Role Of Extracellular Matrix Stiffness Research Articles

Investigating the Role of Extracellular Matrix Stiffness in Modulating the Ferroptosis Process in Hepatocellular Carcinoma Cells via Scanning Electrochemical Microscopy.

Extracellular matrix (ECM) stiffness modulates a variety of cellular processes, including ferroptosis, a process with significant potential implications for hepatocellular carcinoma (HCC) fibrosis and cirrhosis. However, the exact relationship between ECM stiffness and HCC ferroptosis is yet unclarified, partially due to the lack of in situ information on key parameters of the ferroptosis process of living HCC cells. This study pioneers the use of in vitro mechanical microenvironment models of HCC and the scanning electrochemical microscopy (SECM) technique for understanding this interplay. We first cultured HuH7 cells on 4.0, 18.0, and 44.0 kPa polyacrylamide (PA) gels to simulate early, intermediate, and advanced HCC ECM stiffness, respectively. Then, we used SECM to in situ monitor changes in cell membrane permeability, respiratory activity, and reactive oxygen species (ROS) levels of erastin-induced HuH7 cells on PA gels, finding that increasing ECM stiffness potentiates ferroptosis, including increased membrane permeabilization and H2O2 release as well as reduced respiratory activity. Through further transcriptome sequencing and molecular biology measurements, we identified a critical role for focal adhesion kinase (FAK)-mediated yes-associated protein (YAP) in regulating the ferroptosis process dependent on ECM stiffness, which provides novel insights into the mechanical regulation of ferroptosis in HCC cells and may pave the way for innovative therapeutic strategies.

Matrix stiffness regulates neovascular homeostasis through autophagy in nude mice.

One of the major obstacles to the effective application of vascularized fruit is an insufficient understanding of the relationship between the microenvironment and neovascular homeostasis. The role of extracellular matrixstiffness in regulating the structural and functional stability of neovascularization has not yet been elucidated. This study explored the effects of matrix stiffness on neovascular homeostasis in nude mice. Dextran hydrogels with three different stiffnesses were separately combined with mouse bone marrow-derived endothelial progenitor cells (EPCs) and subcutaneously implanted into the backs of nude mice. After 14 days, neovascular homeostasis indicators in the different groups were measured. Cell autophagy levels were evaluated, and inhibitor assays were performed to explore the underlying mechanism. New blood vessels were generated in the three stiffnesses of the EPC-loaded dextran hydrogels 14 days after implantation. The newly formed vessels tended to have better structural stability in softer hydrogels. Endothelial function markers, such as endothelial nitric oxide synthaseand E-selectin, were downregulated as the matrix stiffness increased. Furthermore, we found that cell autophagy levels decreased in stiffer matrices, and autophagy inhibition attenuated neovascular homeostasis. A soft matrix is conducive to maintaining neovascular homeostasis through autophagy in nude mice.

Severe COVID-19-A Review of Suggested Mechanisms Based on the Role of Extracellular Matrix Stiffness.

The severity of COVID-19 commonly depends on age-related tissue stiffness. The aim was to review publications that explain the effect of microenvironmental extracellular matrix stiffness on cellular processes. Platelets and endothelial cells are mechanosensitive. Increased tissue stiffness can trigger cytokine storm with the upregulated expression of pro-inflammatory cytokines, such as tumor necrosis factor alpha and interleukin IL-6, and tissue integrity disruption, leading to enhanced virus entry and disease severity. Increased tissue stiffness in critically ill COVID-19 patients triggers platelet activation and initiates plague formation and thrombosis development. Cholesterol content in cell membrane increases with aging and further enhances tissue stiffness. Membrane cholesterol depletion decreases virus entry to host cells. Membrane cholesterol lowering drugs, such as statins or novel chitosan derivatives, have to be further developed for application in COVID-19 treatment. Statins are also known to decrease arterial stiffness mitigating cardiovascular diseases. Sulfated chitosan derivatives can be further developed for potential use in future as anticoagulants in prevention of severe COVID-19. Anti-TNF-α therapies as well as destiffening therapies have been suggested to combat severe COVID-19. The inhibition of the nuclear factor kappa-light-chain-enhancer of activated B cells pathway must be considered as a therapeutic target in the treatment of severe COVID-19 patients. The activation of mechanosensitive platelets by higher matrix stiffness increases their adhesion and the risk of thrombus formation, thus enhancing the severity of COVID-19.

