AAHS ASPN ASRM - 2013 Annual Meeting - American Association ...

Inside-Out Tissue Engineering: Using Explanted Microcirculatory Beds for Generating Vascularized Neo-Livers
Institution where the work was prepared: Stanford University, Stanford, CA, USA
Robert G. Bonillas, MD1; Cynthia Hamou1; Daniel J. Ceradini, MD2; Shahram Aarabi1; Geoffrey Gurtner1; (1)Stanford University, (2)New York University
Introduction:
Organ level tissue engineering is limited by the incorporation of a functional microvasculature and a reliable means for re-integration into the host circulation.
Our laboratory has described a technique using autologous explanted microcirculatory beds (EMBs) or free flaps as bio-scaffolds for engineering complex 3dimensional
constructs via their intact microvasculature. Here we investigated whether vascularized neo-livers could be generated with differentiated progenitor
cells (MSCs and MAPCs) or hepatocytes using this system.
Methods:
Superficial inferior epigastric EMBs (n=30) were explanted from rats and maintained ex vivo in a perfusion bioreactor system. 4.0x10^6 partially differentiated
progenitor cells (pMSCs or pMAPCs) or hepatocytes were infused via the afferent artery during the prolonged (>12hrs) ex vivo cultivation. Seeded EMBs were
replanted and harvested on post-replantation days 3, 7, 14 and 21. Seeding efficiency was determined by immunohistochemistry and FISH analysis, and proliferation
by BrdU/Ki67 assays. Seeded cell fate was ascertained using real time RT-PCR and albumin staining.
Results:
Progenitor cells and hepatocytes seeded ex vivo egressed in bulk from the microcirculation and formed BrdU+/Ki67+ proliferative clusters in the perivascular
space following re-implantation. Seeded EMBs formed vascularized neo-livers which retained features up to 21 days following replantation. Both cell types
remained localized to the EMB without evidence of re-homing or immunological reaction. Ongoing studies are determining the functional capacity of these
neo-livers in replacing albumin levels in a rat model of analbuminemia.
Conclusion:
Here we demonstrate the construction of vascularized neo-livers using progenitor/stem cells and EMBs. The abundance of autologous EMBs, the sustainability
of them ex vivo, and the ability to seed them with large numbers of progenitor cells makes this "inside-out" tissue engineering paradigm attractive for generating
organ-level tissue constructs.
De Novo Bone Formation by Adult Adipose Derived Stem Cells in Prefabricated Vascularized Capsules in Rats
Institution where the work was prepared: Southern Illinois University School of Medicine, Springfield, IL, USA
Minh-Doan Nguyen, MD; Hans Suchy; Jagadish Hegde; Chris Chambers; Michael Neumeister; Southern Illinois University School of Medicine
Introduction:
Bony defects of the extremities and the mandible secondary to trauma, tumor resection, or congenital deformity present significant morbidity for the patient,
cost to society and a challenging problem for the reconstructive surgeon. Current practices are limited by the size of the defect that can be repaired, poor viability/functionality
post-transplant and morbidity at the donor tissue site. An engineered tissue composed of osteoblast progenitors, a biocompatible scaffold
and functional microvascular network could eliminate most, if not all, of the above mentioned complications. Initial results of this study demonstrate possible
de novo bone formation from adipose derived stem cells (ADSC) in a calcium hydroxyapatite and alginate/collagen matrix.
Methods:
Subcutaneous fibrovascular capsules were created in the inguinal region of adult male Lewis rats. ADSCs obtained from male Lewis rats were suspended in an
alginate/collagen matrix or seeded in a calcium hydroxyapatite matrix and implanted into the prefabricated capsules with and without femoral bone fragments.
X-ray images of the constructs were obtained for 6-12 weeks to monitor changes in bone density. At the end of each time point, the constructs were removed
and histological analysis (H&E) was performed to identify bone formation.
Results:
Radiographic analysis of the composite bone constructs by Faxitron demonstrated an increase in bone density over time. On histological examination, the ADSCs
are viable and there seems to be focal areas of de novo bone formation.
Conclusions:
Both radiographic and histological analysis of the composite bone constructs suggest that there is some de novo bone formation by ADSCs in the prefabricated
vascularized capsules. The osteoconductive environment provided by the biocompatible matrices and the osteoinductive factors provided from the bone
marrow and osteogenic factors facilitate bone formation by implanted ADSCs.
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