Control Grafts Research Articles

Leptin-Induced Angiogenesis of EA.Hy926 Endothelial Cells via the Akt and Wnt Signaling Pathways In Vitro and In Vivo.

Angiogenesis involves the activation of endothelial cells followed by capillary formation. Leptin, the protein product of the ob gene, can induce the angiogenic potential of endothelial cells. However, the underlying cellular mechanism still remains to be elicited. We firstly evaluated the in vitro effects of leptin on proliferation and angiogenic differentiation of endothelial cell line EA.hy926. Leptin was found to potently induced cell proliferation, expression of angiogenic gene, migration and tube formation. Then we investigated the roles of the Akt and Wnt signaling pathways in the aforementioned processes. It showed that Akt and Wnt signaling pathways could be activated by leptin, while inhibition of the Akt and Wnt signaling pathways by siRNAs effectively blocked the leptin-induced angiogenesis. Finally, we used electrospinning to fabricated leptin-immobilized linear poly(L-lactide-co-caprolactone) (PLCL)-leptin. The in vivo vessel formation of PLCL-leptin was evaluated using subcutaneous implants in Sprague-Dawley rats. The histological and immunofluorescence revealed that cell infiltration with PLCL-leptin was much more significant than that with the control PLCL group. More importantly, the number of laminin+ vessels and CD31+ cells in PLCL-leptin grafts was significantly higher than in control grafts. The study demonstrated that it is via Akt and Wnt signaling pathways that leptin promotes the proliferation and angiogenic differentiation of endothelial cells and the capacity of endogenous tissue regeneration makes the novel leptin-conjugated PLCL promising materials for grafts.

Surface-Initiated Initiators for Continuous Activator Regeneration (SI ICAR) ATRP of MMA from 2,2,6,6-tetramethylpiperidine-1-oxy (TEMPO) Oxidized Cellulose Nanofibers for the Preparations of PMMA Nanocomposites.

An effective method of oxidation from paper pulps via 2,2,6,6–tetramethylpiperidine–1–oxy (TEMPO) compound to obtain TEMPO-oxidized cellulose nanofibers (TOCNs) was demonstrated. Following by acylation, TOCN having an atom transfer radical polymerization (ATRP) initiating site of bromoisobutyryl moiety (i.e., TOCN–Br) was successfully obtained. Through a facile and practical technique of surface-initiated initiators for continuous activator regeneration atom transfer radical polymerization (SI ICAR ATRP) of methyl methacrylate (MMA) from TOCN–Br, controllable grafting polymer chain lengths (Mn = ca. 10k–30k g/mol) with low polydispersity (PDI < 1.2) can be achieved to afford TOCN–g–Poly(methyl methacrylate) (PMMA) nanomaterials. These modifications were monitored by Fourier-transform infrared spectroscopy (FT–IR), scanning electron microscopy (SEM), electron spectroscopy for chemical analysis (ESCA), and water contact angle analysis. Eventually, TOCN–g–PMMA/PMMA composites were prepared using the solvent blending method. Compared to the pristine PMMA (Tg = 100 °C; tensile strength (σT) = 17.1 MPa), the composites possessed high transparency with enhanced thermal properties and high tensile strength (Tg = 110 °C and σT = 37.2 MPa in 1 wt% TOCN containing case) that were investigated by ultraviolet-visible spectroscopy (UV-Vis), thermogravimetric analysis (TGA), dynamic mechanical analysis (DMA), and tensile tests. We demonstrated that minor amounts of TOCN–g–PMMA nanofillers can provide high efficacy in improving the mechanical and thermal properties of PMMA matrix.

Indirect Sinus Augmentation With and Without the Addition of a Biomaterial: A Randomized Controlled Clinical Trial.

The aim of this study was to compare the results of indirect sinus augmentation with and without the addition of a biomaterial. Thirty patients aged 40 to 60 years participated in this randomized controlled clinical trial. After closed sinus lift operation, patients were randomly and equally divided into blood clot control and acemannan sponge graft groups. Simultaneous implant placement was then performed. Cone beam computed tomography was performed immediately and at 3 and 6 months postoperation. Bone formation was evaluated by the radiographic endo-sinus bone gain percentage around the implant. Compared with the control group, the acemannan-treated group had a significantly greater radiographic endo-sinus bone gain percentage of approximately 2.4- and 2-fold at 3 and 6 months postsurgery, respectively (P < 0.05). The addition of a biomaterial (Acemannan) with indirect sinus augmentation and simultaneous implant placement significantly enhances bone formation at 3 and 6 months postsurgery.

