IntroductionThe prevalence of nonhealing wounds is predicted to increase due to the growing aging population. Despite the use of novel skin substitutes and wound dressings, poorly vascularized wound niches impair wound repair. Mesenchymal stem cells (MSCs) have been reported to provide paracrine signals to promote wound healing, but the effect of human Wharton’s jelly-derived MSCs (WJ-MSCs) has not yet been described in human normal skin.The aim of this study is to examine the effects of human WJ-MSC paracrine signaling on normal skin fibroblasts in vitro, and in an in vivo preclinical model.MethodsHuman WJ-MSCs and normal skin fibroblasts were isolated from donated umbilical cords and normal adult human skin. Fibroblasts were treated with WJ-MSC-conditioned medium (WJ-MSC-CM) or nonconditioned medium.ResultsExpression of genes involved in re-epithelialization (transforming growth factor-β2), neovascularization (hypoxia-inducible factor-1α) and fibroproliferation (plasminogen activator inhibitor-1) was upregulated in WJ-MSC-CM-treated fibroblasts (P ≤ 0.05). WJ-MSC-CM enhanced normal skin fibroblast proliferation (P ≤ 0.001) and migration (P ≤ 0.05), and promoted wound healing in an excisional full-thickness skin murine model.ConclusionsUnder our experimental conditions, WJ-MSCs enhanced skin wound healing in an in vivo mouse model.

Stem cell therapy has emerged as a promising new approach in almost every medicine specialty. This vast, heterogeneous family of cells are now both naturally (embryonic and adult stem cells) or artificially obtained (induced pluripotent stem cells or iPSCs) and their fates have become increasingly controllable, thanks to ongoing research in this passionate new field. We are at the beginning of a new era in medicine, with multiple applications for stem cell therapy, not only as a monotherapy, but also as an adjunct to other strategies, such as organ transplantation or standard drug treatment. Regrettably, serious preclinical concerns remain and differentiation, cell fusion, senescence and signalling crosstalk with growth factors and biomaterials are still challenges for this promising multidisciplinary therapeutic modality. Severe burns have several indications for stem cell therapy, including enhancement of wound healing, replacement of damaged skin and perfect skin regeneration – incorporating skin appendages and reduced fibrosis –, as well as systemic effects, such as inflammation, hypermetabolism and immunosuppression. The aim of this review is to describe well established characteristics of stem cells and to delineate new advances in the stem cell field, in the context of burn injury and wound healing.

Keloid scars are abnormal benign fibroproliferative tumors with high recurrence rates and no current efficacious treatment. Accumulating evidence suggests that human umbilical cord Wharton's jellyderived mesenchymal stem cells (WJ-MSCs) have antifibrotic properties. Paracrine signaling is considered one of the main underlying mechanisms behind the therapeutic effects of mesenchymal stem cells. However, the paracrine signaling effects of WJ-MSCs on keloids have not yet been reported. The aim of this study is to investigate paracrine signaling effects of human WJ-MSCs on keloid fibroblasts in vitro. Human umbilical cords and keloid skin samples were obtained, and WJ-MSCs and keloid fibroblasts were isolated and cultured. One-way and two-way paracrine culture systems between both cell types were investigated. Plasminogen activator inhibitor-I and transforming growth factor-b2 (TGFb2) transcripts were upregulated in keloid fibroblasts cultured with WJ-MSC-conditioned medium (WJ-MSC-CM) and cocultured with inserts, while showing lower TGF-b3 gene expression. Interleukin (IL)-6, IL-8, TGF-b1, and TGF-b2 protein expression was also enhanced. The WJ-MSC-CM-treated keloid fibroblasts showed higher proliferation rates than their control keloid fibroblasts with no significant change in apoptosis rate or migration ability. In our culture conditions, the indirect application of WJ-MSCs on keloid fibroblasts may enhance their profibrotic phenotype. STEM CELLS TRANSLATIONAL MEDICINE 2014;3:299-307

