Tissue engineering seeks to translate scientific knowledge into tangible
products to advance the repair, replacement, or regeneration of organs and
tissues. Current tissue engineering strategies have progressed recently from a
historical approach that is based primarily on biomaterials to a cell and
tissue-based approach that includes understanding of cell-sourcing and
bioactive stimuli. New options include methods for harvest and transplantation
of tissue-forming cells, bioactive matrix materials that act as tissue
scaffolds, and delivery of bioactive molecules within scaffolds. These
strategies are already benefiting patients, and they place increasing demands
on orthopaedic surgeons to have a solid foundation in the contemporary
concepts and principles of cell-based tissue engineering.
Essentially all orthopaedic tissue engineering strategies can be distilled
to a strategy or combination of strategies that seek to increase the number or
relative performance of bone-forming cells. The global term connective
tissue progenitors has been used to define the heterogeneous populations
of stem and progenitor cells that are found in native tissue and that are
capable of differentiating into one or more connective tissue phenotypes.
These stem or progenitor populations are found in various tissue sources, with
varying degrees of ability to differentiate along connective tissue lineages.
Available cell-based strategies include targeting local cells with use of
scaffolds or bioactive factors, or transplantation of autogenous connective
tissue progenitor cells derived from bone marrow or other tissues, with or
without processing to change their concentration or prevalence. The future may
include means of homing circulating connective tissue progenitor cells with
use of intrinsic chemokine systems, or modifying the biological performance of
connective tissue progenitor cells by means of genetic modifications.