Scaffold Pore Size and Calcium Phosphate Coating Control Chondrogenesis and Endochondral Ossification.

In the United States, 30% of adults suffer joint pain, most commonly in the knee. Knee pain can severely limit mobility and can often be contributed to injury to the cartilage and underlying bone in the joint. Unfortunately, a growing population of young athletes is developing osteochondral knee injuries due to repetitive joint stress and sports-related injuries such as meniscus or ligament tears. Microfracture and autografts are currently primary treatments for small osteochondral defects. However, microfracture results in less resilient fibrocartilage with eventual failure, and autografting can cause donor site morbidity and poor integration. To overcome these significant drawbacks, material scientists and bioengineers have collaborated to design tissue-engineered cartilage-bone grafts as an alternate therapy for small osteochondral defects. Recently, we made significant progress in developing novel nanofibrous, porous polymer scaffolds with a highly uniform, spherical, well-interconnected porous network for tissue regeneration. The goal of this project was to optimize scaffold pore architecture of a polymer/ceramic composite scaffold for both cartilage and bone regeneration. Using a 3D nanofibrous poly(ʟ-lactic acid) (PLLA) scaffold seeded with bone marrow-derived mesenchymal stem cells (BMSCs), the following three specific aims were investigated. Aim 1 determined the effect of scaffold pore size on chondrogenic differentiation and cartilage formation both in vitro and in vivo. Aim 2 optimized scaffold pore size in an ectopic model to control endochondral ossification for bone regeneration. Aim 3 evaluated the effect of electrodeposited calcium phosphate on the porous scaffold on bone formation. In this dissertation, we revealed that chondrogenesis and endochondral ossification can be controlled by scaffold pore architecture and enhanced by a calcium phosphate coating to direct cartilage and bone regeneration. In the future, the tissue-engineered cartilage and bone graft materials could be combined into a biphasic scaffold for an osteochondral knee graft with two unique pore sizes and biphasic growth factor delivery, as shown by preliminary data. This cell-instructive, biomimetic composite material could even serve as a platform to engineer various complex tissues and organ systems.PhDBiomedical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/111634/1/mgupte_1.pd

Development of Channeled Nanofibrous Scaffolds for Oriented Tissue Engineering

A tissue‐engineering scaffold resembling the structure of the natural extracellular matrix can often facilitate tissue regeneration. Nerve and tendon are oriented micro‐scale tissue bundles. In this study, a method combining injection molding and thermally induced phase separation techniques is developed to create single‐ and multiple‐channeled nanofibrous poly( L ‐lactic acid) scaffolds. The overall shape, the number and spatial arrangement of channels, the channel wall matrix architecture, the porosity and mechanical properties of the scaffolds are all tunable. The porous NF channel wall matrix provides an excellent microenvironment for protein adsorption and the attachment of PC12 neuronal cells and tendon fibroblast cells, showing potential for neural and tendon tissue regeneration. A method combining injection molding and thermally induced phase separation is developed to create single‐ and multiple‐channeled nanofibrous polymer scaffolds. The porous nanofibrous channel wall provides an excellent microenvironment for protein adsorption and cell attachment, showing potential for nerve and tendon regeneration.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/92054/1/761_ftp.pd

Regenerating Nucleus Pulposus of the Intervertebral Disc Using Biodegradable Nanofibrous Polymer Scaffolds

Low back pain is a leading health problem in the United States, which is most often resulted from nucleus pulposus (NP) degeneration. To date, the replacement of degenerated NP relies entirely on mechanical devices. However, a biological NP replacement implant is more desirable. Here, we report the regeneration of NP tissue using a biodegradable nanofibrous (NF) scaffold. Rabbit NP cells were seeded on the NF scaffolds to regenerate NP-like tissue both in vitro and in a subcutaneous implantation model. The NP cells on the NF scaffolds proliferated faster than those on control solid-walled (SW) scaffolds in vitro. Significantly more extracellular matrix (ECM) production (glycosaminoglycan and type II collagen) was found on the NF scaffolds than on the control SW scaffolds. The constructs were then implanted in the caudal spine of athymic rats for up to 12 weeks. The tissue-engineered NP could survive, produce functional ECM, remain in place, and maintain the disc height, which is similar to the native NP tissue.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/98480/1/ten%2Etea%2E2011%2E0747.pd

Characterization of a Novel Fibroblast Growth Factor 10 (Fgf10) Knock-In Mouse Line to Target Mesenchymal Progenitors during Embryonic Development

Fibroblast growth factor 10 (Fgf10) is a key regulator of diverse organogenetic programs during mouse development, particularly branching morphogenesis. Fgf10-null mice suffer from lung and limb agenesis as well as cecal and colonic atresia and are thus not viable. To date, the Mlcv1v-nLacZ-24 transgenic mouse strain (referred to as Fgf10LacZ), which carries a LacZ insertion 114 kb upstream of exon 1 of Fgf10 gene, has been the only strain to allow transient lineage tracing of Fgf10-positive cells. Here, we describe a novel Fgf10Cre-ERT2 knock-in line (Fgf10iCre) in which a Cre-ERT2-IRES-YFP cassette has been introduced in frame with the ATG of exon 1 of Fgf10 gene. Our studies show that Cre-ERT2 insertion disrupts Fgf10 function. However, administration of tamoxifen to Fgf10iCre; Tomatoflox double transgenic embryos or adult mice results in specific labeling of Fgf10-positive cells, which can be lineage-traced temporally and spatially. Moreover, we show that the Fgf10iCre line can be used for conditional gene inactivation in an inducible fashion during early developmental stages. We also provide evidence that transcription factors located in the first intron of Fgf10 gene are critical for maintaining Fgf10 expression over time. Thus, the Fgf10iCre line should serve as a powerful tool to explore the functions of Fgf10 in a controlled and stage-specific manner

Nanofibrous Spongy Microspheres Enhance Odontogenic Differentiation of Human Dental Pulp Stem Cells

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/113700/1/adhm201500308.pd

Stem Cells: Injectable Peptide Decorated Functional Nanofibrous Hollow Microspheres to Direct Stem Cell Differentiation and Tissue Regeneration (Adv. Funct. Mater. 3/2015)

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/110635/1/adfm201570016.pd

Macromol. Biosci. 6/2012

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/92018/1/11110_ftp.pd