An immediate access dialysis graft designed to prevent needle-related complications: Results from the initial pre-clinical studies.

No technology has been specifically developed with the intent to reduce needle-related vascular access injuries; a significant source of complications and abandonment. We present the initial pre-clinical study results of a novel, self-sealing, immediate cannulation dialysis graft that aims to prevent needle-related complications; to promote safe, reliable needle access; to reduce catheter use; and could facilitate home hemodialyisis. The innovative graft design consists of two cannulation chambers with self-sealing properties and materials that prevent side and back wall needle puncture. Study and control grafts (expanded polytetrafluoroethylene) were implanted in one pig and 10 sheep in two studies over the course of 1 year. First cannulation occurred immediately post implant for all study grafts. Post-cannulation time to hemostasis, hematoma and seroma formation, infection, and patency were recorded. The two studies account for nearly 60 weeks (average 6.4 weeks/graft) of study graft follow-up. In the ovine study, average study graft time to hemostasis was 27.3 s (standard deviation = 26.3, range = 0-120), and the control averaged 177.2 s (standard deviation = 113.4, range = 60-600), p < 0.0001. Secondary patency was 75% and 67% for the study and control grafts, respectively. Neither study nor control groups experienced seroma, graft infections, or deaths. All novel grafts in the studies were implanted successfully and functioned as intended. There were no complications related to tunneling of the study graft and the chamber prevented back/side wall needle injury. This novel technology may help to mitigate these needle-related complications, while allowing for early/immediate cannulation which could also reduce catheter contact time.

JAK3 inhibitor-based immunosuppression in allogeneic islet transplantation in cynomolgus monkeys

ABSTRACTIslet transplantation is efficacious to prevent severe hypoglycemia and glycemic liability of selected patients of type 1 diabetes. However, since calcineurin inhibitor (CNI) causes β-cell and nephrotoxicity, alternative drug(s) with similar potency and safety profile to CNI will be highly desirable. Here we tested whether JAK3 inhibitor, tofacitinib could be used instead of tacrolimus in CIT07 immunosuppression regimen in cynomolgus nonhuman primate (NHP) model. Five independent streptozotocin (STZ)-induced diabetic monkeys were transplanted with MHC-mismatched allogeneic islets and three animals were further re-transplanted upon insufficient glycemic control or early islet graft rejection. After islet transplantation, blood glucose levels were quickly stabilized and maximal islet graft survival as measured by serum C-peptide concentration was >330, 98, >134, 31, or 22 days, respectively, after transplantation (median survival day; 98 days). Cellular and humoral immune responses were efficiently suppressed by JAK3 inhibitor-based immunosuppression during the follow-up periods. Although intermittent increases of the genome copy number of cynomolgus cytomegalovirus (CMV) were detected by quantitative real-time PCR analyses, serious infections or posttransplant lymphoproliferative disease (PTLD) was not found in all animals. Taken together, we have shown that JAK3 inhibitor could be used in replacement of tacrolimus in a highly translatable NHP islet transplantation model and these results suggest that JAK3 inhibitor will be potentially incorporated in human allogeneic islet transplantation.

Controlled reactive modification of polypropylene with maleic anhydride via solvent-free technique

The effect of radical scavengers on the control of β-scission of polypropylene (PP) during the free-radical grafting with maleic anhydride (MAH) in melt was investigated. The main interest was the evaluation of the effective concentration of radical scavengers Irganox 1010 (IRN1010) and Irgafos 168 (IRF168) for better control of grafting process. For this purpose, radical grafting of non-stabilized PP was performed in order to describe specifically the effect of proposed additives with no effect of additives in commercial PP grades. For this purpose, the influence of the initial concentration of IRN1010 ([IRN1010]0) on the reaction course was predicted with respect to the change of kinetic parameters, thermal and rheological properties of PP-g-MAH. Obtained results showed that the efficiency of IRN1010 and IRF168 is not proportional to their concentration above critical level as evidenced by rheological properties of PP-g-MAH. Above that point, both the grafting efficiency and grafting rate decrease and thus the determination of effective cIRN1010 is the key for approaching controlled radical grafting of PP.

