Objective To determine the in vivo biocompatibility of septal neocartilage constructs developed in vitro by an alginate intermediate step. Study Design Prospective, animal model. Setting Research laboratory. Subjects and Methods A murine model was used to examine the maturation of neocartilage constructs in vivo. Chondrocytes collected from patients undergoing septoplasty were expanded in monolayer and suspended in alginate beads for three-dimensional culture in media containing human serum and growth factors. After in vitro incubation for 5 weeks, the constructs were implanted in the dorsum of athymic mice for 30 and 60 days (n=9). After the mice were sacrificed, the constructs were recovered for assessment of their morphological, histochemical, biochemical, and biomechanical properties. Results The mice survived and tolerated the implants well. Infection and extrusion were not observed. Neocartilage constructs maintained their general shape and size, and demonstrated cell viability after implantation. The implanted constructs were firm and opaque, sharing closer semblance to native septal tissue relative to the gelatinous, translucent pre-implant constructs. Histochemical staining with hematoxylin and eosin (H&E) revealed that the constructs exhibited distinct morphologies characteristic of native tissue, which were not observed in pre-implant constructs. DNA and type II collagen increased with duration of implantation, whereas type I collagen and glycoaminoglycans (GAG) decreased. Mechanical testing of a 60-day implanted construct demonstrated characteristics similar to native human septal cartilage. Conclusions Neocartilage constructs are viable in an in vivo murine model. The histologic, biochemical, and biomechanical features of implanted constructs closely resemble native septal tissue when compared to pre-implant constructs.

The ability to engineer virtually limitless quantities of autologous cartilage could have a profound impact on facial plastic and reconstructive surgery. The strategies used to refine human cartilage culture techniques have successfully produced neocartilage constructs with biochemical and biomechanical properties approaching those of native septal tissue. With the steady progress achieved in recent years, there is great capacity for the proximate realization of surgically implantable tissue-engineered cartilage constructs.

Objectives/Hypothesis Tissue-engineered septal cartilage may provide a source of autologous cartilage for repair of nasal defects. Production of clinically useful neocartilage involves multiple steps that include manipulating the culture environment. Partial pressure of oxygen (ppO2) is a property that has been shown to influence cartilage development. Specifically, studies suggest low ppO2 augments in vitro growth of articular cartilage. Although in vivo measurements of articular cartilage ppO2 have demonstrated hypoxic conditions, measurements have not been performed in septal cartilage. The objective of this study was to determine the ppO2 of septal cartilage in vivo. Study Design Prospective, basic science. Methods The ppO2 was measured in 14 patients (mean ± standard deviation age, 35.9 ± 14.5 years; range, 18–63 years) during routine septoplasty or septorhinoplasty using the OxyLab pO2 monitor (Oxford Optronix Ltd., Oxford, UK). Measurements were taken from the septum and inferior turbinate. Each patient’s age and sex were recorded. Results The average ppO2 measured at the septum and inferior turbinate was 10.5 ± 10.1 mm Hg (1.4 ± 1.3%) and 27.6 ± 12.4 mm Hg (3.6 ± 1.6%), respectively. The ppO2 of these locations was significantly different (P < .005). Advancing age was positively correlated with septal ppO2 (R2 = 0.42; P < .05). Septal ppO2 showed no significant sex variation. Conclusions This is the first report of in vivo measurement of ppO2 in septal cartilage. The data demonstrate reduced oxygenation of septal cartilage relative to the inferior turbinate. This elucidates an important characteristic of the in vivo milieu that can be applied to septal cartilage tissue engineering.

Objective To determine and compare the bending moduli of native and engineered human septal cartilage. Study Design Prospective, basic science. Setting Research laboratory. Subjects and Methods Neocartilage constructs were fabricated from expanded human septal chondrocytes cultured in differentiation medium for 10 weeks. Constructs (n=10) and native septal cartilage (n=5) were tested in a 3-point bending apparatus, and the bending moduli were calculated using Euler–Bernoulli beam theory. Results All samples were tested successfully and returned to their initial shape after unloading. The bending modulus of engineered constructs (0.32 ± 0.25 MPa, mean ± SD) was 16% of that of native septal cartilage (1.97 ± 1.25 MPa). Conclusion Human septal constructs, fabricated from cultured human septal chondrocytes, are more compliant in bending than native human septal tissue. The bending modulus of engineered septal cartilage can be measured, and this modulus provides a useful measure of construct rigidity while undergoing maturation relative to native tissue.

Although scars are a normal part of the healing process, facial scars have significant implications on a patient's well-being, both physically and psychologically. Facial scars are one of the most common reasons a patient presents to the facial plastic and reconstructive surgeon. The ability to evaluate facial scars and choose the most appropriate technique for revision is of paramount importance to obtain the best result. A thorough understanding of superficial facial anatomy and principles of wound healing is equally as important as meticulous technical execution. Above all, the expectations of the patient must be assessed and considered when formulating a surgical plan.

