Stem cell-derived cell-sheets for connective tissue engineering

Let-7a promotes periodontal bone regeneration of bone marrow mesenchymal stem cell aggregates via the Fas/FasL-autophagy pathway

Periodontal bone regeneration using bone marrow mesenchymal stem cell (BMMSC) transplantation is a promising method; however, the method for osteogenic differentiation of BMMSCs needs to be improved. In this research, we sought to identify the roles of let-7a in the osteogenesis of BMMSCs and to provide a potential method for periodontal bone regeneration. Our previous study revealed that Fas/FasL is a target of let-7a. In this study, we demonstrated that let-7a overexpression significantly enhanced BMMSC-CAs osteogenesis both in vitro and in vivo. Mechanistically, upregulation of Fas/FasL using the rfas/rfaslg plasmid obstructed the osteogenesis of BMMSCs by inhibiting autophagy. Furthermore, we confirmed that overexpression of let-7a activated autophagy and alleviated the inhibited osteogenesis by the autophagy inhibitor 3-MA and the rfas/rfaslg plasmid of BMMSCs. In general, our findings showed that let-7a promoted the osteogenesis of BMMSCs through the Fas/FasL-autophagy pathway, suggesting that the application of let-7a in BMMSC-CAs based periodontal bone regeneration could be a promising strategy.

Engineering an enthesis-like graft for rotator cuff repair: An approach to fabricate highly biomimetic scaffold capable of zone-specifically releasing stem cell differentiation inducers

Rotator cuff (RC) attaches to humerus across a triphasic yet continuous tissue zones (bone-fibrocartilage-tendon), termed "enthesis". Regrettably, rapid and functional enthesis regeneration is challenging after RC tear. The existing grafts bioengineered for RC repair are insufficient, as they were engineered by a scaffold that did not mimic normal enthesis in morphology, composition, and tensile property, meanwhile cannot simultaneously stimulate the formation of bone-fibrocartilage-tendon tissues. Herein, an optimized decellularization approach based on a vacuum aspiration device (VAD) was developed to fabricate a book-shaped decellularized enthesis matrix (O-BDEM). Then, three recombinant growth factors (CBP-GFs) capable of binding collagen were synthesized by fusing a collagen-binding peptide (CBP) into the N-terminal of BMP-2, TGF-β3, or GDF-7, and zone-specifically tethered to the collagen of O-BDEM to fabricate a novel scaffold (CBP-GFs/O-BDEM) satisfying the above-mentioned requirements. After ensuring the low immunogenicity of CBP-GFs/O-BDEM by a novel single-cell mass cytometry in a mouse model, we interleaved urine-derived stem cell-sheets into this CBP-GFs/O-BDEM to bioengineer an enthesis-like graft. Its high-performance on regenerating enthesis was determined in a canine model. These findings indicate this CBP-GFs/O-BDEM may be an excellent scaffold for constructing enthesis-like graft to patch large/massive RC tears, and provide breakthroughs in fabricating graded interfacial tissue.

Cruciate Ligament Cell Sheets Can Be Rapidly Produced on Thermoresponsive poly(glycidyl ether) Coating and Successfully Used for Colonization of Embroidered Scaffolds

Anterior cruciate ligament (ACL) cell sheets combined with biomechanically competent scaffolds might facilitate ACL tissue engineering. Since thermoresponsive polymers allow a rapid enzyme-free detachment of cell sheets, we evaluated the applicability of a thermoresponsive poly(glycidyl ether) (PGE) coating for cruciate ligamentocyte sheet formation and its influence on ligamentocyte phenotype during sheet-mediated colonization of embroidered scaffolds. Ligamentocytes were seeded on surfaces either coated with PGE or without coating. Detached ligamentocyte sheets were cultured separately or wrapped around an embroidered scaffold made of polylactide acid (PLA) and poly(lactic-co-ε-caprolactone) (P(LA-CL)) threads functionalized by gas-phase fluorination and with collagen foam. Ligamentocyte viability, protein and gene expression were determined in sheets detached from surfaces with or without PGE coating, scaffolds seeded with sheets from PGE-coated plates and the respective monolayers. Stable and vital ligamentocyte sheets could be produced within 24 h with both surfaces, but more rapidly with PGE coating. PGE did not affect ligamentocyte phenotype. Scaffolds could be colonized with sheets associated with high cell survival, stable gene expression of ligament-related type I collagen, decorin, tenascin C and Mohawk after 14 d and extracellular matrix (ECM) deposition. PGE coating facilitates ligamentocyte sheet formation, and sheets colonizing the scaffolds displayed a ligament-related phenotype.

