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Edited* by Robert Langer, Massachusetts Institute of Technology, Cambridge, MA, and approved March 31, 2014 (received for review December 30, 2013)
Significance
The ability to regenerate functional cartilage from adult human mesenchymal stem cells would have tremendous clinical impact. Despite significant efforts, mechanically functional human cartilage has not been grown in vitro. We report engineering of functional human cartilage from mesenchymal stem cells, by mimicking the physiologic developmental process of mesenchymal cell condensation. Condensed mesenchymal bodies were induced to fuse and form mechanically functional cartilaginous tissue interfacing with bone, without using a scaffolding material. We demonstrate that this simple “biomimetic” approach can be used to generate centimeter-sized, anatomically shaped pieces of human cartilage with physiologic stratification and mechanical properties. Functional human cartilage grown from a patient’s own cells using this method could greatly accelerate the development of new therapeutic modalities for cartilage repair.
Abstract
The efforts to grow mechanically functional cartilage from human mesenchymal stem cells have not been successful. We report that clinically sized pieces of human cartilage with physiologic stratification and biomechanics can be grown in vitro by recapitulating some aspects of the developmental process of mesenchymal condensation. By exposure to transforming growth factor-β, mesenchymal stem cells were induced to condense into cellular bodies, undergo chondrogenic differentiation, and form cartilagenous tissue, in a process designed to mimic mesenchymal condensation leading into chondrogenesis. We discovered that the condensed mesenchymal cell bodies (CMBs) formed in vitro set an outer boundary after 5 d of culture, as indicated by the expression of mesenchymal condensation genes and deposition of tenascin. Before setting of boundaries, the CMBs could be fused into homogenous cellular aggregates giving rise to well-differentiated and mechanically functional cartilage. We used the mesenchymal condensation and fusion of CMBs to grow centimeter-sized, anatomically shaped pieces of human articular cartilage over 5 wk of culture. For the first time to our knowledge biomechanical properties of cartilage derived from human mesenchymal cells were comparable to native cartilage, with the Young’s modulus of >800 kPa and equilibrium friction coeffcient of <0.3. We also demonstrate that CMBs have capability to form mechanically strong cartilage–cartilage interface in an in vitro cartilage defect model. The CMBs, which acted as “lego-like” blocks of neocartilage, were capable of assembling into human cartilage with physiologic-like structure and mechanical properties.
Footnotes
- ↵1To whom correspondence should be addressed. E-mail: gv2131{at}columbia.edu.
Author contributions: S.B. and G.V.-N. designed research; S.B., R.E.E., and S.R.O. performed research; S.B., R.E.E., S.R.O., L.Q.W., G.A.A., and G.V.-N. analyzed data; and S.B. and G.V.-N. wrote the paper.
The authors declare no conflict of interest.
↵*This Direct Submission article had a prearranged editor.
This article contains supporting information online at www.pnas.org/lookup/suppl/doi:10.1073/pnas.1324050111/-/DCSupplemental.
Functional human cartilage grown in vitro
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