Large Tissue Defects Research Articles

A case report of necrotizing soft tissue infection of the chest wall: Effective management with serial debridement.

IntroductionNecrotizing soft tissue infection (NSTI) of the chest wall is a rare, rapidly spreading, highly lethal surgical disease. Radical debridement interferes with the important anatomical function of the chest wall. We report a case of chest wall NSTI that was successfully managed with early diagnosis and serial debridement.Presentation of caseA 43-year-old, previously healthy woman presented with severe malaise and worsening right axillary pain. She was severely lethargic and had a painful, large, pale lesion with surrounding erythema of the right chest and trunk. Computed tomography revealed NSTI, with diffuse soft tissue inflammation extending from the axilla to the lower abdomen. There was no obvious entry portal. Prompt surgical drainage was established. Group A streptococcus infection was diagnosed. During her 3-month postoperative course, she underwent four more surgeries, including two debridements. This treatment proved successful and avoided the need for complicated muscle flap reconstruction. She was discharged on postoperative day 109.DiscussionGroup A streptococcus can cause NSTI even in immunocompetent patients without an entry portal. Radical debridement is recommended for infection control. Preserving anatomical chest wall function, however, is also important. Serial debridement with close follow-up solved the problem in this patient.ConclusionsSerial debridement with close follow-up enabled to avoid large tissue deficits and complicated reconstruction in the case of NSTI of the chest wall.

Reconstruction of Large Tissue Defects After the Resection of Brain Tumors Using a Skin Flap With Vascular Pedicle.

The reconstruction of large tissue defects after the resection of brain tumors is challenging for every neurosurgeon. The authors describe the benefits of a skin flap with vascular pedicle in the reconstruction of large tissue defects after the resection of brain tumors. In this retrospective analysis, a skin flap with vascular pedicle reconstruction was used in 5 patients who underwent intracranial tumor resection, accompanied by tissue defects, cerebrospinal fluid leakage and scalp infection. The surgical techniques are described, and the outcomes were discussed. The harvested flaps showed well-vascularized healing of the transplanted skin without partial necrosis in all 5 patients. One patient had cerebrospinal rhinorrhea, which was successfully treated by endoscopic repair. Another patient had cerebrospinal fluid leakage, which was successfully treated by continuous lumbar drainage. A skin flap with vascular pedicle is an effective choice for the reconstruction of large tissue defects after the resection of brain tumors.

Update on the role of emerging stem cell technology in head and neck medicine.

Head and neck surgery is a broad discipline that involves the management of complex conditions such as burns, skin cancer, head and neck cancer, congenital abnormalities, and facial rejuvenation. For patients with cancer, surgery, radiotherapy, and chemotherapy are often the main modes of treatment. Many patients require follow-up reconstructive surgery, and the use of stem cells offers novel treatments that could aid recovery. Laryngeal, tracheal, and neuronal tissues are frequently damaged by surgery in the head and neck and these tissues have little intrinsic regenerative ability. Pluripotent embryonic stem cells retain the ability to differentiate into a wide variety of cells meaning that large tissue defects can be reduced by stimulating new cell growth. Research has demonstrated potential benefits of using stem cells in facial rejuvenation procedures and the management of burns sequelae. The advancements made in the use of adult progenitor stem cells as a possible source for pluripotent stem cells (induced pluripotent stem cells) mean that ethical considerations around the use of embryological tissue can be minimized, allowing for more research to take place. Currently, the evidence base for the use of stem cells in head and neck surgery is limited, but it has now been proven that stem cells can act as a source for lost or damaged tissue in the head and neck. With continuous advancements being made in the fields of tissue engineering, it is likely that stem cells will play a major role in head and neck surgery in the future.

