Commitments and Contingencies - Additional Information (Detail)	1 Months Ended			3 Months Ended		9 Months Ended
	Feb. 28, 2017 USD ($)	Sep. 30, 2015	Jun. 30, 2012 USD ($)	Sep. 30, 2018 USD ($)	Sep. 30, 2017 USD ($)	Sep. 30, 2018 USD ($) Option	Sep. 30, 2017 USD ($)
Loss Contingencies [Line Items]
Rent expense under operating lease agreements				$ 400,000	$ 200,000	$ 1,200,000	$ 700,000
Research and development expense				4,563,000	$ 3,488,000	12,307,000	$ 12,200,000
Collagen Supply Agreement [Member]
Loss Contingencies [Line Items]
Amount to be paid upon FDA approval				0		$ 0
Supplier agreement description						The initial term of the agreement is three years and will automatically renew from year to year thereafter unless otherwise terminated with at least 180 days’ notice by either party.
Initial term of the agreement		3 years
Minimum amount of material and/or services	$ 100,000
Amount paid during period for amending the agreement						$ 100,000
OCS Agreement [Member]
Loss Contingencies [Line Items]
Accrued and received grants, aggregate				1,100,000		1,100,000
Tissue Processor Sub License Agreement [Member]
Loss Contingencies [Line Items]
Research and development expense						1,100,000
Reimbursement for development cost			$ 300,000
Additional non-refundable royalty fee						$ 30,000
Additional non-refundable royalty fee payment description						2016 through 2019
Potential milestone payments				10,200,000		$ 10,200,000
Hydrogel License Agreement [Member]
Loss Contingencies [Line Items]
Research and development expense						3,200,000
Amount to be paid upon FDA approval				3,000,000		3,000,000
Tissue Regeneration License Agreement [Member]
Loss Contingencies [Line Items]
Research and development expense						800,000
Amount to be paid upon FDA approval				300,000		$ 300,000
Percentage of royalty offsetting						50.00%
Maximum [Member] | OCS Agreement [Member]
Loss Contingencies [Line Items]
Royalties payment, rate						5.00%
Royalty payment percentage as percentage of grant received						300.00%
Minimum [Member] | OCS Agreement [Member]
Loss Contingencies [Line Items]
Royalties payment, rate						3.00%
Royalty payment percentage as percentage of grant received						100.00%
Minimum [Member] | Tissue Processor Sub License Agreement [Member]
Loss Contingencies [Line Items]
Non-refundable royalty fee						$ 20,000
Minimum [Member] | Tissue Regeneration License Agreement [Member]
Loss Contingencies [Line Items]
Non-refundable royalty fee						10,000
Waltham [Member]
Loss Contingencies [Line Items]
Tenant improvement allowance for future rental payments						500,000
Waltham [Member] | Maximum [Member]
Loss Contingencies [Line Items]
Tenant improvement allowance				$ 900,000		$ 900,000
Waltham [Member] | Massachusetts [Member]
Loss Contingencies [Line Items]
Effective date of amended lease						Jan. 01, 2018
Lease termination date						Dec. 31, 2024
Number of additional renewal terms | Option						1
Additional operating lease term				5 years		5 years
Lexington [Member] | Maximum [Member]
Loss Contingencies [Line Items]
Construction allowances to total cost of tenant improvements						$ 1,000,000
Lexington [Member] | Massachusetts [Member]
Loss Contingencies [Line Items]
Lease expiration period						2023
Number of additional renewal terms | Option						1
Additional operating lease term				5 years		5 years