Human placental-derived stem cell therapy ameliorates experimental necrotizing enterocolitis.

Necrotizing enterocolitis (NEC), a life-threatening intestinal disease, is becoming a larger proportionate cause of morbidity and mortality in premature infants. To date, therapeutic options remain elusive. Based on recent cell therapy studies, we investigated the effect of a human placental-derived stem cell (hPSC) therapy on intestinal damage in an experimental NEC rat pup model. NEC was induced in newborn Sprague-Dawley rat pups for 4 days via formula feeding, hypoxia, and LPS. NEC pups received intraperitoneal (ip) injections of either saline or hPSC (NEC-hPSC) at 32 and 56 h into NEC induction. At 4 days, intestinal macroscopic and histological damage, epithelial cell composition, and inflammatory marker expression of the ileum were assessed. Breastfed (BF) littermates were used as controls. NEC pups developed significant bowel dilation and fragility in the ileum. Further, NEC induced loss of normal villi-crypt morphology, disruption of epithelial proliferation and apoptosis, and loss of critical progenitor/stem cell and Paneth cell populations in the crypt. hPSC treatment improved macroscopic intestinal health with reduced ileal dilation and fragility. Histologically, hPSC administration had a significant reparative effect on the villi-crypt morphology and epithelium. In addition to a trend of decreased inflammatory marker expression, hPSC-NEC pups had increased epithelial proliferation and decreased apoptosis when compared with NEC littermates. Further, the intestinal stem cell and crypt niche that include Paneth cells, SOX9+ cells, and LGR5+ stem cells were restored with hPSC therapy. Together, these data demonstrate hPSC can promote epithelial healing of NEC intestinal damage.NEW & NOTEWORTHY These studies demonstrate a human placental-derived stem cell (hPSC) therapeutic strategy for necrotizing enterocolitis (NEC). In an experimental model of NEC, hPSC administration improved macroscopic intestinal health, ameliorated epithelial morphology, and supported the intestinal stem cell niche. Our data suggest that hPSC are a potential therapeutic approach to attenuate established intestinal NEC damage. Further, we show hPSC are a novel research tool that can be utilized to elucidate critical neonatal repair mechanisms to overcome NEC.

Long-term therapeutic effect of cell therapy on improvement in erectile function in a rat model with pelvic neurovascular injury.

OBJECTIVE: To determine the long-term therapeutic effect amongst three human cell types on erectile function recovery in a rat model of dual neurovascular-injury erectile dysfunction (NVED). MATERIALS AND METHODS: A dual NVED model was established in athymic rats by crushing the bilateral cavernous nerves and ligating the bilateral internal pudendal neurovascular bundles. At the time of defect creation, three different types of human cell populations (2.5 × 106  cells/0.2 mL: umbilical vein endothelial cells, adipose-derived stem cells, and amniotic fluid-derived stem cells) were injected intracavernously into the penile tissue. Saline injection (0.2 mL) served as a control group. Erectile function and histomorphological analyses of penile tissues were assessed 12 weeks after defect creation and cell or saline injection. RESULTS: The ratio of intracavernous pressure to mean arterial pressure (functional indicator) was significantly higher in the cell therapy groups compared to the saline-injected control group (P < 0.05). Immunofluorescence staining showed more cells expressing biomarkers of endothelial, smooth muscle, and nerve cells within the penile tissue in the cell therapy groups when compared to the control group. CONCLUSIONS: Cell therapy enhanced erectile function and ameliorated the histological changes 12 weeks after pelvic neurovascular injury in vivo, indicating that cell therapy may improve the long-term outcomes in neurogenic, myogenic and vascular tissue regeneration in the treatment of NVED.

Multicellular bioprinted skin facilitates human-like skin architecture in vivo.

Bioprinting is a promising alternative method to generate skin substitutes because it can replicate the structural organization of the skin into biomimetic layers in vitro. In this study, six primary human skin cell types were used to bioprint a trilayer skin construct consisting of epidermis, dermis, and hypodermis. Transplantation of the bioprinted skin with human cells onto full-thickness wounds of nu/nu mice promoted rapid vascularization and formation of epidermal rete ridges analogous to the native human epidermis, with a normal-looking extracellular matrix. Cell-specific staining confirmed the integration of the implanted cells into the regenerated skin. Using a similar approach, a 5 centimeter-by-5 centimeter bioprinted autologous porcine skin graft was transplanted onto full-thickness wounds in a porcine excisional wound model. The bioprinted skin graft improved epithelialization, reduced skin contraction, and supported normal collagen organization with reduced fibrosis. Differential gene expression demonstrated pro-remodeling protease activity in wounds transplanted with bioprinted autologous skin grafts. These results demonstrate that bioprinted skin can support skin regeneration to allow for nonfibrotic wound healing and suggest that the skin bioprinting technology may be applicable for human clinical use.

