Stem cell therapies have shown promise for regenerative treatment for musculoskeletal conditions, but their success is mixed. To enhance regenerative effects, growth factors are utilized to induce differentiation into native cell types, but uncontrollable in vivo conditions inhibit differentiation, and precise control of expressed matrix proteins is difficult to achieve. To address these issues, we investigated a novel method of enhancing regenerative phenotype through direct upregulation of major cartilaginous tissue proteins, aggrecan (ACAN), and collagen II (COL2A1) using dCas9-VPR CRISPR gene activation systems. We demonstrated increased expression and deposition of targeted proteins independent of exogenous growth factors in pellet culture. Singular upregulation of COL2A1/ACAN interestingly indicates that COL2A1 upregulation mediates the highest sulfated glycosaminoglycan (sGAG) deposition, in addition to collagen II deposition. Through RNA-seq analysis, this was shown to occur by COL2A1 upregulation mediating broader chondrogenic gene expression changes. Multiplex upregulation of COL2A1 and ACAN together resulted in the highest sGAG, and collagen II deposition, with levels comparable to those in chondrogenic growth factor-differentiated pellets. Overall, this work indicates dCas9-VPR systems can robustly upregulate COL2A1 and ACAN deposition without growth factors, to provide a novel, precise method of controlling stem cell phenotype for cartilage and intervertebral disc cell therapies and tissue engineering.

Low back pain (LBP) ranks among the leading causes of disability worldwide and generates a tremendous socioeconomic cost. Disc degeneration, a leading contributor to LBP, can be characterized by the breakdown of the extracellular matrix of the intervertebral disc (IVD), disc height loss, and inflammation. The inflammatory cytokine TNF-alpha; has multiple pathways and has been implicated as a primary mediator of disc degeneration. We tested our ability to regulate the multiple TNF-alpha; inflammatory signaling pathways in vivo utilizing CRISPR receptor modulation to slow the progression of disc degeneration in rats. Sprague-Dawley rats were treated with CRISPRi-based epigenome-editing therapeutics targeting TNFR1 and showed a decrease in behavioral pain in a disc degeneration model. Surprisingly, while treatment with the vectors alone was therapeutic, TNF-alpha injection itself became therapeutic after TNFR1 modulation. These results suggest direct inflammatory receptor modulation, to harness beneficial inflammatory signaling pathways, as a potent strategy for treating disc degeneration.

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Engineered bone tissue synthesized from mesenchymal stem cell progenitors has numerous applications throughout the fields of regenerative medicine and tissue engineering. However, these multipotent cells offer little tissue-building assistance without differentiation direction from environmental cues such as bone morphogenetic proteins (BMPs). Unfortunately, BMP dosing and environmental cues can be difficult to control both in vitro and after in vivo delivery. Several BMP antagonists are expressed by cells in response to BMP dosing that bind extracellular BMPs and reduce their effective concentration. Here, we use CRISPR-guided gene-modulation technology to downregulate the expression of three BMP antagonists, noggin, gremlin-1, and gremlin-2, in adipose-derived stem cells (ASCs). We show that regulating noggin using this method results in ASC osteogenesis without the need for exogenous growth factors. To demonstrate the versatility and the precision capabilities of these engineered cells, we employ them with CRISPRa multiplex-engineered chondrogenic cells as a proof-of-concept tissue engineering application by creating a tissue gradient similar to the fibrocartilage-to-mineralized-fibrocartilage gradient in the tendon/ligament enthesis or intervertebral disc attachment. In doing so, we show that multiple CRISPR multiplex-engineered cell types can be utilized in concert to provide a high degree of tissue developmental control without the use of exogenous growth factors.