Growth Factor Stimulation Improves the Structure and Properties of Scaffold-Free Engineered Auricular Cartilage Constructs

Abstract

The reconstruction of the external ear to correct congenital deformities or repair following trauma remains a significant challenge in reconstructive surgery. Previously, we have developed a novel approach to create scaffold-free, tissue engineering elastic cartilage constructs directly from a small population of donor cells. Although the developed constructs appeared to adopt the structural appearance of native auricular cartilage, the constructs displayed limited expression and poor localization of elastin. In the present study, the effect of growth factor supplementation (insulin, IGF-1, or TGF-β1) was investigated to stimulate elastogenesis as well as to improve overall tissue formation. Using rabbit auricular chondrocytes, bioreactor-cultivated constructs supplemented with either insulin or IGF-1 displayed increased deposition of cartilaginous ECM, improved mechanical properties, and thicknesses comparable to native auricular cartilage after 4 weeks of growth. Similarly, growth factor supplementation resulted in increased expression and improved localization of elastin, primarily restricted within the cartilaginous region of the tissue construct. Additional studies were conducted to determine whether scaffold-free engineered auricular cartilage constructs could be developed in the 3D shape of the external ear. Isolated auricular chondrocytes were grown in rapid-prototyped tissue culture molds with additional insulin or IGF-1 supplementation during bioreactor cultivation. Using this approach, the developed tissue constructs were flexible and had a 3D shape in very good agreement to the culture mold (average error <400 µm). While scaffold-free, engineered auricular cartilage constructs can be created with both the appropriate tissue structure and 3D shape of the external ear, future studies will be aimed assessing potential changes in construct shape and properties after subcutaneous implantation.

Stem Cell Therapy for Cartilage Defects

“…They found that the effects of insulin were similar to that of the IGF1 and thus posed an interesting proposal of employing insulin as a potent substance to improve tissue-engineered cartilage. These additive effects of IGF1 have been supported by a plethora of other researchers Blunk et al 2002;Rosa et al 2014). Transforming growth factors, especially TGF β1 (Rosa et al 2014;Morales 1991) and TGF β3 (Almeida et al 2014;Wang et al 2014), and bone morphogenetic proteins (BMP), especially BMP-2 and BMP-7 (Park et al 2005;Kaps et al 2002;Carreira et al 2014), and fibroblast growth factor (FGF)-2 (Veilleux and Spector 2005) have all shown a qualitative effect on chondrogenesis.…”

Bioengineering pediatric scaffold‐free auricular cartilaginous constructs

“…Thus, elastogenic expression profile likely was affected during dedifferentiation of chondrocytes through cellular attachment and expansion in monolayer culture and was not reinitiated properly with the current standard of elastic chondrogenesis differentiation cocktail . Rosa et al have demonstrated that insulin‐like growth factor 1 treatments can enhance elastic fiber deposition in rabbit auricular cartilaginous constructs . Conversely, abandoning in vitro monolayer expansion and utilizing aggregate expansion of porcine auricular chondrocytes has been shown to maintain their in vitro elastic fiber deposition .…”

Nanomaterials for cartilage tissue engineering

“…Current developments in cartilage tissue engineering is focused on yielding engineered tissues that have improved structure and functionality. [122] or a mold [99], or (C) directly into a bioreactor. A bioreactor may be just a static dish or more sophisticated systems that can provide shear stress and control oxygen tension.…”

“…(D) The constructs are grown until reaching desired properties that mimic the native tissue. The image here shows an engineered ear using a mold placed in a continuous flow bioreactor [99]. (E) The engineered tissues can potentially be implanted into the patient.…”

“…The proliferation of chondrocytes, when seeded at low densities, was increased by adding combinations of growth factors such as TGF-β1, fibroblast growth factor 2 (FGF-2) and platelet-derived growth factor BB (PDGF-BB) into the bioreactor [98]. In a separate study, elastic cartilage constructs grown by culturing rabbit auricular chondrocytes in the continuous flow bioreactor showed increased deposition of cartilaginous extracellular matrix, improved expression and localization of elastin, improved mechanical properties and greater thickness when insulin or IGF-1 was added [99]. These constructs had properties comparable to the native auricular cartilage after a 4 week cultivation period.…”