Vaccines, Blood & Biologics

Developing Ways to Measure Safety and Efficacy for Tissue-engineered Products

Principal Investigator: Brenton McCright, PhD
Office / Division / Lab: OCTGT / DCGT / CTTB

General Overview

The primary purpose of cell and tissue engineering is to fulfill the growing need for tissues and organs required to treat patients with degenerative diseases. Collections of transplanted cells that are poorly engineered and uncharacterized (i.e., cells whose biological characteristics are not fully identified) may not function reliably in the body after being transplanted. Moreover, such cells might even damage other organ systems of the patient receiving them, or may form tumors.

Therefore, our laboratory is studying the key processes that determine how cells mature and contribute to the formation of organs and tissues. Identifying the biological factors controlling growth and development of organs and tissues is providing data the FDA can use to advise sponsors on how to measure the behavior of cell populations or tissue-engineered products administered to patients. It will also help agency scientists develop needed new approaches for quality assessment of novel cell-based therapies with improved ability to predict safety and efficacy over standard methods used for conventional therapies and biologics.

We are especially interested in understanding the molecular signals that determine whether a cell remains immature and continues to multiply, or stops dividing and matures into a cell that performs a specific function in the body. The goal of our work is to identify and understand those molecular signals that might help us to predict how a cell will function after being administered to patients. The molecular signals we study are evolutionarily conserved (present in all animals) and widely used (present in many cell types) signaling pathways such as the Notch and Wnt pathways. We have developed genetically engineered mice in which these molecules can be turned on or off in response to certain stimuli. This allows us to study when these signals are needed during tissue repair and organ development. Our laboratory uses the mouse as a model to study how tissues mature and how biological signals determine the fate of cells in the body because organ development in mice is very similar to that of humans.

In addition to studying the function of key pathways of biochemical signaling that guide the development of organs, we are analyzing the function of these pathways in progenitor cells such as those used for cellular therapies. Progenitor cells are between embryonic stem cells and mature, functional, specific cells as far as their potential to form new tissues is concerned. Progenitors are more mature than embryonic stem cells and therefore limited in the type(s) of cells they can become.

The aim of these studies is to generate data and knowledge that the FDA can use to ensure that cellular therapies will successfully treat human disease. The studies are providing tools needed to evaluate potential cell sources, techniques for growing cells, and identifying markers that can predict how such cells will behave. These tools and techniques will enable FDA to evaluate these complex products for safety and effectiveness. We believe that understanding the evolutionarily conserved signaling pathways involved in the regulation of mammalian organ development and stem cell differentiation is critical to successful cell therapy since these factors are also required for tissue repair and regeneration.

Scientific Overview

Our research is focused on elucidating the function of key cell-fate-determining factors important in evaluating the safety and efficacy of cellular therapies and tissue engineered products. The research projects are focused on evaluating requirements for specific molecules during embryonic organ development and in mouse models of cellular therapies. Because successful repair and regeneration of damaged tissue will require the same signaling pathways used for embryonic organ formation we expect findings from these two approaches to complement each other.

Function of Notch and PP2A on heart development:

We have used transgenic mice that allow the deletion or activation of Notch2 to study the functional requirements for Notch signaling during murine heart development. We are now performing studies on mice in which the B56 regulatory subunits of Protein Phosphatase 2a have been inactivated. Our findings demonstrate that mis-regulation of these conserved signaling pathways disrupt the normal expansion and differentiation of cardiac progenitor cells. This suggests that monitoring the expression of these molecules might be useful in evaluating the developmental status of cardiac progenitor cells used in therapies.

Mesenchymal stem cell (MSC) project:

The purpose of this collaborative project is to identify MSC biomarkers that correlate with their safe and effective use. Other members of the group are performing microarray, proteomic, and cell surface marker analyses on both human and murine MSCs. Our laboratory will compare cells from early passage to cells from later passages in order to identify molecular differences. We will then place cells in a mouse hind limb ischemia model to evaluate the correlation of these differences with their effects in vivo. The recipient animals will contain transgenes that report activity of molecules known to be required for angiogenic repair, such as Notch2, Tie2, Ephrin 2B. We will also evaluate the effects of the transplanted MSCs by imaging the limbs of the mice using laser doppler imaging to visualize blood flow. We will then perform histological analyses to determine if the transplanted cells persist and if they contribute to the formation of new blood vessels.


Dev Dyn 2014 Jun;243(6):778-90
The protein phosphatase 2A B56gamma regulatory subunit is required for heart development.
Varadkar P, Despres D, Kraman M, Lozier J, Phadke A, Nagaraju K, McCright B

J Immunol 2011 Nov 15;187(10):5114-22
A disintegrin and metalloproteinase 10 regulates antibody production and maintenance of lymphoid architecture.
Chaimowitz NS, Martin RK, Cichy J, Gibb DR, Patil P, Kang DJ, Farnsworth J, Butcher EC, McCright B, Conrad DH

Dev Biol 2010 Jan 15;337(2):386-95
The contribution of Notch1 to nephron segmentation in the developing kidney is revealed in a sensitized Notch2 background and can be augmented by reducing Mint dosage.
Surendran K, Boyle S, Barak H, Kim M, Stomberski C, McCright B, Kopan R

Genesis 2009 Aug;47(8):573-8
Generation of mice that conditionally express the activation domain of Notch2.
Varadkar PA, Kraman M, McCright B

Tissue Eng Part A 2009 Mar;15(3):455-60
Synopsis of the Food and Drug Administration-National Institute of Standards and Technology Co-Sponsored "In Vitro Analyses of Cell/Scaffold Products" Workshop.
McCright B, Dang JM, Hursh DA, Kaplan DS, Ballica R, Benton KA, Plant AL

Dev Dyn 2008 Apr;237(4):1144-52
Notch2 is required for the proliferation of cardiac neural crest-derived smooth muscle cells.
Varadkar P, Kraman M, Despres D, Ma G, Lozier J, McCright B

PLoS One 2008 Mar 26;3(3):e1851
Notch signaling regulates bile duct morphogenesis in mice.
Lozier J, McCright B, Gridley T

Immunity 2007 Jul;27(1):89-99
Direct regulation of gata3 expression determines the T helper differentiation potential of notch.
Amsen D, Antov A, Jankovic D, Sher A, Radtke F, Souabni A, Busslinger M, McCright B, Gridley T, Flavell RA

Genesis 2006 Jan;44(1):29-33
Generation of new Notch2 mutant alleles.
McCright B, Lozier J, Gridley T

FASEB J 2005 Aug;19(10):1311-3
Functional conservation of Notch1 and Notch2 intracellular domains.
Kraman M, McCright B


Contact FDA

(800) 835-4709
(240) 402-8010
Consumer Affairs Branch (CBER)

Division of Communication and Consumer Affairs

Office of Communication, Outreach and Development

Food and Drug Administration

10903 New Hampshire Avenue

Building 71 Room 3103

Silver Spring, MD 20993-0002

Page Last Updated: 05/16/2017
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