Previous work in our laboratory showed the potential of using a human recombinant elastin-like polypeptide (ELP) as a thromboresistant coating. In this work we investigate the use of three particular ELPs (ELP1, ELP2 and ELP4), that differ by molecular weight and number of repeating hydrophobic and cross-linking domains, as coatings to improve blood-contacting properties. All three ELPs were passively adsorbed on Mylar surfaces. Differences in water contact angle and surface concentration were found among the three ELP coatings, with the shortest polypeptide, ELP1, being the most hydrophilic and abundant on the surface (55°, 0.76 μg/cm(2)), followed by ELP2 (55°, 0.35 μg/cm(2)) and ELP4, the longest of the three (66°, 0.25 μg/cm(2)), respectively. The blood interactions of the ELP coatings were investigated by measuring fibrinogen adsorption and platelet adhesion in whole blood under laminar flow in a cone and plate viscometer configuration. In general, platelet adhesion to the ELP-coated surfaces was found to correlate with fibrinogen adsorption. Decreases in fibrinogen accretion and platelet adhesion were observed for ELP-coated compared to uncoated surfaces. The magnitude of the decreases was found to depend on the ELP sequence length, with ELP4 exhibiting the lowest levels of fibrinogen adsorption and platelet adhesion at 43 ± 24 ng/cm(2) and 113 ± 77 platelets/mm(2), respectively.

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To accelerate the cardiac drug discovery pipeline, we set out to develop a platform that would be capable of quantifying tissue-level functions such as contractile force and be amenable to standard multiwell-plate manipulations. We report a 96-well-based array of 3D human pluripotent stem cell (hPSC)-derived cardiac microtissues -termed Cardiac MicroRings (CaMiRi) -in custom 3D-printmolded multiwell plates capable of contractile force measurement. Within each well, two elastomeric microcantilevers are situated above a circumferential ramp. The wells are seeded with cell-laden collagen, which, in response to the gradual slope of the circumferential ramp, self-organizes around tip-gated microcantilevers to form contracting CaMiRi. The contractile force exerted by the CaMiRi is measured and calculated using the deflection of the cantilevers. Platform responses were robust and comparable across wells, and we used it to determine an optimal tissue formulation. We validated the contractile force response of CaMiRi using selected cardiotropic compounds with known effects. Additionally, we developed automated protocols for CaMiRi seeding, image acquisition, and analysis to enable the measurement of contractile force with increased throughput. The unique tissue fabrication properties of the platform, and the consequent effects on tissue function, were demonstrated upon adding hPSC-derived epicardial cells to the system. This platform represents an open-source contractile force screening system useful for drug screening and tissue engineering applications.Screening using engineered heart tissue is limited by the high cost associated with the large cell numbers required for high-fidelity in vitro cardiac models, the lack of long-term function and viability of the tissues, and the challenge of imaging for data acquisition. Miniaturization of self-organizing cardiac organoids is a strategic approach to address these challenges using photolithography-and micromachining-based fabrication techniques 1-12 . Unfortunately, some of these systems are difficult to manufacture on a macroscale, and production often requires a high level of skill. Furthermore, these methods are restrictive to specific design geometries (for instance, vertical walls spanning either the micrometer or centimeter scale but not both) and are occasionally expensive to prototype (due to requiring access to a cleanroom, cost of materials, and time). Another challenge typically associated with these microfluidic-and microstructure-based devices is adaptation to existing tissue culture equipment such as microscope stage adapters and liquid dispensing tools. Potential complications may also arise upon the

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ABSTRACTTo accelerate the cardiac drug discovery pipeline, we set out to develop a platform that would be amenable to standard multiwell-plate manipulations and be capable of quantifying tissue-level functions such as contractile force. We report a 96-well-based array of 3D human pluripotent stem cell (hPSC)-derived cardiac microtissues - termed Cardiac MicroRings (CaMiRi) - in custom printed multiwell plates capable of contractile force measurement. Within each well, two elastomeric microcantilevers are situated above a ramp. The wells are seeded with cell-laden collagen which, in response to the slope of the ramp, self-organizes around tip-gated microcantilevers to form contracting CaMiRi. The contractile force exerted by the CaMiRi is measured and calculated using the deflection of the cantilevers. Platform responses were robust and comparable across wells and we used it to determine an optimal tissue formulation. We validated contractile force response of CaMiRi using selected cardiotropic compounds with known effects. Additionally, we developed automated protocols for CaMiRi seeding, image acquisition, and analysis to enable measurement of contractile force with increased throughput. The unique tissue fabrication properties of the platform, and the consequent effects on tissue function, were demonstrated upon adding hPSC-derived epicardial cells to the system. This platform represents an open-source contractile force screening system useful for drug screening and tissue engineering applications.