Objectives Evaluate safety of autogenous engineered septal neocartilage grafts. Compare properties of implanted grafts versus in vitro controls. Study Design Prospective, basic science Setting Research laboratory Methods Constructs were fabricated from septal cartilage and serum harvested from adult rabbits and then cultured in vitro or implanted on the nasal dorsum as autogenous grafts for 30 or 60 days. Rabbits were monitored for local and systemic complications. Histological, biochemical and biomechanical properties of implanted and in vitro constructs were evaluated and compared. Results No systemic or serious local complications were observed. After 30 and 60 days, implanted constructs contained more DNA (p<0.01) and less sGAG per DNA (p<0.05) when compared with in vitro controls. Confined compressive aggregate moduli were also higher in implanted constructs when compared with in vitro controls (p<0.05) and increased with longer in vivo incubation time (p<0.01). Implanted constructs displayed resorption rates of 20–45 percent. Calcium deposition in implanted constructs was observed using alizarin red histochemistry and microtomographic analyses. Conclusion Autogenous engineered septal cartilage grafts were well tolerated. As seen in experiments with athymic mice, implanted constructs accumulated more DNA and less sGAG when compared with in vitro controls. Confined compressive aggregate moduli were also higher in implanted constructs. Implanted constructs displayed resorption rates similar to previously published studies using autogenous implants of native cartilage. The basis for observed calcification in implanted constructs and its effect on long-term graft efficacy is unknown at this time and will be a focus of future studies.

Importance Cartilaginous craniofacial defects range in size and autologous cartilaginous tissue is preferred for repair of these defects. Therefore, it is important to have the ability to produce large size cartilaginous constructs for repair of cartilaginous abnormalities. Objectives To produce autologous human septal neocartilage constructs substantially larger in size than previously produced constructs To demonstrate that volume expanded neocartilage constructs possess comparable histological and biochemical properties to standard size constructs To show that volume expanded neocartilage constructs retain similar biomechanical properties to standard size constructs Design Prospective, basic science Setting Laboratory Participants The study used remnant human septal specimens removed during routine surgery at the University of California, San Diego Medical Center or San Diego Veterans Affairs Medical Center. Cartilage from a total of 8 donors was collected. Main Outcomes Measured Human septal chondrocytes from 8 donors were used to create 12mm and 24mm neocartilage constructs. These were cultured for a total of 10 weeks. Photo documentation, histological, biochemical, and biomechanical properties were measured and compared. Results The 24mm diameter constructs were qualitatively similar to the 12mm constructs. They possessed adequate strength and durability to be manually manipulated. Histological analysis of the constructs demonstrated similar staining patterns in standard and volume expanded constructs. Proliferation, as measured by DNA content, was similar in 24mm and 12mm constructs. Additionally, glycosaminoglycan (GAG) and total collagen content did not significantly differ between the two construct sizes. Biomechanical analysis of the 24mm and 12mm constructs demonstrated comparable compressive and tensile properties. Conclusion and Relevance Volume expanded human septal neocartilage constructs are qualitatively and histologically similar to standard 12mm constructs. Biochemical and biomechanical analysis of the constructs demonstrated equivalent properties. This study shows that modification of existing protocols is not required to successfully produce neocartilage constructs in larger sizes for reconstruction of more substantial craniofacial defects. Level of Evidence NA.

Tissue-engineered nasal septal cartilage may provide a source of autologous tissue for repair of craniofacial defects. Although advances have been made in manipulating the chondrocyte culture environment for production of neocartilage, consensus on the best oxygen tension for in vitro growth of tissue-engineered cartilage has not been reached. The objective of this study was to determine whether in vitro oxygen tension influences chondrocyte expansion and redifferentiation. Proliferation of chondrocytes from 12 patients expanded in monolayer under hypoxic (5% or 10%) or normoxic (21%) oxygen tension was compared over 14 days of culture. The highest performing oxygen level was used for further expansion of the monolayer cultures. At confluency, chondrocytes were redifferentiated by encapsulation in alginate beads and cultured for 14 days under hypoxic (5 or 10%) or normoxic (21%) oxygen tension. Biochemical and histological properties were evaluated. Chondrocyte proliferation in monolayer and redifferentiation in alginate beads were supported by all oxygen tensions tested. Chondrocytes in monolayer culture had increased proliferation at normoxic oxygen tension (p = 0.06), as well as greater accumulation of glycosaminoglycan (GAG) during chondrocyte redifferentiation (p < 0.05). Chondrocytes released from beads cultured under all three oxygen levels showed robust accumulation of GAG and type II collagen with a lower degree of type I collagen immunoreactivity. Finally, formation of chondrocyte clusters was associated with decreasing oxygen tension (p < 0.05). Expansion of human septal chondrocytes in monolayer culture was greatest at normoxic oxygen tension. Both normoxic and hypoxic culture of human septal chondrocytes embedded in alginate beads supported robust extracellular matrix deposition. However, GAG accumulation was significantly enhanced under normoxic culture conditions. Chondrocyte cluster formation was associated with hypoxic oxygen tension.