Comparative effect of physicomechanical and biomolecular cues on zone-specific chondrogenic differentiation of mesenchymal stem cells

Abstract

Current tissue engineering approaches to regeneration of articular cartilage rarely restore the tissue to its normal state because the generated tissue lacks the intricate zonal organization of the native cartilage. Zonal regeneration of articular cartilage is hampered by the lack of knowledge for the relation between physical, mechanical, and biomolecular cues and zone-specific chondrogenic differentiation of progenitor cells. This work investigated in 3D the effect of TGF-β1, zone-specific growth factors, optimum matrix stiffness, and adding nanofibers on the expression of chondrogenic markers specific to the superficial, middle, and calcified zones of articular cartilage by the differentiating human mesenchymal stem cells (hMSCs). Growth factors included BMP-7, IGF-1, and hydroxyapatite (HA) for the superficial, middle, and calcified zones, respectively; optimum matrix stiffness was 80 kPa, 2.1 MPa, and 320 MPa; and nanofibers were aligned horizontal, random, and perpendicular to the gel surface. hMSCs with zone-specific cell densities were encapsulated in engineered hydrogels and cultured with or without TGF-β1, zone-specific growth factor, optimum matrix modulus, and fiber addition and cultured in basic chondrogenic medium. The expression of encapsulated cells was measured by mRNA, protein, and biochemical analysis. Results indicated that zone-specific matrix stiffness had a dominating effect on chondrogenic differentiation of hMSCs to the superficial and calcified zone phenotypes. Addition of aligned nanofibers parallel to the direction of gel surface significantly enhanced expression of Col II in the superficial zone chondrogenic differentiation of hMSCs. Conversely, biomolecular factor IGF-1 in combination with TGF-β1 had a dominating effect on the middle zone chondrogenic differentiation of hMSCs. Results of this work could potentially lead to the development of multilayer grafts mimicking the zonal organization of articular cartilage.

Biomimetic multidirectional scaffolds for zonal osteochondral tissue engineering via a lyophilization bonding approach

“…Fortunately, this challenge may be mitigated by understanding the relationship between the zonal microstructure and bulk tissue function. Both the arcade‐like architecture of the collagenous network and graded glycosaminoglycan content play a major role in conferring function to osteochondral tissue by dictating both the phenotype of embedded chondrocytes and mechanical properties of each zone . Without the appropriate structural and compositional cues, regenerated tissue will lack zonal properties and have comprised function; it is critical to impart zonal character in engineered osteochondral tissue.…”

“…Furthermore, the smaller elongated pore channels [48 µm, Fig. (A2)] may encourage infiltrating MSCs to adopt an elongated morphology which may help establish a superficial zone phenotype …”

“…(A4)]. This zone mimics the structure of the native calcified cartilage zone, consisting of vertically oriented mineralized collagen and the subchondral bone (osseous zone) . A slightly lower degree of anisotropy (0.8) is present compared to the osseous zone (0.84), which can be attributed to the infiltrated isotropic transition zone.…”

The Functional Response of Mesenchymal Stem Cells to Electron‐Beam Patterned Elastomeric Surfaces Presenting Micrometer to Nanoscale Heterogeneous Rigidity

“…[7] Critically, substrates possessing bulk rigidity of circa 20-50 kPa have been previously shown to induce stem cell differentiation to cartilage and bone specific lineages in vitro. [7,17] Poly(dimethylsiloxane) (PDMS), in particular, has recently found widespread use in cell adhesion/migration assays [18] microfluidic and MEMS technologies [19] due to its favorable optical, biocompatible and mechanical properties. Indeed, PDMS substrates have been used to study the role of extracellular rigidity on cellular adhesion [20] and differentiation, [21] due to the ease by which its rigidity may be precisely controlled by simply varying the base:accelerator ratio.…”

Current developments in 3D bioprinting for tissue engineering

“…Another principle used to enhance the mechanical properties of hydrogels is the use of nanofibers. These can be used to enforce a hydrogel by forming an internal random network [22] or, by aligning them, increasing the tensile strength [23] or tune the matrix compressive modulus [24].…”