Well-Defined Alkyl Functional Poly(Styrene-co-Maleic Anhydride) Architectures as Pour Point and Viscosity Modifiers for Lubricating Oil

A series of well-defined poly(styrene-co-maleic anhydride) copolymers (PSMA) allowing controlled grafting density and distribution of long alkyl side chains (C12 and C22) was synthesized and invest...

Optimization and Stability of Cell-Polymer Hybrids Obtained by "Clicking" Synthetic Polymers to Metabolically Labeled Cell Surface Glycans.

Re-engineering of mammalian cell surfaces with polymers enables the introduction of functionality including imaging agents, drug cargoes or antibodies for cell-based therapies, without resorting to genetic techniques. Glycan metabolic labeling has been reported as a tool for engineering cell surface glycans with synthetic polymers through the installation of biorthogonal handles, such as azides. Quantitative assessment of this approach and the robustness of the engineered coatings has yet to be explored. Here, we graft poly(hydroxyethyl acrylamide) onto azido-labeled cell surface glycans using strain-promoted azide–alkyne “click” cycloaddition and, using a combination of flow cytometry and confocal microscopy, evaluate the various parameters controlling the outcome of this “grafting to” process. In all cases, homogeneous cell coatings were formed with >95% of the treated cells being covalently modified, superior to nonspecific “grafting to” approaches. Controllable grafting densities could be achieved through modulation of polymer chain length and/or concentration, with longer polymers having lower densities. Cell surface bound polymers were retained for at least 72 h, persisting through several mitotic divisions during this period. Furthermore, we postulate that glycan/membrane recycling is slowed by the steric bulk of the polymers, demonstrating robustness and stability even during normal biological processes. This cytocompatible, versatile and simple approach shows potential for re-engineering of cell surfaces with new functionality for future use in cell tracking or cell-based therapies.

Nitric oxide-releasing vascular grafts: A therapeutic strategy to promote angiogenic activity and endothelium regeneration

Small-diameter vascular grafts (SDVGs) are associated with a high incidence of failure due to infection and obstruction. Although several vascular grafts are commercially available, specific anatomical differences of defect sites require patient-based design and fabrication. Design and fabrication of such custom-tailored grafts are possible with 3d-printing technology. The aim of this study is to develop 3d-printed SDVGs with a nitric oxide (NO)-releasing coating to improve the success rate of implantation. The SDVGs were printed from polylactic acid and coated with blending of 10 wt% S-nitroso-N-acetyl-D-penicillamine into the polymeric substrate consisting of poly (ethylene glycol) and polycaprolactone. Our results show that NO is released in the physiological range (0.5–4 × 10−10 mol·cm−2·min−1) for 14 days and NO-releasing coating showed significant antibacterial potential against Gram-positive and Gram-negative strains. It was shown that both NO-releasing and control grafts are biocompatible in-vitro and in-vivo. Interestingly, the NO-releasing SDVGs dramatically enhanced ECs proliferation and significantly enhanced ECs migration in-vitro compared to control grafts. In addition, the NO-releasing SDVGs showed angiogenic potential in-vivo which can further prove the results of our in-vitro study. These findings are expected to facilitate tissue regeneration and integration of custom-made vascular implants with enhanced clinical success. Statement of significanceA series of 3d-printed small-diameter vascular grafts (SDVGs, <6 mm) with controlled release of nitric oxide (NO) were prepared to combine the advantages of 3D printing technology and NO-releasing systems. The resulting NO-releasing grafts were promisingly showing sustained NO release in the physiological range over a two weeks period. In addition to the evaluation of endothelial cell migration in-vitro, we implanted for the first time the NO-releasing vascular grafts in a chick chorioallantoic membrane (CAM) to investigate the effect of the prepared grafts on the angiogenesis in-vivo. The fabricated grafts also exhibited bactericidal properties which prevent the formation of a biofilm layer and can thereby enhance the chance of endothelialization on the surface. Taken together, the innovative combination of rapid and highly accurate 3d-printing technology as a patient-specific fabrication method with NO-releasing coating represents a promising approach to develop bactericidal SDVGs with improved endothelialization.

