Student research award in the doctoral degree candidate category, Society for Biomaterials 23rd Annual Meeting, New Orleans, LA, April 30-May 4, 1997: Ectopic bone formation by marrow stromal osteoblast transplantation using poly(DL-lactic-co-glycolic acid) foams implanted into the rat mesentery

Abstract

Porous biodegradable poly(DL-lactic-co-glycolic acid) foams were seeded with rat marrow stromal cells and implanted into the rat mesentery to investigate in vivo bone formation at an ectopic site. Cells were seeded at a density of 6.83 x 10(5) cells/cm2 onto polymer foams having pore sizes ranging from either 150 to 300 to 710 microns and cultured for 7 days in vitro prior to implantation. The polymer/cell constructs were harvested after 1, 7, 28, or 49 days in vivo and processed for histology and gel permeation chromatography. Visual observation of hematoxylin and eosin-stained sections and von Kossa-stained sections revealed the formation of mineralized bonelike tissue in the constructs within 7 days postimplantation. Ingrowth of vascular tissue was also found adjacent to the islands of bone, supplying the necessary metabolic requirements to the newly formed tissue. Mineralization and bone tissue formation were investigated by histomorphometry. The average penetration depth of mineralized tissue in the construct ranged from 190 +/- 50 microns for foams with 500-710-microns pores to 370 +/- 160 microns for foams with 150-300-microns pores after 49 days in vivo. The mineralized bone volume per surface area and total bone volume per surface area had maximal values of 0.28 +/- 0.21 mm (500-710-microns pore size, day 28) and 0.038 +/- 0.024 mm (150-300-microns, day 28), respectively. As much as 11% of the foam volume penetrated by bone tissue was filled with mineralized tissue. No significant trends over time were observed for any of the measured values (penetration depth, bone volume/surface area, or percent mineralized bone volume). These results suggest the feasibility of bone formation by osteoblast transplantation in an orthotopic site where not only bone formation from transplanted cells but also ingrowth from adjacent bone may occur.

Scaffold Sheet Design Strategy for Soft Tissue Engineering

“…Many scaffold fabrication techniques previously reported have resulted in an uneven distribution of cells within the construct [13,14,15]. In the case of most in vivo tissue , a network of vascularization offers a maximum nutrient diffusion distance of about 200 μm, which is most likely the reason why most successful tissue engineered applications have resulted in the growth of tissues with cross sections less than 500 μm from the external surface of the scaffold [17,26].…”

“…Many scaffold processing and fabrication techniques such as fiber meshes [5], phase separation [6], solvent casting and particulate leaching [7], membrane lamination [8], and melt molding [9] have been utilized in a wide variety of applications including bone [10], cartilage [11], blood vessels [12], and heart valves [13]. Although these scaffolds have demonstrated promise, uneven cell distribution and nutrient delivery in the deep portion of the synthetic scaffolds (> 200 μm) due to the random mobility of cell suspension often compromise their successful uses in tissue engineering [14,15]. The seeded cells and matrix produced by cells at the scaffold periphery also act as a barrier to the diffusion of oxygen and nutrients into the interior of the scaffold.…”

Bone Tissue Engineering: State of the Art and Future Trends

“…Their chemical versatility and processability varies according to their structure and nature, and hence a direct comparison with the natural polymers can not be established. The most widely used are poly( α ‐hydroxy acids),106–129 poly( ε ‐caprolactone),130–135 poly(propylene fumarates),127,136–144 poly(carbonates),145–149 poly(phosphazenes),127,150–152 and poly(anhydrides) 127,153,154. Further details on the origin and characteristics of these materials can be found in Table 3.…”

“…Current state of the art within the bone TE field consists of the use of MSCs isolated from the bone marrow combined with 3D biodegradable porous scaffolds 34,55,57,60–63,108,120,279–282. It is known that when exposed to dexamethasone they differentiate towards the osteogenic lineage 210.…”

Bioactive polymeric scaffolds for tissue engineering

“…In order to fulfill both the mechanical strength and provide environment conducive for vascularization, PLGA scaffolds have especially been deemed viable candidates for bone tissue engineering, particularly when blended with other bioactive materials for greater cell attachment [64,182]. Sheik et al recently presented a novel PLGA/silk hybrid scaffold for bone tissue engineering applications in which the degradation rate of PLGA was combined with the hydrophilic silk polymer, as well as hydroxyapatite nanoparticles to further improve biocompatibility, and effectiveness was evaluated both in vitro and in vivo [183].…”