Adipose-Derived Stromal Cell-Sheets Sandwiched, Book-Shaped Acellular Dermal Matrix Capable of Sustained Release of Basic Fibroblast Growth Factor Promote Diabetic Wound Healing

The management of diabetic wounds is a therapeutic challenge in clinical settings. Current tissue engineering strategies for diabetic wound healing are insufficient, owing to the lack of an appropriate scaffold that can load a large number of stem cells and induce the interaction of stem cells to form granulation tissue. Herein we fabricated a book-shaped decellularized dermal matrix (BDDM), which shows a high resemblance to native dermal tissue in terms of its histology, microstructure, and ingredients, is non-cytotoxic and low-immunogenic, and allows adipose-derived stromal cell (ASC) attachment and proliferation. Then, a collagen-binding domain (CBD) capable of binding collagen was fused into basic fibroblast growth factor (bFGF) to synthetize a recombinant growth factor (termed as CBD-bFGF). After that, CBD-bFGF was tethered onto the collagen fibers of BDDM to improve its endothelial inducibility. Finally, a functional scaffold (CBD-bFGF/BDDM) was fabricated. In vitro and in vivo experiments demonstrated that CBD-bFGF/BDDM can release tethered bFGF with a sustained release profile, steadily inducing the interaction of stem cells down to endothelial differentiation. ASCs were cultured to form a cell sheet and then sandwiched by CBD-bFGF/BDDM, thus enlarging the number of stem cells loaded into the scaffold. Using a rat model, the ASC sheets sandwiched with CBD-bFGF/BDDM (ASCs/CBD-bFGF/BDDM) were capable of enhancing the formation of granulation tissue, promoting angiogenesis, and facilitating collagen deposition and remodeling. Therefore, the findings of this study demonstrate that ASCs/CBD-bFGF/BDDM could be applicable for diabetic wound healing.

Application of Autogenous Urine-Derived Stem Cell Sheet Enhances Rotator Cuff Healing in a Canine Model

BACKGROUND

A repaired rotator cuff (RC) often heals with interposed scar tissue, making repairs prone to failure. Urine-derived stem cells (USCs), with robust proliferation ability and multilineage differentiation, can be isolated from urine, avoiding invasive and painful surgical procedures for harvesting the cells. These advantages make it a novel cell source for autologous transplantation to enhance RC healing.

HYPOTHESIS

Implantation of an autogenous USC sheet to the injury site will enhance RC healing.

STUDY DESIGN

Controlled laboratory study.

METHODS

USCs isolated from urine were cultured using ascorbic acid and transforming growth factor β3 to form a cell sheet. Sixteen male mature beagles underwent bilateral shoulder surgery. The right shoulder underwent infraspinatus tendon (IT) insertion detachment and repair only, and the other was subjected to IT insertion detachment and repair, followed by autogenous USC sheet implantation. Among the animals, 3 received a Dil (1,1'-dioctadecyl-3,3,3',3'-tetramethylindocarbocyanine perchlorate)- labeled USC sheet implant in the right shoulder and were sacrificed at postoperative 6 weeks for cell tracking. The other animals were sacrificed at postoperative 12 weeks, and the IT-humerus complexes were harvested for gross observation, micro-computed tomography evaluation and histological analysis (n = 5), and mechanical testing (n = 8). Additionally, 13 unpaired canine cadaveric shoulders were included as native controls.

RESULTS

Micro-computed tomography analysis showed that the USC sheet group had a significant increase in bone volume/total volume and trabecular thickness at the RC healing site when compared with the control group (P < .05 for all). Histologically, the Dil-labeled USC sheet was still visible at the RC healing site, which suggested that the implanted USCs remained viable at postoperative 6 weeks. Meanwhile, the healing interface in the USC sheet group regenerated significantly more enthesis-like tissue than did that of the control group (P < .05). Additionally, the healing interface in the USC sheet group presented a larger fibrocartilage area, more proteoglycan deposition, and higher collagen birefringence than did that of the control group (P < .05 for all). Biomechanically, the USC sheet group showed significantly higher failure load and stiffness versus the control group (P < .05 for all).

CONCLUSION

A USC sheet was able to enhance RC healing in a canine model.

CLINICAL RELEVANCE

The findings of the study showed that USC sheet implantation could serve as a practical application for RC healing.

