The Ridky Lab

Research Program: MFG-H: New models

MFG-H has been developed using 2 major experimental platforms, organotypic tissue generated in vitro using human epithelial and mesenchymal cells within an intact dermal stromal architecture, and human skin tissue regenerated in vivo on immune deficient mice.

Organotypic tissue in culture is a powerful, high-throughput experimental MFG-H platform which utilizes intact human mesenchymal dermis, mesenchymal fibroblasts and overlying stratified epithelial cells. This forms skin tissue nearly identical to skin on humans at levels of gene expression, morphology and tissue architecture. Although lacking the durability and link to systemic circulation and non-amamnestic inflammatory cells that characterize the in vivo model, the organotypic model incorporates many of its advantages and also has unique strengths that include:

  1. Experimental speed; organotypic experiments commonly take 7 to 10 days
  2. Freedom from animal use
  3. Accessibility to pharmacologic agents that often cannot be used in animal models due to cost, systemic toxicity and drug absorption, distribution, metabolism and dosing.
  4. Accessibility to antibody agents for inhibitor and activations studies that can use far smaller amounts than would be needed for animal studies
  5. Ability to rapidly alter function of a larger number of target genes via RNAi, antibodies, drugs, and gene delivery
  6. Tractability to the use of siRNA oligonucleotide duplexes which are typically effective for only 3-7 days

In vivo genetically modified human tissue regenerated in the context of full-thickness human skin on immune deficient mice offers a potent new model for the study of human stem cell biology, cancer and molecular therapeutics. The in vivo human tissue model complements the in vitro 3-D tissues and displays unique strengths that include:

  1. Capability to simultaneously alter function of 10 or more alleles genetically within architecturally faithful human tissue, providing “Multi-Functional Genetics” capabilities as well as the ability to alter the function of multiple additional proteins by antibody targeting
  2. Experimentation within the context of multiple non-transformed human cell lineages, including epithelial and mesenchymal cells, as well as 3-dimensionally intact human extracellular matrix, and functioning vasculature and lymphatic systems
  3. Study of endogenous human genes and proteins, which represent the actual molecular targets for potential human clinical application
  4. Capacity for long-term experiments in that human tissue can be followed out for over 1 year, a timepoint that permits rigorous assessment of stem cell function and tissue self-renewal.
  5. Ability to generate human tissue mosaics to distinguish cell autonomous from non-cell autonomous mechanisms in stem cell biology and cancer
  6. Expression of conditional and constitutively active or dominant negative alleles, as well as shRNAs via high efficiency lenti or retroviruses.
University of Pennsylvania | Perelman School of Medicine