Radiation therapy affects YAP expression and intracellular localization by modulating lamin A/C levels in breast cancer.

The microenvironment of breast cancer actively participates in tumorigenesis and cancer progression. The changes observed in the architecture of the extracellular matrix initiate an oncogene-mediated cell reprogramming, that leads to a massive triggering of YAP nuclear entry, and, therefore, to cancer cell proliferation, invasion and probably to increased radiation-resistance. However, it is not yet fully understood how radiotherapy regulates the expression and subcellular localization of YAP in breast cancer cells experiencing different microenvironmental stiffnesses. To elucidate the role of extracellular matrix stiffness and ionizing radiations on YAP regulation, we explored the behaviour of two different mammary cell lines, a normal epithelial cell line (MCF10A) and a highly aggressive and invasive adenocarcinoma cell line (MDA-MB-231) interacting with polyacrylamide substrates mimicking the mechanics of both normal and tumour tissues (∼1 and ∼13 kPa). We report that X-ray radiation affected in a significant way the levels of YAP expression, density, and localization in both cell lines. After 24 h, MCF10A and MDA-MB-231 increased the expression level of YAP in both nucleus and cytoplasm in a dose dependent manner and particularly on the stiffer substrates. After 72 h, MCF10A reduced mostly the YAP expression in the cytoplasm, whereas it remained high in the nucleus of cells on stiffer substrates. Tumour cells continued to exhibit higher levels of YAP expression, especially in the cytoplasmic compartment, as indicated by the reduction of nuclear/cytoplasmic ratio of total YAP. Then, we investigated the existence of a correlation between YAP localization and the expression of the nuclear envelope protein lamin A/C, considering its key role in modulating nuclear deformability and changes in YAP shuttling phenomena. As supposed, we found that the effects of radiation on YAP nucleus/cytoplasmic expression ratio, increasing in healthy cells and decreasing in tumour ones, were accompanied by lower and higher lamin A/C levels in MCF10A and MDA-MB-231 cells, respectively. These findings point to obtain a deeper knowledge of the role of the extracellular matrix and the effects of X-rays on YAP and lamin A/C expression that can be used in the design of doses and timing of radiation therapy.

Adhesion and Migration Response to Radiation Therapy of Mammary Epithelial and Adenocarcinoma Cells Interacting with Different Stiffness Substrates.

The structural and mechanical properties of the microenvironmental context have a profound impact on cancer cell motility, tumor invasion, and metastasis formation. In fact, cells react to their mechanical environment modulating their adhesion, cytoskeleton organization, changes of shape, and, consequently, the dynamics of their motility. In order to elucidate the role of extracellular matrix stiffness as a driving force in cancer cell motility/invasion and the effects of ionizing radiations on these processes, we evaluated adhesion and migration as biophysical properties of two different mammary cell lines, over a range of pathophysiological stiffness (1–13 kPa) in a control condition and after the exposure to two different X-ray doses (2 and 10 Gy, photon beams). We concluded that the microenvironment mimicking the normal mechanics of healthy tissue has a radioprotective role on both cell lines, preventing cell motility and invasion. Supraphysiological extracellular matrix stiffness promoted tumor cell motility instead, but also had a normalizing effect on the response to radiation of tumor cells, lowering their migratory capability. This work lays the foundation for exploiting the extracellular matrix-mediated mechanism underlying the response of healthy and tumor cells to radiation treatments and opens new frontiers in the diagnostic and therapeutic use of radiotherapy.