3D bioprinting of prevascularised implants for the repair of critically-sized bone defects

For 3D bioprinted tissues to be scaled-up to clinically relevant sizes, effective prevascularisation strategies are required to provide the necessary nutrients for normal metabolism and to remove associated waste by-products. The aim of this study was to develop a bioprinting strategy to engineer prevascularised tissues in vitro and to investigate the capacity of such constructs to enhance the vascularisation and regeneration of large bone defects in vivo. From a screen of different bioinks, a fibrin-based hydrogel was found to best support human umbilical vein endothelial cell (HUVEC) sprouting and the establishment of a microvessel network. When this bioink was combined with HUVECs and supporting human bone marrow stem/stromal cells (hBMSCs), these microvessel networks persisted in vitro. Furthermore, only bioprinted tissues containing both HUVECs and hBMSCs, that were first allowed to mature in vitro, supported robust blood vessel development in vivo. To assess the therapeutic utility of this bioprinting strategy, these bioinks were used to prevascularise 3D printed polycaprolactone (PCL) scaffolds, which were subsequently implanted into critically-sized femoral bone defects in rats. Micro-computed tomography (µCT) angiography revealed increased levels of vascularisation in vivo, which correlated with higher levels of new bone formation. Such prevascularised constructs could be used to enhance the vascularisation of a range of large tissue defects, forming the basis of multiple new bioprinted therapeutics. Statement of significanceThis paper demonstrates a versatile 3D bioprinting technique to improve the vascularisation of tissue engineered constructs and further demonstrates how this method can be incorporated into a bone tissue engineering strategy to improve vascularisation in a rat femoral defect model.

Reconstruction of firearm and blast injuries in Syrian war refugees.

War injuries differ from other injuries owing to the large tissue defects they cause and their high risk of contamination. As fragments scattered by high-energy firearms and explosives cause serious composite tissue damage, repair of such injuries is difficult and requires a long treatment period. We discuss the treatment methods used for injured Syrian War refugees admitted to our clinic and present the most effective repair methods for war-related tissue defects for each region of the body. A total of 61 patients treated between June 2012 and April 2015 were retrospectively evaluated in terms of age, gender, duration of hospitalisation, injury site and repair method employed. The patients were grouped by region injured (head/neck, extremities and trunk). The female-to-male ratio of the patients was 16/45, and their mean age was 25.2 (range, 3-51) years. Twenty-two patients were under the age of 18. The mean duration of hospitalisation was 28.5days. A total of 130 operations were performed on the patients, including debridement and revisions. Repairs were conducted with free flaps in 17 patients (6 on the head/neck region, 11 on extremities) and with pedicle flaps in 28 patients (11 on the head/neck region, 12 on extremities, 5 on the trunk). Two patients experienced flap loss without other complications, and other patients experienced complications including bleeding, infection, flap detachment, hematoma and seroma. War injuries cause tissue damage of a composite and extensive nature. Most affect the extremities, followed by the head/neck and trunk regions. They are primarily sustained by the young population, not usually easy to treat, and require long hospitalisation periods. A variety of methods may be preferred to treat these injuries.

Applications of 3D printed bone tissue engineering scaffolds in the stem cell field.

Due to traffic accidents, injuries, burns, congenital malformations and other reasons, a large number of patients with tissue or organ defects need urgent treatment every year. The shortage of donors, graft rejection and other problems cause a deficient supply for organ and tissue replacement, repair and regeneration of patients, so regenerative medicine came into being. Stem cell therapy plays an important role in the field of regenerative medicine, but it is difficult to fill large tissue defects by injection alone. The scientists combine three-dimensional (3D) printed bone tissue engineering scaffolds with stem cells to achieve the desired effect. These scaffolds can mimic the extracellular matrix (ECM), bone and cartilage, and eventually form functional tissues or organs by providing structural support and promoting attachment, proliferation and differentiation. This paper mainly discussed the applications of 3D printed bone tissue engineering scaffolds in stem cell regenerative medicine. The application examples of different 3D printing technologies and different raw materials are introduced and compared. Then we discuss the superiority of 3D printing technology over traditional methods, put forward some problems and limitations, and look forward to the future.

A paintable phosphorescent bandage for postoperative tissue oxygen assessment in DIEP flap reconstruction.

Flaps are common in plastic surgery to reconstruct large tissue defects in cases such as trauma or cancer. However, most tissue oximeters used for monitoring ischemia in postoperative flaps are bulky, wired devices, which hinder direct flap observation. Here, we present the results of a clinical trial using a previously untried paintable transparent phosphorescent bandage to assess the tissue's partial pressure of oxygen (pO2). Statistical analysis revealed a strong relationship (P < 0.0001) between the rates of change of tissue oxygenation measured by the bandage and blood oxygen saturation (%stO2) readings from a standard-of-care ViOptix near-infrared spectroscopy oximeter. In addition, the oxygen-sensing bandage showed no adverse effects, proved easy handling, and yielded bright images across all skin tones with a digital single-lens reflex (DSLR) camera. This demonstrates the feasibility of using phosphorescent materials to monitor flaps postoperatively and lays the groundwork for future exploration in other tissue oxygen sensing applications.

