Mechanisms of Vertebrate Regeneration and Tissue Engineering

Comprehensive vocabulary flashcards covering vertebrate regeneration mechanisms, stem cell plasticity, skin repair stages, tissue engineering approaches, biomaterials, decellularization, and vascularized constructs for diabetic wound healing.

Regenerative Bioscience

A field of study that assesses ways to replace, repair, or regenerate human and animal cells, tissues, or organs from a pathologic or diseased condition.

Regenerative Biology

The study of endogenous repair and regeneration mechanisms of multicellular organisms.

Regenerative Medicine

A field of study encompassing cell therapies, tissue engineering and biomaterials, gene therapies, and devices or diagnostics to replace, repair, or regenerate cells, tissues, or organs from a pathologic condition.

Physiological Regeneration

A maintenance repair process that maintains normal tissue architecture and function through continual cell turnover and replacement.

Compensatory Hyperplasia

A form of regeneration from parent differentiated cells in which differentiated cells proliferate while maintaining their normal structure and function, such as in hepatocytes, $\beta$-islet cells, and liver sinusoidal endothelial cells (LSECs).

Dedifferentiation / Redifferentiation

A repair process involving the loss of morphological, functional, or molecular characteristics of the differentiated state to regain an immature progenitor status, followed by proliferation and redifferentiation back into the parent cell type.

Epithelial-to-Mesenchymal Transition (EMT)

A biological process in which epithelial cells lose their characteristic polar and cell-adhesion features and acquire mesenchymal cell traits.

Direct Transdifferentiation

The direct conversion of one differentiated cell type into another differentiated cell type without passing through an intermediate progenitor state, such as glucagon-producing $\alpha$-cells converting into insulin-producing $\beta$-cells.

Indirect Transdifferentiation

The conversion of one differentiated cell type into another differentiated cell type through an intermediate progenitor stage, such as somatostatin-producing $\delta$-cells converting into $\beta$-cells.

Totipotent Stem Cells

Stem cells with total differentiation potential capable of generating all embryonic and extra-embryonic tissues (chorion, yolk sac, amnion, allantois) to form a fully functional living organism, such as a fertilized egg or zygote.

Pluripotent Stem Cells

Stem cells capable of indefinite self-renewal that can differentiate into cell types derived from all three germ layers (ectoderm, mesoderm, endoderm), such as Embryonic Stem Cells (ESCs) and Induced Pluripotent Stem Cells (iPSCs).

Multipotent Stem Cells

Lineage-restricted stem cells capable of self-renewal that can differentiate into a specific range of cell types within a single germ layer, such as Mesenchymal Stem Cells (MSCs) and Hematopoietic Stem Cells (HSCs).

Oligopotent Stem Cells

Stem cells that can self-renew and differentiate into a small range of closely related cell types, such as Myeloid Progenitor Cells, Airway Basal Stem Cells, Mammary Stem Cells, and Intestinal Stem Cells.

Unipotent Stem Cells

Stem cells with the most limited differentiation potential that can self-renew and undergo unidirectional differentiation into only a single specific cell type, such as Spermatogonial Stem Cells, Satellite Cells, and Chondroprogenitors.

Epidermis

The outermost layer of skin composed of stratified squamous epithelium (including stratum basale, spinosum, granulosum, lucidum, and corneum) that acts as a waterproof and antimicrobial infection barrier.

Stratum Basale

The deepest layer of the epidermis where epidermal stem cells undergo asymmetric division to give rise to proliferating keratinocytes.

Dermis

The connective tissue layer of skin located beneath the epidermis containing blood vessels, cutaneous nerves, hair follicles, sebaceous glands, sweat glands, and extracellular matrix synthesized by fibroblasts.

Hemostasis Phase

The immediate initial stage of wound healing triggered by blood vessel rupture, involving factor release from damaged endothelial cells, platelet activation/accumulation, and formation of a protective fibrin clot.

Inflammatory Phase

The second stage of wound healing characterized by chemoattractant signal release ($TGF\text{-}\beta$, $PDGF$, DAMPs), recruitment of tissue-resident lymphocytes and neutrophils, and arrival of monocytes/macrophages to clear pathogens.