A Review of Zein as a Potential Biopolymer for Tissue Engineering and Nanotechnological Applications

Tissue engineering (TE) is one of the most challenging fields of research since it provides current alternative protocols and materials for the regeneration of damaged tissue. The success of TE has been mainly related to the right selection of nano-sized biocompatible materials for the development of matrixes, which can display excellent anatomical structure, functionality, mechanical properties, and histocompatibility. Today, the research community has paid particular attention to zein as a potential biomaterial for TE applications and nanotechnological approaches. Considering the properties of zein and the advances in the field, there is a need to reviewing the current state of the art of using this natural origin material for TE and nanotechnological applications. Therefore, the goal of this review paper is to elucidate the latest (over the last five years) applications and development works in the field, including TE, encapsulations of drugs, food, pesticides and bandaging for external wounds. In particular, attention has been focused on studies proving new breakthroughs and findings. Also, a complete background of zein’s properties and features are addressed.

Advanced Biomaterials and Processing Methods for Liver Regeneration: State-of-the-Art and Future Trends

Liver diseases contribute markedly to the global burden of mortality and disease. The limited organ disposal for orthotopic liver transplantation results in a continuing need for alternative strategies. Over the past years, important progress has been made in the field of tissue engineering (TE). Many of the early trials to improve the development of an engineered tissue construct are based on seeding cells onto biomaterial scaffolds. Nowadays, several TE approaches have been developed and are applied to one vital organ: the liver. Essential elements must be considered in liver TE-cells and culturing systems, bioactive agents or growth factors (GF), and biomaterials and processing methods. The potential of hepatocytes, mesenchymal stem cells, and others as cell sources is demonstrated. They need engineered biomaterial-based scaffolds with perfect biocompatibility and bioactivity to support cell proliferation and hepatic differentiation as well as allowing extracellular matrix deposition and vascularization. Moreover, they require a microenvironment provided using conventional or advanced processing technologies in order to supply oxygen, nutrients, and GF. Herein the biomaterials and the conventional and advanced processing technologies, including cell-sheets process, 3D bioprinting, and microfluidic systems, as well as the future trends in these major fields are discussed.

Isolation and Characterization of Multipotent Canine Urine-Derived Stem Cells

Current cell-based therapies on musculoskeletal tissue regeneration were mostly determined in rodent models. However, a direct translation of those promising cell-based therapies to humans exists a significant hurdle. For solving this problem, canine has been developed as a new large animal model to bridge the gap from rodents to humans. In this study, we reported the isolation and characterization of urine-derived stem cells (USCs) from mature healthy beagle dogs. The isolated cells showed fibroblast-like morphology and had good clonogenicity and proliferation. Meanwhile, these cells positively expressed multiple markers of MSCs (CD29, CD44, CD90, and CD73), but negatively expressed for hematopoietic antigens (CD11b, CD34, and CD45). Additionally, after induction culturing, the isolated cells can be differentiated into osteogenic, adipogenic, chondrogenic, and tenogenic lineages. The successful isolation and verification of USCs from canine were useful for studying cell-based therapies and developing new treatments for musculoskeletal injuries using the preclinical canine model.

Regenerative and engineered options for urethroplasty

Surgical correction of urethral strictures by substitution urethroplasty - the use of grafts or flaps to correct the urethral narrowing - remains one of the most challenging procedures in urology and is frequently associated with complications, restenosis and poor quality of life for the affected individual. Tissue engineering using different cell types and tissue scaffolds offers a promising alternative for tissue repair and replacement. The past 30 years of tissue engineering has resulted in the development of several therapies that are now in use in the clinic, especially in treating cutaneous, bone and cartilage defects. Advances in tissue engineering for urethral replacement have resulted in several clinical applications that have shown promise but have not yet become the standard of care.