Accelerating bone healing in vivo by harnessing the age-altered activation of c-Jun N-terminal kinase 3

We have recently demonstrated that c-Jun N-terminal kinase 3 (JNK3) is a key modulator of the enhanced osteogenic potential of stem cells derived from children when compared to those derived from adults. In this study, we formulated a JNK3-activator nanoparticle (JNK3*) that recapitulates the immense osteogenic potential of juvenile cells in adult stem cells by facilitating JNK3 activation. Moreover, we aimed to functionalize a collagen-based scaffold by incorporating the JNK3* in order to develop an advanced platform capable of accelerating bone healing by recruitment of host stem cells. Our data, in vitro and in vivo, demonstrated that the immense osteogenic potential of juvenile cells could be recapitulated in adult stem cells by facilitating JNK3 activation. Moreover, our results revealed that the JNK3* functionalized 3D scaffold induced the fastest bone healing and greatest blood vessel infiltration when implanted in critical-size rat calvarial defects in vivo. JNK3*scaffold fastest bone healing in vivo was associated with its capacity to recruit host stem cells to the site of injury and promote angiogenic-osteogenic coupling (e.g. Vegfa, Tie1, Runx2, Alp and Igf2 upregulation). In summary, this study has demonstrated the potential of harnessing knowledge of age-altered stem cell mechanobiology in order to develop a materials-based functionalization approach for the repair of large tissue defects.

3D Bioprinting of Prevascularised Implants for the Repair of Critically Sized Bone Defects

For 3D bioprinted tissues to be scaled-up to clinically relevant sizes, effective prevascularisation strategies are required to provide the necessary nutrients for normal metabolism and to remove associated waste by-products. The aim of this study was to develop a bioprinting strategy to engineer prevascularised tissues in vitro and to investigate the capacity of such constructs to enhance the vascularisation and regeneration of large bone defects in vivo. From a screen of different bioinks, a fibrin-based hydrogel was found to best support human umbilical vein endothelial cell (HUVEC) sprouting and the establishment of a microvessel network. When this bioink was combined with HUVECs and supporting human bone marrow stem/stromal cells (hBMSCs), these microvessel networks persisted in vitro. Furthermore, only bioprinted tissues containing both HUVECs and hBMSCs, that were first allowed to mature in vitro, supported robust blood vessel development in vivo. To assess the therapeutic utility of this bioprinting strategy, these bioinks were used to prevascularise 3D printed polycaprolactone (PCL) scaffolds, which were subsequently implanted into critically sized femoral bone defects in rats. Microcomputed tomography (µCT) angiography revealed increased levels of vascularisation in vivo, which correlated with higher levels of new bone formation. Such prevascularised constructs could be used to enhance the vascularisation of a range of large tissue defects, forming the basis of multiple new bioprinted therapeutics.

Human Umbilical Vein Endothelial Cell Support Bone Formation of Adipose-Derived Stem Cell-Loaded and 3D-Printed Osteogenic Matrices in the Arteriovenous Loop Model.

Introduction: For the regeneration of large volume tissue defects, the interaction between angiogenesis and osteogenesis is a crucial prerequisite. The surgically induced angiogenesis by means of an arteriovenous loop (AVL), is a powerful methodology to enhance vascularization of osteogenic matrices. Moreover, the AVL increases oxygen and nutrition supply, thereby supporting cell survival as well as tissue formation. Adipose-derived stem cells (ADSCs) are interesting cell sources because of their simple isolation, expansion, and their osteogenic potential. This study targets to investigate the coimplantation of human ADSCs after osteogenic differentiation and human umbilical vein endothelial cells (HUVECs), embedded in a vascularized osteogenic matrix of hydroxyapatite (HAp) ceramic for bone tissue engineering. Materials and Methods: An osteogenic matrix consisting of HAp granules and fibrin has been vascularized by means of an AVL. Trials in experimental groups of four settings were performed. Control experiments without any cells (A) and three cell-loaded groups using HUVECs (B), ADSCs (C), as well as the combination of ADSCs and HUVECs (D) were performed. The scaffolds were implanted in a porous titanium chamber, fixed subcutaneously in the hind leg of immunodeficient Rowett Nude rats and explanted after 6 weeks. Results: In all groups, the osteogenic matrix was strongly vascularized. Moreover, remodeling processes and bone formation in the cell-containing groups with more bone in the coimplantation group were proved successful. Conclusion: Vascularization and bone formation of osteogenic matrices consisting of ADSCs and HUVECs in the rat AVL model could be demonstrated successfully for the first time. Hence, the coimplantation of differentiated ADSCs with HUVECs may therefore be considered as a promising approach for bone tissue engineering.

