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Modeling stem/progenitor cell-induced neovascularization and oxygenation around solid implants.

ABSTRACT: Tissue engineering constructs and other solid implants with biomedical applications, such as drug delivery devices or bioartificial organs, need oxygen (O(2)) to function properly. To understand better the vascular integration of such devices, we recently developed a novel model sensor containing O(2)-sensitive crystals, consisting of a polymeric capsule limited by a nanoporous filter. The sensor was implanted in mice with hydrogel alone (control) or hydrogel embedded with mouse CD117/c-kit+ bone marrow progenitor cells in order to stimulate peri-implant neovascularization. The sensor provided local partial O(2) pressure (pO(2)) using noninvasive electron paramagnetic resonance signal measurements. A consistently higher level of peri-implant oxygenation was observed in the cell-treatment case than in the control over a 10-week period. To provide a mechanistic explanation of these experimental observations, we present in this article a mathematical model, formulated as a system of coupled partial differential equations, that simulates peri-implant vascularization. In the control case, vascularization is considered to be the result of a foreign body reaction, while in the cell-treatment case, adipogenesis in response to paracrine stimuli produced by the stem cells is assumed to induce neovascularization. The model is validated by fitting numerical predictions of local pO(2) to measurements from the implanted sensor. The model is then used to investigate further the potential for using stem cell treatment to enhance the vascular integration of biomedical implants. We thus demonstrate how mathematical modeling combined with experimentation can be used to infer how vasculature develops around biomedical implants in control and stem cell-treated cases.

SUBMITTER: Jain HV

PROVIDER: S-EPMC3400277 | biostudies-literature | 2012 Jul

REPOSITORIES: biostudies-literature

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Modeling stem/progenitor cell-induced neovascularization and oxygenation around solid implants.

Jain Harsh Vardhan HV Moldovan Nicanor I NI Byrne Helen M HM

Tissue engineering. Part C, Methods 20120302 7

Tissue engineering constructs and other solid implants with biomedical applications, such as drug delivery devices or bioartificial organs, need oxygen (O(2)) to function properly. To understand better the vascular integration of such devices, we recently developed a novel model sensor containing O(2)-sensitive crystals, consisting of a polymeric capsule limited by a nanoporous filter. The sensor was implanted in mice with hydrogel alone (control) or hydrogel embedded with mouse CD117/c-kit+ bon ...[more]

PMID: 22224628

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Project description:An urgent need exists to develop large animal models for preclinical testing of new cell therapies designed to replace lost or damaged tissues. Patients receiving irradiation for treatment of head and neck cancers frequently develop xerostomia/dry mouth, a condition that could one day be treated by cell therapy to repopulate functional saliva-producing cells. Using immunosuppression protocols developed for patients receiving whole face transplants, we successfully used immunosuppressed miniswine as a suitable host animal to evaluate the long-term stability, biocompatibility, and fate of matrix-modified hyaluronate (HA) hydrogel/bioscaffold materials containing encapsulated salivary human stem/progenitor cells (hS/PCs). An initial biocompatibility test was conducted in parotids of untreated miniswine. Subsequent experiments using hS/PC-laden hydrogels were performed in animals, beginning an immunosuppression regimen on the day of surgery. Implant sites included the kidney capsule for viability testing and the parotid gland for biointegration time periods up to eight weeks. No transplant rejection was seen in any animal assessed by analysis of the tissues near the site of the implants. First-generation implants containing only cells in hydrogel proved difficult to handle in the surgical suite and were modified to adhere to a porcine small intestinal submucosa (SIS) membrane for improved handling and could be delivered through the da Vinci surgical system. Several different surgical techniques were assessed using the second-generation 3D-salivary tissue (3D-ST) for ease and stability both on the kidney capsule and in the capsule-less parotid gland. For the kidney, sliding the implant under the capsule membrane and quick stitching proved superior to other methods. For the parotid gland, creation of a tissue "pocket" for placement and immediate multilayer tissue closure were well tolerated with minimal tissue damage. Surgical clips were placed as fiduciary markers for tissue harvest. Some implant experiments were conducted with miniswine 90 days post-irradiation when salivation decreased significantly. Sufficient parotid tissue remained to allow implant placement, and animals tolerated immunosuppression. In all experiments, viability of implanted hS/PCs was high with clear signs of both vascular and nervous system integration in the parotid implants. We thus conclude that the immunosuppressed miniswine is a high-value emerging model for testing human implants prior to first-in-human trials.

Project description:Intestinal crypt progenitor/stem (ICPS) cell apoptosis and vascular endothelial cell apoptosis are responsible for the initiation and development of ionizing radiation (IR)-evoked gastrointestinal syndrome. The signaling mechanisms underlying IR-induced ICPS cell apoptosis remain largely unclear. Our findings provide evidence that ?-arrestin-2 (?arr2)-mediated ICPS cell apoptosis is crucial for IR-stimulated intestinal injury. ?Arr2-deficient mice exhibited decreased ICPS cell and intestinal Lgr5(+) (leucine-rich repeat-containing G-protein-coupled receptor 5-positive) stem cell apoptosis, promoted crypt proliferation and reproduction, and protracted survival following lethal doses of radiation. Radioprotection in the ICPS cells isolated from ?arr2-deficient mice depended on prolonged nuclear factor-?B (NF-?B) activation via direct interaction of ?arr2 with I?B? and subsequent inhibition of p53-upregulated modulator of apoptosis (PUMA)-mediated mitochondrial dysfunction. Unexpectedly, ?arr2 deficiency had little effect on IR-induced intestinal vascular endothelial cell apoptosis in mice. Consistently, ?arr2 knockdown also provided significant radioresistance by manipulating NF-?B/PUMA signaling in Lgr5(+) cells in vitro. Collectively, these observations show that targeting the ?arr2/NF-?B/PUMA novel pathway is a potential radiomitigator for limiting the damaging effect of radiotherapy on the gastrointestinal system. Significance statement: acute injury to the intestinal mucosa is a major dose-limiting complication of abdominal radiotherapy. The issue of whether the critical factor for the initiation of radiation-induced intestinal injury is intestinal stem cell apoptosis or endothelial cell apoptosis remains unresolved. ?Arrs have recently been found to be multifunctional adaptor of apoptosis. Here, we found that ?-arrestin-2 (?arr2) deficiency was associated with decreased radiation-induced ICPS cell apoptosis, which prolonged survival in abdominally irradiated mice. Moreover, ?arr2 deficiency-mediated intestinal progenitor/stem cell radioprotection relied on protracted NF-?B activation and subsequent suppression of PUMA induction. Our results suggest that ICPS cell apoptosis is the factor involved in the initiation and development of radiation-induced gastrointestinal syndrome. ?Arr2 is a potential target for lessening radiation-induced ICPS cell apoptosis.

Dataset Information

Modeling stem/progenitor cell-induced neovascularization and oxygenation around solid implants.

Publications

Modeling stem/progenitor cell-induced neovascularization and oxygenation around solid implants.

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