Additively Manufactured Multiphasic Bone-Ligament-Bone Scaffold for Scapholunate Interosseous Ligament Reconstruction

The scapholunate interosseous ligament (SLIL) is a frequently torn wrist ligament, and current surgical options for SLIL tears are suboptimal. This research aims to develop a novel multiphasic bone-ligament-bone scaffold (BLB) with a porous interface using 3D-printing and cell sheet technology for the reconstruction of the dorsal scapholunate interosseous ligament. The BLB comprises two bone compartments bridged by aligned polycaprolactone fibers mimicking the architecture of the native tissue. Mechanical testing of the BLBs shows their ability to withstand physiological forces. Combination of the BLB with human bone marrow mesenchymal stem cell sheet demonstrates that the harvesting did not compromise cell viability, while allowing homogeneous distribution in the ligament compartment. The BLBs are loaded with cell sheets and bone morphogenetic protein-2 in the ligament and bone compartment respectively prior to ectopic implantation into athymic rats. The histology demonstrates rapid tissue infiltration, high vascularization, and more importantly the maintenance of the compartmentalization as bone formation remains localized to the bone compartment despite the porous interface. The cells in the ligament compartment become preferentially aligned, and this proof-of-concept study demonstrates that the BLB can provide sufficient compartmentalization and fiber guiding properties necessary for the regeneration of the dorsal SLIL.

Book-Shaped Acellular Fibrocartilage Scaffold with Cell-loading Capability and Chondrogenic Inducibility for Tissue-Engineered Fibrocartilage and Bone-Tendon Healing

Functional fibrocartilage regeneration is a bottleneck during bone-tendon healing, and the currently available tissue-engineering strategies for fibrocartilage regeneration are insufficient because of a lack of appropriate scaffold that can load large seeding-cells and induce chondrogenesis of stem cells. The acellular fibrocartilage scaffold (AFS) contains active growth factors as well as tissue-specific epitopes for cell-matrix interactions, which make it a potential scaffold for tissue-engineered fibrocartilage. A limitation to this scaffold is that its low porosity inhibits cells loading and infiltration. Here, inspired by book appearance, we sectioned native fibrocartilage tissue (NFT) into book-shape to improve cells loading and infiltration, and then decellularized with four protocols: (1) 2% SDS for 6-h, (2) 2% SDS for 24-h, (3) 4 SDS for 6-h, (4) 4% SDS for 24-h, followed by nuclease digestion. The optimal protocol was screened with respect to microstructures, DNA residence, native ingredients reservation, and chondrogenic inducibility of the AFS. In vitro studies demonstrated that this screened scaffold is noncytotoxicity and low-immunogenicity, allows adipose-derived stromal cells (ASCs) attachment and proliferation, shows superior chondrogenic inducibility, and stimulates collagen or glycosaminoglycans secretion. The underlying mechanism for this chondrogenic inducibility may be related to hedgehog pathway activating. Additionally, a novel pattern for fabricating tissue-engineered fibrocartilage was developed to enlarge seeding-cells loading, namely, cell-sheets sandwiched by book-shaped scaffold. In-vivo studies indicate that this screened scaffold alone could induce endogenous cells to satisfactorily regenerate fibrocartilage at 16-week, as characterized by fibrocartilaginous extracellular matrix (ECM) deposition and good interface integration. Interleaving this book-shaped AFS with autologous ASCs-sheets significantly enhanced its ability to regenerate fibrocartilage. Cell tracking demonstrated that fibrochondrocytes, osteoblasts, and osteocytes in the healing interface at postoperative 8-week partly originated from the sandwiched ASCs-sheets. On that basis, we propose the use of this book-shaped AFS and cell sheet technique for fabricating tissue-engineered fibrocartilage to improve bone-tendon healing.

Transplantation of Adipose-derived Cells for Periodontal Regeneration: A Systematic Review

This systematic review evaluated the transplantation of cells derived from adipose tissue for applications in dentistry. SCOPUS, PUBMED and LILACS databases were searched for in vitro studies and pre-clinical animal model studies using the keywords "ADIPOSE", "CELLS", and "PERIODONTAL", with the Boolean operator "AND". A total of 160 titles and abstracts were identified, and 29 publications met the inclusion criteria, 14 in vitro and 15 in vivo studies. In vitro studies demonstrated that adipose- derived cells stimulate neovascularization, have osteogenic and odontogenic potential; besides adhesion, proliferation and differentiation on probable cell carriers. Preclinical studies described improvement of bone and periodontal healing with the association of adipose-derived cells and the carrier materials tested: Platelet Rich Plasma, Fibrin, Collagen and Synthetic polymer. There is evidence from the current in vitro and in vivo data indicating that adipose-derived cells may contribute to bone and periodontal regeneration. The small quantity of studies and the large variation on study designs, from animal models, cell sources and defect morphology, did not favor a meta-analysis. Additional studies need to be conducted to investigate the regeneration variability and the mechanisms of cell participation in the processes. An overview of animal models, cell sources, and scaffolds, as well as new perspectives are provided for future bone and periodontal regeneration study designs.