A novel skin-stretching device for closing large skin-soft tissue defects after soft tissue sarcoma resection

BackgroundClosure of large skin-soft tissue defects following soft tissue sarcoma (STS) resection has been a great challenge. The objective of this study was to evaluate the effectiveness of a novel, simple, and cheap skin-stretching device (bidirectional regulation-hook skin closure system, BHS) for closing large skin-soft tissue defects resulting from the removal of STS and the complications associated with the use of the BHS.MethodsFrom January 2017 to September 2018, 25 patients with STS underwent BHS therapy after tumor resection. BHS was used for two main clinical applications: securing wound closure after high-tension suture closure and delayed wound closure. We described a detailed reconstruction procedure regarding this therapy. Wound closure and complications associated with BHS therapy were recorded. We also analyzed tumor recurrence and metastases.ResultsAll patients were observed for 16–36 months with an average follow-up of 25.6 months. During the follow-up period, no significant functional restriction was observed and the final scar was aesthetically acceptable. Superficial wound infection occurred in six patients, wound edge ischemia in two patients, and small skin tears in two patients. Two patients developed pulmonary metastasis, two patients had a local recurrence, and one patient died of pulmonary metastasis.ConclusionsBHS therapy can effectively close large skin-soft tissue defects following STS resection and obtain acceptable functional results, without severe complications. However, larger studies are required to further evaluate the effectiveness, indications, and complications of BHS therapy.

Bottom‐up Tissue Engineering: TGase‐Enhanced Microtissue Assembly in 3D‐Printed‐Template‐Scaffold (3D‐MAPS) for Large Tissue Defect Reparation (Adv. Healthcare Mater. 18/2020)

Bottom‐up Tissue Engineering: TGase‐Enhanced Microtissue Assembly in 3D‐Printed‐Template‐Scaffold (3D‐MAPS) for Large Tissue Defect Reparation (Adv. Healthcare Mater. 18/2020)

Determination of transcutaneous oxygen tension for evaluating the degree of ischemia in patients with diabetic foot syndrome

One of the main syndromes that poses a direct threat to the patient's ability to work and life is diabetic foot syndrome (DFS). It is known that DFS is caused by a complex of disorders of the anatomical and functional state of the foot due to neuro-ischemic changes caused by prolonged hyperglycemia. The aim of styding was to investigate the value of transcutaneous oxygen tension during the performance of revascularization and rehabilitation interventions in patients with DFS. We studied 114 patients with purulent-necrotic forms of DFS with moderate and severe diabetes, who were determined by the value of transcutaneous oxygen tension during hospital treatment.Therefore, determination of transcutaneous oxygen tension is the most informative way to assess the degree of ischemia before and after revascularization operations. When the value of TcpO2 at the foot ≤25 mmHg we recommend performing the first stage of revascularization intervention. At TcPO2 values &gt;25 mmHg, revascularization was recommended for post-primary remediation of purulent-necrotic lesions and to accelerate healing in patients with large foot tissue defects after surgery for purulent-necrotic complications of DFS. When restoring the value of the transcutaneous voltage above25 mmHg it can be performed remediation interventions at almost any distal level. At values of 10-25 mmHg – it should be done more proximal level (where the determined transcutaneous value of TcpO2 is about 15-25 mmHg) of the demarcation line necrosis, as the risk of reamputation is higher than 75 %. At values of ≤10 mmHg, we recommend performing high amputations.

TGase-Enhanced Microtissue Assembly in 3D-Printed-Template-Scaffold (3D-MAPS) for Large Tissue Defect Reparation.

