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Tessa Hadlock

Publications and source records attributed to Tessa Hadlock.

5 recordsLinked to original sources
PubMed2003

Manufacture of porous polymer nerve conduits by a novel low-pressure injection molding process.

A method to fabricate porous, biodegradable conduits using a combined injection molding, thermally induced phase transition technique was developed which produced conduits with dimensionally toleranced, longitudinally aligned channels. The geometry of the channels was designed to approximate the architecture of peripheral nerves and to support the monolayer adherence of physiologically relevant numbers of Schwann cells. The channel configuration could be varied from a single 1.35 mm diameter channel up to 100 0.08 mm diameter channels. A conduit with 100 channels has approximately 12.5 times the lumenal surface area of a single channel conduit and supports the adherence of five times the number of Schwann cells in the native peripheral nerve. In this study, poly(DL-lactide-co-glycolide) (DL-PLGA) was dissolved in acetic acid and injected into a cold mold which induced solid-liquid phase separation and, ultimately, solidification of the polymer solution. The acetic acid was removed by sublimation and the resulting foam had a macrostructure of high anisotropy. Semi-permeable skins formed on the outer and lumen diameters of the conduit as a consequence of rapid quenching. Macropores were organized into bundles of channels, up to 20 microm wide, in the DL-PLGA matrix and represented remnants of acetic acid that crystallized during solidification.

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PubMed2003

Tissue engineered muscle implantation for tongue reconstruction: a preliminary report.

OBJECTIVES/HYPOTHESIS: Because current tongue reconstructive methods introduce adynamic, variably sensate tissue into the mouth, the critical functions of the tongue in articulation and deglutition may be compromised. The objective of this work was to introduce a combination of myoblasts and scaffolding material into rat hemiglossectomy defects and to examine the extent of neomuscle formation in the reconstructed area, under the hypothesis that the presence of myoblasts leads to formation of new muscle. STUDY DESIGN: Randomized, prospective animal study. METHODS: Myoblasts were harvested from neonatal Lewis rats, and a growth factor enriched collagen gel was prepared. Syngeneic adult animals received either hemiglossectomy alone or reconstruction with one of four experimental reconstructive preparations: collagen gel alone, collagen gel with suspended myoblasts, the gel-cell combination in undifferentiated muscle construct form by way of tissue culture for 7 days in a preformed mold, or differentiated constructs, cultured in myoblast fusion medium. After 6 or 16 weeks, animal weight gain was recorded, animals were killed, and the tongues harvested. The tissue was examined histologically, and quality of the muscular regenerate was rated on a scale according to predefined criteria. RESULTS: Animals in all groups gained weight appropriately. In groups receiving hemiglossectomy alone or acellular (gel only) reconstruction, there was significant scarring and lack of neomuscle formation. In groups receiving myoblast transplantation, either by way of gel suspension or in the form of undifferentiated or differentiated constructs, muscle quality was superior to controls. CONCLUSIONS: Myoblast transplantation into hemiglossectomy defects appears to lead to new muscle formation and does not inhibit normal weight gain in animals after tongue implantation.

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PubMedDate not supplied

Muscle tissue engineering for partial glossectomy defects.

BACKGROUND: Tongue reconstruction represents a difficult reconstructive problem, based on the tongue's complex multimodality function. Existing methods of tongue reconstruction often result in significant deficits in speech and deglutition. A functional neotongue requires adequate soft tissue bulk and restoration of coordinated muscle function. Tissue engineering, a scientific approach that allows introduction of isolated cell populations of interest within 3-dimensional polymer scaffolds to create new tissue, may allow the generation of more highly functional tissue in tongue reconstruction. OBJECTIVES: To apply muscle-tissue engineering techniques in the reconstruction of partial glossectomy defects in rats, and to compare the gross and histological nature of tissue found after reconstruction of the hemiglossectomy defect with acellular vs tissue-engineered composite material. MATERIALS AND METHODS: Thirty mature Lewis rats underwent a left-sided mucosa-sparing partial glossectomy. The defects were then filled with 1 of the following 3 substances: isotonic sodium chloride solution, a collagen-rich hydrogel, or hydrogel containing a suspension of neonatal myoblasts from syngeneic rats. The animals were killed after 6 weeks and the tongues were harvested. The control and operated-on tongue halves were evaluated for weight differences and histological features. RESULTS: The group receiving the hydrogel-myoblast composite injections demonstrated a statistically significant increase in tongue weight of the operated-on side compared with the control side. In contrast, the isotonic sodium chloride solution and hydrogel groups demonstrated loss of tongue weight. These findings correlated with the results of the histological evaluation. Hemitongues from the composite group demonstrated formation of new tissue with areas of musclelike tissue extending from islands of residual hydrogel, and we found evidence of neovascularization and possible neurotization. In contrast, the isotonic sodium chloride solution group exhibited dense fibrous scar with loss of muscle architecture and dramatic loss of tongue volume. The hydrogel group demonstrated preservation of tongue volume with persistent islands of gel, but no clear evidence of new tissue formation. CONCLUSIONS: The introduction of a hydrogel into the rat hemiglossectomy pocket appears to promote volume preservation and/or muscle regeneration. The addition of myoblasts suspended in collagen gel supports the development of new tissue that preserves weight and volume after hemiglossectomy and may possess muscle properties similar to the tissue desired. This tissue-engineering approach represents a promising new strategy in tongue reconstruction and merits further investigation into the possible functional advantages it offers compared with current techniques.

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PubMedDate not supplied

Baiting the cross-face nerve graft with temporary hypoglossal hookup.

BACKGROUND: Cross-face nerve grafting yields inconsistent neural regeneration, and methods that promote more robust axonal traversing of the graft would expand the indications for this procedure. OBJECTIVE: To test the hypothesis that hooking a cross-face nerve graft distally to a source of denervated muscle, rather than leaving it in the subcutaneous space, would positively affect neural ingrowth across the graft, based on elaboration of neurotrophins from the musculature. METHODS: Twenty-four rats underwent cross-face nerve grafting in which the right facial nerve buccal branch was transected and coapted to the graft. The graft was placed across the neck and into the left side of the face. The distal end of the graft was placed either in the left subcutaneous space, coapted to the marginal mandibular branch of the left facial nerve, or coapted to the distal stump of the transected left hypoglossal nerve. Eight control animals underwent right buccal branch transection and placement of a cross-face nerve graft without any proximal and distal hookup. After 12 weeks, all experimental groups underwent hookup of the distal nerve graft to the left facial nerve buccal branch. Vibrissal function was assessed during the ensuing 12 weeks, and then the graft was harvested for histomorphometric analysis. RESULTS: After 12 weeks, there was a significant difference in axon counts between the group coapted distally to the tongue (hypoglossal hookup) and that coapted to the facial musculature (marginal hookup). Twelve weeks later, after distal cross-face nerve graft hookup, this difference was not statistically significant, although the hypoglossally baited group demonstrated statistically significantly greater fiber maturity. Recovery of vibrissal movement did not differ among treatment groups. CONCLUSION: Baiting the cross-face nerve graft via temporary hookup to the distal hypoglossal nerve and tongue musculature appears to improve nerve ingrowth through a nerve graft across the face, although a corresponding improvement in facial muscle function was not observed.

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