The Role of Extracellular Matrix Stiffness on Cardiac Metabolic Activity

The cardiac L-type Ca2+ channel (LTCC) can regulate mitochondrial metabolic activity via calcium-independent mechanisms. The sarcomeric network plays an important role in this response. Hypertrophic cardiomyopathy (HCM) occurs due to mutations in sarcomeric proteins. Using murine models of human HCM, we have shown that mutations in sarcomeric proteins are associated with altered LTCC kinetics, impaired structural-functional communication between LTCC and mitochondria, and increased metabolic activity (consistent with the human phenotype). However, the mechanisms by which mutations in sarcomeric proteins lead to alterations in metabolic activity remain unknown. Cardiomyocytes can ‘sense’ extracellular matrix (ECM) mechanics via a process called mechanotransduction. This involves conversion of mechanical stimuli into biochemical events that can alter myocardial function. Since human HCM is characterised by a stiff myocardium, we developed an in vitro model to determine the role of increased ECM stiffness on metabolic activity. Wild-type cardiomyocytes were cultured on hydrogels with stiffnesses mimicking healthy (10 kPa) or HCM (40 kPa) myocardium. Cardiomyocytes on 40 kPa hydrogels exhibited increased stiffness versus 10 kPa (atomic force microscopy; 3.8 ± 0.4 kPa, n = 53 versus 1.5 ± 0.2 kPa, n = 31; p < 0.05). Cardiomyocytes on 40 kPa hydrogels also exhibited a larger increase in metabolic activity in response to activation of LTCC (flavoprotein autofluorescence; 40 kPa: 64.6 ± 4.3% increase, n = 35 versus 10 kPa: 20.3 ± 1.8%, n = 27 p < 0.05), that was attenuated by sarcomeric protein depolymerising agents latrunculin A (F-actin) or colchicine (β-tubulin). We conclude that ECM stiffness may regulate cardiac metabolic activity. Increased ECM stiffness may contribute to increased metabolic activity and development of HCM.

The role of extracellular matrix stiffness in regulating cytoskeletal remodeling via vinculin in synthetic smooth muscle cells

Vinculin is a key player in sensing and responding to external mechanical cues such as extracellular matrix stiffness. Increased matrix stiffness is often associated with certain pathological conditions including hypertension induced cellular cytoskeleton changes in vascular smooth muscle (VSM) cells. However, little is known on how stiffness affects cytoskeletal remodeling via vinculin in VSM cells. Thus, we utilized matrices with elastic moduli that simulate vascular stiffness in different stages of hypertension to investigate how matrix stiffness regulates cell cytoskeleton via vinculin in synthetic VSM cells. Through selecting a suitable reference gene, we found that an increase in physiologically relevant extracellular matrix stiffness (2–50 kPa) downregulates vinculin gene expression but upregulates vinculin protein expression. This discrepancy, which was not observed previously for non-muscle cells, suggests that the vinculin-mediated mecahnotransduction mechanism in synthetic VSM cells may be more complex than those proposed for non-muscle cells. Also adding to previous findings, we found that VSM cell growth may be impeded by substrates that are either too soft or too rigid.

Tissue stiffening promotes keratinocyte proliferation through activation of epidermal growth factor signaling.

Tissue biomechanics regulate a wide range of cellular functions, but the influences on epidermal homeostasis and repair remain unclear. Here, we examined the role of extracellular matrix stiffness on human keratinocyte behavior using elastomeric substrates with defined mechanical properties. Increased matrix stiffness beyond normal physiologic levels promoted keratinocyte proliferation but did not alter the ability to self-renew or terminally differentiate. Activation of epidermal growth factor (EGF) signaling mediated the proliferative response to matrix stiffness and depended on focal adhesion assembly and cytoskeletal tension. Comparison of normal skin with keloid scar tissue further revealed an upregulation of EGF signaling within the epidermis of stiffened scar tissue. We conclude that matrix stiffness regulates keratinocyte proliferation independently of changes in cell fate and is mediated by EGF signaling. These findings provide mechanistic insights into how keratinocytes sense and respond to their mechanical environment, and suggest that matrix biomechanics may play a role in the pathogenesis keloid scar formation.

The role of extracellular matrix stiffness in megakaryocyte and platelet development and function.

The extracellular matrix (ECM) is a key acellular structure in constant remodeling to provide tissue cohesion and rigidity. Deregulation of the balance between matrix deposition, degradation, and crosslinking results in fibrosis. Bone marrow fibrosis (BMF) is associated with several malignant and nonmalignant pathologies severely affecting blood cell production. BMF results from abnormal deposition of collagen fibers and enhanced lysyl oxidase-mediated ECM crosslinking within the marrow, thereby increasing marrow stiffness. Bone marrow stiffness has been recently recognized as an important regulator of blood cell development, notably by modifying the fate and differentiation process of hematopoietic or mesenchymal stem cells. This review surveys the different components of the ECM and their influence on stem cell development, with a focus on the impact of the ECM composition and stiffness on the megakaryocytic lineage in health and disease. Megakaryocyte maturation and the biogenesis of their progeny, the platelets, are thought to respond to environmental mechanical forces through a number of mechanosensors, including integrins and mechanosensitive ion channels, reviewed here.