In Vivo Phenotyping of Familial Parkinson's Disease with Human Induced Pluripotent Stem Cells: A Proof-of-Concept Study.

Parkinson's disease (PD) is the second most common neurodegenerative disorder. We have previously developed a disease-in-a-dish model for familial PD using induced pluripotent stem cells (iPSCs) from two patients carrying the p.A53T α-synuclein (αSyn) mutation. By directed differentiation, we generated a model that displays disease-relevant phenotypes, including protein aggregation, compromised neurite outgrowth, axonal neuropathology and synaptic defects. Here we investigated the in vivo phenotypes of iPSCs, derived from one patient, after transplantation in a lesion mouse model established by unilateral intrastriatal 6-hydroxydopamine injection in the immunosuppressed NOD/SCID strain. Immunohistochemistry revealed that despite the disease-related characteristics that mutant cells displayed when maintained up to 70 days in vitro, they could survive and differentiate in vivo over a 12-week period. However, some differences were noted between patient-derived and control grafts, including a significant rise in αSyn immunoreactivity that might signal a first step towards pathology. Moreover, control-derived grafts appeared to integrate better than PD grafts within the host tissue extending projections that formed more contacts with host striatal neurons. Our data suggest that the distinct disease-related characteristics which p.A53T cells develop in vitro, may be attenuated or take longer to emerge in vivo after transplantation within the mouse brain. Further analysis of the phenotypes that patient cells acquire over longer periods of time as well as the use of multiple iPSC clones from different patients should extend our current proof-of-concept study and provide additional evidence for in vivo disease modeling.

Polyimide Electrode-Based Electrical Stimulation Impedes Early Stage Muscle Graft Regeneration.

Given the increasing use of regenerative free muscle flaps for various reconstructive procedures and neuroprosthetic applications, there is great interest and value in their enhanced regeneration, revascularization, and reinnervation for improved functional recovery. Here, we implant polyimide-based mircroelectrodes on free flap grafts and perform electrical stimulation for 6 weeks in a murine model. Using electrophysiological and histological assessments, we compare outcomes of stimulated grafts with unstimulated control grafts. We find delayed reinnervation and abnormal electromyographic (EMG) signals, with significantly more polyphasia, lower compound muscle action potentials and higher fatigability in stimulated animals. These metrics are suggestive of myopathy in the free flap grafts stimulated with the electrode. Additionally, active inflammatory processes and partial necrosis are observed in grafts stimulated with the implanted electrode. The results suggest that under this treatment protocol, implanted epimysial electrodes and electrical stimulation to deinnervated, and devascularized flaps during the early recovery phase may be detrimental to regeneration. Future work should determine the optimal implantation and stimulation window for accelerating free muscle graft regeneration.

Intrapulmonary Immune Regulation by Pre-Transplant Infusion of Recipient-Derived Regulatory T Cells in a Rat Model of Ex Vivo Lung Perfusion Followed by Transplantation

Purpose Regulatory T cells (Tregs) are a potential therapeutic option in lung transplantation (LTx). We have shown that expanded recipient Tregs can be seeded pre-transplant in the donor lung graft using normothermic ex vivo lung perfusion (EVLP). Here, we examined whether this therapy can alleviate lung injury early post-transplant. Methods Study design is shown in Fig A. CD4+CD25hi Tregs were isolated from Wistar Kyoto rats (WKy, RT1l) and expanded for 7d-14d. Fischer 344 (F344 RT1lv1) heart-lung blocks were flushed and placed on EVLP. Lungs were perfused with SteenTM solution (37°C, 4h). Expanded Tregs (5-120 × 106) were infused after 1h. Control lungs received no Tregs. The right lung was used for assessment at end-EVLP, and left LTx into WKy recipients was performed after 60min cold preservation. Necropsy was performed on day 3 post-LTx. Results Wet-dry ratio was lower in Treg-treated grafts compared to controls (Fig B). Transcripts for FoxP3, IL-10, CTLA-4 and GITR were elevated in Treg-treated grafts (Fig B). Tregs isolated from the right donor lung at end-EVLP suppressed CD4+CD25− T cell proliferation in vitro (Fig C). On day 3 post-LTx, ICAM1 and CD44 (adhesion molecules) expression on both CD4+ and CD8+ T cells were lower in Treg-treated grafts compared to untreated controls (Fig D). Histologically, both Treg-treated and control grafts had minor lung injury and cellular rejection on day 3 post-LTx: acute lung injury scores (4.10 ± 1.66 and 3.88 ± 1.36), ISHLT A grades (0.60 ± 0.516 and 0.625 ± 0.744), B grades (0.400 ± 0.516 and 0.313 ± 0.458). Conclusion Expanded recipient Tregs directly delivered to the lung allograft prior to transplantation exert immune regulatory effects in vivo and in vitro. Further work is needed to optimize this pre-transplant therapeutic approach.

