A perioperative layered autologous tissue expansion graft for hollow organ repair

Tissue engineering has not been widely adopted in clinical settings for several reasons, including technical challenges, high costs, and regulatory complexity. Here, we introduce the Perioperative Layered Autologous Tissue Expansion graft (PLATE graft), a composite biomaterial and collagen-reinforced construct with autologous epithelium on one side and smooth muscle tissue on the other. Designed to mimic the structure and function of natural hollow organs, the PLATE graft is unique in that it can be produced in a standard operating theatre and is cost-effective. In this proof-of-principle study, we test its regenerative performance in eight different organs, present biomechanical and permeability tests, and finally explore its in vivo performance in live rabbits.

Insights into cellular behavior and micromolecular communication in urothelial micrografts

Autologous micrografting is a technique currently applied within skin wound healing, however, the potential use for surgical correction of other organs with epithelial lining, including the urinary bladder, remains largely unexplored. Currently, little is known about the micrograft expansion potential and the micromolecular events that occur in micrografted urothelial cells. In this study, we aimed to evaluate the proliferative potential of different porcine urothelial micrograft sizes in vitro, and, furthermore, to explore how urothelial micrografts communicate and which microcellular events are triggered. We demonstrated that increased tissue fragmentation subsequently potentiated the yield of proliferative cells and the cellular expansion potential, which confirms, that the micrografting principles of skin epithelium also apply to uroepithelium. Furthermore, we targeted the expression of the extracellular signal-regulated kinase (ERK) pathway and demonstrated that ERK activation occurred predominately at the micrograft borders and that ERK inhibition led to decreased urothelial migration and proliferation. Finally, we successfully isolated extracellular vesicles from the micrograft culture medium and evaluated their contents and relevance within various enriched biological processes. Our findings substantiate the potential of applying urothelial micrografting in future tissue-engineering models for reconstructive urological surgery, and, furthermore, highlights certain mechanisms as potential targets for future wound healing treatments.

Molecular and histological studies of bladder wound healing in a rodent model

The field of regenerative medicine encounters different challenges. The success of tissue-engineered implants is dependent on proper wound healing. Today, the process of normal urinary bladder wound healing is poorly characterized. We aspired to explore and elucidate the natural response to injury in an in vivo model in order to further optimize tissue regeneration in future studies. In this study, we aimed to characterize histological and molecular changes during normal healing in a rat model by performing a standardized incisional wound followed by surgical closure. We used a rodent model (n = 40) to follow the healing process in the urinary bladder for 28 days. Surgical exposure of the bladder without incision (n = 40) was performed in controls. Histological characterization and western blot analyses of proteins was carried out using specific staining and markers for inflammation, proliferation, angiogenesis, and tissue maturation. For the molecular characterization of gene expression total RNA was collected for RT² -PCR in wound healing pathway arrays. Analysis of histology revealed distinct, but overlapping, phases of healing with a local inflammatory response (days 1-8) simultaneous with a rapid formation of granulation tissue and proliferation (days 2-8). We also identified significant changes in gene expression related to inflammation, proliferation, and extracellular matrix formation. Healing of an incisional wound in a rodent urinary bladder demonstrated that all the classical phases of wound healing: hemostasis, inflammation, proliferation followed by tissue maturation were present. Our data suggest that the bladder and the skin share similar molecular signaling during wound healing, although we noted differences in the duration of each phase compared to previous studies in rat skin. Further studies will address whether our findings can be extrapolated to the human bladder.

Minced Tissue in Compressed Collagen: A Cell-containing Biotransplant for Single-staged Reconstructive Repair

Conventional techniques for cell expansion and transplantation of autologous cells for tissue engineering purposes can take place in specially equipped human cell culture facilities. These methods include isolation of cells in single cell suspension and several laborious and time-consuming events before transplantation back to the patient. Previous studies suggest that the body itself could be used as a bioreactor for cell expansion and regeneration of tissue in order to minimize ex vivo manipulations of tissues and cells before transplanting to the patient. The aim of this study was to demonstrate a method for tissue harvesting, isolation of continuous epithelium, mincing of the epithelium into small pieces and incorporating them into a three-layered biomaterial. The three-layered biomaterial then served as a delivery vehicle, to allow surgical handling, exchange of nutrition across the transplant, and a controlled degradation. The biomaterial consisted of two outer layers of collagen and a core of a mechanically stable and slowly degradable polymer. The minced epithelium was incorporated into one of the collagen layers before transplantation. By mincing the epithelial tissue into small pieces, the pieces could be spread and thereby the propagation of cells was stimulated. After the initial take of the transplants, cell expansion and reorganization would take place and extracellular matrix mature to allow ingrowth of capillaries and nerves and further maturation of the extracellular matrix. The technique minimizes ex vivo manipulations and allow cell harvesting, preparation of autograft, and transplantation to the patient as a simple one-stage intervention. In the future, tissue expansion could be initiated around a 3D mold inside the body itself, according to the specific needs of the patient. Additionally, the technique could be performed in an ordinary surgical setting without the need for sophisticated cell culturing facilities.

