No abstract

Our work focuses on development of a collagen-glycosamimoglycan (CC) scaffold to facilitate ligament healing in the gap between the ruptured ends of the human anterior cruciate ligament (ACL). In the present investigation, we evaluated the effects of selected growth factors on human ACL cell responses important in tissue regeneration, namely cell migration, proliferation, collagen production, and expression of a-smooth muscle actin (SMA).Methods: Explants from six human ACLs were cultured on top of a CG scaffold. Culture conditions were with either 2% FBS (control), or 2% FBS supplemented with TGF-01, PDGF-AB, EGF, or FGF-2. Histologic cell distribution, total DNA content, proliferation rate, rate of collagen synthesis, scaffold diameter and percentage of SMA positive cells were determined at two, three and four weeks.Results: The addition of TGF-01 to the culture medium resulted in increased cell number, increased collagen production and increased expression of SMA within the scaffold. Supplementation with PDGF-AB resulted in increased cell proliferation rates within the scaffold and increased collagen production. The addition of FGF-2 resulted in increased cell proliferation rates and slowed rates of scaffold shrinkage when compared with the control group.Discussion: This work suggests that certain growth factors can alter the biologic functions of human ACL cells in a CG scaffold implanted as a bridge at the site of an ACL rupture. Based on these findings, the addition of selected growth factors to an implantable CG scaffold may facilitate ligament healing in the gap between the ruptured ends of the human ACL.

To investigate the long-term in vivo effect of laser dosimetry on rabbit septal cartilage integrity, viability, and mechanical behavior. Methods: Nasal septal cartilage specimens (control and irradiated pairs) were harvested from 18 rabbits. Specimens were mechanically deformed and irradiated with an Nd:YAG laser across a broad dosimetry range (4-8 W and 6-16 seconds). Treated specimens and controls were autologously implanted into a subperichondrial auricular pocket. Specimens were harvested an average±SD of 208±35 days later. Tissue integrity, histology, chondrocyte viability, and mechanical property evaluations were performed. Tissue damage results were compared with Monte Carlo simulation models. Results: All laser-irradiated specimens demonstrated variable tissue resorption and calcification, which increased with increased dosimetry. Elastic moduli of the specimens were significantly either lower or higher than controls (all PϽ.05). Viability assays illustrated a total loss of viable chondrocytes within the laser-irradiated zones in all treated specimens. Histologic examination confirmed these findings. Experimental results were consistent with damage profiles determined using numerical simulations. Conclusion: The loss of structural integrity and chondrocyte viability observed across a broad dosimetry range underscores the importance of spatially selective heating methods prior to initiating application in human subjects.

The critical transition temperature region was determined by the sharp increase in bend angle at consecutive times of immersion at the same temperature. This range was determined to be 59-68 degrees C and 62-68 degrees C for porcine and rabbit cartilage, respectively. Similar transition zones for dosimetry occurred below 20.4 W/cm2 during cartilage irradiation in both species.