Manipulation of Grafting Location via Photografting To Fabricate High-Performance Ethylene Vinyl Alcohol Copolymer Membrane for Protein Separation.

Ethylene vinyl alcohol copolymer (EVAL) membrane has great potential for applications in protein separation and purification, but the uncontrollable distribution of grafting location when membranes are modified by the grafting method limits the membrane performance. Herein, an effective strategy for controlling the distribution of grafting location was designed to fabricate a high-performance EVAL membrane via photografting. The UV intensity through the membranes was weakened when the local concentration of the photoinitiator benzophenone (BP) on the topside of the membrane increased; thus, the grafting location inside the EVAL membrane changed from homogenous to asymmetric distribution based on the UV absorbability of BP. The grafting inside the membrane pores can be promoted when the loose and porous surface of the EVAL membrane was used as the UV-facing side. More importantly, the varied distribution of grafting location played different roles on improving the membrane performance. For protein binding, the limited convection in the membrane bed was avoided, and the desorption efficiency could be improved when the grafting location enriched inside the membrane pores. For protein filtration, the antifouling properties of the EVAL membrane were enhanced when the grafting location enriched on the topside. This research offers a novel approach to achieve controllable grafting location distribution of membranes and provides a perspective to design the high-performance EVAL membranes for protein separation.

Polyethylene Grafted Silica Nanoparticles Prepared via Surface-Initiated ROMP.

Polyethylene and nanosilica represent the most ubiquitous commodity plastic and nanocomposite filler, respectively. Despite their potential utility, few examples exist in the literature of successfully combining these two materials to form polyethylene nanocomposites. Synthesizing well-defined polyethylene grafted to a surface is a significant challenge in the nanocomposites community. Presented here is a synthetic approach toward polyethylene grafted nanoparticles with controllable graft density and molecular weight of the grafted polymer. The variably grafted nanoparticles were then incorporated into a commercial high density polyethylene matrix. The synthesis, characterization, and challenges in making these materials are discussed.

Cytomegalovirus infection is not a major cause of corneal graft failure in the United Kingdom

Cytomegalovirus (CMV) endotheliitis is a significant cause for acute corneal allograft rejection in East Asian populations, where there is a high CMV seroprevalence. To determine how frequently CMV is associated with corneal graft failure in the UK, we looked for the presence of CMV DNA in grafts that had failed and had been removed at repeat keratoplasty. We also looked for CMV DNA in corneal rims discarded after corneal transplantation. In this retrospective study, we identified 54 cases of corneal graft failure following endothelial rejection and 38 control grafts that had failed without a history of endothelial rejection. For these groups archived formalin-fixed paraffin-embedded (FFPE) tissue samples were retrieved. We also prospectively examined 80 non-fixed cornea rims following transplantation surgery. In all samples nested quantitative PCR was used to identify CMV, herpes simplex virus (HSV) and varicella zoster virus (VZV) DNA. We also used in situ hybridisation to examine for CMV DNA in the FFPE samples. No CMV or VZV DNA was detected in any of the archived case or control FFPE tissues. One corneal rim from the control group was positive for HSV. In situ hybridisation for CMV was negative for CMV in all FFPE samples. No CMV, VZV or HSV DNA was detected in the donor corneal rim samples. CMV DNA was not identified in excised failed corneal tissue or from tissue prior to transplantation. We infer that CMV infection is not a significant factor risk for corneal graft failure in the United Kingdom.

Clinical analysis of application of antibiotic bone cement spacer combined with membrane induction technology in treatment of osteomyelitis after femoral intramedullary nail operation - A case series.

