RESUMO
PURPOSE: To investigate the biomechanical response of the cornea, lamina cribrosa (LC), and prelaminar tissue (PT) to an acute intraocular pressure (IOP) increase in patients with markedly asymmetrical glaucoma and in healthy controls. PATIENTS AND METHODS: A total of 24 eyes of 12 patients with markedly asymmetrical primary open-angle glaucoma (POAG) and 12 eyes of 12 healthy patients were examined with spectral-domain optical coherence tomography (SD-OCT) and ocular response analyzer (ORA) at baseline and during acute IOP elevation by means of an ophthalmodynamometer. The displacement of the LC and PT and the change in corneal hysteresis (CH) and corneal resistance factor (CRF) were evaluated. RESULTS: Following a mean IOP increase of 12.3±2.4 mmHg, eyes with severe glaucoma demonstrated an overall mean anterior displacement of the LC (-6.58±26.09 µm) as opposed to the posterior laminar displacement in eyes with mild glaucoma (29.08±19.28 µm) and in healthy eyes (30.3±10.9; p≤0.001 and p=0.001, respectively). The PT displaced posteriorly during IOP elevation in all eyes. The CH decreased in eyes with severe glaucoma during IOP elevation (from 9.30±3.65 to 6.92±3.04 mmHg; p=0.012), whereas the CRF increased markedly in eyes with mild glaucoma (from 8.61±2.30 to 12.38±3.64; p=0.002) and in eyes with severe glaucoma (from 9.02±1.48 to 15.20±2.06; p=0.002). The increase in CRF correlated with the anterior displacement of the LC in eyes with severe glaucoma. CONCLUSION: Eyes with severe glaucoma exhibited a mean overall anterior displacement of the anterior laminar surface, while eyes with mild glaucoma and healthy eyes showed a posterior displacement of the LC during IOP elevation. The CH decreased significantly from baseline only in eyes with severe glaucoma, but the CRF increased significantly in all glaucomatous eyes. The CRF increase correlated with the anterior displacement of the LC in eyes with severe glaucoma.
RESUMO
Tendon ruptures are common sports-related injuries that are often treated surgically by the use of sutures followed by immobilization. However, tendon repair by standard technique is associated with long healing time and often suboptimal repair. Methods to enhance tendon repair time as well as the quality of repair are currently unmet clinical needs. Our hypothesis is that the introduction of a unique stem cell population at the site of tendon transection would result in an improved rate and quality of repair. Achilles tendons of fifty-one Sprague-Dawley rats were transected and suture-repaired. In half of the rats, a biodegradable scaffold seeded with allogenic circulating stem cells was placed as an onlay to the defect site in addition to the suture repair. The other half was treated with suture alone to serve as the control group. Animals were randomized to a two-, four-, or six-week time group. At the time of necropsy, tendons were harvested and prepared for either biomechanical or histological analysis. Histological slides were evaluated in a blinded fashion with the use of a grading scale. By two weeks, the experimental group demonstrated a significant improvement in repair compared to controls with no failures. Average histological scores of 0.6 and 2.6 were observed for the experimental and control group respectively. The experimental group demonstrated complete bridging of the transection site with parallel collagen fiber arrangement. By four weeks, both groups showed a continuing trend of healing, with the scaffold group exceeding the histological quality of the tissue repaired with suture alone. Biomechanically, the experimental group had a decreasing cross-sectional area with time which was also associated with a significant increase in the ultimate tensile strength of the tendons, reaching 4.2MPa by six weeks. The experimental group also achieved a significantly higher elastic toughness by six weeks and saw an increase in the tensile modulus, reaching 31Mpa by six weeks. The use of circulating stem cells as an adjunct in tendon repair demonstrates superior biomechanical properties and an improved level of histological organization, when compared to the suture alone control group. These improvements were not previously observed when gene therapy, protein therapy, or current tissue engineering technologies were used.