The Role of Extracellular Matrix Stiffness on Regulation of Cardiac Metabolic Activity: Implications for the Development of Hypertrophic Cardiomyopathy

The Role of Extracellular Matrix Stiffness on Regulation of Cardiac Metabolic Activity: Implications for the Development of Hypertrophic Cardiomyopathy

Contact guidance diversity in rotationally aligned collagen matrices.

Collagen fiber alignment in the tumor microenvironment directs migration, a process called contact guidance, enhancing the efficiency of cancer invasion and metastasis. 3D systems that assess contact guidance by locally orienting collagen fiber alignment are lacking. Furthermore, cell type differences and the role of extracellular matrix stiffness in tuning contact guidance fidelity are not well characterized. In this paper rotational alignment of collagen fibers is used as a 3D contact guidance cue to illuminate cell type differences and the role of extracellular matrix stiffness in guiding cell migration along aligned fibers of collagen. This local alignment offers a simple approach by which to couple collagen alignment with gradients in other directional cues in devices such as microfluidic chambers.

Extracellular Matrix Stiffness Regulates Osteogenic Differentiation through MAPK Activation.

Mesenchymal stem cell (MSC) differentiation is regulated by the extracellular matrix (ECM) through activation of intracellular signaling mediators. The stiffness of the ECM was shown to be an important regulatory factor for MSC differentiation, and transcriptional coactivator with PDZ-binding motif (TAZ) was identified as an effector protein for MSC differentiation. However, the detailed underlying mechanism regarding the role of ECM stiffness and TAZ in MSC differentiation is not yet fully understood. In this report, we showed that ECM stiffness regulates MSC fate through ERK or JNK activation. Specifically, a stiff hydrogel matrix stimulates osteogenic differentiation concomitant with increased nuclear localization of TAZ, but inhibits adipogenic differentiation. ERK and JNK activity was significantly increased in cells cultured on a stiff hydrogel. TAZ activation was induced by ERK or JNK activation on a stiff hydrogel because exposure to an ERK or JNK inhibitor significantly decreased the nuclear localization of TAZ, indicating that ECM stiffness-induced ERK or JNK activation is important for TAZ-driven osteogenic differentiation. Taken together, these results suggest that ECM stiffness regulates MSC differentiation through ERK or JNK activation.

Abstract B02: Matrix stiffness regulates local metabolism of breast carcinoma cells

Abstract Dense breast tissue is one of the single largest risk factors for the development of breast cancer, and one of the primary proteins responsible for increased breast density is the core extracellular matrix (ECM) component, collagen. Similar to other ECM proteins, collagen plays a structural role underlying tissue organization and increased collagen deposition correlates to a stiffer ECM and cellular microenvironment. Interestingly, changes to the stiffness of the ECM or microenvironment have profound and poorly-understood effects on cell migration, cell proliferation, and cancer progression. Consistent with an expanding role of ECM stiffness in cell signaling, we report that increased matrix stiffness also affects cellular metabolism and respiration. Using specific pharmacological inhibitors and quantitative imaging modalities like fluorescence lifetime microscopy, we are able to show that changes in collagen stiffness can cause a metabolic shift towards a more glycolytic, Warburg-like equilibrium in breast carcinoma cells. Matrix stiffness regulates the expression of several metabolic enzymes, including PDHK-1, which is poised to regulate this shift. Note: This abstract was not presented at the conference. Citation Format: Brian Burkel, Suzanne Ponik, Brett Morris, Kevin Eliceiri, Patricia Keely. Matrix stiffness regulates local metabolism of breast carcinoma cells. [abstract]. In: Abstracts: AACR Special Conference on Cellular Heterogeneity in the Tumor Microenvironment; 2014 Feb 26-Mar 1; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2015;75(1 Suppl):Abstract nr B02. doi:10.1158/1538-7445.CHTME14-B02

