Table 1 |.

Troubleshooting table

Step	Problem	Possible reason	Solution
13A(vii)	Spheroids do not develop into HOs	Insufficient number of medium changes	Change the medium every 3-4 d
		Absence of growth factors/low growth factor activity	Ensure that the growth factors are freshly added
	Spheroids sink to the bottom of the dish and fail to develop into HOs	The hydrogel is degrading too quickly or is not properly polymerized	Reduce the spheroid density per hydrogel Increase the frequency of passages to every 5-7 d
		Spheroids were too close to the bottom of the dish during hydrogel cross-linking	During hydrogel cross-linking, flip the plate upside-down to ensure that spheroids are not too close to the bottom of the dish
11, 13B(xi)	Hydrogels do not form	Inadequate pH adjustment of the peptide solutions	Adjust the pH to 7.4
		The purity level of the peptides was not considered when calculating mass	Consider the peptide purity provided by the vendor as shown in Box 1
			Determine the peptide purity by UV absorption spectroscopy, as previously described29
		Incomplete tissue penetration of the needle bevel at the wound site (only for Step 13B(xi))	Penetrate the tissue slightly past the needle bevel to ensure full delivery of hydrogel solution
13B(xii)	Low or no HO engraftment into host tissue	Settling of HOs to one end of the syringe due to gravity	Shake the syringe gently before each injection
	Clogging in the tubing caused by hydrogel cross-linking	Untimely mixing of the hydrogel precursor solutions in the tube before injection	Verify that there is no leakage from the syringe into the tube before injections
		The pH is too high	Reduce the pH of the cross-linker solution to delay the reaction during injection