Engineering large and functional tissue constructs with complex structures (e.g., external ear or nose) for reparation and reconstruction of tissue defects remains one of the major challenges in regenerative medicine, which demands abundant cell sources, advanced biofabrication schemes, and satisfactory integration with the host for long-term efficacy post implantation. Here the 'Microtissue Assembly in 3D-Printed-template-Scaffold' (3D-MAPS), as a platform technology to rapidly fabricate centimeter-sized functional tissue constructs with complex structures, is developed. 3D-MAPS facilitates bottom-up assembly of large-scale manufactured microtissues within the 3D-printed hollow polymeric templates with pre-defined architectures. The assembly and fusion of 2×106 mesenchymal stem cell-based microtissues within the defined 3D-printed template is further enhanced by addition of a natural protein crosslinker (i.e., transglutaminase (TGase)), and thereby achieves construction of centimeter-sized tissue with high cell viability and mechanical stability in vitro within 30 min. Further in vivo implantation of the 3D-MAPS-fabricated ear-like tissue construct in rabbit models assisted by flap prefabrication technique results in increased structural vascular support and strengthened functional survival. Thus, the TGase-enhanced 3D-MAPS demonstrates its potential and feasibility as a powerful biofabrication platform for tissue engineering application.

Early Results of Supporting Free Flap Coverage of Mangled Lower Extremities with Long Saphenous Arteriovenous Loop Grafts.

The ability to salvage the mangled lower extremity is both technically challenging and time consuming. It requires the collaborative efforts among multiple surgical specialties in addition to comprehensive post-traumatic wound follow-up. Our institution has integrated a dynamic effort among these specialists in the planning and facilitating a successful limb salvage program with creation of a mangled extremity algorithm. An integral part in this process is the vascular inflow to prepare coverage for large tissue defects lacking adequate recipient targets. Utilization of long saphenous arteriovenous (AV) loop has been cited with minimal data available using larger inflow vessels in the acute trauma setting. We performed a retrospective review and describe our early experience using our protocol with AV loop creation with free flap reconstruction to salvage traumatic leg injuries. Using the data, we sought to develop a mangled extremity protocol for trauma centers to guide mangled limb salvage. Since June 2016, 398 patients were admitted to our level II trauma facility with isolated traumatic wounds to the lower extremities. Thirty-one limbs were deemed mangled in which 21 received primary amputations due to multiple factors. Ten patients admitted from the trauma service with isolated mangled lower extremities injuries were identified for review. All 10 patients sustained severe crush injuries with large soft tissue defects and decreased perfusion for healing but deemed salvageable by multispecialty assessment. Mangled extremity severity scores were tabulated. Patients age ranged from 21-44 years, with 8 men and 2 women. Repeated debridements until successful sterilization of the wounds were accomplished. Ten long saphenous vein AV loops were anastomosed to the at or above knee popliteal vessels for free flap reconstruction. All patients were followed post-AV loop creation for vascular complications and wound assessments. All 10 patients had sterilization of the wounds with repair of the fracture site before vascular reconstruction. Mean debridement to surgical site sterilization was 4.3 washouts (range 2-7). Successful AV loop creation with long saphenous vein was completed in 100% of patients without vascular complications nor steal events. Free flap tissue transfers directly connected to the loop were completed using 6 rectus abdominis, 3 latissimus dorsi, and 1 anterior thigh graft within 10days of its creation. Patency rates of the AV loop was 100% with 10 successful flap transfers and 90% amputation free survival. One flap did not survive due to recurrent bacterial infection of the hardware. The 9 patients with successful procedures reached preoperative ambulatory status within 3months after their final surgery. At 24months follow-up, 90% amputation free survival is still maintained. Although a small patient cohort, utilization of long saphenous vein AV loop is successful as a bridge to free flap transfer for isolated mangled lower extremities. Development and incorporation of our mangled extremity protocol to guide limb salvage has proven successful in our early experience. Long-term data need to be complied to assess patency of the free flap transfer and quality of life outcomes.

Free Tarsal Graft and Free Skin Graft for Lower Eyelid Reconstruction.