Clinical analysis of antibiotic bone cement spacer combined with membrane induction technology in the treatment of osteomyelitis after intramedullary nail fixation operation for femoral shaft fracture was retrospectively performed on 12 cases in Department of Orthopaedics Centre, Renmin Hospital, Hubei University of Medicine from February 2013 to November 2016. The healing time of bone defect, infection recurrence and other complications were observed. Membrane induced series treatment scheme was given to all patients. Membrane-induced sequence therapy consisted of the first stage which included complete debridement, removal of the original internal fixation of intramedullary nail, intraoperative preparation of antibiotic bone cement rod into the medullary cavity and full drainage. The second stage included replacement of the interlocking intramedullary nail after infection control and autologous iliac bone graft was then used at the bone defect. Followup visits for bone situations were conducted for all the cases and the duration was 12-35 min (25.75 min on average). Fractures of all patients healed clinically. The healing duration was 4-11 min (7.33 min on average).After treatment, patients had no significant shortening of the limbs and their gait was normal at 12 months follow-up. This study is of femoral shaft fracture with no involvement of the joints and range of movement was not measured. No apparent relevant complications were seen.

Invited commentary

This basic science study's goal is to address an area of clinical ambiguity: how to coat an endovascular stent graft with rifampin in a standard and optimized manner for immediate use in an infected field. It optimizes two variables, concentration and incubation period, in an ex vivo experiment and on the basis of the results suggests a rapid real-time perioperative protocol. The graft chosen to study is a standard Dacron endograft of various diameters and lengths. There are reports of using a rifampin-coated endograft in an infected field with preparation extrapolated from methods used during open operation (60 mg/mL rifampin incubated for 1 hour). A dedicated scientific study to determine optimal endograft coating would allow a more reasonable comparison of results when applied in the clinical condition. This study demonstrates that a rifampin solution of 10 mg/mL delivered as one 20-mL aliquot with an incubation time of 10 minutes will provide a well-coated endograft, not improved by higher concentrations or longer periods of intubation. This allows the surgeon to save both resources (drug, supplies) and time during an urgent or emergent case. An overnight bathing in methanol solvent demonstrates that the concentration or incubation time had no effect on the amount of rifampin trapped (coating) on the graft. Bathing in a saline bath demonstrates that the coated rifampin is essentially gone at 50 hours. The well-coated endograft does not retain as much rifampin as a similarly coated control graft, probably because the control graft is a gelatin-sealed graft. The endograft is not made with a gelatin coating, so the authors have no control of this processing step, and the comparison is somewhat artificial. As with most good basic research, more questions come to mind than are answered by the original work. This study does not evaluate the prepared graft under conditions that might greatly influence its performance in the clinical situation. The lack of evaluation in a flow chamber does not allow an estimate of rifampin loss over time from both the flow and sac surface. Dacron endografts generally leak through the material interstices until anticoagulation is reversed, so the loss may be rapid from both surfaces. Under such circumstances, what antimicrobial activity remains even minutes after deployment? In vivo animal experiments with implantation in an infected field would yield some estimate of the potential clinical impact of this method of in situ repair. Would presealing with a gelatin coating before rifampin coating better mimic the open scenario and improve the results? All these factors being considered, this study does provide a logical basic science first step to a clinical problem that can now be further studied to provide greater insight into its clinic use. The opinions or views expressed in this commentary are those of the authors and do not necessarily reflect the opinions or recommendations of the Journal of Vascular Surgery or the Society for Vascular Surgery Optimization of rifampin coating on covered Dacron endovascular stent grafts for infected aortic aneurysmsJournal of Vascular SurgeryVol. 69Issue 1PreviewIn the treatment of an infected aorta, open repair and replacement with a rifampin-impregnated Dacron vascular graft decrease the risk of prosthetic graft infections, with several protocols available in the literature. We hypothesize that the same holds true for endovascular aneurysm repair, and after studying and optimizing rifampin solution concentration and incubation period to maximize the coating process of rifampin on Dacron endovascular stent grafts (ESGs), we propose a rapid real-time perioperative protocol. Full-Text PDF Open Archive

