Bioprinting: Chapter 5

Cells can be categorised by

• source

• potential for expansion and differentiation

• cell format

  • (individual or aggregates)

Cell Sources

• autologous cells

• allogeneic cells

• xenogeneic cells

Autologous cells

• taken from the patient and then provided for the patient

  • blood would be taken, stored, and used after the surgery

  • ex: blood marrow transplantation

advantages:

• no rejection, no disease transmission

disadvantages:

• limitation on how much can be taken

Allogeneic cells

• taken from different individuals of the same species

• ex: bone marrow transplantations

advantages:

• can be used from a diseased person

disadvantages:

• risk of transmitting pathogens

• risk of introducing diseases

• weakens host’s defense mechani

Xenogeneic cells

• taking cells from a different species

advantages:

• can be provided from a broad range of sources

• immediate availability

disadvantages:

• risk of transmitting pathogens

• risk of introducing diseases

• commonly rejected

• difficult to maintain long term

• weakens host’s defense mechanisms

2 major sources of cells

• specialised

• stem

  • expansion capacity is high

  • availability is low

Specialised cells

• terminally differentiated

  • potential for differentiation is low

• availability is high

• ex: fat cell, nerve cell, bone cell, smooth muscle cell

advantages

• straight forwards process (isolate and use)

• have correct characteristics and can perform natural functions

disadvantages

• poor in vitro differentiation

• limited expansion capacity

Stem cells

• capable of

  • self-renewing

  • can differentiate (become specialized cells_

3 main types of stem cells

1. embryonic stem cells (hESCs)

2. adult stem cells (somatic)

• (includes MSC, HSC, and progenitor cells)

3. Induced pluripotent stem cells

Embryonic stem cells hESCs

• found in blastocyst

• can differentiate to almost any type of cell

  • done in vitro (like a culture)

    • results in a variety of cells

    • (aka, results in cell pop. with heterogeneity)

Mesenchymal stem cells (MSC)

• Multipotent adult stem cells that can self-renew and differentiate into multiple cell types.

• Mainly found in bone marrow and adipose tissue.

• Differentiate into bone, cartilage, and fat cells

Mesenchymal stem cells advantages & disadvantages

advantages:

• Easily obtained from many tissue sources.

• Simple isolation procedure.

• Can be expanded in large numbers for therapies.

• Widely used in clinical applications.

disadvantages:

• Undergo replicative senescence (stop dividing over time)

• Risk of malignant transformation (becoming cancer-like).

• Can have chromosomal abnormalities/genetic instability.

• Can differentiate into unwanted cell types.

Haematopoietic stem cells

• stem cells that produce all types of blood cells.

• Differentiate into:

  • Myeloid cells (e.g., red blood cells, platelets, some immune cells)

  • Lymphoid cells (e.g., B cells, T cells, NK cells)

• Found in cord blood (ex: bone marrow)

induced pluripotent stem cells (iPSC)

• adult somatic cells are reprogrammed to form pluripotent stem cells

• can self-renew + differentiate

• cell reprogramming efficiency is low

iPSC advantages & disadvantages

advantages:

• no need for embryos

• less ethical issues

• less chances of rejection

• accessible

disadvantages:

• reprogramming…

  • can cause tumor formation

  • may be linked to disease

• instable

Cell format for bioprinting

• individual cells or cell spheroid

• in solution or in hydrogel

Cell spheroid requirements

• of sufficient quantity and cell density

• well-compatible with the bioprinting strategies

Cell spheroids can look like…

1. round (exactly how you image it)

2. mass (connected)

3. stellate (like a pain splatter, messy)

4. grape (little grapes, tiny spheres connected)

Characteristics of cell spheroids

• complex fluid

  • rounding

  • fusion

  • enveloping

  • sorting

  • spreading

ronald fights evil sorta sneaky

Fusion

• when 2 spheroids come in contact, they fuse together to create…. a larger spheroid!

Enveloping

first.. cohesion is

• how strongly cells stick together

less cohesive spheroids envelop more cohesive spheroids

Sorting

• when cells contain different populations, they sort out without human intervention

Spreading

• spheroids spread on a wettable substrate

How many types of vascular tissue spheroids are there

3

What do we use in experiments

• primary cells

• cell lines

• stem cells

cell lines

• cultures of animal cells

• can be propagated repeatedly (sometimes indefinitely)