Matrix Biol. 2014 Aug 26. pii: S0945-053X(14)00159-0. doi: 10.1016/j.matbio.2014.08.006. [Epub ahead of print]

Genesis and morphogenesis of limb synovial joints and articular cartilage.

Decker RS¹, Koyama E², Pacifici M².

Abstract

Limb synovial joints are intricate structures composed of articular cartilage, synovial membranes, ligaments and capsule. Each joint has a unique shape, organization and biomechanical function, and articular cartilage itself is rather complex and organized in distinct zones, including the superficial zone that produces lubricans and contains stem/progenitor cells. There has been a great of interest for many years to decipher the mechanisms by which the joints form and come to acquire such unique structural features and diversity. Decades ago, classic embryologists discovered that the first overt sign of joint formation at each prescribed limb site is the appearance of a dense and compact population of mesenchymal cells collectively called the interzone. Work carried out since by several groups has provided evidence that the interzone cells do actively participate in joint tissue formation over developmental time. This minireview provides a succinct but comprehensive description of the many and important recent advances in this field of research. These includes: studies using various conditional reporter mice to genetically trace and track the origin, fate and possible function of joint progenitor cells; studies on the involvement and roles in signaling pathways and transcription factors in joint cell determination and functioning; and studies using advanced methods of gene expression analyses to uncover novel genetic determinants of joint formation and diversity. The overall advances are impressive, and the findings are not only of obvious interest and importance, but have major implications to conceive future translational medicine tools to repair and regenerate defective, overused or aging joints.