An apparatus to enhance bone regeneration, comprising: a conduit (202, 311) having first and second open ends, wherein the apparatus, in use, connects a bone regeneration site to a source of multipotent mesenchymal cells; wherein the conduit (202, 311) is divided into first and second segments (326,320), the first segment formed from a material comprising calcium phosphate, the first segment having the first open end for ingress of physiological signals proximal to a bone regeneration site that promote multipotent mesenchymal cell differentiation and egress of mesenchymal cell differentiation products; and the second segment formed from a material comprising calcium phosphate, the second segment having the second open end configured to penetrate the source of multipotent mesenchymal cells for egress of the physiological signals and ingress of the mesenchymal cell differentiation products; wherein the segments (326,320), in use, directly connect the bone regeneration site and the source of multipotent mesenchymal cells to provide the conduit (202, 311) as an extravascular or transvascular conduit to enhance the bone regeneration in use; wherein the first segment and the second segment forming the conduit (202, 311) are arranged to have at least a partial opening between the segments at the intersection of the first and second segments (326, 320) for ingress and transit of additional functional cells, cytokines, growth factors, blood, and blood vessels to enhance the bone regeneration in use, characterized in that at least a portion of an inner surface of at least one segment (320, 326) is coated with calcium phosphate having a controlled rate of solubility in biological fluids in use. a conduit (202, 311) having first and second open ends, wherein the apparatus, in use, connects a bone regeneration site to a source of multipotent mesenchymal cells; wherein the conduit (202, 311) is divided into first and second segments (326,320), the first segment formed from a material comprising calcium phosphate, the first segment having the first open end for ingress of physiological signals proximal to a bone regeneration site that promote multipotent mesenchymal cell differentiation and egress of mesenchymal cell differentiation products; and the second segment formed from a material comprising calcium phosphate, the second segment having the second open end configured to penetrate the source of multipotent mesenchymal cells for egress of the physiological signals and ingress of the mesenchymal cell differentiation products; wherein the segments (326,320), in use, directly connect the bone regeneration site and the source of multipotent mesenchymal cells to provide the conduit (202, 311) as an extravascular or transvascular conduit to enhance the bone regeneration in use; wherein the first segment and the second segment forming the conduit (202, 311) are arranged to have at least a partial opening between the segments at the intersection of the first and second segments (326, 320) for ingress and transit of additional functional cells, cytokines, growth factors, blood, and blood vessels to enhance the bone regeneration in use, characterized in that at least a portion of an inner surface of at least one segment (320, 326) is coated with calcium phosphate having a controlled rate of solubility in biological fluids in use.