Abstract 220: Role of ECM Stiffness in Microvascular Inflammation

Nitric oxide (NO) produced by endothelial nitric oxide synthase (eNOS) is a critical regulator of inflammation as it inhibits leukocyte adhesion to vessel endothelium. Notably, reduced eNOS activity/NO bioavailability and chronic inflammation are key features, and often major determinants, of atherosclerosis and diabetic cardiovascular complications. Past approaches aimed at normalizing eNOS activity have focused primarily on the role of soluble, genetic or shear stress-mediated physical factors. However, extracellular matrix (ECM) mechanics also plays a crucial role in endothelial cell (EC) activation and function. Importantly, tissue mechanics is altered in both atherosclerosis and diabetes that are marked by chronic inflammation and impaired eNOS activity. Thus, we investigated whether there exists a causal relationship between ECM stiffness and eNOS/NO-dependent endothelial inflammation. To test this hypothesis, we cultured ECs on fibronectin-coated elastic substrates of varying stiffness (220 Pa/soft, 1000 Pa/intermediate and 4000 Pa/stiff). EC mechanosensitivity was first confirmed by quantifying the density of actin cytoskeletal filaments, which increased with increasing ECM stiffness. EC-leukocyte adhesion (inflammation) on these substrates, however, followed a biphasic trend where ECs on both 220 Pa (soft) and 4000 Pa (stiff) substrates exhibited greater leukocyte adhesion than those cultured on intermediate 1000 Pa substrates. This biphasic effect of ECM stiffness on endothelial inflammation correlated inversely with levels of eNOS-activation and NO production on these substrates. Consistent with these data, NF-kB activation was enhanced on 220 Pa and 4000 Pa while being suppressed on 1000 Pa substrates. Preliminary data implicate differential levels of calcium influx via mechanosensitive calcium ion channels in this ECM stiffness-dependent eNOS activation and endothelial inflammation. These new findings can potentially lead to superior cardiovascular disease management as they identify ECM stiffness both as a novel therapeutic target for immunomodulatory strategies as well as a key physical design criterion for the development of instructive biomaterials for cardiovascular tissue engineering.

Abstract 1099: Mapping matrix mechanics in 3D to study the role of stiffness in breast tumor progression.

Abstract Introduction Evidence suggests that the Extra Cellular Matrix (ECM) stiffness may be a driving factor in tumor progression and may sensitize epithelial cells towards the invasive phenotype. In fact, high mammographic density is linked to a higher risk of tumor. In vitro, stiffness in naturally derived ECMs is commonly increased via changing concentration or cross-linking. Either process will change ligand density, porosity, architecture, and diffusivity. Therefore, it is difficult to determine whether the resulting tumor phenotype is due to stiffness changes or other factors. ECM stiffness is conventionally measured via parallel plate rheology or AFM. But, while one only provides an average ensemble of the entire sample, the other lacks the axial resolution required to measure deep within the gels. We use our stiffness gradient device (SGD) to tune stiffness independent of concentration or crosslinking. In the SGD, the ECM is polymerized around a post, which is rotated to induce strain, and a stiffness gradient is established. Stiffness can be tuned from 100 - 1000 Pa within one dish, the range of normal and malignant breast tissue. We have combined SGD with active microrheology (AMR) to investigate the role of ECM stiffness in sensitizing epithelial cells towards an invasive phenotype. AMR allows deep measurements within the sample to map ECM stiffness in 3D and around cells. We can correlate these maps with the function and signaling of mechanoreceptors such as integrins. Materials and Methods Cells were cultured inside hydrogels (Collagen or Matrigel) containing 2 um silica beads to be used as probes for AMR. AMR was conducted to calculate the complex shear modulus (G*). G* is a measure of material stiffness (G’) and loss (G’’). MCF10A.ErbB2 cells (courtesy of the Muthuswamy lab) were cultured inside 3D hydrogels within the SGD. These cells can be driven towards malignancy with the addition of a synthetic dimerizer that activates the ErbB2/Her2 pathway. The cells were allowed to reach their growth arrested acini phase, at which time the appropriate matrices were stiffened. After an additional 2 weeks, dimerizer was added to the culture. Non-linear imaging in regions of high stiffness and low stiffness reveals acini morphology and molecular distributions. Results and Discussion In dimerizer-free culture, we observed an organized tubule network connecting acini, which lost their growth control only in stiffened regions. In the non-stiffened regions we saw growth arrested hollow acini. With the addition of dimerizer, in soft regions we observed, consistent with published results, thin disorganized tubules. Interestingly, in the stiffened region, we saw a partial rescue of the organized morphology suggesting that stiffness may play an orthogonal role to Her2 signaling. Further observations suggested that a stiff ECM sensitizes mammary epithelial cells to the actions of the Her2 pathway. Citation Format: Abhishek Kurup, Elliot Botvinick. Mapping matrix mechanics in 3D to study the role of stiffness in breast tumor progression. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 1099. doi:10.1158/1538-7445.AM2013-1099

