Normal age-related viscoelastic properties of chondrons and chondrocytes isolated from rabbit knee / 中华医学杂志(英文版)

<p><b>BACKGROUND</b>The mechanical microenvironment of the chondrocytes plays an important role in cartilage homeostasis and in the health of the joint. The pericellular matrix, cellular membrane of the chondrocytes, and their cytoskeletal structures are key elements in the mechanical environment. The aims of this study are to measure the viscoelastic properties of isolated chondrons and chondrocytes from rabbit knee cartilage using micropipette aspiration and to determine the effect of aging on these properties.</p><p><b>METHODS</b>Three age groups of rabbit knees were evaluated: (1) young (2 months, n = 10); (2) adult (8 months, n = 10); and (3) old (31 months, n = 10). Chondrocytes were isolated from the right knee cartilage and chondrons were isolated from left knees using enzymatic methods. Micropipette aspiration combined with a standard linear viscoelastic solid model was used to quantify changes in the viscoelastic properties of chondrons and chondrocytes within 2 hours of isolation. The morphology and structure of isolated chondrons were evaluated by optical microscope using hematoxylin and eosin staining and collagen-6 immunofluorescence staining.</p><p><b>RESULTS</b>In response to an applied constant 0.3 - 0.4 kPa of negative pressure, all chondrocytes exhibited standard linear viscoelastic solid properties. Model predictions of the creep data showed that the average equilibrium modulus (E(∞)), instantaneous modulus (E(0)), and apparent viscosity (m) of old chondrocytes was significantly lower than the young and adult chondrocytes (P < 0.001); however, no difference was found between young and adult chondrocytes (P > 0.05). The adult and old chondrons generally possessed a thicker pericellular matrix (PCM) with more enclosed cells. The young and adult chondrons exhibited the same viscoelastic creep behavior under a greater applied pressure (1.0 - 1.1 kPa) without the deformation seen in the old chondrons. The viscoelastic properties (E(∞), E(0), and m) of young and adult chondrons were significantly greater than that observed in young and adult cells, respectively (P < 0.001). The adult chondrons were stiffer than the young chondrons under micropipette aspiration (P < 0.001).</p><p><b>CONCLUSIONS</b>Our findings provide a theoretical model to measure the viscoelastic properties of the chondrons as a whole unit by micropipette aspiration, and further suggest that the properties of the chondrocytes and PCM have an important influence on the biomechanical microenvironment of the knee joint cartilage degeneration that occurs with aging.</p>

Repair of concurrent skin and nerve defect at palm and carpal on ulnar side with free medial plantar flap / 中华整形外科杂志

<p><b>OBJECTIVE</b>To explore a new method for repair of concurrent skin and nerve defect at palm and carpal on ulnar side.</p><p><b>METHODS</b>From April 2000 to August 2009, five cases with concurrent skin and nerve defect at palm and carpal on ulnar side were reconstructed with free medial plantar flaps. Palmar nervous proprii defect at ulnar side of little finger was repaired by the first toe tibia nervous proprii in one case. The superficial branch of radial nerve was applied to repair the defect of ulnar nerve, as well as its deep or superficial branch in two cases. The superficial branch of radial nerve was also used to repair the defect of superficial branch of ulnar nerve, common palmar digital nerve of the fourth finger, Little finger ulnar palmar nervous proprii in one case. The dorsal branch of ulnar nerve was applied to repair the defect of superficial branch of ulnar nerve, common palmar digital nerve of the fourth finger, little finger ulnar palmar nervous proprii in one case. The vascular bundle of medial plantar flap was anastomosed with ulnar vascular bundle. The wounds at donor sites were covered with free skin grafts which were obtained from upper leg.</p><p><b>RESULTS</b>All the flaps and skin grafts were survived completely. The five patients were followed up for six months to four years with no muscular atrophy or claw hand deformity. The esthetic result was satisfied. The Sensory of flaps and fingers recovered to S3 to S3+. The two-point discrimination distance on flaps was range from 7 mm to 10 mm. The postoperative comprehensive evaluation was excellent in the cases whose superficial and deep branches of ulnar nerve were repaired.</p><p><b>CONCLUSIONS</b>Free medial plantar flap is an effective method to repair concurrent skin and nerve defect at palm and carpal on the ulnar side.</p>