Histopathological Changes in Knee Joint Components after Spinal Cord Injury in Rats

Morphology of the stifle in agouti (Dasyprocta prymnolopha, Wagler 1831)

The agouti (Dasyprocta prymnolopha, Wagler 1831) is a wild rodent of great zootechnical potential, a fact that enables anatomical and morphological studies to support management actions with this animal. In this perspective, this study aimed to describe the anatomy and histology of the agouti stifle joint. Four adult agoutis were used, two females and two males. The animals were submitted to dissection and identification of the structures of the stifle joint. For light microscopy study, samples of the patellar ligament, cranial and caudal cruciate ligaments, medial and lateral collateral ligaments were used. Agouti has a highly congruent patellofemoral joint; elongated patella; medial and lateral fabellae at the proximal insertion of the gastrocnemius muscle; medial and lateral meniscus with lunula; in addition to the presence of the following ligament structures: patellar ligament, cranial and caudal cruciate ligaments, medial and lateral collateral ligaments, meniscofemoral ligament, caudal meniscal ligament of the medial meniscus, and medial and lateral cranial ligaments. The patellar ligament presents bundles of parallel collagen fibers with a straight path and coated fibroblasts; collateral and cruciate ligaments had loose and dense connective tissue, coated fibroblasts and collagen bundle undulations, the latter most expressive in the caudal cruciate ligament. Thus, except for the shape and angulation of the stifle, which allows specific movements, the agouti stifle has structures analogous to that of other rodents and domestic animals.

Differences in Cartilage Repair between Loading and Unloading Environments in the Rat Knee

We investigated the histopathological and immunohistochemical effects of loading on cartilage repair in rat full-thickness articular cartilage defects. A total of 40 male 9-week-old Wistar rats were studied. Full-thickness articular cartilage defects were created over the capsule at the loading portion in the medial condyle of the femur. Twenty rats were randomly allocated into each of the 2 groups: a loading group and a unloading group. Twenty rats from these 2 groups were later randomly allocated to each of the 2 groups for evaluation at 1 and 2 weeks after surgery. At the end of each period, knee joints were examined histopathologically and immunohistochemically. In both groups at 1 and 2 weeks, the defects were filled with a mixture of granulation tissue and some remnants of hyaline cartilage. The repair tissue was not stained with toluidine blue in both groups. Strong staining of type I collagen was observed in the repair tissue of both groups. The area stained with type I collagen was smaller in the unloading group than in the loading groups, and the stained area was smaller at 2 weeks than at 1 week. In the staining for type II collagen, apparent staining of type II collagen was observed in the repair tissue of both groups at 1 week. At 2 weeks, there was a tendency toward a higher degree of apparent staining in the loading group than in the unloading group. Accordingly, these results indicated that loading and unloading in the early phase of cartilage repair have both merits and demerits.