Stem Cells and Cartilage Development: Complexities of a Simple Tissue

Abstract

Cartilage is considered to be a simple tissue that should be easy to engineer because it is avascular and contains just one cell type, the chondrocyte. Despite this apparent simplicity, regenerating cartilage in a form that can function effectively after implantation in the joint has proven difficult. This may be because we have not fully appreciated the importance of different structural regions of articular cartilage or of understanding the origins of chondrocytes and how this cell population is maintained in the normal tissue. This review considers what is known about different regions of cartilage and the types of stem cells in articulating joints and emphasizes the potential importance of regeneration of the lamina splendens at the joint surface and calcified cartilage at the junction with bone for long-term survival of regenerated tissue in vivo. Stem Cells 2010;28:1992–1996

Transient vascularization of transplanted human adult–derived progenitors promotes self-organizing cartilage

“…In addition, we quantified the number of Ki67-positive cells in the chondral layer, and the results tissue. Due to the simplicity of this tissue, tissue engineering is considered to be the most promising and relevant method for treating chondrogenic defects (10). Although previous molecular studies have shown that mesenchymal progenitors or dedifferentiated chondrocytes can be stimulated to adopt a chondrogenic fate by extrinsic factors, such as TGFs or FGFs (11), little is known about the cellular dynamics that allow progenitor cells to form a 3D mass of cartilage.…”

Bilayer Implants

“…66 Since our acellular implants accommodated MSCs they theoretically should be able to form some zonal organization even throughout the uniform scaffold. 41 As summarized by Hollander et al, 44 bone marrow-derived MSCs have a tendency to differentiate into hypertrophic chondrocytes in the deep zones of articular cartilage, whereas the same population of MSCs located in the upper layers remain in a prehypertrophic state. Moreover, the superficial zone seems to originate from MSCs that have a different phenotype than MSCs found in the deeper zones.…”

miRNA Control of Tissue Repair and Regeneration

“…Under in vivo conditions, the artificial implant undergoes terminal differentiation, followed by ossification. 104 Addition of miR-133 prevents such unwanted ossification. 105 Furthermore, addition of miR-675 and miR-221 promotes expression of collagen II and proliferation of mature chondrocytes.…”