB, Gosain AK. Acellular Dermal Matrix Cover Improves Skin Growth during Tissue Expansion by Affecting Distribution of Mechanical Forces. Plast Reconstr Surg 2024; 153:663e-672e. [PMID: 37220332 DOI: 10.1097/prs.0000000000010709] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
BACKGROUND Biological cover over tissue expander prostheses has been introduced to provide soft-tissue support for tissue expanders during breast reconstruction. However, its impact on mechanically induced skin growth remains unknown. This study investigates the hypothesis that covering the tissue expander with acellular dermal matrix (ADM) affects mechanotransduction without compromising the efficacy of tissue expansion. METHODS Tissue expansion, with and without use of ADM, was performed on a porcine model. The tissue expanders were inflated twice with 45 mL of saline, and the full-thickness skin biopsy specimens were harvested from expanded and control unexpanded skin 1 week and 8 weeks after the final inflation. Histologic evaluation, immunohistochemistry staining, and gene expression analysis were performed. Skin growth and total deformation were evaluated using isogeometric analysis. RESULTS The authors' results demonstrate that use of ADM as a biological cover during tissue expansion does not impede mechanotransduction that leads to skin growth and blood vessel formation. Isogeometric analysis revealed similar total deformation and growth of expanded skin with and without a biological cover, confirming that its use does not inhibit mechanically induced skin growth. In addition, the authors found that use of an ADM cover results in more uniform distribution of mechanical forces applied by the tissue expander. CONCLUSIONS These results suggest that ADM improves mechanically induced skin growth during tissue expansion by facilitating a more uniform distribution of mechanical forces applied by the tissue expander. Therefore, the use of a biological cover has potential to improve outcomes in tissue expansion-based reconstruction.
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Affiliation(s)
- Joanna K Ledwon
- Northwestern University Feinberg School of Medicine, Division of Plastic Surgery, Chicago, IL, USA
- Ann and Robert H. Lurie Children's Hospital of Chicago, Department of Plastic and Reconstructive Surgery, Stanley Manne Children's Research Institute, Chicago, IL, USA
| | - Sarah A Applebaum
- Northwestern University Feinberg School of Medicine, Division of Plastic Surgery, Chicago, IL, USA
- Ann and Robert H. Lurie Children's Hospital of Chicago, Department of Plastic and Reconstructive Surgery, Stanley Manne Children's Research Institute, Chicago, IL, USA
| | - Bianka Progri
- Ann and Robert H. Lurie Children's Hospital of Chicago, Department of Plastic and Reconstructive Surgery, Stanley Manne Children's Research Institute, Chicago, IL, USA
| | - Tianhong Han
- Purdue University, Department of Mechanical Engineering, West Lafayette, IN, USA
| | - Oveyaa Vignesh
- Ann and Robert H. Lurie Children's Hospital of Chicago, Department of Plastic and Reconstructive Surgery, Stanley Manne Children's Research Institute, Chicago, IL, USA
| | - Kristof S Gutowski
- Ann and Robert H. Lurie Children's Hospital of Chicago, Department of Plastic and Reconstructive Surgery, Stanley Manne Children's Research Institute, Chicago, IL, USA
| | - Alec B Chang
- Ann and Robert H. Lurie Children's Hospital of Chicago, Department of Plastic and Reconstructive Surgery, Stanley Manne Children's Research Institute, Chicago, IL, USA
| | - Narainsai K Reddy
- Ann and Robert H. Lurie Children's Hospital of Chicago, Department of Plastic and Reconstructive Surgery, Stanley Manne Children's Research Institute, Chicago, IL, USA
| | - Adrian B Tepole
- Purdue University, Department of Mechanical Engineering, West Lafayette, IN, USA
| | - Arun K Gosain
- Northwestern University Feinberg School of Medicine, Division of Plastic Surgery, Chicago, IL, USA
- Ann and Robert H. Lurie Children's Hospital of Chicago, Department of Plastic and Reconstructive Surgery, Stanley Manne Children's Research Institute, Chicago, IL, USA
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Song Z, Zhang X, Xu Y, You J, Wang H, Zheng R, Tian L, Guo J, Fan F. The Dynamic Changes in Hemodynamics of the Forehead Flap During Tissue Expansion. Facial Plast Surg Aesthet Med 2024; 26:135-140. [PMID: 37358573 DOI: 10.1089/fpsam.2023.0042] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/27/2023] Open
Abstract
Background: The tissue expansion process brings changes in hemodynamics. Objective: To measure the change in vessel diameter, blood flow, and resistance in the blood vessels using ultrasound before, during, and after tissue expansion. Methods: Patients undergoing the embedment of a forehead expander from September 2021 to October 2022 were included. Hemodynamics parameters, including vessel diameter, blood flow velocity, and resistance index (RI) of the supraorbital artery (SOA), supratrochlear artery (STrA), and frontal branch of the superficial temporal artery (FBSTA), were measured with ultrasound before and 1, 2, 3, and 4 months after expansion. Results: Nine males and six females with ages ranging from 15 to 26 years (mean, 20 years) were included. After 4 months of expansion, the diameter of the STrA, SOA, and FBSTA increased significantly, the RI decreased significantly, and except the right SOA, peak systolic flow velocity increased significantly. Conclusion: The parameters of flap perfusion were significantly improved in the first 2 months of expansion and tended to stable values.
