Alison Hart

Harvard Medical School, Boston, Massachusetts, United States

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Publications (5)17.91 Total impact

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    ABSTRACT: Clinical protocols utilize bone marrow to seed synthetic and decellularized allogeneic bone grafts for enhancement of scaffold remodeling and fusion. Marrow-derived cytokines induce host neovascularization at the graft surface, but hypoxic conditions cause cell death at the core. Addition of cellular components that generate an extensive primitive plexus-like vascular network that would perfuse the entire scaffold upon anastomosis could potentially yield significantly higher-quality grafts. We used a mouse model to develop a two-stage protocol for generating vascularized bone grafts using mesenchymal stem cells (hMSCs) from human bone marrow and umbilical cord-derived endothelial cells. The endothelial cells formed tube-like structures and subsequently networks throughout the bone scaffold 4-7 days after implantation. hMSCs were essential for stable vasculature both in vitro and in vivo; however, contrary to expectations, vasculature derived from hMSCs briefly cultured in medium designed to maintain a proliferative, nondifferentiated state was more extensive and stable than that with hMSCs with a TGF-beta-induced smooth muscle cell phenotype. Anastomosis occurred by day 11, with most hMSCs associating closely with the network. Although initially immature and highly permeable, at 4 weeks the network was mature. Initiation of scaffold mineralization had also occurred by this period. Some human-derived vessels were still present at 5 months, but the majority of the graft vasculature had been functionally remodeled with host cells. In conclusion, clinically relevant progenitor sources for pericytes and endothelial cells can serve to generate highly functional microvascular networks for tissue engineered bone grafts.
    Proceedings of the National Academy of Sciences 02/2010; 107(8):3311-6. · 9.74 Impact Factor
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    ABSTRACT: The complex intricate architecture of the liver is crucial to hepatic function. Standard protocols used for enzymatic digestion to isolate hepatocytes destroy tissue structure and result in significant loss of synthetic, metabolic, and detoxification processes. We describe a process using mechanical dissociation to generate hepatic organoids with preserved intrinsic tissue architecture from swine liver. Oxygen-supplemented perfusion culture better preserved organoid viability, morphology, serum protein synthesis, and urea production, compared with standard and oxygen-supplemented static culture. Hepatic organoids offer an alternative source for hepatic assist devices, engineered liver, disease modeling, and xenobiotic testing.
    Artificial Organs 01/2010; 34(1):75-8. · 1.96 Impact Factor
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    ABSTRACT: The objectives of this study were to evaluate the efficacy of poly(glycerol) sebacate (PGS) films for the prevention of visceroparietal peritoneal (VP) adhesions and demonstrate the ease of laparoscopic PGS film placement. Peritoneal adhesions occur in nearly 95% of all abdominal operations. VP adhesions can cause serious postoperative complications. The interposition of a barrier between damaged peritoneal areas during re-epithelialization has been shown to prevent adhesion formation. Current barrier products have serious drawbacks, including poor degradability, variable efficacy, and difficult handling characteristics. The efficacy of PGS films to prevent VP adhesions was evaluated in a rat peritoneal adhesion model. The animals were evaluated for the presence of VP adhesions at 3, 5, and 8 weeks. The laparoscopic applicability of PGS films was demonstrated by placement into a juvenile porcine abdomen using standard laparoscopic equipment and techniques. A statistically significant 94% reduction in VP adhesion formation rate was observed between control animals (75%) and animals with a PGS film barrier (4.8%). PGS films were easily placed in the juvenile porcine abdomen and could be readily repositioned without material loss or tissue damage. PGS films possess a unique combination of properties, including biocompatibility, resorbability, and ease of handling. PGS barrier films were shown to be efficacious in reducing VP adhesions in the rat model. They also can be placed using standard laparoscopic techniques. These promising results suggest that PGS films will be effective barriers to adhesion formation for patients undergoing open and laparoscopic abdominal operations.
    Surgery 10/2009; 146(3):490-7. · 3.37 Impact Factor
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    ABSTRACT: Poly(glycerol sebacate) (PGS), a promising scaffold material for soft tissue engineering applications, is a soft, tough elastomer with excellent biocompatibility. However, the rapid in vivo degradation rate of PGS limits its use as a scaffold material. To determine the impact of crosslink density on degradation rate, a family of PGS materials was synthesized by incrementally increasing the curing time from 42 to 144 h, at 120 degrees C and 10 mTorr vacuum. As expected, PGS became a stiffer, tougher, and stronger elastomer with increasing curing time. PGS disks were subcutaneously implanted into rats and periodically harvested; only mild tissue responses were observed and the biocompatibility remained excellent. Regardless of crosslink density, surface erosion degradation was observed. The sample dimensions linearly decreased with implantation time, and the mass loss rates were constant after 1-week implantation. As surface erosion degradation frequently correlates with enzymatic digestion, parallel in vitro digestion studies were conducted in lipase solutions which hydrolyze ester bonds. Enzymatic digestion played a significant role in degrading PGS, and the mass loss rates were not a function of curing time. Alternative chemistry approaches will be required to decrease the enzymatic hydrolysis rate of the ester bonds in PGS polymers.
    Journal of Biomedical Materials Research Part A 01/2009; 91(4):1038-47. · 2.83 Impact Factor
  • Otolaryngology-head and Neck Surgery - OTOLARYNGOL HEAD NECK SURG. 01/2009; 141(3).