Nasal augmentation using injectable alginate and mesenchymal stem cells in the rabbit

Customizable, biocompatible implants for dorsal nasal augmentation: An in vivo pilot study of eight polylactic acid scaffold designs

Augmentation of the nasal dorsum often requires implantation of structural material. Existing methods include autologous, cadaveric or alloplastic materials and injectable hydrogels. Each of these options is associated with considerable limitations. There is an ongoing need for precise and versatile implants that produce long-lasting craniofacial augmentation. Four separate polylactic acid (PLA) dorsal nasal implant designs were 3D-printed. Two implants had internal PLA rebar of differing porosities and two were designed as "shells" of differing porosities. Shell designs were implanted without infill or with either minced or zested processed decellularized ovine cartilage infill to serve as a "biologic rebar", yielding eight total treatment groups. Scaffolds were implanted heterotopically on rat dorsa (N = 4 implants per rat) for explant after 3, 6, and 12 months followed by volumetric, histopathologic, and biomechanical analysis. Low porosity implants with either minced cartilage or PLA rebar infill had superior volume retention across all timepoints. Overall, histopathologic and immunohistochemical analysis showed a resolving inflammatory response with an M1/M2 ratio consistently favoring tissue regeneration over the study course. However, xenograft cartilage showed areas of degradation and pro-inflammatory infiltrate contributing to volume and contour loss over time. Biomechanical analysis revealed all constructs had equilibrium and instantaneous moduli higher than human septal cartilage controls. Biocompatible, degradable polymer implants can induce healthy neotissue ingrowth resulting in guided soft tissue augmentation and offer a simple, customizable and clinically-translatable alternative to existing craniofacial soft tissue augmentation materials. PLA-only implants may be superior to combination PLA and xenograft implants due to contour irregularities associated with cartilage degradation.

Activated platelet-rich plasma improves cartilage regeneration using adipose stem cells encapsulated in a 3D alginate scaffold

In the current study, the effect of superimposing platelet-rich plasma (PRP) on different culture mediums in a three-dimensional alginate scaffold encapsulated with adipose-derived mesenchymal stem cells for cartilage tissue repair is reported. The three-dimensional alginate scaffolds with co-administration of PRP and/or chondrogenic supplements had a significant effect on the differentiation of adipose mesenchymal stem cells into mature cartilage, as assessed by an evaluation of the expression of cartilage-related markers of Sox9, collagen II, aggrecan and collagen, and glycosaminoglycan assays. For in vivo studies, following induction of osteochondral lesion in a rabbit model, a high degree of tissue regeneration in the alginate plus cell group (treated with PRP plus chondrogenic medium) compared with other groups of cell-free alginate and untreated groups (control) were observed. After 8 weeks, in the alginate plus cell group, functional chondrocytes were observed, which produced immature matrix, and by 16 weeks, the matrix and hyaline-like cartilage became completely homogeneous and integrated with the natural surrounding cartilage in the defect site. Similar effect was also observed in the subchondral bone. The cell-free scaffolds formed fibrocartilage tissue, and the untreated group did not form a continuous cartilage over the defect by 16 weeks.

Effect of bFGF and fibroblasts combined with hyaluronic acid-based hydrogels on soft tissue augmentation: an experimental study in rats

Background

Hyaluronic acid (HA) has been applied as a primary biomaterial for temporary soft tissue augmentation and as a carrier for cells and the delivery of growth factors to promote tissue regeneration. Although HA derivatives are the most versatile soft tissue fillers on the market, they are resorbed early, within 3 to 12 months. To overcome their short duration, they can be combined with cells or growth factors. The purpose of this study was to investigate the stimulating effects of human fibroblasts and basic fibroblast growth factors (bFGF) on collagen synthesis during soft tissue augmentation by HA hydrogels and to compare these with the effects of a commercial HA derivative (Restylane®).

Methods

The hydrogel group included four conditions. The first condition consisted of hydrogel (H) alone as a negative control, and the other three conditions were bFGF-containing hydrogel (HB), human fibroblast-containing hydrogel (HF), and human fibroblast/bFGF-containing hydrogel (HBF). In the Restylane® group (HGF), the hydrogel was replaced with Restylane® (R, RB, RF, RBF). The gels were implanted subdermally into the back of each nude mouse at four separate sites. Twelve nude mice were used for the hydrogel (n = 6) and Restylane® groups (n = 6). The specimens were harvested 8 weeks after implantation and assessed histomorphometrically, and collagen synthesis was evaluated by RT-PCR.