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Affiliation(s)
- Zhen Song
- Department of Rhinoplasty, Plastic Surgery Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Shijingshan, Beijing, China
| | - Xulong Zhang
- Department of Rhinoplasty, Plastic Surgery Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Shijingshan, Beijing, China
| | - Yihao Xu
- Department of Rhinoplasty, Plastic Surgery Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Shijingshan, Beijing, China
| | - Jianjun You
- Department of Rhinoplasty, Plastic Surgery Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Shijingshan, Beijing, China
| | - Huan Wang
- Department of Rhinoplasty, Plastic Surgery Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Shijingshan, Beijing, China
| | - Ruobing Zheng
- Department of Rhinoplasty, Plastic Surgery Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Shijingshan, Beijing, China
| | - Le Tian
- Department of Rhinoplasty, Plastic Surgery Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Shijingshan, Beijing, China
| | - Junsheng Guo
- Department of Rhinoplasty, Plastic Surgery Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Shijingshan, Beijing, China
| | - Fei Fan
- Department of Rhinoplasty, Plastic Surgery Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Shijingshan, Beijing, China
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4
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Song Z, Zhang X, Xu Y, You J, Wang H, Zheng R, Tian L, Guo J, Fan F. The Dynamic Changes in Skin Thickness of Forehead during Tissue Expansion. Facial Plast Surg 2024; 40:61-67. [PMID: 37023772 DOI: 10.1055/s-0043-1767769] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/08/2023] Open
Abstract
In addition to providing extra flap size, the tissue expansion process also brings changes in flap thickness. This study aims to identify the changes in the forehead flap thickness during the tissue expansion period. Patients undergoing forehead expander embedment from September 2021 to September 2022 were included. The thickness of the forehead skin and subcutaneous tissue were measured with ultrasound before and 1, 2, 3, and 4 months after expansion. Twelve patients were included. The average expansion period was 4.6 months, and the mean expansion volume was 657.1 mL. The thickness of skin and subcutaneous tissue in the central forehead changed from 1.09 ± 0.06 to 0.63 ± 0.05 mm and from 2.53 ± 0.25 to 0.71 ± 0.09 mm, respectively. In the left frontotemporal region, skin and subcutaneous tissue thickness changed from 1.03 ± 0.05 to 0.52 ± 0.05 mm and 2.02 ± 0.21 to 0.62 ± 0.08 mm. On the right side, skin and subcutaneous tissue thickness changed from 1.01 ± 0.05 to 0.50 ± 0.04 mm and 2.06 ± 0.21 to 0.50 ± 0.05 mm. This study measured the dynamic changes in the thickness of the forehead flap during expansion. The thickness of the forehead flap decreased the fastest in the first 2 months of expansion, and the changes in skin and subcutaneous thickness slowed down in the third and fourth months and tended to a minimum value. Additionally, the thickness of subcutaneous tissue decreased greater in magnitude than the dermal tissue.
