Lesions in the joint surface are commonly treated with osteoarticular autograft transfer system (OATS), autologous cell implantation (ACI/MACI), or microfracture. Tissue formed buy the latter commonly results in mechanically inferior fibrocartilage that fails to integrate with the surrounding native cartilage, rather than durable hyaline cartilage. Fractional laser treatment to make sub-millimeter (<500 µm) channels has been employed for tissue regeneration in the skin to facilitate rejuvenation without typical scarring. Additionally, we have pioneered a means to generate articular cartilage matrix from chondrocytes—dynamic Self-Regenerating Cartilage (dSRC). Combining these two approaches by performing fractional laser treatment of the joint cartilage and treating with dSRC is a new paradigm for joint surface restoration. This approach was refined in a series of in vitro experiments and tested in swine knee defects during a 6-month study in 12 swine.

dSRC are generated by placing 10⁷ swine knee chondrocytes into sealed 15-mL polypropylene tubes and cultured on a rocker at 40 cycles per minute for 14 days at 37°C. The chondrocytes aggregate and generate new extracellular matrix to form a pellet of dSRC. Channels of approximately 300-500 µm diameter were created by infrared laser ablation in swine cartilage (in vitro) and swine knees (in vivo). The diameter and depth of the ablated channel in the cartilage was controlled by the light delivery parameters (power, spot size, pulse duration) from a fractional 2.94 µm Erbium laser. The specimens were evaluated with histology (H&E, safranin O, toluidine blue) and polarized-sensitive optical coherence tomography for collagen orientation.

We can consistently create laser-ablated channels in the swine knee and successfully implant new cartilage from dSRC to generate typical hyaline cartilage in terms of morphology and biochemical properties. The neocartilage integrates with host cartilage in vivo.

These findings demonstrate our novel combinatorial approach for articular cartilage rejuvenation.

The purpose of this study was to assess the physical, biochemical and biomechanical properties of a cartilage matrix-chondrocyte-fibrin glue composite as biological tool for cartilage repair.

Chondrocytes were enzymatically isolated from pig joints and resuspended in fibrinogen solution. Articular cartilage was harvested from pig joints, chopped into small chips and lyophiliaed. Cartilage chips were rehydrated and mixed with the cell/fibrinogen solution and with thrombin, in order to form a fibrin glue gel composite with cells and chips (group A). Control composites were made from lyophilised cartilage chips assembled with fibrin glue, but not containing chondrocytes (group B). Other control groups included fibrin glue/chondrocyte specimens without cartilage chips (group C) and specimens made of the fibrin glue alone (group D). All samples were weighed and implanted into subcutaneous pouches of nude mice. Animals were sacrificed at 2 and 9 weeks. Samples were evaluated grossly and the final/initial mass ratio was calculated. Samples were evaluated histologically, biomechanically, and biochemically.

Upon retrieval, only the samples in experimental group A retained their original pre-implantation mass. Histological analysis showed newly formed cartilage matrix in the specimens from group A and C. Biomechanical analysis showed significantly higher modulus in experimental samples, with respect to the other groups at the latest time point. Analysis of hydraulic permeability showed significantly decreasing values for all groups throughout the experimental times and lowest values for the experimental samples of group A in the latest time point, although there was no statistically significant difference among the groups. Biochemical analysis demonstrated higher values in the latest time point for samples prepared with cells for water and GAG content, whereas highest values for hydroxyproline were recorded for samples assembled with cartilage chips. DNA analysis showed higher values of samples prepared with chondrocytes and fibrin glue and also an important increase in values of the samples made of fibrin glue only, indicating a possible host fibroblast growth inside the samples over time. This tissue-engineered composite presents cartilaginous appearance and biomechanical integrity after 9 weeks in vivo.