Ferret acute lung injury model induced by repeated nebulized lipopolysaccharide administration.

Inflammatory lung diseases affect millions of people worldwide. These diseases are caused by a number of factors such as pneumonia, sepsis, trauma, and inhalation of toxins. Pulmonary function testing (PFT) is a valuable functional methodology for better understanding mechanisms of lung disease, measuring disease progression, clinical diagnosis, and evaluating therapeutic interventions. Animal models of inflammatory lung diseases are needed that accurately recapitulate disease manifestations observed in human patients and provide an accurate prediction of clinical outcomes using clinically relevant pulmonary disease parameters. In this study, we evaluated a ferret lung inflammation model that closely represents multiple clinical manifestations of acute lung inflammation and injury observed in human patients. Lipopolysaccharide (LPS) from Pseudomonas aeruginosa was nebulized into ferrets for 7 repeated daily doses. Repeated exposure to nebulized LPS resulted in a restrictive pulmonary injury characterized using Buxco forced maneuver PFT system custom developed for ferrets. This is the first study to report repeated forced maneuver PFT in ferrets, establishing lung function measurements pre- and post-injury in live animals. Bronchoalveolar lavage and histological analysis confirmed that LPS exposure elicited pulmonary neutrophilic inflammation and structural damage to the alveoli. We believe this ferret model of lung inflammation, with clinically relevant disease manifestations and parameters for functional evaluation, is a useful pre-clinical model for understanding human inflammatory lung disease and for the evaluation of potential therapies.

Amnion membrane hydrogel and amnion membrane powder accelerate wound healing in a full thickness porcine skin wound model.

There is a need for effective wound treatments that retain the bioactivity of a cellular treatment, but without the high costs and complexities associated with manufacturing, storing, and applying living biological products. Previously, we developed an amnion membrane-derived hydrogel and evaluated its wound healing properties using a mouse wound model. In this study, we used a full thickness porcine skin wound model to evaluate the wound-healing efficacy of the amnion hydrogel and a less-processed amnion product comprising a lyophilized amnion membrane powder. These products were compared with commercially available amnion and nonamnion wound healing products. We found that the amnion hydrogel and amnion powder treatments demonstrated significant and rapid wound healing, driven primarily by new epithelialization versus closure by contraction. Histological analysis demonstrated that these treatments promote the formation of a mature epidermis and dermis with similar composition to healthy skin. The positive skin regenerative outcomes using amnion hydrogel and amnion powder treatments in a large animal model further demonstrate their potential translational value for human wound treatments.

Bioprinted Skin Recapitulates Normal Collagen Remodeling in Full-Thickness Wounds.

Over 1 million burn injuries are treated annually in the United States, and current tissue engineered skin fails to meet the need for full-thickness replacement. Bioprinting technology has allowed fabrication of full-thickness skin and has demonstrated the ability to close full-thickness wounds. However, analysis of collagen remodeling in wounds treated with bioprinted skin has not been reported. The purpose of this study is to demonstrate the utility of bioprinted skin for epidermal barrier formation and normal collagen remodeling in full-thickness wounds. Human keratinocytes, melanocytes, fibroblasts, dermal microvascular endothelial cells, follicle dermal papilla cells, and adipocytes were suspended in fibrinogen bioink and bioprinted to form a tri-layer skin structure. Bioprinted skin was implanted onto 2.5 × 2.5 cm full-thickness excisional wounds on athymic mice, compared with wounds treated with hydrogel only or untreated wounds. Total wound closure, epithelialization, and contraction were quantified, and skin samples were harvested at 21 days for histology. Picrosirius red staining was used to quantify collagen fiber orientation, length, and width. Immunohistochemical (IHC) staining was performed to confirm epidermal barrier formation, dermal maturation, vascularity, and human cell integration. All bioprinted skin treated wounds closed by day 21, compared with open control wounds. Wound closure in bioprinted skin treated wounds was primarily due to epithelialization. In contrast, control hydrogel and untreated groups had sparse wound coverage and incomplete closure driven primarily by contraction. Picrosirius red staining confirmed a normal basket weave collagen organization in bioprinted skin-treated wounds compared with parallel collagen fibers in hydrogel only and untreated wounds. IHC staining at day 21 demonstrated the presence of human cells in the regenerated dermis, the formation of a stratified epidermis, dermal maturation, and blood vessel formation in bioprinted skin, none of which was present in control hydrogel treated wounds. Bioprinted skin accelerated full-thickness wound closure by promoting epidermal barrier formation, without increasing contraction. This healing process is associated with human cells from the bioprinted skin laying down a healthy, basket-weave collagen network. The remodeled skin is phenotypically similar to human skin and composed of a composite of graft and infiltrating host cells. Impact statement We have demonstrated the ability of bioprinted skin to enhance closure of full-thickness wounds through epithelialization and normal collagen remodeling. To our knowledge, this article is the first to quantify collagen remodeling by bioprinted skin in full-thickness wounds. Our methods and results can be used to guide further investigation of collagen remodeling by tissue engineered skin products to improve ongoing and future bioprinting skin studies. Ultimately, our skin bioprinting technology could translate into a new treatment for full-thickness wounds in human patients with the ability to recapitulate normal collagen remodeling in full-thickness wounds.