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Affiliation(s)
- Zhen Song
- The Department of Rhinoplasty, Plastic Surgery Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Shijingshan District, Beijing, People's Republic of China
| | - Xulong Zhang
- The Department of Rhinoplasty, Plastic Surgery Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Shijingshan District, Beijing, People's Republic of China
| | - Yihao Xu
- The Department of Rhinoplasty, Plastic Surgery Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Shijingshan District, Beijing, People's Republic of China
| | - Jianjun You
- The Department of Rhinoplasty, Plastic Surgery Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Shijingshan District, Beijing, People's Republic of China
| | - Huan Wang
- The Department of Rhinoplasty, Plastic Surgery Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Shijingshan District, Beijing, People's Republic of China
| | - Ruobing Zheng
- The Department of Rhinoplasty, Plastic Surgery Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Shijingshan District, Beijing, People's Republic of China
| | - Le Tian
- The Department of Rhinoplasty, Plastic Surgery Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Shijingshan District, Beijing, People's Republic of China
| | - Junsheng Guo
- The Department of Rhinoplasty, Plastic Surgery Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Shijingshan District, Beijing, People's Republic of China
| | - Fei Fan
- The Department of Rhinoplasty, Plastic Surgery Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Shijingshan District, Beijing, People's Republic of China
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Shan S, He J, Sun Q, Zhu K, Li Y, Reid B, Li Q, Zhao M. Dynamics of cutaneous atmospheric oxygen uptake in response to mechanical stretch revealed by optical fiber microsensor. Exp Dermatol 2023; 32:2112-2120. [PMID: 37859506 PMCID: PMC10843412 DOI: 10.1111/exd.14957] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2023] [Revised: 09/17/2023] [Accepted: 10/06/2023] [Indexed: 10/21/2023]
Abstract
Skin expands and regenerates in response to mechanical stretch. This important homeostasis process is critical for skin biology and can be exploited to generate extra skin for reconstructive surgery. Atmospheric oxygen uptake is important in skin homeostasis. However, whether and how cutaneous atmospheric oxygen uptake changes during mechanical stretch remains unclear, and relevant research tools to quantify oxygen flux are limited. Herein, we used the scanning micro-optrode technique (SMOT), a non-invasive self-referencing optical fiber microsensor, to achieve real-time measurement of cutaneous oxygen uptake from the atmosphere. An in vivo mechanical stretch-induced skin expansion model was established, and an in vitro Flexcell Tension system was used to stretch epidermal cells. We found that oxygen influx of skin increased dramatically after stretching for 1 to 3 days and decreased to the non-stretched level after 7 days. The enhanced oxygen influx of stretched skin was associated with increased epidermal basal cell proliferation and impaired epidermal barrier. In conclusion, mechanical stretch increases cutaneous oxygen uptake with spatial-temporal characteristics, correlating with cell proliferation and barrier changes, suggesting a fundamental mechanistic role of oxygen uptake in the skin in response to mechanical stretch. Optical fiber microsensor-based oxygen uptake detection provides a non-invasive approach to understand skin homeostasis.