The human antimicrobial peptide LL-37 suppresses apoptosis in keratinocytes

The human cathelicidin antimicrobial peptide LL-37 is involved in various aspects of skin biology, including protection against infection, wound healing, and also in psoriasis. The tight regulation of apoptosis is critical in tissue repair and its deregulation is a part of the psoriasis phenotype. Despite being involved in cell death of several cell types, virtually nothing is known about the function of LL-37 in keratinocyte apoptosis. Here we report that LL-37 peptide protects primary human keratinocytes and HaCaT cells from apoptosis induced by the topoisomerase I inhibitor camptothecin (CAM). In particular, pretreatment with LL-37 significantly decreased caspase-3 activity after CAM-treatment. Expression profiling of keratinocytes treated with LL-37 identified the upregulation of cyclooxygenase-2 (COX-2) expression, a gene implicated in protection from apoptosis. In addition to inducing COX-2 expression, LL-37 stimulated the production of its product, prostaglandin E-2 (PGE-2). Moreover, LL-37 induced the expression of inhibitor of apoptosis-2 (IAP-2), implicated in the COX-2/PGE-2 antiapoptotic pathway. Pretreatment with a selective COX-2 inhibitor abolished the antiapoptotic effect of LL-37 and reduced IAP-2 expression implicating that the antiapoptotic effect of LL-37 in keratinocytes is mediated by a COX-2-dependent mechanism involving IAP-2. Thus, overexpression of LL-37 may contribute to reduced keratinocyte apoptosis in conditions such as psoriasis.

Diagnostic usefulness of inflammatory markers in acute cellular rejection after heart transplantation

BACKGROUND

Acute cellular rejection (ACR) affects early morbidity and mortality after heart transplantation. The diagnostic technique of choice is endomyocardial biopsy. Our aim was to evaluate the diagnostic usefulness of inflammatory markers as a noninvasive method to monitor cellular rejection.

MATERIAL AND METHODS

We prospectively analyzed 73 cardiac transplant patients by determining the serum levels of protein fibrinogen (fgpro), functional fibrinogen (fgfun), C-reactive protein (CRP), and sialic acid (SA) coinciding with an endomyocardial biopsy (5.1 revisions/patient). The statistical methods were chi(2), Student's t-test, and ROC curves.

RESULTS

Of the 373 controls, significant rejection was detected in 19%. Analysis of the relationship between ACR and the markers showed significantly elevated levels of fgpro (345 +/- 90 versus 307 +/- 74 mg/dL; P = .03), fgfun (361 +/- 101 versus 318 +/- 89 mg/dL; P = .04), and SA (74 +/- 22 versus 66 +/- 15 mg/dL; P = .02), but not CRP (19 +/- 29 versus 10 +/- 21 mg/dL; P = .07). SA displayed a better diagnostic utility (area under the curve 0.7; P < .01), 35% sensitivity, 85% specificity, and 82% negative predictive value for a cutoff point of 80 mg/dL.

CONCLUSIONS

Among the inflammatory markers increased in ACR, SA was the most useful noninvasive tool for screening.

Do Cardiovascular Risk Factors Influence Cardiac Allograft Vasculopathy?

BACKGROUND

Cardiac allograft vasculopathy (CAV) is the leading cause of heart transplant failure after the first year. The etiological factors involved are currently a controversial matter. Intravascular ultrasound (IVUS) is considered the diagnostic procedure of choice. We assessed the relationship of cardiovascular risk factors with CAV.

MATERIALS

We analyzed prospectively 22 patients. We conducted a first study with coronary angiography and IVUS at 36 +/- 3 days and a second at 598 +/- 49 days. We performed an average of 5.6 clinical revisions per patient, assessing the effect of the classic cardiovascular risk factors, the cause of heart failure, and the age of the patient and donor. The statistics used were chi(2), Fisher exact test, and Student t test.

RESULTS

CAV was found in 10 subjects (45.5%). Univariate analysis showed statistically significant differences in the assessment of the presence of diabetes and dyslipidemia posttransplantation, but not pretransplantation. Among the patients with CAV there was a higher percentage of diabetics (32.8% vs 12%, P < .01). The patients with CAV also had higher levels of total cholesterol (211 +/- 40 mg/dL vs 195 +/- 35 mg/dL, P = .02), triglycerides (172 +/- 108 mg/dL vs 136 +/- 66 mg/dL, P = .03), low-density lipoprotein (133 +/- 35 mg/dL vs 117 +/- 30 mg/dL, P = .01), and lower high-density lipoprotein levels (46 +/- 15 mg/dL vs 52 +/- 12 mg/dL, P = .03).

CONCLUSIONS

Only the diabetes and dyslipidemia present in the posttransplantation period were associated with CAV, which highlights the fact that it is a condition that both shares and has different features with atherosclerosis and probably requires a different diagnostic-therapeutic approach.

Usefulness of von Willebrand Factor in Cardiac Allograft Vasculopathy: Preliminary Experience

BACKGROUND

Cardiac allograft vasculopathy (CAV) is a disease that significantly limits the survival of transplant patients intravascular ultrasound (IVUS) is considered the method of choice for its diagnosis. von Willebrand factor (vWf) has been used as a marker of endothelial malfunction. We sought to evaluate the usefulness of vWf as a CAV marker.

MATERIALS AND METHODS

We prospectively analyzed 22 cardiac transplant subjects, on whom we performed a first study using coronary angiography and IVUS at 36 +/- 3 days and a second study at 598 +/- 49 days. During the follow-up period, five vWf serum controls were performed per patient. We analyzed the results with the repeated-measures ANOVA test and a ROC curve.

RESULTS

CAV was detected in 10 (45.5%) of the 22 patients. Although vWf levels tended to diminish progressively during evolution, this trend was not statistically significant (P = .3). However, differences were appreciated based on the presence versus absence of CAV (298 +/- 139 mg/dL versus 212 +/- 105 mg/dL, P = .02). The ROC curve showed a sensitivity of 40%, a specificity of 83%, and a negative predictive value of 82% with a cutoff point of 300 mg/dL.

CONCLUSIONS

Subjects with CAV showed significantly higher vWf serum concentrations, particularly during the preliminary phases of cardiac transplantation decreasing during its evolution. This marker could be useful for early screening of CAV.