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Rotator cuff repair (RCR) is a crucial surgical procedure, but has unacceptable mechanical failure rates between 25–60%. Examining supplemental synergistic interventions, such as biological augmentations (ex: growth factors) to improve fibrocartilage formation rather than scar tissue formation, would make tears more amenable to surgical repair. Due to the large number of agents and application methods (and times), improved techniques are needed for assessing RCR in animals. In particular, high-resolution real-time imaging is needed to guide tissue engineering in animal models. Optical coherence tomography (OCT) is well suited for this role, with resolutions 25 × greater than any clinical imaging modality and an ability to identify organized collagen with polarization sensitive techniques. For example, it can determine severe collagen depletion in visually normal tendons. The images here show the first OCT and PS-OCT of the rotator cuff in male Wistar rats. The structure of the supraspinatus tendon, enthesis, and humerus are well defined. For histological comparison, this sample was stained with both Masson's Trichrome, to expose any structural abnormalities, and Picrosirius Red, to determine collagen content using a polarization filter. OCT studies offer the potential of understanding RCR failure mechanisms and potential tissue altering agents, substantially impacting outcomes.

Cartilage can redistribute human body’s daily loads and decrease the friction force in the diarthrodial joints. However, it may be injured due to trauma, sports injury, biomechanical imbalance, and genetic disease. Microfracture (MF), osteochondral autograft transplantation (OAT), and autologous chondrocyte implantation (ACI) are the most common treatment procedures in the hospital. Recently, the concept of tissue engineering involving the combination of cells, scaffolds, and bioactive signals has inspired researchers. Our team of researchers synthesized a tri-copolymer from biological polymer by using gelatin, chondroitin-6-sulfate, and hyaluronic acid through cross-linking reaction. Lacuna formation could be seen in the tri-copolymer surrounding the chondrocytes, and some newly formed glycosaminoglycan was found in the engineered cartilage. Considering the dedifferentiation possibility of chondrocyte, bone marrow mesenchymal stem cells (BMSCs) become an ideal cell source for cartilage tissue regeneration, since they can be easily harvested from adult tissue, and be expanded in vitro. In an in-vivo porcine pilot study, the results showed that the defect site could be regenerated by BMSCs/collagen gel, and is formed with fibro/hyaline mixed cartilage tissue after implantation for six months. Several clinical studies using BMSCs for cartilage defect treatment were also conducted recently; clinical outcomes such as IKDC, Lysholm, and Tegner scores improved when the cartilage defects were repaired by several millions of mesenchymal stem cells, and there is no tumor formation after being treated with BMSCs during the 10-year follow-up. Moreover, recently a commercial BMSCs/collagen gel composite for cartilage repair was developed in Taiwan and clinical trial was conducted in 2008; the results showed that there is an improvement in IKDC and MRI scores during the nine-year follow-up. It seems that using an engineered cartilage made from BMSCs/collagen gel for cartilage defect treatment is a promising method.

The chemical reactions and physical effects involved in the cessation of bone formation with age, the formation of blood and other cells in bone marrow plus the development of osteoporosis and the link of the latter to anaemia and diabetes are reconsidered with respect to the physical and biochemical conditions present in the human body.