About our lab

The basic science studies of the lab presently include the characterization of progenitor cells from articular cartilage that have the potential to form stable articular cartilage when differentiated. These cells are clonable and can be expanded to provide sufficient cells for tissue engineering of novel implants for articular cartilage regeneration. We are currently exploring the molecular signature of these cells and defining markers for isolating them.

In applied studies, we are studying the effects of different cues on the development of cartilage from human clonal progenitor cells and comparing their responses with mesenchymal stem cells and articular cartilage chondrocytes. This work has allowed us to build tissue from the various cell types for potential implantation to fix cartilage pathologies. We are currently exploring how this work can be scaled up with use of scaffolds to provide implants of a clinically relevant size.

Recently, we have also extended the principles we have learned about stem cells in skeletal tissues such as the knee to examine the temporomandibular joint; studying potential ideas for the repair and regeneration of the joint articular disc.

In other work with scaffolds, the Johnstone lab is exploring alternative formulations of implants for use in spinal fusion surgery. These implants contain osteogenic cells and/or bioactive factors that stimulate local stem cells to differentiate into cartilage and bone. These implants will potentially reduce patients’ dependence on bone harvested from other sites in the body.

International recognition

As part of the International Combined Orthopaedic Research Societies (ICORS) global mission to promote the advancement of learning, scholarship, and excellence, the ICORS Fellow of International Orthopaedic Research (FIOR) was established. Dr Johnstone was honored to be inducted in the inaugural class in 2016. Fellows selected display a status of excellent professional standing and high achievements in the field of orthopaedic research. In 2019, Dr. Johnstone was elected Chair of the ICORS International College of Fellows.

Dr. Johnstone received the Marshall R. Urist MD Award at the 2017 Orthopaedic Research Society annual meeting in San Diego. The prestigious award honors an investigator who has established him/herself as a cutting-edge researcher in tissue regeneration research and has done so with a sustained ongoing body of focused research in the area of tissue regeneration as it relates to the musculoskeletal system. Dr. Johnstone dedicated his award to his most frequent co-author, Dr. Jung Yoo, former chair of OHSU’s Department of Orthopaedics and Rehabilitation. This dedication emphasized their long-standing and productive research partnership.

In March 2018, Dr. Johnstone was inducted into the inaugural class of ORS Fellows. The ORS Fellows Program recognizes individuals who have demonstrated service and leadership, substantial achievement, expert knowledge, and significant contributions to the field of musculoskeletal research and the Orthopaedic Research Society (ORS). Fellows represent the ORS as thought leaders and topic experts in their respective disciplines. Fellows will also serve as role models in the ORS membership community and in the field of musculoskeletal research.

Selected recent publications

• "Physioxia Promotes the Articular Chondrocyte-Like Phenotype in Human Chondroprogenitor-Derived Self-Organized Tissue." Tissue Engineering - Part A  In: , Vol. 24, No. 3-4, 01.02.2018, p. 264-274.
• "Dynamic mechanical compression of chondrocytes for tissue engineering : A critical review." Frontiers in Bioengineering and Biotechnology  In: , Vol. 5, No. DEC, 76, 11.12.2017.
• "Responses to altered oxygen tension are distinct between human stem cells of high and low chondrogenic capacity." Stem Cell Research and Therapy  In: , Vol. 7, No. 1, 154, 20.10.2016.
• "Use of MicroRNA biomarkers to distinguish enchondroma from low-grade chondrosarcoma." Connective Tissue Research  In: , 30.06.2016, p. 1-7.
• "Reoxygenation enhances tumour necrosis factor alpha-induced degradation of the extracellular matrix produced by chondrogenic cells." European Cells and Materials  In: , Vol. 31, 01.01.2016, p. 425-439.
• "Hypoxia-inducible factor 3-alpha expression is associated with the stable chondrocyte phenotype." Journal of Orthopaedic Research  In: , Vol. 33, No. 11, 01.11.2015, p. 1561-1570.
• "Effectiveness of posterolateral lumbar fusion varies with the physical properties of demineralized bone matrix strip." Asian Spine Journal In: , Vol. 9, No. 3, 2015, p. 433-439.
• "Transforming growth factor beta-releasing scaffolds for cartilage tissue engineering." Tissue Engineering - Part B: Reviews  In: , Vol. 20, No. 2, 01.04.2014, p. 106-125.
• "Stem cell-derived endochondral cartilage stimulates bone healing by tissue transformation." Journal of Bone and Mineral Research In: , Vol. 29, No. 5, 2014, p. 1269-1282.
• "Hypoxia promotes redifferentiation and suppresses markers of hypertrophy and degeneration in both healthy and osteoarthritic chondrocytes." Arthritis Research and Therapy  In: , Vol. 15, No. 4, R92, 21.08.2013.
• "Tissue engineering for articular cartilage repair - The state of the art." European Cells and Materials In: , Vol. 25, 2012, p. 248-267.
• "Visible light photoinitiation of mesenchymal stem cell-laden bioresponsive hydrogels." European Cells and Materials In: , Vol. 22, 12.2011, p. 43-55.
• "A bioresponsive hydrogel tuned to chondrogenesis of human mesenchymal stem cells." FASEB Journal  In: , Vol. 25, No. 5, 05.2011, p. 1486-1496.
• "A novel bioreactor for the dynamic stimulation and mechanical evaluation of multiple tissue-engineered constructs." Tissue Engineering - Part C: Methods  In: , Vol. 17, No. 3, 01.03.2011, p. 367-374.
• "Temporal exposure to chondrogenic factors modulates human mesenchymal stem cell chondrogenesis in hydrogels." Tissue Engineering - Part A  In: , Vol. 17, No. 3-4, 01.02.2011, p. 371-380.