In vivo study of the angiogenesis potential of bone marrow-derived mesenchymal stem cell aggregates in their niche like environment

Background: Sufficient blood vessel formation in bioengineered tissues is essential in order to keep the viability of the organs. Impaired development of blood vasculatures results in failure of the implanted tissue. The cellular source which is seeded in the scaffold is one of the crucial factors involved in tissue engineering methods. Materials and methods: Considering the notable competence of Bone Marrow derived Mesenchymal Stem Cell aggregates for tissue engineering purposes, in this study BM-aggregates and expanded BM-MSCs were applied without any inductive agent or co-cultured cells, in order to investigate their own angiogenesis potency in vivo. BM-aggregates and BM-MSC were seeded in Poly-L Lactic acid (PLLA) scaffold and implanted in the peritoneal cavity of mice. Result: Immunohistochemistry results indicated that there was a significant difference ( p < 0.050) in CD31+ cells between PLLA scaffolds contained cultured BM-MSC; PLLA scaffolds contained BM-aggregates and empty PLLA. According to morphological evidence, obvious connections with recipient vasculature and acceptable integration with surroundings were established in MSC and aggregate-seeded scaffolds. Conclusion: Our findings revealed cultured BM-MSC and BM-aggregates, capacity in order to develop numerous connections between PLLA scaffold and recipient’s vasculature which is crucial to the survival of tissues, and considerable tendency to develop constructs containing CD31+ endothelial cells which can contribute in vessel’s tube formation.

3D perfusion culture of mouse insulinoma in macro-porous scaffolds enhanced insulin production response

To address the remaining issue of poor cell immobilization and insufficient mass transfer in scaffold-based tissue engineering approach for future islet transplantation, we employed a macro-porous poly-l-lactide (PLLA) scaffold immobilizing mouse insulinoma cells and studied its function toward an implantable pancreatic tissue in 7-day perfusion culture. The murine pancreatic β cells could be immobilized in the PLLA scaffold at a high density of 107 cells per cm3 close to the estimated range in normal pancreas. The perfusion culture promoted the 3D cellular organization as observed with live/dead staining and histological staining. The insulin production was significantly enhanced in comparison with static 2D culture and 3D rotational suspension culture by two and six folds, respectively ( p < 0.001). As enhanced insulin response was only observed where both the perfusion and 3D cellular organization were present, this could represent important elements in engineering a functional bioartificial pancreas.

Osteogenic Potential of 3-D printed Multilayered Poly L-lactic Acid (PLLA) Scaffold on the Healing of Critical-sized Bone Defect in Dogs

Critical sized bone defect is a major challenge for orthopedic surgeons. These defects result following any pathologic condition leading to massive bone loss. Synthetic and biological based tissue engineered biomaterials and their combinations provide a promising substitute to fill the defect site. The aim of the present study was to evaluate the osteogenic potential of 3-D printed multilayered medical grade PLLA scaffold with collagen and nano hydroxyapatite for the healing of induced critical-sized bone defect in dogs. An experimental study was conducted on 12 skeletally mature male dogs. Critical defect (25mm) was induced into the right femur of all dogs. Dogs were randomly allocated into one of the following groups (4 dogs/group). PLLA scaffold seeded with nano hydroxyapatite and collagen molded on the defect (PLLA/Collagen/nHA group), the second group; the defect seeded with collagen and nano hydroxyapatite (Collagen/nHA group), the third one was left without scaffold or additives (Sham operated group), and the operated animals were left for 12 weeks. Animals were evaluated clinically, radiographically and histopathologicaly. In (PLLA/Collagen/nHA group), all dogs showed an improvement in lameness degree from sever to apparently free from lameness. Radiography showed newly formed bone filling the defect with no inter zone. Histopathology showed more maturation of the newly formed bone in the defect site had occurred as well as defined bone trabeculae in comparing to other groups. In conclusion, 3D printed multilayered medical grade PLLA with collagen and nano hydroxyapatite provide biodegradable osteoconductive scaffold for enhancing the healing of critical sized bone defect.

Graphene Oxide Induces Ester Bonds Hydrolysis of Poly-l-lactic Acid Scaffold to Accelerate Degradation

Poly-l-lactic acid (PLLA) possesses good biocompatibility and bioabsorbability as scaffold material, while slow degradation rate limits its application in bone tissue engineering. In this study, graphene oxide (GO) was introduced into the PLLA scaffold prepared by selective laser sintering to accelerate degradation. The reason was that GO with a large number of oxygen-containing functional groups attracted water molecules and transported them into scaffold through the interface microchannels formed between lamellar GO and PLLA matrix. More importantly, hydrogen bonding interaction between the functional groups of GO and the ester bonds of PLLA induced the ester bonds to deflect toward the interfaces, making water molecules attack the ester bonds and thereby breaking the molecular chain of PLLA to accelerate degradation. As a result, some micropores appeared on the surface of the PLLA scaffold, and mass loss was increased from 0.81% to 4.22% after immersing for 4 weeks when 0.9% GO was introduced. Besides, the tensile strength and compressive strength of the scaffolds increased by 24.3% and 137.4%, respectively, due to the reinforced effect of GO. In addition, the scaffold also demonstrated good bioactivity and cytocompatibility.

Fabrication and evaluation of a chitin whisker/poly(l-lactide) composite scaffold by the direct trisolvent-ink writing method for bone tissue engineering

Our work constructed a PLLA scaffold with chitin whiskers via direct trisolvent ink writing method and as-prepared scaffold exhibited the good mechanical as well as excellent biological properties.

Preparation and characterization of nano biphasic calcium phosphate/poly-L-lactide composite scaffold

Nano biphasic calcium phosphate (BCP) particles were synthesized using the sol-gel method. As-prepared BCP particles were combined with poly-L-lactide (PLLA) to fabricate nano-BCP/PLLA composite scaffold through a series of processing steps containing solvent self-diffusion, hot-pressing, and particulate leaching. The composite had a suitable porous structure for bone tissue engineering scaffold. In comparison, micro-BCP/PLLA scaffold was studied as well. Nano-BCP particles were distributed homogeneously in the PLLA matrix, and much more tiny crystallites exposed on the surface of the pore wall. Due to the finer inorganic particle distribution in the PLLA phase and the larger area of the bioactive phase exposed in the pore wall surface, nano-BCP/PLLA scaffold had enhanced compressive strength, good bioactivity, and superior cell viability. A nonstoichiometric apatite layer could be rapidly formed on the surface of nano- BCP/PLLA when soaked in simulated body fluid. The MG-63 cell viability of nano-BCP/PLLA scaffold is significantly higher than that of micro-BCP/PLLA scaffold. Therefore, nano-BCP/PLLA composite may be a suitable alternative for bone tissue engineering scaffold.