Microenvironment and tumor cell plasticity: An easy way out

Cancer cells undergo genetic changes allowing their adaptation to environmental changes, thereby obtaining an advantage during the long metastatic route, disseminated of several changes in the surrounding environment. In particular, plasticity in cell motility, mainly due to epigenetic regulation of cancer cells by environmental insults, engage adaptive strategies aimed essentially to survive in hostile milieu, thereby escaping adverse sites. This review is focused on tumor microenvironment as a collection of structural and cellular elements promoting plasticity and adaptive programs. We analyze the role of extracellular matrix stiffness, hypoxia, nutrient deprivation, acidity, as well as different cell populations of tumor microenvironment.

Endothelial barrier disruption and recovery is controlled by substrate stiffness

Circulating barrier disruptive agonists bind specific cell membrane receptors and trigger signal transduction pathways leading to the activation of cell contractility and endothelial cell (EC) permeability. Although all cells in tissues including vascular EC are surrounded by compliant extracellular matrix, the impact of matrix stiffness on agonist-induced signaling, cytoskeletal remodeling and EC barrier regulation is not well understood. This study examined agonist-induced cytoskeletal and signaling changes associated with EC barrier disruption and recovery using pulmonary EC grown on compliant substrates of physiologically relevant (8.6kPa) stiffness, very low (0.55kPa) and very high (42kPa) stiffness. Human pulmonary microvascular and macrovascular EC grown on 0.55kPa substrate contained a few actin stress fibers, while stress fiber amount increased with increasing matrix stiffness. Thrombin-induced stress fiber formation was maximal in EC grown on 42kPa substrate, diminished on 8.6kPa substrate, and was minimal on 0.55kPa substrate. These effects were linked to a stiffness-dependent increase in thrombin-induced phosphorylation of the Rho kinase target, myosin light chain phosphatase (MYPT1), and regulatory myosin light chains (MLC). Surprisingly, EC barrier recovery and activation of Rac GTPase-dependent barrier protective signaling reached maximal levels in EC grown on 8.6kPa, but not on 0.55kPa substrate. In conclusion, these data show a critical role of extracellular matrix stiffness in the regulation of the Rac/Rho signaling balance during onset and resolution of agonist-induced EC permeability. The optimal conditions for the Rho/Rac signaling switch, which provides an effective and reversible EC cytoskeletal and permeability response to agonist, are reached in cells grown on the matrix of physiologically relevant stiffness.

Mechanotransduction is enhanced by the synergistic action of heterotypic cell interactions and TGF‐β1

With the use of planar substrates and collagen gels, the field of mechanotransduction has focused on the role of extracellular matrix stiffness, mechanical tension, and TGF-β1 in generating a more contractile fibroblast. However, little is known about the role of cell-cell interactions in inducing cellular contraction. We used 3-dimensional self-assembled microtissues, in which cell-cell interactions dominate, and a recently developed cell power assay (an assay for mechanotransduction) to quantify the effects of TGF-β1 vs. the heterotypic cell interface on the power exerted by pure normal human fibroblast (NHF) and pure rat hepatocyte 35 (H35) microtissues and their mixes. As a control, we found that TGF-β1 only doubled the power output of pure NHF and pure H35 microtissues, whereas the heterotypic environment resulted in a 5-fold increase in cell power (0.24±0.05 to 1.17±0.13 fJ/h). Seeding TGF-β1-treated NHFs with untreated H35 cells demonstrated that the heterotypic environment and TGF-β1 synergistically increase cell power by 22× by maximizing heterotypic cell interactions. Using a mathematical simulation of stress generation, we showed that tensile forces can be enhanced by heterotypic cell interactions. These data render a new understanding of how heterotypic cell interactions may increase cellular force generation during wound healing.