To determine whether reconstruction of lower eyelid defects involving the eyelid margin with a free tarsal graft and an overlying free skin graft, without retention or provision of any vascular support, would yield acceptable functional and cosmetic results. We present here a clinical series of 4 patients treated between April 2019 and September 2019 who underwent reconstruction of large postcarcinoma excision, eyelid-margin-inclusive eyelid defects. Surgery was performed by the same surgeon (J.G.B.) at the Westchester Medical Center, Department of Ophthalmology and Dobbs Ferry Hospital in New York. Without retaining a conjunctival pedicle (modified Hughes procedure), and without a myocutaneous or other vascularized flap, the lower eyelids were reconstructed with a free tarsal graft and a separate overlying free skin graft. The primary outcomes measured were eyelid apposition to the globe, margin reflex distance 2 at least 6 months postoperatively, ocular surface integrity, and patient comfort and patient satisfaction with the procedure. The patients included in the clinical series ranged in age from 73 to 82, 3 were men and 1 women. Each had recent Moh's excision of carcinoma (3 basal; 1 squamous) resulting in large tissue defects of the lower eyelids. All carcinomas were T1N0M0. The mean postoperative margin reflex distance 2 of the reconstructed eyelids was 5.5 mm, range 5-7.5 mm. Two of the 4 patients underwent a secondary revision within 2-3 weeks following initial reconstruction for lateral ectropion or dehiscence. All eyelids were well-opposed to the globes after revision (except for the nasal eyelid in patient number 2 who had a preexisting ectropion from prior carcinoma excision in the same eyelid). Functional and esthetic results were on par with those of the modified Hughes procedure. All 4 patients were pleased that they had chosen to undergo the procedure being discussed. In this clinical series of 4 patients, reconstruction of lower eyelid defects with a free tarsal graft and overlying free skin graft resulted in an acceptable functional and esthetic lower eyelid suggesting that retention of or provision of vascular support in either the anterior or posterior lamella may not be necessary.

Wound Healing in the Long-Term Acute Care Setting Using an Air Fluidized Therapy/Continuous Low-Pressure Therapeutic Bed: A Multiple Case Series.

We evaluated a new bed that updates the functionality of the current air fluidized therapy (AFT)/continuous low-pressure (CLP) pressure redistributing beds. This bed was evaluated in conjunction with standard wound care interventions in a long-term acute care hospital (LTACH). The AFT feature is designed to provide pressure distribution via a fluid-like medium that forces air though millions of tiny silicone beads that float the patient's body to achieve maximum immersion and envelopment. The CLP feature of the bed provides pressure distribution for the upper body. Standard wound care was provided that included debridement, topical treatments, and biophysical therapies such as negative pressure wound therapy, as indicated. Our multiple case series comprised 10 medically compromised patients with 25 wounds. Their mean age was 63 years, 50% were male, and the mean cumulative Braden Scale score was 12.4 out of 23, indicating a high risk for pressure injury (PI). Seven of 10 patients were incontinent of urine, 6 had fecal incontinence, and 2 had ostomies. Types of wounds treated included 2 large tissue defects from surgical excisions for the treatment of gangrene and 23 PIs. On admission, wounds had an average surface area of 139.1 cm. The mean percentage of reduction in wound surface area was 59.3% over an average of 31.3 days of therapy. No new wounds formed during their course of care despite being at elevated risk. Findings from this multiple case series suggest that the AFT/CLP bed facilitates healing of advanced wounds in medically complex patients when included as part of a wound care program. Despite mild to high risk, no new PIs developed, and severe PIs and large tissue defects significantly improved or completely resolved. One hundred percent of surveyed staff members recommend use of the AFT/CLP bed.

Tissue-engineered PLLA/gelatine nanofibrous scaffold promoting the phenotypic expression of epithelial and smooth muscle cells for urethral reconstruction.

The repair and regeneration of tissues using tissue-engineered scaffolds represent the ultimate goal of regenerative medicine. Despite rapid developments in the field, urethral tissue engineering methods are still insufficient to replicate natural urethral tissue because the bioactivity of existing scaffolds is inefficient, especially for large tissue defects, which require large tissue-engineered scaffolds. Here, we describe the efficiency of gelatine-functionalized, tubular nanofibrous scaffolds of poly(l-lactic acid) (PLLA) in regulating the phenotypic expression of epithelial cells (ECs) and smooth muscle cells (SMCs) for urethral reconstruction. Flexible PLLA/gelatine tubular nanofibrous scaffolds with hierarchical architecture were fabricated by electrospinning. The PLLA/gelatine nanofibrous scaffold exhibited enhanced hydrophilicity and significantly promoted the adhesion, oriented elongation, and proliferation of New Zealand rabbit autologous ECs and SMCs simultaneously. Compared with pure PLLA nanofibrous scaffold, PLLA/gelatine nanofibrous scaffolds upregulated the expression of keratin (AE1/AE3) in ECs and actin (α-SMA) in SMCs as well as the synthesis of elastin. Three months of in vivo scaffold replacement of New Zealand rabbit urethras indicated that a tubular cellularized PLLA/gelatine nanofibrous scaffold maintained urethral patency and facilitated oriented SMC remodeling, lumen epithelialization, and angiogenesis. Our observations showed the synergistic effects of nano-morphology and biochemical clues in the design of biomimetic scaffolds, which can effectively promote urethral regeneration.