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Affiliation(s)
- Shengzhou Shan
- Department of Dermatology, Institute for Regenerative Cures, University of California, Davis, 2921 Stockton Boulevard, Sacramento, CA 95817, USA
- Department of Plastic and Reconstructive Surgery, Shanghai Ninth People’s Hospital, Shanghai Jiao Tong University School of Medicine, 639 Zhizaoju Road, Shanghai 200011, China
| | - Jiahao He
- Department of Plastic and Reconstructive Surgery, Shanghai Ninth People’s Hospital, Shanghai Jiao Tong University School of Medicine, 639 Zhizaoju Road, Shanghai 200011, China
| | - Qin Sun
- Department of Dermatology, Institute for Regenerative Cures, University of California, Davis, 2921 Stockton Boulevard, Sacramento, CA 95817, USA
- School of Life Science, Yunnan Normal University, Yuhua District, Kunming, Yunnan 650500, China
| | - Kan Zhu
- Department of Dermatology, Institute for Regenerative Cures, University of California, Davis, 2921 Stockton Boulevard, Sacramento, CA 95817, USA
- Department of Ophthalmology & Vision Science, Institute for Regenerative Cures, University of California, Davis, 1 Shields Avenue, CA 95616, USA
| | - Yuanyuan Li
- Department of Dermatology, Institute for Regenerative Cures, University of California, Davis, 2921 Stockton Boulevard, Sacramento, CA 95817, USA
| | - Brian Reid
- Department of Dermatology, Institute for Regenerative Cures, University of California, Davis, 2921 Stockton Boulevard, Sacramento, CA 95817, USA
- Department of Ophthalmology & Vision Science, Institute for Regenerative Cures, University of California, Davis, 1 Shields Avenue, CA 95616, USA
| | - Qingfeng Li
- Department of Plastic and Reconstructive Surgery, Shanghai Ninth People’s Hospital, Shanghai Jiao Tong University School of Medicine, 639 Zhizaoju Road, Shanghai 200011, China
| | - Min Zhao
- Department of Dermatology, Institute for Regenerative Cures, University of California, Davis, 2921 Stockton Boulevard, Sacramento, CA 95817, USA
- Department of Ophthalmology & Vision Science, Institute for Regenerative Cures, University of California, Davis, 1 Shields Avenue, CA 95616, USA
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6
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Singh G, Chanda A. Biomechanical modeling of progressive wound healing: A computational study. BIOMEDICAL ENGINEERING ADVANCES 2022. [DOI: 10.1016/j.bea.2022.100055] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
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7
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Han T, Ahmed KS, Gosain AK, Tepole AB, Lee T. Multi-Fidelity Gaussian Process Surrogate Modeling of Pediatric Tissue Expansion. J Biomech Eng 2022; 144:121005. [PMID: 35986450 PMCID: PMC9632473 DOI: 10.1115/1.4055276] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2022] [Revised: 08/16/2022] [Indexed: 11/12/2023]
Abstract
Growth of skin in response to stretch is the basis for tissue expansion (TE), a procedure to gain new skin area for reconstruction of large defects. Unfortunately, complications and suboptimal outcomes persist because TE is planned and executed based on physician's experience and trial and error instead of predictive quantitative tools. Recently, we calibrated computational models of TE to a porcine animal model of tissue expansion, showing that skin growth is proportional to stretch with a characteristic time constant. Here, we use our calibrated model to predict skin growth in cases of pediatric reconstruction. Available from the clinical setting are the expander shapes and inflation protocols. We create low fidelity semi-analytical models and finite element models for each of the clinical cases. To account for uncertainty in the response expected from translating the models from the animal experiments to the pediatric population, we create multifidelity Gaussian process surrogates to propagate uncertainty in the mechanical properties and the biological response. Predictions with uncertainty for the clinical setting are essential to bridge our knowledge from the large animal experiments to guide and improve the treatment of pediatric patients. Future calibration of the model with patient-specific data-such as estimation of mechanical properties and area growth in the operating room-will change the standard for planning and execution of TE protocols.
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Affiliation(s)
- Tianhong Han
- Department of Mechanical Engineering, Purdue University, West Lafayette, IN 47907
| | - Kaleem S. Ahmed
- McCormick School of Engineering, Northwestern University, Chicago, IL 60611
| | - Arun K. Gosain
- Surgery (Pediatric Surgery), Plastic Surgery, Lurie Children’s Hospital, Northwestern University, Feinberg School of Medicine, Chicago, IL 60611
| | | | - Taeksang Lee
- Department of Mechanical Engineering, Myongji University, Yongin 17058, South Korea
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Ledwon JK, Vaca EE, Huang CC, Kelsey LJ, McGrath JL, Topczewski J, Gosain AK, Topczewska JM. Langerhans cells and SFRP2/Wnt/beta-catenin signalling control adaptation of skin epidermis to mechanical stretching. J Cell Mol Med 2022; 26:764-775. [PMID: 35019227 PMCID: PMC8817127 DOI: 10.1111/jcmm.17111] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2021] [Revised: 10/08/2021] [Accepted: 10/29/2021] [Indexed: 12/01/2022] Open
Abstract
Skin can be mechanically stimulated to grow through a clinical procedure called tissue expansion (TE). Using a porcine TE model, we determined that expansion promptly activates transcription of SFRP2 in skin and we revealed that in the epidermis, this protein is secreted by Langerhans cells (LCs). Similar to well‐known mechanosensitive genes, the increase in SFRP2 expression was proportional to the magnitude of tension, showing a spike at the apex of the expanded skin. This implies that SFRP2 might be a newly discovered effector of mechanotransduction pathways. In addition, we found that acute stretching induces accumulation of b‐catenin in the nuclei of basal keratinocytes (KCs) and LCs, indicating Wnt signalling activation, followed by cell proliferation. Moreover, TE‐activated LCs proliferate and migrate into the suprabasal layer of skin, suggesting that LCs rebuild their steady network within the growing epidermis. We demonstrated that in vitro hrSFRP2 treatment on KCs inhibits Wnt/b‐catenin signalling and stimulates KC differentiation. In parallel, we observed an accumulation of KRT10 in vivo in the expanded skin, pointing to TE‐induced, SFRP2‐augmented KC maturation. Overall, our results reveal that a network of LCs delivers SFRP2 across the epidermis to fine‐tune Wnt/b‐catenin signalling to restore epidermal homeostasis disrupted by TE.