M1 Macrophages

Pro-inflammatory macrophages that clear cellular debris and pathogens while secreting cytokines such as $TNF\text{-}\theta$, $IL\text{-}1\beta$, $IL\text{-}6$, $IL\text{-}8$, and $IL\text{-}12$.

M2 Macrophages

Reparative macrophages that release $VEGF$ to stimulate angiogenesis, secrete anti-inflammatory cytokines ($IL\text{-}4$, $IL\text{-}10$), and signal for fibroblast recruitment and ECM remodeling.

Structural Repair Phase

The third stage of wound healing (proliferative phase, lasting 1--2 weeks) featuring fibroblast migration, granulation tissue deposition, angiogenesis, myofibroblast contraction, and keratinocyte re-epithelialization.

Myofibroblasts

Specialized contractile cells expressing $\alpha$-smooth muscle actin microfilaments that bind collagen fibers to pull wound edges together during wound contraction.

Granulation Tissue

A provisional extracellular matrix composed of collagen, proteoglycans, elastin, and hyaluronic acid produced by fibroblasts to plug tissue gaps, protect against infection, and support vascularization.

Re-epithelialization

The process of resurfacing a wound through the activation, proliferation, and migration of adjacent keratinocyte stem cells to restore skin barrier integrity.

Remodeling Phase

The final stage of wound healing (lasting >2 weeks to years) marked by reduced myofibroblast counts, blood vessel regression, decreased immune cells, and dense collagen deposition resulting in scar formation.

Fibrosis

The formation of dense fibrous connective tissue via excessive collagen deposition by fibroblasts that patches tissue gaps without restoring original specialized architecture or appendages.

Chronic Wounds

Pathological wounds (such as lower extremity ulcers from pressure, diabetes, or venous incompetence) characterized by persistent inflammation, failure to re-epithelialize, and defective ECM production/remodeling.

Avotermin

A recombinant, active human $TGF\beta_3$ polypeptide drug administered intradermally to significantly improve visual analog scale (VAS) skin scarring scores following incision.

Exosomes

Small membrane-bound extracellular vesicles ($30\text{--}200$\text{ nm} in diameter) formed by intracellular endosomes and secreted via exocytosis that transfer proteins, lipids, and nucleic acids for cell-cell communication.

Apligraf

An FDA-approved, commercially available allogeneic cellular skin substitute containing foreskin-derived human neonatal keratinocytes and fibroblasts cultured in a bovine type I collagen matrix.

Tissue Engineering

The field that applies the principles of engineering and life sciences toward the development of biological substitutes that restore, maintain, or improve tissue function.

Autologous Cells

Cells harvested from a patient's own body for therapeutic use, minimizing immune rejection risks but potentially causing donor-site morbidity.

Allogeneic Cells

Cells harvested from a donor individual of the same species as the recipient, carrying a potential risk of immune rejection.

Xenogenic Cells

Cells harvested from an individual of a different species than the recipient, posing a strong risk of host immune rejection.

Electrospinning

A fabrication method that uses applied voltage to draw polymer solutions into microscale and nanoscale fibers with high surface-to-volume ratios mimicking natural ECM architecture.

Decellularization Standard Metrics

Quantitative parameters for acellular scaffolds ensuring complete cell removal, defined as $< 50\,\text{ng}$ dsDNA per $\text{mg}$ ECM dry weight, DNA fragment lengths $< 200\,\text{bp}$, and an absence of visible nuclear material in stained sections.

Type 1 Diabetes Mellitus

An autoimmune disorder characterized by the destruction of pancreatic insulin-producing $\beta$-islet cells, leading to an inability to synthesize insulin and excess blood glucose.

Type 2 Diabetes Mellitus

A metabolic condition where body cells develop resistance to insulin action, and the pancreas fails to produce sufficient insulin to overcome this resistance.

Endothelial Colony Forming Cells (ECFCs)

Outgrowth precursor cells that differentiate into endothelial cells and self-assemble into microvascular networks inside hydrogel matrices to promote tissue vascularization.

Early Vascular Cells (EVCs)

Human iPSC-derived lineage precursors that differentiate into both endothelial cells ($VEcad^+CD31^+$) and pericytes ($NG2^+PDGFR\beta^+$) to establish functional microvascular beds.