Perspectives on endogenous and exogenous tissue engineering following injury to tissues of the knee

Abstract

The knee is a multi-component organ system comprised of several tissues which function coordinately to provide mobility. Injury to any one component compromises the integrity of the system and leads to adaptation of the other components. Over time, such events often lead to dysfunction and degeneration of the knee. Therefore, there has been considerable research emphasis to repair injured components in the knee including cartilage, menisci, and ligaments. Approaches to improving healing and repair/regeneration of knee tissues have included surgery, anti-sense gene therapy, injection of growth factors and inflammatory cytokine antagonists, transplantation of in vitro expanded chondrocytes, enhancement of endogenous cells via microfracture, injection of mesenchymal stem cells, and implantation of in vitro tissue engineered constructs. Some of these approaches have led to temporary improvement in knee functioning, while others offer the potential to restore function and tissue integrity for longer periods of time. This article will review the status of many of these approaches, and provide a perspective on their limitations and potential to contribute to restoration of knee function across the lifespan.

Messenger RNA profiling of rabbit quadriceps femoris after repeat injections of botulinum toxin: Evidence for a dynamic pattern without further structural alterations

“…It is known that muscle contains MSCs, which are capable of differentiating toward the adipogenic, chondrogenic, and osteogenic lineages . Such MSCs may be maintained in their undifferentiated state by the biomechanical environment of the muscle, which after induction of atrophy leads to the MSCs escaping such regulation and the preferential induction of the adipocyte lineage . In addition, exogenous MSCs may migrate into the modified muscle, and subsequently also differentiate into adipocyte‐lineage cells.…”

“…14,15 Such MSCs may be maintained in their undifferentiated state by the biomechanical environment of the muscle, which after induction of atrophy leads to the MSCs escaping such regulation and the preferential induction of the adipocyte lineage. 12,26 In addition, exogenous MSCs may migrate into the modified muscle, and subsequently also differentiate into adipocytelineage cells. To begin to determine whether expression of MSC-related molecular markers was altered in the BoNT-A-treated animals, we assessed expression of a marker for each of the 3 lineages.…”

Why Mesenchymal Stem/Progenitor Cell Heterogeneity in Specific Environments? <br/>—Implications for Tissue Engineering Applications Following Injury or Degeneration of Connective Tissues

“…While the above discussion has raised issues regarding MSC/MPC cell heterogeneity, and the potential basis for such heterogeneity, it is clear that generating TEC in vitro with undifferentiated MSC/MPC leads to constructs that can adhere in vivo to defects in articular hyaline cartilage and adapt to become an effective repair tissue out to 1 year post-implantation in either adolescent or adult porcine models (discussed in [25]- [27]). Furthermore, osteo-TEC constructs also become integrated in both porcine and rabbit models [28] [29].…”

The Characterization of Acid Soluble Collagen from Sheep Tail Tendon

“…Tendons are functional connective tissue, have a rich extracellular matrix, while the cellular structure constitutes approximately 20% of total tissue volume, the remaining cells form 80% of the extracellular matrix. The cellular matrix is mainly composed of collagen fibers and other connective proteins such as proteoglycan, elastin, and other proteins [1,2].…”