Comparative analysis of two porcine kidney decellularization methods for maintenance of functional vascular architectures.

Kidney transplantation is currently the only definitive solution for the treatment of end-stage renal disease (ESRD), however transplantation is severely limited by the shortage of available donor kidneys. Recent progress in whole organ engineering based on decellularization/recellularization techniques has enabled pre-clinical in vivo studies using small animal models; however, these in vivo studies have been limited to short-term assessments. We previously developed a decellularization system that effectively removes cellular components from porcine kidneys. While functional re-endothelialization on the porcine whole kidney scaffold was able to improve vascular patency, as compared to the kidney scaffold only, the duration of patency lasted only a few hours. In this study, we hypothesized that significant damage in the microvasculatures within the kidney scaffold resulted in the cessation of blood flow, and that thorough investigation is necessary to accurately evaluate the vascular integrity of the kidney scaffolds. Two decellularization protocols [sodium dodecyl sulfate (SDS) with DNase (SDS + DNase) or Triton X-100 with SDS (TRX + SDS)] were used to evaluate and optimize the levels of vascular integrity within the kidney scaffold. Results from vascular analysis studies using vascular corrosion casting and angiograms demonstrated that the TRX + SDS method was able to better maintain intact and functional microvascular architectures such as glomeruli within the acellular matrices than that by the SDS + DNase treatment. Importantly, in vitro blood perfusion of the re-endothelialized kidney construct revealed improved vascular function of the scaffold by TRX + SDS treatment compared with the SDS + DNase. Our results suggest that the optimized TRX + SDS decellularization method preserves kidney-specific microvasculatures and may contribute to long-term vascular patency following implantation. STATEMENT OF SIGNIFICANCE: Kidney transplantation is the only curative therapy for patients with end-stage renal disease (ESRD). However, in the United States, the supply of donor kidneys meets less than one-fifth of the demand; and those patients that receive a donor kidney need life-long immunosuppressive therapy to avoid organ rejection. In the last two decades, regenerative medicine and tissue engineering have emerged as an attractive alternative to overcome these limitations. In 2013, Song et al. published the first experimental orthotopic transplantation of a bioengineering kidney in rodents. In this study, they demonstrated evidences of kidney tissue regeneration and partial function restoration. Despite these initial promising results, there are still many challenges to achieve long-term blood perfusion without graft thrombosis. In this paper, we demonstrated that perfusion of detergents through the renal artery of porcine kidneys damages the glomeruli microarchitecture as well as peritubular capillaries. Modifying dynamic parameters such as flow rate, detergent concentration, and decellularization time, we were able to establish an optimized decellularization protocol with no evidences of disruption of glomeruli microarchitecture. As a proof of concept, we recellularized the kidney scaffolds with endothelial cells and in vitro perfused whole porcine blood successfully for 24 h with no evidences of thrombosis.

Bioengineered transplantable porcine livers with re-endothelialized vasculature.

Donor shortage remains a continued challenge in liver transplantation. Recent advances in tissue engineering have provided the possibility of creating functional liver tissues as an alternative to donor organ transplantation. Small bioengineered liver constructs have been developed, however a major challenge in achieving functional bioengineered liver in vivo is the establishment of a functional vasculature within the scaffolds. Our overall goal is to bioengineer intact livers, suitable for transplantation, using acellular porcine liver scaffolds. We developed an effective method for reestablishing the vascular network within decellularized liver scaffolds by conjugating anti-endothelial cell antibodies to maximize coverage of the vessel walls with endothelial cells. This procedure resulted in uniform endothelial attachment throughout the liver vasculature extending to the capillary bed of the liver scaffold and greatly reduced platelet adhesion upon blood perfusion in vitro. The re-endothelialized livers, when transplanted to recipient pigs, were able to withstand physiological blood flow and maintained for up to 24 h. This study demonstrates, for the first time, that vascularized bioengineered livers, of clinically relevant size, can be transplanted and maintained in vivo, and represents the first step towards generating engineered livers for transplantation to patients with end-stage liver failure.