Effect of teriparatide on bone regenerate after distraction osteogenesis.

OBJECTIVE: To determine the effect of teriparatide on new bone formation in a rat model of distraction osteogenesis. METHODS: The experimental study was conducted at the Aga Khan University Hospital, Karachi, in November-December 2010, and comprised male Sprague-Dawley rats weighing 250gm each who were allocated to two treatment groups, teriparatide and saline, both given subcutaneously for 7 weeks. Femoral distraction was done for 3 weeks at the rate of 0.4mm/day, followed by a further 4 weeks for consolidation. New bone formation was assessed using X-ray scoring system, bone densitometry and histology. RESULTS: The 12 rats in the study were divided into two groups of 6(50%) each. All rats in the teriparatide group showed new bone formation whereas bone formation was present only in 2(33.3%) rats in the saline group. Bone densitometry showed that area (size) of the new bone formed adjacent to the margins of the osteotomy site as well as the total bone mineral content of the new bone was significantly higher (p<0.05) in the teriparatide group. Histological analysis showed larger but statistically insignificant (p>0.05) area of woven and trabecular new bone in the teriparatide group. CONCLUSIONS: The results suggested a promising role of parathyroid analogue therapy in distraction osteogenesis for promoting bone formation and consolidation. This may have strong clinical implications in cases of limb lengthening and bone transport.

Neuronal regeneration in denervated muscle following sensory and muscular neurotization.

BACKGROUND AND PURPOSE: Neurotization of denervated muscles has been shown to improve muscle bulk, but the neuronal regeneration response has not been compared previously in different surgical techniques of neurotization. Thus, using a rat model of experimental skeletal muscle denervation, we studied neuronal regeneration following sensory neurotization by two methods: sensory nerve to motor branch of muscle and direct sensory nerve implantation to muscle. MATERIAL AND METHODS: The lateral head of the gastrocnemius muscle was denervated in 36 rats, of which the first 12 served as denervated controls. In the second group of 12, the sural nerve was anastomosed to the motor branch of the gastrocnemius muscle (sensory-to-motor nerve neurotization) and in the remaining 12 rats the sural nerve was split into 4 fascicles and embedded into 4 quadrants of the muscle (direct sensory nerve-to-muscle neurotization). Immunohistochemistry was used to examine nerve fibers in muscle containing the sensory neuropeptides substance P (SP) and calcitonin gene-related peptide (CGRP), and general neuronal marker protein gene product 9.5 (PGP 9.5). RESULTS: Semiquantitative analysis showed that, compared to the control side, the number of nerve fibers on the experimental side was highest (p < 0.01) for group III (direct sensory nerve-to-muscle neurotization) for all 3 markers. The difference was 71%, 298%, and 254% for PGP 9.5, CGRP, and SP, respectively. INTERPRETATION: This method may be a good option for inducing neuronal regeneration in denervated muscles, and has therapeutic implications for prevention of atrophy of denervated muscles and as an adjunct for reconstruction of soft tissue defects.

Anti-inflammatory role of methotrexate in adjuvant arthritis: effect on substance p and calcitonin gene-related Peptide in thymus and spleen.

OBJECTIVE: To investigate the anti-inflammatory effect of methotrexate (MTX) in rats with adjuvant arthritis through its influence on the expression of proinflammatory neuropeptides, substance P (SP) and calcitonin gene-related peptide (CGRP) in immune organs, thymus and spleen. DESIGN: Phase-I pre-clinical trial. PLACE AND DURATION OF STUDY: The Aga Khan University, Karachi, from July to December 2003. MATERIALS AND METHOD: Adjuvant arthritis was induced in rats by inoculation with heat-killed mycobacteria. One group of arthritic rats (n=6) was treated with MTX (0.2 mg/kg body weight, subcutaneously) on every 4th day for a period of 18 weeks, while another group of arthritic rats (n=6) was treated with physiological saline served as control. At the end of experiment, animals were sacrificed and thymus and spleen were dissected and prepared for immunohistochemical analysis. The neuronal density of SP and CGRP immunoreactivity in thymus and spleen was assessed by semi-quantitative analysis. RESULTS: There was a marked reduction in hind paw swelling and inflammation in the MTX-treated rats after 18 weeks of treatment. Restoration of joint spaces (tibiotalar and subtalar) was seen after 9 weeks of MTX treatment. CGRP-positive nerve fibres were significantly reduced (p=0.0001) in thymus of rats treated with MTX compared to control rats. SP-positive nerve fibers were also found to be decreased in thymus of rats treated with MTX compared to controls, however, the decrease was not statistically significant. The neuronal density of SP and CGRP-immunoreactivity in spleen was not significantly different in MTX-treated and placebo-treated rats. CONCLUSION: In arthritic rats, MTX significantly reduced CGRP expression in thymus. Suppression of pro-inflammatory neuropeptides, such as CGRP and probably SP could be another mechanism by which MTX produces its anti-inflammatory effect in adjuvant arthritis.