Matrix Production in Large Engineered Cartilage Constructs Is Enhanced by Nutrient Channels and Excess Media Supply

Abstract

Cartilage tissue engineering is a promising approach to resurfacing osteoarthritic joints. Existing techniques successfully engineer small-sized constructs with native levels of extracellular matrix (glycosaminoglycans [GAG] or collagen). However, a remaining challenge is the growth of large-sized constructs with properties similar to those of small constructs, due to consumption and transport limitations resulting in inadequate nutrient availability within the interior of large constructs. This study employed system-specific computational models for estimating glucose requirements of large constructs, with or without channels, to enhance nutrient availability. Based on glucose requirements for matrix synthesis in cartilage constructs, computational simulations were performed to identify the media volume (MV) and the number of nutrient channels (CH) needed to maintain adequate glucose levels within tissue constructs over the 3-day period between media replenishments. In Study 1, the influence of MV (5, 10, 15 mL/construct) and number of nutrient channels (CH: 0, 3, 7, 12 per construct) on glucose availability was investigated computationally for B10 · 2.34 mm cylindrical constructs. Results showed that the conventionally used MV 5 led to deleterious glucose depletion after only 40 h of culture, and that MV 15 was required to maintain sufficient glucose levels for all channel configurations. Study 2 examined experimentally the validity of these predictions, for tissue constructs cultured for 56 days. Matrix elaboration was highest in MV 15/CH 12 constructs (21.6% -2.4%/ww GAG, 5.5% -0.7%/ww collagen, normalized to wet weight (ww) on day 0), leading to the greatest amount of swelling (3.0 -0.3 times day-0 volume), in contrast to the significantly lower matrix elaboration of conventional culture, MV 5/CH 0 (11.8% -1.6%/ww GAG and 2.5% -0.6%/ww collagen, 1.6 -0.1 times day-0 volume). The computational analyses correctly predicted the need to increase the conventional media levels threefold to support matrix synthesis in large channeled engineered constructs. Results also suggested that more elaborate computational models are needed for accurate predictive tissue engineering simulations, which account for a broader set of nutrients, cell proliferation, matrix synthesis, and swelling of the constructs.

Anatomic Mesenchymal Stem Cell-Based Engineered Cartilage Constructs for Biologic Total Joint Replacement

“…Indeed, our work and that of others show that even small hydrogel constructs develop significant mechanical heterogeneities over relatively small thicknesses. [41][42][43] Thus, the in vitro culture conditions for molded constructs will need to be optimized to produce improved cell viability, better ECM deposition, and higher mechanical stiffness at the center. This may be accomplished by dynamic loading, 20 culture in hydrodynamic environments that encourage nutrient exchange, 24,44 or even the ordered introduction of channels within the construct to facilitate more consistent nutrient exchange to the central regions of these large constructs.…”

Anatomically shaped tissue-engineered cartilage with tunable and inducible anticytokine delivery for biological joint resurfacing

“…Meeting these criteria would provide the ability to support a regenerative response for long-term restoration of joint function. Despite this, there have been several initial studies on cartilage joint resurfacing (11)(12)(13)(14). Hung et al (13) and Hung and colleagues (14) demonstrated proof of concept for joint Significance Whereas some success has been realized treating isolated, focal defects or lesions of articular cartilage, the complete resurfacing of synovial joints remains an important challenge for the treatment of osteoarthritis.…”

“…Despite this, there have been several initial studies on cartilage joint resurfacing (11)(12)(13)(14). Hung et al (13) and Hung and colleagues (14) demonstrated proof of concept for joint Significance Whereas some success has been realized treating isolated, focal defects or lesions of articular cartilage, the complete resurfacing of synovial joints remains an important challenge for the treatment of osteoarthritis. Here, we develop an anatomically shaped, functional cartilage construct based on a 3D woven scaffold that can provide for total joint resurfacing, with capabilities for tunable and inducible production of anticytokine therapy to protect diseased or injured joints from pathologic inflammation.…”

Nutrient Channels Aid the Growth of Articular Surface-Sized Engineered Cartilage Constructs

“…36,37 The system was scaled up such that each Ø40 mm construct was cast in a three-dimensional (3D) printed mold and held by a culture rack within a 473 mL polypropylene container with a polyethylene lid (Fig. 1).…”

“…10,35 In our recent studies, the combination of suspension culture and sufficient glucose supply permitted Ø10 mm constructs with 3 or 12 evenlyspaced Ø1 mm channels (CH3 or CH12, respectively) to attain functional properties on par with those of Ø4 mm constructs, including native E Y and GAG content. 36,37 Many tissue engineering studies using bovine chondrocytes opt for the use of primary cells. 19,[38][39][40] In this approach, numerous calf joints may be harvested and pooled together to obtain enough chondrocytes for large-scale studies.…”