DESCRIPTION (provided by applicant): Bone scaffolds should provide adequate load bearing and enhance tissue regeneration. However, at present, there is little rigorous comparative information that will tell one that a given material with a given architecture design will provide adequate load bearing and give the best bone regeneration. As a starting point, we associate load bearing with effective elasticity and strength, and enhanced tissue regeneration with permeability material as design variables. Then the fundamental question becomes "can scaffolds be designed to maintain minimum loading bearing characteristics while maximizing permeability and how important is permeability for bone regeneration relative to material osteoconductivity?" We hypothesize that Bone tissue engineering scaffolds should be fabricated from the most osteoconductive material with maximal permeability to enhance bone regeneration. Furthermore, the scaffold design should be such that the mechanical properties at time 0 can achieve a modulus of 50 MPa and compressive strength of 2 MPa, within the range of human trabecular bone. Related to this hypothesis, we seek to answer the questions: 1) can scaffolds be designed to meet the minimum 50/2 MPa stiffness/strength criteria and how does degradation of these mechanical properties depend on permeability and material?, and 2) does permeability play a significant role in bone regeneration or is material an overwhelming factor? We will answer these fundamental scaffold design questions through three specific aims: Specific Aim 1: Computationally design and fabricate scaffolds architectures from HA/TCP, PLLA, and PCL at a single porosity of 60% with maximal and sub-maximal permeability Specific Aim 2: Determine elastic modulus and ultimate strength of designed scaffolds at 0 meet minimum human trabecular bone values. Determine how design/material influence degradation of mechanical properties. Specific Aim 3: Determine the influence of designed permeability and material on bone regeneration in a mouse model at 8, and 16 weeks by delivering BMP-7 transduced human fibroblasts. This study will give bone tissue engineers critical information as to as to the relative importance of scaffold permeability and material bone tissue scaffold design, which will be crucial for clinical bone tissue engineering applications.