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Affiliation(s)
- Joanna K Ledwon
- Department of Surgery, Plastic Surgery Division, Northwestern University Feinberg School of Medicine, Stanley Manne Children's Research Institute, Ann and Robert H. Lurie Children's Hospital of Chicago, Chicago, Illinois, USA
| | - Elbert E Vaca
- Department of Surgery, Plastic Surgery Division, Northwestern University Feinberg School of Medicine, Stanley Manne Children's Research Institute, Ann and Robert H. Lurie Children's Hospital of Chicago, Chicago, Illinois, USA
| | - Chiang C Huang
- University of Wisconsin, Joseph J Zilber School of Public Health, Milwaukee, Illinois, USA
| | - Lauren J Kelsey
- Department of Surgery, Plastic Surgery Division, Northwestern University Feinberg School of Medicine, Stanley Manne Children's Research Institute, Ann and Robert H. Lurie Children's Hospital of Chicago, Chicago, Illinois, USA
| | - Jennifer L McGrath
- Department of Surgery, Plastic Surgery Division, Northwestern University Feinberg School of Medicine, Stanley Manne Children's Research Institute, Ann and Robert H. Lurie Children's Hospital of Chicago, Chicago, Illinois, USA
| | - Jacek Topczewski
- Department of Pediatrics, Northwestern University Feinberg School of Medicine, Stanley Manne Children's Research Institute, Ann and Robert H. Lurie Children's Hospital of Chicago, Chicago, Illinois, USA
| | - Arun K Gosain
- Department of Surgery, Plastic Surgery Division, Northwestern University Feinberg School of Medicine, Stanley Manne Children's Research Institute, Ann and Robert H. Lurie Children's Hospital of Chicago, Chicago, Illinois, USA
| | - Jolanta M Topczewska
- Department of Surgery, Plastic Surgery Division, Northwestern University Feinberg School of Medicine, Stanley Manne Children's Research Institute, Ann and Robert H. Lurie Children's Hospital of Chicago, Chicago, Illinois, USA.,Department of Pediatrics, Northwestern University Feinberg School of Medicine, Stanley Manne Children's Research Institute, Ann and Robert H. Lurie Children's Hospital of Chicago, Chicago, Illinois, USA
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Han T, Lee T, Ledwon J, Vaca E, Turin S, Kearney A, Gosain AK, Tepole AB. Bayesian calibration of a computational model of tissue expansion based on a porcine animal model. Acta Biomater 2022; 137:136-146. [PMID: 34634507 PMCID: PMC8678288 DOI: 10.1016/j.actbio.2021.10.007] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2021] [Revised: 10/04/2021] [Accepted: 10/05/2021] [Indexed: 01/03/2023]
Abstract
Tissue expansion is a technique used clinically to grow skin in situ to correct large defects. Despite its enormous potential, lack of fundamental knowledge of skin adaptation to mechanical cues, and lack of predictive computational models limit the broader adoption and efficacy of tissue expansion. In our previous work, we introduced a finite element model of tissue expansion that predicted key patterns of strain and growth which were then confirmed by our porcine animal model. Here we use the data from a new set of experiments to calibrate the computational model within a Bayesian framework. Four 10×10cm2 patches were tattooed in the dorsal skin of four 12 weeks-old minipigs and a total of six patches underwent successful tissue expander placement and inflation to 60cc for expansion times ranging from 1 h to 7 days. Six patches that did not have expanders implanted served as controls for the analysis. We find that growth can be explained based on the elastic deformation. The predicted area growth rate is k∈[0.02,0.08] [h-1]. Growth is anisotropic and reflects the anisotropic mechanical behavior of porcine dorsal skin. The rostral-caudal axis shows greater deformation than the transverse axis, and the time scale of growth