Quadriceps augmentation of undersized hamstrings during ACL reconstruction

BackgroundDouble hamstring autograft for anterior cruciate ligament (ACL) reconstruction is a well-established graft option; however, a major concern with this method arises when the prepared graft is too small. Resorting to allograft can be a solution to this problem, but some surgeons prefer to use autograft in particular situations and some patients may refuse allograft. We investigate the merits of using autogenous quadriceps tendons to augment the insufficient hamstrings and compare the autograft composite graft to a standard hamstrings graft of equal size. MethodsSemitendinosus, gracilis, and quadriceps tendons were harvested from 10 matched pairs of human cadaver lower extremities. Within each pair, a routine hamstring ACL graft (control) consisting of the semitendinosus and gracilis tendons, and an quadriceps augmented hamstrings graft of equal size comprised of the semitendinosus and quadriceps tendons, were prepared. A freeze-clamp mount was used to biomechanically test each graft construct. Tensile failure load, displacement, energy absorbed, and stiffness were determined and statistically compared within each pair and mode of graft failure was established. ResultsNo statistically significant differences were found between the quadriceps augmented hamstrings graft versus standard control grafts. Average values for peak failure load and graft displacement at the point of first failure were nearly identical. All ACL graft constructs failed at the mid-substance. ConclusionsThis study demonstrates no statistical difference in the biomechanical properties of an isolated hamstring ACL autograft versus a quadriceps augmented ACL autograft of equal size at time zero. Clinical relevanceThis is a potentially new and reliable method for quadriceps tendon autograft augmentation of hamstring autograft for ACL reconstruction.

In situ blood vessel regeneration using neuropeptide substance P-conjugated small-diameter vascular grafts.

In situ blood vessel regeneration through host stem/progenitor cell mobilization may hold great promise for vascular reconstruction. Neuropeptide substance P (SP) has been shown to accelerate tissue repair by endogenous cell mobilization and recruitment. This study was aimed to evaluate the vascular regeneration potential of SP and heparin co-tethered vascular grafts. Polycaprolactone (PCL), PCL/SP-conjugated poly(L-lactide-co-ε-caprolactone) (PLCL-SP) (SP), and PCL/PLCL-SP/heparin-conjugated PLCL (Hep/SP) vascular grafts were implanted as rat abdominal aorta substitutes for up to 2 weeks and 4 weeks. Ex vivo results delineate that heparin can improve the hemocompatibility and SP can recruit mesenchymal stem cells. Histological and immunohistochemical staining reveal higher cellular infiltration and homogeneous cell distribution in SP and Hep/SP grafts than that of the control grafts. At 4 weeks, SP and Hep/SP grafts show the presence of cobblestone-like cells on the luminal side, whereas the surface of PCL grafts remains bare. Immunoflourescence staining using von Willibrand factor (vWF) antibody shows improved endothelialization in SP and Hep/SP grafts compared with the PCL grafts. SP and Hep/SP grafts also exhibit more numbers of α-smooth muscle actin-positive cells and laminin+ blood vessels than that of the control group. Evaluation of inflammatory response reveals that three groups did not differ in terms of the numbers of CD68+ macrophages, whereas SP and Hep/SP grafts show higher numbers of CD206+ macrophages. These results indicate that SP can induce endogenous tissue regeneration in cell-free grafts, which may be of great interest for regenerative medicine and tissue engineering applications. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 107B: 1669-1683, 2019.

Murine type VII collagen distorts outcome in human skin graft mouse model for dystrophic epidermolysis bullosa

Human skin graft mouse models are widely used to investigate and develop therapeutic strategies for the severe generalized form of recessive dystrophic epidermolysis bullosa (RDEB), which is caused by biallelic null mutations in COL7A1 and the complete absence of type VII collagen (C7). Most therapeutic approaches are focused on reintroducing C7. Therefore, C7 and anchoring fibrils are widely used as readouts in therapeutic research with skin graft models. In this study, we investigated the expression pattern of human and murine C7 in a grafting model, in which human skin is reconstituted out of in vitro cultured keratinocytes and fibroblasts. The model revealed that murine C7 was deposited in both human healthy control and RDEB skin grafts. Moreover, we found that murine C7 is able to form anchoring fibrils in human grafts. Therefore, we advocate the use of human‐specific antibodies when assessing the reintroduction of C7 using RDEB skin graft mouse models.