Three-dimensional osteogenic and chondrogenic systems to model osteochondral physiology and degenerative joint diseases

Abstract

Tissue engineered constructs have the potential to function as in vitro pre-clinical models of normal tissue function and disease pathogenesis for drug screening and toxicity assessment. Effective high throughput assays demand minimal systems with clearly defined performance parameters. These systems must accurately model the structure and function of the human organs and their physiological response to different stimuli. Musculoskeletal tissues present unique challenges in this respect, as they are load-bearing, matrix-rich tissues whose functionality is intimately connected to the extracellular matrix and its organization. Of particular clinical importance is the osteochondral junction, the target tissue affected in degenerative joint diseases, such as osteoarthritis (OA), which consists of hyaline articular cartilage in close interaction with subchondral bone. In this review, we present an overview of currently available in vitro three-dimensional systems for bone and cartilage tissue engineering that mimic native physiology, and the utility and limitations of these systems. Specifically, we address the need to combine bone, cartilage and other tissues to form an interactive microphysiological system (MPS) to fully capture the biological complexity and mechanical functions of the osteochondral junction of the articular joint. The potential applications of three-dimensional MPSs for musculoskeletal biology and medicine are highlighted.

Keywords: Tissue engineering; biomaterial scaffold; bone; cartilage; drug screening; osteoarthritis.

Figure 1

Structure of the osteochondral complex (modified from Thompson et al.)

Figure 2

Hematoxylin and eosin (H&E) staining of a section of native osteochondral tissue in which tidemark, calcified cartilage and columnar chondrocytes are highlighted as prominent features in the osteochondral junction. Bar = 100 μm. (A color version of this figure is available in the online journal.)

Figure 3

Limb bud mesenchymal micromass. Embryonic chick limb bud micromass cultured for 21 days and stained with Safranin O/Fast green (Saf O/FG), and immunostained for collagen type I (Col 1), collagen type II (Col 2), alkaline phosphatase (Alk Phos), and Indian hedgehog (IHH). Bar =50 μm, Inset Bar 100 μm. (A color version of this figure is available in the online journal.)

Figure 4

MSC pellet culture. Human bone marrow-derived MSCs were pelleted and cultured in TGF-β1 containing chondrogenic medium for 21 days. Samples were processed for histology and stained with Safranin O/Fast green. Red staining indicates matrix sulfated glycosaminoglycan deposition. Bar =250 μm in a and 50 μm in b. (A color version of this figure is available in the online journal.)

Figure 5

MSCs chondrogenic differentiation in 3D. Human bone marrow derived MSCs were seeded within 1 mg/mL collagen type I gels and cultured for 21 days with TGF-β1 or TGF-β3 containing chondrogenic medium or control medium. Samples were processed for histology and stained with Safranin O/Fast green staining. Red staining indicates matrix sulfated glycosaminoglycan deposition. Bar =50 μm. (A color version of this figure is available in the online journal.)

Figure 6

Schematics of a multiwell, dual chamber bioreactor system (modified from Lozito et al.). On the left, a representation of a single bioreactor well. A removable, non-permeable insert (b) hosts the chondral tissue (d) and the bone tissue (e) constructs. The insert with the osteochondral construct is placed within a well of the bioreactor platform as shown on the right, and the O-rings (c) seal the separation of the well in an upper and lower chamber. A stream of chondrogenic medium (yellow) is perfused through the upper compartments in communication with the chondral tissue, while osteogenic medium (orange) is perfused through the lower chamber in communication with the bone tissue. Sealing is further ensured by a lid (a) equipped with an O-ring (c). On the right, a representation of the multiwell bioreactor platform for the simultaneous culture of 96 osteochondral constructs. The multiwell platform replicates the well dimensions and arrangement of standard 96-well tissue culture plates. Representative inserts and sealing lids with O-rings depicted in red are shown. The microfluidics connects eight wells in each column allowing for averaging of the experimental conditions along each array. (A color version of this figure is available in the online journal.)