in the rostral-caudal direction is given by rate parameters k1∈[0.04,0.1] [h-1] compared to k2∈[0.01,0.05] [h-1] in the transverse direction. Moreover, the calibration results underscore the high variability in biological systems, and the need to create probabilistic computational models to predict tissue adaptation in realistic settings. STATEMENT OF SIGNIFICANCE: Tissue expansion is a widely used technique in reconstructive surgery because it triggers growth of skin for the correction of large skin lesions and for breast reconstruction after mastectomy. Despite of its potential, complications and undesired outcomes persist due to our incomplete understanding of skin mechanobiology. Here we quantify the deformation and growth fields induced by an expander over 7 days in a porcine animal model and use these data to calibrate a computational model of skin growth using finite element simulations and a Bayesian framework. The calibrated model is a leap forward in our understanding skin growth, we now have quantitative understanding of this process: area growth is anisotropic and it is proportional to stretch with a characteristic rate constant of k∈[0.02,0.08] [h-1].
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Affiliation(s)
- Tianhong Han
- School of Mechanical Engineering, Purdue University, West Lafayette, IN, USA
| | - Taeksang Lee
- School of Mechanical Engineering, Purdue University, West Lafayette, IN, USA
| | - Joanna Ledwon
- Ann and Robert H. Lurie Children's Hospital, Chicago, IL, USA
| | - Elbert Vaca
- Ann and Robert H. Lurie Children's Hospital, Chicago, IL, USA
| | - Sergey Turin
- Ann and Robert H. Lurie Children's Hospital, Chicago, IL, USA
| | - Aaron Kearney
- Ann and Robert H. Lurie Children's Hospital, Chicago, IL, USA
| | - Arun K Gosain
- Ann and Robert H. Lurie Children's Hospital, Chicago, IL, USA
| | - Adrian B Tepole
- School of Mechanical Engineering, Purdue University, West Lafayette, IN, USA; Weldon School of Biomedical Engineering, Purdue University, West Lafayette, IN, USA.
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10
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Transcriptomic analysis reveals dynamic molecular changes in skin induced by mechanical forces secondary to tissue expansion. Sci Rep 2020; 10:15991. [PMID: 32994433 PMCID: PMC7524724 DOI: 10.1038/s41598-020-71823-z] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2020] [Accepted: 08/07/2020] [Indexed: 12/19/2022] Open
Abstract
Tissue expansion procedures (TE) utilize mechanical forces to induce skin growth and regeneration. While the impact of quick mechanical stimulation on molecular changes in cells has been studied extensively, there is a clear gap in knowledge about sequential biological processes activated during long-term stimulation of skin in vivo. Here, we present the first genome-wide study of transcriptional changes in skin during TE, starting from 1 h to 7 days of expansion. Our results indicate that mechanical forces from a tissue expander induce broad molecular changes in gene expression, and that these changes are time-dependent. We revealed hierarchical changes in skin cell biology, including activation of an immune response, a switch in cell metabolism and processes related to muscle contraction and cytoskeleton organization. In addition to known mechanoresponsive genes (TNC, MMPs), we have identified novel candidate genes (SFRP2, SPP1, CCR1, C2, MSR1, C4A, PLA2G2F, HBB), which might play crucial roles in stretched-induced skin growth. Understanding which biological processes are affected by mechanical forces in TE is important for the development of skin treatments to maximize the efficacy and minimize the risk of complications during expansion procedures.
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