Progenitor cells: role and usage in bone tissue engineering approaches for spinal fusion.

Advancement of in vitro osteogenesis, or the production of bone, is a complex process that has significant clinical implications. Surgical intervention of several spinal disorders entails decompression of the spinal cord and nerves which can lead to subsequent biomechanical instability of the spine. Spinal arthrodesis (fusion) is often required to correct this instability and necessary to eliminate the resulting pathological motion of vertebral segments.

Vascularized bone tissue engineering: approaches for potential improvement.

Significant advances have been made in bone tissue engineering (TE) in the past decade. However, classical bone TE strategies have been hampered mainly due to the lack of vascularization within the engineered bone constructs, resulting in poor implant survival and integration. In an effort toward clinical success of engineered constructs, new TE concepts have arisen to develop bone substitutes that potentially mimic native bone tissue structure and function.

Engineering articular cartilage with spatially-varying matrix composition and mechanical properties from a single stem cell population using a multi-layered hydrogel.

Despite significant advances in stem cell differentiation and tissue engineering, directing progenitor cells into three-dimensionally (3D) organized, native-like complex structures with spatially-varying mechanical properties and extra-cellular matrix (ECM) composition has not yet been achieved. The key innovations needed to achieve this would involve methods for directing a single stem cell population into multiple, spatially distinct phenotypes or lineages within a 3D scaffold structure. We have previously shown that specific combinations of natural and synthetic biomaterials can direct marrow-derived stem cells (MSC) into varying phenotypes of chondrocytes that resemble cells from the superficial, transitional, and deep zones of articular cartilage.

Unique biomaterial compositions direct bone marrow stem cells into specific chondrocytic phenotypes corresponding to the various zones of articular cartilage.

Numerous studies have reported generation of cartilage-like tissue from chondrocytes and stem cells, using pellet cultures, bioreactors and various biomaterials, especially hydrogels. However, one of the primary unsolved challenges in the field has been the inability to produce tissue that mimics the highly organized zonal architecture of articular cartilage; specifically its spatially varying mechanical properties and extra-cellular matrix (ECM) composition. Here we show that different combinations of synthetic and natural biopolymers create unique niches that can "direct" a single marrow stem cell (MSC) population to differentiate into the superficial, transitional, or deep zones of articular cartilage.