Results

The hydrogel group showed good biocompatibility with the surrounding tissues and stimulated the formation of a fibrous matrix. HBF and HF showed significantly higher soft tissue synthesis compared to H (p < 0.05), and human collagen type I was well expressed in HB, HF, and HBF; HBF showed the strongest expression. The Restylane® filler was surrounded by a fibrous capsule without any soft tissue infiltration from the neighboring tissue, and collagen synthesis within the Restylane® filler could not be observed, even though no inflammatory reactions were observed.

Conclusion

This study revealed that HA-based hydrogel alone or hydrogel combined with fibroblasts and/or bFGF can be effectively used for soft tissue augmentation.

Nasal reconstruction using tissue engineered constructs: an update

Currently, the gold standard for reconstruction after rhinectomy or severe trauma to the nose, includes transposition of autologous mucosal flaps plus autologous cartilage grating and coverage using a skin flap. Difficulties with this approach arise where; cartilage and mucosa harvested from autologous donor sites is insufficient to achieve a passable aesthetic and functional reconstruction. Skin flaps are often bulky, poor color matches with hair follicles that reduce the aesthetic quality of the reconstruction. We suggest that tissue engineering could be a source of functional replacement tissues for nasal reconstructive surgery. However, the advancement of such an approach is dependent on the dissemination of scientific information into the clinical community, regarding the engineering of tissues such as mucosa, skin, and cartilage. This paper therefore reviews how the tissue engineering strategies available for producing clinically viable tissues could help resolve issues around reconstructing the human nose.

Repair of calvarial defects in rabbits with platelet-rich plasma as the scaffold for carrying bone marrow stromal cells

OBJECTIVE

Platelet-rich plasma (PRP) is becoming a new application in tissue engineering and a developing area for clinicians and researchers because it is a natural source of growth factors, many of which can accelerate and promote bone regeneration. However, few studies have reported the potentiality of using PRP as a scaffold in bone tissue engineering. The present study investigated the feasibility of using PRP as a scaffold to carry bone marrow stromal cells (BMSCs) to repair calvarial defects in a rabbit model.

STUDY DESIGN

The primary cultured BMSCs were divided into 2 groups. One group was induced with dexamethasone and the other was not induced. Full-thickness bone defects of 5-mm diameter (4 defects per calvarium) were created on the calvaria of 10 New Zealand white rabbits. PRP or whole blood was used, respectively to incorporate the induced or uninduced BMSCs. Then, the composites were activated and applied to repair the defects. The samples were harvested 8 weeks later and bone regeneration was assessed grossly and analyzed by radiographic or histologic examination.

RESULTS

Eight weeks after the implantation of the materials, substantial bone regeneration was observed at the calvarial defect restored with PRP incorporating the induced BMSCs. Less new bone formation was observed at the defect implanted with PRP incorporating the uninduced BMSCs. In contrast, no bone regeneration was detected at the defects implanted with the whole blood incorporating BMSCs, whether the BMSCs were induced or not.

CONCLUSIONS

PRP can be used as a scaffold to carry in vitro expanded BMSCs to repair a rabbit's calvarial defect, but its inductive ability to BMSCs was limited.

Neovascularization and free microsurgical transfer of in vitro cartilage-engineered constructs

Cartilage tissue engineering shows to have tremendous potential for the reconstruction of three-dimensional cartilage defects. To ensure survival, shape, and function, in vitro cartilage-engineered constructs must be revascularized. This article presents an effective method for neovascularization and free microsurgical transfer of these in vitro constructs. Twelve female Chinchilla Bastard rabbits were used. Cartilage-engineered constructs were created by isolating chondrocytes from auricular biopsies, amplifying in monolayer culture, and then seeding them onto polycaprolactone scaffolds. In each prefabricated skin flap, three in vitro cartilage-engineered constructs (2 x 2 x 0.5 cm) and one construct without cells (served as the control) were implanted beneath an 8 x 15 cm random-pattern skin flap, neovascularized by implantation of an arteriovenous vascular pedicle with maximal blood flow. Six weeks later, the neovascularized flaps with embedded cartilage-engineered constructs were completely removed based on the newly implanted vascular pedicle, and then freely retransferred into position using microsurgery. Macroscopic observation, selective microangiography, histology, and immunohistochemistry were performed to determine the construct vitality, neovascularization, and new cartilage formation. The results showed that all neovascularized skin flaps with embedded constructs were successfully free-transferred as free flaps. The implanted constructs were well integrated and protected within the flap. All constructs were well neovascularized and showed histologically stability in both size and form. Immunohistology showed the existence of cartilage-like tissue with extracellular matrix neosynthesis.