Decorating 3D Printed Scaffolds with Electrospun Nanofiber Segments for Tissue Engineering.

Repairing large tissue defects often represents a great challenge in clinics due to issues regarding lack of donors, mismatched sizes, irregular shapes, and immune rejection. 3D printed scaffolds are attractive for growing cells and producing tissue constructs because of the intricate control over pore size, porosity, and geometric shape, but the lack of biomimetic surface nanotopography and limited biomolecule presenting capacity render them less efficacious in regulating cell responses. Herein, a facile method for coating 3D printed scaffolds with electrospun nanofiber segments is reported. The surface morphology of modified 3D scaffolds changes dramatically, displaying a biomimetic nanofibrous structure, while the bulk mechanical property, pore size, and porosity are not significantly compromised. The short nanofibers-decorated 3D printed scaffolds significantly promote adhesion and proliferation of pre-osteoblasts and bone marrow mesenchymal stem cells (BMSCs). Further immobilization of bone morphogenetic protein-2 mimicking peptides to nanofiber segments-decorated 3D printed scaffolds show enhanced mRNA expressions of osteogenic markers Runx2, Alp, OCN, and BSP in BMSCs, indicating the enhancement of BMSCs osteogenic differentiation. Together, the combination of 3D printing and electrospinning is a promising approach to greatly expand the functions of 3D printed scaffolds and enhance the efficacy of 3D printed scaffolds for tissue engineering.

Low-Molecular-Weight Heparin-Functionalized Chitosan-Chondroitin Sulfate Hydrogels for Controlled Release of TGF-β3 and in vitro Neocartilage Formation.

Repair of hyaline cartilage remains a huge challenge in clinic because of the avascular and aneural characteristics and the paucity of endogenous repair cells. Recently, tissue engineering technique, possessing unique capacity of repairing large tissue defects, avoiding donor complications and two-stage invasive surgical procedures, has been developed a promising therapeutic strategy for cartilage injury. In this study, we incorporated low-molecular-weight heparin (LMWH) into carboxymethyl chitosan-oxidized chondroitin sulfate (CMC-OCS) hydrogel for loading transforming growth factor-β3 (TGF-β3) as matrix of peripheral blood mesenchymal stem cells (PB-MSCs) to construct tissue-engineered cartilage. Meanwhile, three control hydrogels with or without LMWH and/or TGF-β3 were also prepared. The gelling time, microstructures, mechanical properties, degradation rate, cytotoxicity, and the release of TGF-β3 of different hydrogels were investigated. In vitro experiments evaluated the tri-lineage differentiation potential of PB-MSCs, combined with the proliferation, distribution, viability, morphology, and chondrogenic differentiation. Compared with non-LMWH-hydrogels, LMWH-hydrogels (LMWH-CMC-OCS-TGF-β3) have shorter gelling time, higher mechanical strength, slower degradation rate and more stable and lasting release of TGF-β3. After two weeks of culture in vitro, expression of cartilage-specific genes collagen type-2 (COL-2) and aggrecan (AGC), and secretion of glycosaminoglycan (GAG), and COL-2 proteins in LMWH-CMC-OCS-TGF-β3 group were significantly higher than those in other groups. COL-2 immunofluorescence staining showed that the proportion of COL-2 positive cells and immunofluorescence intensity in LMWH-CMC-OCS-TGF-β3 hydrogel were significantly higher than those in other groups. The LMWH-CMC-OCS-TGF-β3 hydrogel can slowly release TGF-β3 in a long term, and meanwhile the hydrogel can provide a biocompatible microenvironment for the growth and chondrogenic differentiation of PB-MSCs. Thus, LMWH functionalized CMC-OCS hydrogels proposed in this work will be beneficial for constructing functional scaffolds for tissue-engineered cartilage.