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ABSTRACT: Herein, we report a first citric acid (CA)-derived in situ crosslinkable biodegradable polymer, poly(ethylene glycol) maleate citrate (PEGMC). The synthesis of PEGMC could be carried out via a one-pot polycondensation reaction without using organic solvents or catalysts. PEGMC could be in situ crosslinked into elastomeric PPEGMC hydrogels. The performance of hydrogels in terms of swelling, degradation, and mechanical properties were highly dependent on the molar ratio of monomers, crosslinker concentration, and crosslinking mechanism used in the synthesis process. Cyclic conditioning tests showed that PPEGMC hydrogels could be compressed up to 75% strain without permanent deformation and with negligible hysteresis. Water-soluble PEGMC demonstrated excellent cytocompatibilty in vitro. The degradation products of PPEGMC also showed minimal cytotoxicity in vitro. Animal studies in rats clearly demonstrated the excellent injectability of PEGMC and degradability of the in situ-formed PPEGMC. PPEGMC elicited minimal inflammation in the early stages post-injection and was completely degraded within 30 days in rats. In conclusion, the development of CA-derived injectable biodegradable PEGMC presents numerous opportunities for material innovation and offers excellent candidate materials for in situ tissue engineering and drug delivery applications.
Biomaterials 12/2010; 31(34):9092-105. · 7.40 Impact Factor
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ABSTRACT: Muscle stiffness and joint contractures are currently regarded as the most common complications of limb lengthening. To better understand the mechanisms of joint contractures, architectural changes of all involved muscles were analyzed in 9 goats after 20% tibial lengthening with standard distraction protocol.All 13 muscles of the goat's tibia were found to be organized into an anterior compartment with 2 longitudinal and 4 pennate muscles and a posterior compartment with 1 longitudinal and 6 pennate muscles. Longitudinal muscles showed better compliance to distraction than pinnate muscles. Although muscle-to-bone lengthening ratio ranged widely (0-1.2), most of the muscles and especially those located in the posterior compartment showed much less lengthening than the bone. Muscular portions of the muscles lengthened more substantially (average, 17%) than their associated tendons (average, 7%). Muscle fiber length changes varied greatly between muscles (range, 0%-88%). Normalization of muscle fiber length revealed considerable elongation of anterior muscles fibers (25%) that was associated with an addition of new sarcomeres in series. Fiber length increase of all posterior muscles but one occurred by stretching of existing sarcomeres, with little addition or even dissolution of sarcomeres in series. This correlated with muscle mass changes showing significant muscle atrophy in the posterior compartment and better mass preservation in the anterior compartment.The study revealed striking difference in response to limb lengthening between individual muscles and muscles from antagonistic compartments in particular. Poor sarcomerogenesis in the posterior muscles leading to their insufficient length increase seems to play major role in the development of joint contractures.
Journal of pediatric orthopedics 04/2009; 29(2):175-81. · 1.23 Impact Factor
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ABSTRACT: The purpose of this investigation was to examine the changes in unipennate muscle architecture after distraction osteogenesis. Nine adult goats underwent 20% tibial lengthening in one of the hind limbs. Immediately after distraction, lengthened and contralateral (untreated) tibialis caudalis (TC) muscles were harvested. Lengths of the muscle belly, muscle fiber (FL), sarcomere (SL), tendon (TL), and superficial aponeurosis, as well as muscle mass, pennation angle (PA), and physiological cross-sectional area (PCSA), were compared between the treated and contralateral sides. Lengthened TC muscle demonstrated 20.8% increase in belly length, 4.39% increase in TL, and 36.7% increase in FL, while PA decreased by 37.2% (P = 008). Muscle length increase was mainly due to lengthening of muscle belly, which resulted both from FL increase and 15.3% length increase in the aponeurosis component of muscle belly, without significant effect of the PA decrease. The FL increase was due to SL increase, not to sarcomere neogenesis, while mass and PCSA did not change. We concluded that although muscle architecture can be adversely affected by distraction because of deficient sarcomere neogenesis, PCSA can remain unchanged, giving false impression of preserved function. Change in PA plays only minimal role in muscle adaptation to distraction.
The Anatomical Record Advances in Integrative Anatomy and Evolutionary Biology 06/2007; 290(5):461-7. · 1.47 Impact Factor
